The document discusses a conjectured derivative morphology of pheophytin that could facilitate proton conduction and hydrogen decomposition. Quantum simulations showed the derivative structure was energetically favorable. Spectral analyses of extracted pheophytin matched the simulated derivative structure more than the textbook structure. Battery experiments demonstrated pheophytin-catalyzed electrodes produced more discharge than non-catalyzed electrodes, providing evidence pheophytin can catalyze hydrogen decomposition. The findings suggest a derivative pheophytin form may exist that could better explain experimental observations than the accepted textbook structure.
Dr. Chungpin Liao is a Taiwanese inventor born in 1959. He received his PhD in plasma science and fusion technology from MIT in 1992. Since then, he has founded his own research lab focused on cross-disciplinary fields like nanotechnology and photonics. Some of his key inventions include the chlorophyll organic cell, which can generate electricity when wet and can power LED lights for a week. It is biodegradable and can be reused 3-4 times. He has received media coverage and recognition for his inventions in Taiwan.
• Background and motivation – the success of pheophytin (pheo, 脫鎂葉綠素) catalyst
• Porphyrin-ring family and roles of their derivative morphologies
• Similar derivatives within DNA base pairs
• 1st-principle simulation of simplified H2 decomposition steps involving derivative DNA base pairs à energetically favorable?
• Wet DNA-catalyzed chemical battery experiment and result
• Dry DNA-catalyzed hydrogen fuel cell under room temperature
• Summary and conclusions
The document summarizes the electrochemical properties of various metalloporphyrin complexes in non-aqueous media. The authors examined how the central metal ion and porphyrin counteranion affect the redox processes. They identified three groups of complexes based on their electrochemical behavior. Group A complexes undergo three irreversible or quasi-reversible reductions. Group B complexes have more than three reductions due to the metal ions having lower electronegativity. Group C complexes exhibit a reversible metal-based reduction prior to other processes. Overall, the study provides insight into the redox mechanisms and multi-electron transfer processes of these complexes.
This document discusses cisplatin, an anticancer drug. It summarizes computational studies examining the effects of substituting different ligands on cisplatin's central platinum atom. Bond lengths, angles, and electrostatic charges were calculated. Iodine substitution caused the greatest increase in bond length due to iodine's large size. Bromine substitution most affected bond angles. More electronegative ligands led to more positive charges on the platinum atom. In general, larger and less electronegative ligands had greater effects on geometry and charge distribution compared to the original cisplatin molecule.
This document discusses isotopes and radioactive decay. It defines isotopes as forms of a chemical element with the same number of protons but different numbers of neutrons. It describes the history of discoveries in radioactivity by Henri Becquerel, Frederick Soddy, and Ernest Rutherford. It discusses the types of radioactive particles (alpha, beta, gamma rays), their properties, and how radioactive decay occurs. It also covers radioactive decay rates, units of radioactivity like curies, and the concept of half-life.
1) Biology is governed by the basic laws of chemistry and physics. Living organisms are composed of elements that form molecules through chemical bonds.
2) Atoms are made up of subatomic particles like protons, neutrons, and electrons. The number of protons defines an element and its properties depend on electron arrangement. Elements combine through ionic bonds or covalent bonds to form compounds with unique properties.
3) Molecular shape is important for function, as biological molecules recognize each other based on shape. Weak bonds like hydrogen bonds also allow large biological molecules to maintain functional shapes.
The document summarizes key aspects of photosynthesis including the structure and function of the cytochrome b6f complex and photosystem I. It discusses:
1) The cytochrome b6f complex transfers electrons from photosystem II to photosystem I while pumping protons across the thylakoid membrane. It is composed of four large subunits including cytochrome f and b6 and four small subunits.
2) Photosystem I contains a reaction center called P700 and associated antenna pigments that absorb light and transfer energy to P700. It is a multi-subunit protein complex located in the stroma lamellae.
3) Both complexes play important roles in the light-dependent reactions of
By the end of this lecture you will be able to:
Understand that ENERGY can be transformed from one form to another.
Know that energy exist in two forms; free energy - available for doing work or as heat - a form unavailable for doing work.
Appreciate that the Sun provides most of the energy needed for life on Earth.
Explain why photosynthesis is so important to energy and material flow for life on earth.
Know why plants tend to be green in appearance.
Equate the organelle of photosynthesis in eukaryotes with the chloroplast.
Describe the organization of the chloroplast.
Understand that photosynthesis is a two fold process composed of the light-dependent reactions (i.e., light reactions) and the light independent reactions (i.e. Calvin Cycle or Dark Reactions).
Tell where the light reactions and the CO2 fixation reactions occur in the chloroplast.
Define chlorophylls giving their basic composition and structure.
Draw the absorption spectrum of chlorophyll and compare it to the action spectrum of photosynthesis.
Define the Reaction Centers and Antennae and describe how it operates.
Describe cyclic photophosphorylation of photosynthesis.
Describe noncyclic photophosphorylation of photosynthesis.
Dr. Chungpin Liao is a Taiwanese inventor born in 1959. He received his PhD in plasma science and fusion technology from MIT in 1992. Since then, he has founded his own research lab focused on cross-disciplinary fields like nanotechnology and photonics. Some of his key inventions include the chlorophyll organic cell, which can generate electricity when wet and can power LED lights for a week. It is biodegradable and can be reused 3-4 times. He has received media coverage and recognition for his inventions in Taiwan.
• Background and motivation – the success of pheophytin (pheo, 脫鎂葉綠素) catalyst
• Porphyrin-ring family and roles of their derivative morphologies
• Similar derivatives within DNA base pairs
• 1st-principle simulation of simplified H2 decomposition steps involving derivative DNA base pairs à energetically favorable?
• Wet DNA-catalyzed chemical battery experiment and result
• Dry DNA-catalyzed hydrogen fuel cell under room temperature
• Summary and conclusions
The document summarizes the electrochemical properties of various metalloporphyrin complexes in non-aqueous media. The authors examined how the central metal ion and porphyrin counteranion affect the redox processes. They identified three groups of complexes based on their electrochemical behavior. Group A complexes undergo three irreversible or quasi-reversible reductions. Group B complexes have more than three reductions due to the metal ions having lower electronegativity. Group C complexes exhibit a reversible metal-based reduction prior to other processes. Overall, the study provides insight into the redox mechanisms and multi-electron transfer processes of these complexes.
This document discusses cisplatin, an anticancer drug. It summarizes computational studies examining the effects of substituting different ligands on cisplatin's central platinum atom. Bond lengths, angles, and electrostatic charges were calculated. Iodine substitution caused the greatest increase in bond length due to iodine's large size. Bromine substitution most affected bond angles. More electronegative ligands led to more positive charges on the platinum atom. In general, larger and less electronegative ligands had greater effects on geometry and charge distribution compared to the original cisplatin molecule.
This document discusses isotopes and radioactive decay. It defines isotopes as forms of a chemical element with the same number of protons but different numbers of neutrons. It describes the history of discoveries in radioactivity by Henri Becquerel, Frederick Soddy, and Ernest Rutherford. It discusses the types of radioactive particles (alpha, beta, gamma rays), their properties, and how radioactive decay occurs. It also covers radioactive decay rates, units of radioactivity like curies, and the concept of half-life.
1) Biology is governed by the basic laws of chemistry and physics. Living organisms are composed of elements that form molecules through chemical bonds.
2) Atoms are made up of subatomic particles like protons, neutrons, and electrons. The number of protons defines an element and its properties depend on electron arrangement. Elements combine through ionic bonds or covalent bonds to form compounds with unique properties.
3) Molecular shape is important for function, as biological molecules recognize each other based on shape. Weak bonds like hydrogen bonds also allow large biological molecules to maintain functional shapes.
The document summarizes key aspects of photosynthesis including the structure and function of the cytochrome b6f complex and photosystem I. It discusses:
1) The cytochrome b6f complex transfers electrons from photosystem II to photosystem I while pumping protons across the thylakoid membrane. It is composed of four large subunits including cytochrome f and b6 and four small subunits.
2) Photosystem I contains a reaction center called P700 and associated antenna pigments that absorb light and transfer energy to P700. It is a multi-subunit protein complex located in the stroma lamellae.
3) Both complexes play important roles in the light-dependent reactions of
By the end of this lecture you will be able to:
Understand that ENERGY can be transformed from one form to another.
Know that energy exist in two forms; free energy - available for doing work or as heat - a form unavailable for doing work.
Appreciate that the Sun provides most of the energy needed for life on Earth.
Explain why photosynthesis is so important to energy and material flow for life on earth.
Know why plants tend to be green in appearance.
Equate the organelle of photosynthesis in eukaryotes with the chloroplast.
Describe the organization of the chloroplast.
Understand that photosynthesis is a two fold process composed of the light-dependent reactions (i.e., light reactions) and the light independent reactions (i.e. Calvin Cycle or Dark Reactions).
Tell where the light reactions and the CO2 fixation reactions occur in the chloroplast.
Define chlorophylls giving their basic composition and structure.
Draw the absorption spectrum of chlorophyll and compare it to the action spectrum of photosynthesis.
Define the Reaction Centers and Antennae and describe how it operates.
Describe cyclic photophosphorylation of photosynthesis.
Describe noncyclic photophosphorylation of photosynthesis.
1) Porphyrin-fullerene dyads were synthesized where the two chromophores are linked by a bicyclic bridge.
2) Time-resolved fluorescence measurements showed substantial quenching of the porphyrin singlet lifetime in both the zinc and free base dyads due to singlet-singlet energy transfer to the fullerene.
3) In toluene, a transient absorption was detected for the free base dyad with a lifetime of ~10 ps, assigned to the fullerene triplet state, while electron transfer was unfavorable. In the more polar benzonitrile, electron transfer from the porphyrin to the fullerene was observed.
a substance can absorb any visible light or external radiation and then again emit it. this called fluorescence and the process of reduction in fluorescence intensity is called quenching. this presentation is all about quenching of fluorescence.
The document discusses the use of radioactive isotopes in geology and forensics. It describes the components of atoms, including protons, neutrons, and electrons. Isotopes are variants of the same element that differ in their number of neutrons. Unstable isotopes decay over time, while stable isotopes can be used for radiometric dating. Examples are given of carbon-14 dating of artifacts like the Dead Sea Scrolls and Stonehenge. Forensic cases show how carbon-14 has been used to date things like the Shroud of Turin and nuclear test fallout in teeth.
This document provides an overview of metabolism and energy transformation in living cells. It discusses key topics including:
1) Metabolism transforms matter and energy through chemical reactions in metabolic pathways catalyzed by enzymes. Catabolic pathways release energy by breaking down molecules, while anabolic pathways use energy to build complex molecules.
2) The first law of thermodynamics states that energy cannot be created or destroyed, only transferred or transformed. The second law states that every transformation increases entropy and some energy is lost as heat.
3) ATP powers cellular work by coupling exergonic reactions, which release free energy, to endergonic reactions like biosynthesis, transport, and mechanical work that require energy. Most energy coupling
This document summarizes an investigation into the low-temperature oxidation reactions of 2-phenylethanol using photoionization mass spectrometry. The reaction was initiated using 248 nm photolysis of chlorine at 298 K and 550 K, with and without oxygen present. A variety of reaction products were identified using mass spectrometry coupled to synchrotron radiation. Key findings include that the aromatic ring remains intact, all chemistry occurs on the side chain, and decomposition explains products with lower mass-to-charge ratios. More products need to be identified to determine branching fractions.
The document summarizes the development and validation of a photocalorimetry technique. It outlines the design of the photocalorimeter instrument and describes validation methods using chemical actinometers like 2-nitrobenzaldehyde and ferrioxalate in solution. Nifedipine degradation experiments were used to validate the technique for solids. Results showed 2-NB provided more stable calibration than ferrioxalate. Future work will apply the technique to study effects of wavelength, moisture and temperature on solid-state reactions.
Computational chemistry methods can be used to predict the photophysical properties of BODIPY dyes. The author performed preliminary work validating their computational approach by comparing excited state calculations on 26 BODIPY dyes to experimental data. Molecular dynamics simulations were carried out to sample potential energy surfaces and check for non-parallelity between time-dependent density functional theory and restricted open-shell Kohn-Sham methods. Interactions between BODIPY dyes and oxygen were modeled to study singlet oxygen generation pathways.
This document describes the synthesis and characterization of a ruthenium polypyridyl complex. Key steps include:
1) Synthesizing a bipyridine ligand functionalized with a bromomethyl group and methyl substituent.
2) Attaching this ligand to diethyl malonate using a Mitsunobu reaction to form a chelating ligand.
3) Reacting this ligand with cis-bis(bipyridine)dichlororuthenium(II) dihydrate to form the target ruthenium complex.
4) Purifying and characterizing the complex using NMR spectroscopy and mass spectrometry. The complex exhibits photophysical properties suitable for applications
Literature Seminar on Expansion of Pd chains through Beta-Carotene & Tetrapho...Nina Saraei
The document summarizes two papers on the expansion of palladium chains using β-carotene and tetraphosphine ligands. The first paper discusses the stepwise expansion of homonuclear and heteronuclear palladium chains from binuclear Pd(I) complexes supported by tetraphosphine ligands. Characterization data showed the complexes adopt linear structures with reversible metalation/demetalation. The second paper examines a bis-β-carotene ligand's ability to bind decanuclear palladium and palladium-platinum complexes into infinite π-stacked columns. Both papers demonstrate the use of multidentate ligands to control the assembly of extended metal atom chains.
Transition Metals As Spectroscopic Probes for Structure and ReactivityBrandon Alexander
Transition metals can be used as spectroscopic probes to study the structure and reactivity of biologically important metal centers that are otherwise "spectroscopically silent". Common replacements include using cobalt for zinc, manganese for magnesium, and lanthanides for calcium. NMR techniques such as using shift reagents and relaxation reagents allow the study of metal binding sites and environments through analysis of signals from nearby nuclei that are perturbed by the paramagnetic metal ion substitute.
The document provides an exam review for the AP Chemistry exam, covering six big ideas: properties of matter, stoichiometry, thermochemistry, electronic structure, bonding, and reactions. It includes learning objectives, summaries of key concepts, example problems, and videos for each big idea to help students prepare for the exam. Project contributors include chemistry teachers, AP readers, and question writers who developed the review materials.
In previous published articles, formulae-based mnemonics by counting the total number of σ bonds with a lone pair of electrons (LP), a localized negative charge (LNC), or a localized lone pair of electrons (LLP) and subtracting one (01) from this total value (TSLP, TSLNC, or TSLLP) to predict the power of the hybridization state of simple molecules or ions and organic compounds, including heterocyclic compounds have been discussed. These are the innovative and time-efficient methods of enhancing student interest. Here, in this new article, the limitations of conventional formulae in comparison to the use of innovative formulae have been discussed along with the application of the hybridization state in different fields of chemical education. This article encourages students to solve multiple choice type questions (MCQs) at different competitive examinations in a time economic ground on the prediction of hybridization state of simple molecules or ions to know their normal and subnormal geometry and prediction of hybridization state of hetero atom in different heterocyclic compounds to know the planarity of the compounds, which is very essential factor for prediction of aromaticity of heterocyclic compounds. Educators can use this comparative study in their classroom lectures to make chemistry authentic and intriguing. Because the use of mnemonics in classroom lectures is an essential tool to become a distinguished educator.
General consideration (organic chemistry- heterocycles)Taj Khan
1. The document discusses whether lone pairs should be considered part of aromatic π systems. In pyridine the lone pair is not included, in pyrrole it is included, and in furan one lone pair is included but the other is not.
2. The hybridization of the atom with the lone pair must be considered. Only electrons that can shift via resonance and contribute p-orbitals to the π system are included.
3. In pyrrole, all six π electrons shift together via resonance, but in pyridine the lone pair does not shift with the double bonds. In furan, one lone pair shifts with the double bonds while the other does not.
The document discusses bio-inspired catalysts for hydrogen production. It begins by noting the importance of hydrogen as an energy carrier and limitations of existing platinum-based catalysts. It then discusses how hydrogenase enzymes provide an efficient model but have limitations as well. Recent research has focused on developing bio-inspired catalysts that incorporate features of the hydrogenase active site and outer coordination sphere to improve catalytic efficiency. Some promising systems discussed include macrocyclic cobalt complexes and nickel bis(diphosphine) complexes containing amino acid groups to mimic the outer coordination sphere, which have shown activity under broader conditions than hydrogenases. Evaluation of catalytic performance focuses on turnover frequency and overpotential.
This document describes Michael Ludden's synthesis and characterization of various molybdenum complexes. Three complexes were synthesized - [CpMo(CO)3Me], [CpMo(CO)3Et], and [CpMo(CO)2(COMe)(PPh3)]. They were characterized using NMR and IR spectroscopy. The results confirmed the structures of the complexes and showed how changing ligands affects properties. Kinetic measurements of migratory insertion reactions will be taken using these complexes to understand reaction rate dependence on factors like solvent, temperature and ligand type.
Photosynthesis is the process by which plants, algae and some bacteria use sunlight, water and carbon dioxide to produce oxygen and energy in the form of glucose. It occurs in two phases - the light-dependent reactions and the light-independent reactions. The light-dependent reactions use energy from sunlight to produce ATP and NADPH through the process of photophosphorylation. These products are then used in the light-independent reactions, also known as the Calvin cycle, to fix carbon from carbon dioxide into organic carbon compounds like glucose.
Bio-Molecular Engineering is the Future of Molecular BiologyBob Eisenberg
Bio-Molecular Engineering is the Future of Molecular Biology: Now that we have large numbers of excellent structures, we molecular biologists must turn to studying how they work. That is the task of BioMolecular Engineering that uses almost the same tools as classical membrane biophysics. Both treat systems as devices, with inputs, outputs and power supplies, that ONLY function with flow, away from equilibrium.
Radiopharmacy involves the compounding and dispensing of radioactive materials for use in nuclear medicine procedures. Radiopharmaceuticals are radioactive drugs used for diagnostic or therapeutic purposes. They consist of radioactive isotopes attached to other molecules to allow for localization within the body. Radiopharmaceuticals are prepared following stringent quality control procedures to ensure safety, purity and sterility prior to administration. Effective shielding is also required to protect personnel from radiation exposure during preparation and handling.
This review summarizes rare earth doped apatite nanomaterials and their potential for biological applications. Rare earth doped apatite nanoparticles (REAnps) have advantages over traditional fluorophores like long fluorescence lifetimes, sharp emission peaks, and resistance to photobleaching. REAnps can be synthesized through various methods and doped with lanthanide ions like Eu3+, Tb3+, and Er3+ to emit different colors. REAnps show potential for use as biological labels due to their photostability and low toxicity. The review discusses the characteristics, synthesis, and applications of REAnps as well as future studies needed for their effective use in biology.
This document summarizes research on engineering a subcomplex of the hydrogenase enzyme from Pyrococcus furiosus that is capable of producing hydrogen. Key points:
- Researchers successfully produced a heterodimeric form of the cytoplasmic hydrogenase I from P. furiosus (SHI) containing only two of the four subunits in the native enzyme.
- The engineered heterodimer is highly active in producing hydrogen using an artificial electron donor and is thermostable.
- Unlike the native enzyme, the heterodimer directly utilizes reducing power from pyruvate ferredoxin oxidoreductase without needing an intermediate electron carrier.
- This represents a two-enzyme system
1) Porphyrin-fullerene dyads were synthesized where the two chromophores are linked by a bicyclic bridge.
2) Time-resolved fluorescence measurements showed substantial quenching of the porphyrin singlet lifetime in both the zinc and free base dyads due to singlet-singlet energy transfer to the fullerene.
3) In toluene, a transient absorption was detected for the free base dyad with a lifetime of ~10 ps, assigned to the fullerene triplet state, while electron transfer was unfavorable. In the more polar benzonitrile, electron transfer from the porphyrin to the fullerene was observed.
a substance can absorb any visible light or external radiation and then again emit it. this called fluorescence and the process of reduction in fluorescence intensity is called quenching. this presentation is all about quenching of fluorescence.
The document discusses the use of radioactive isotopes in geology and forensics. It describes the components of atoms, including protons, neutrons, and electrons. Isotopes are variants of the same element that differ in their number of neutrons. Unstable isotopes decay over time, while stable isotopes can be used for radiometric dating. Examples are given of carbon-14 dating of artifacts like the Dead Sea Scrolls and Stonehenge. Forensic cases show how carbon-14 has been used to date things like the Shroud of Turin and nuclear test fallout in teeth.
This document provides an overview of metabolism and energy transformation in living cells. It discusses key topics including:
1) Metabolism transforms matter and energy through chemical reactions in metabolic pathways catalyzed by enzymes. Catabolic pathways release energy by breaking down molecules, while anabolic pathways use energy to build complex molecules.
2) The first law of thermodynamics states that energy cannot be created or destroyed, only transferred or transformed. The second law states that every transformation increases entropy and some energy is lost as heat.
3) ATP powers cellular work by coupling exergonic reactions, which release free energy, to endergonic reactions like biosynthesis, transport, and mechanical work that require energy. Most energy coupling
This document summarizes an investigation into the low-temperature oxidation reactions of 2-phenylethanol using photoionization mass spectrometry. The reaction was initiated using 248 nm photolysis of chlorine at 298 K and 550 K, with and without oxygen present. A variety of reaction products were identified using mass spectrometry coupled to synchrotron radiation. Key findings include that the aromatic ring remains intact, all chemistry occurs on the side chain, and decomposition explains products with lower mass-to-charge ratios. More products need to be identified to determine branching fractions.
The document summarizes the development and validation of a photocalorimetry technique. It outlines the design of the photocalorimeter instrument and describes validation methods using chemical actinometers like 2-nitrobenzaldehyde and ferrioxalate in solution. Nifedipine degradation experiments were used to validate the technique for solids. Results showed 2-NB provided more stable calibration than ferrioxalate. Future work will apply the technique to study effects of wavelength, moisture and temperature on solid-state reactions.
Computational chemistry methods can be used to predict the photophysical properties of BODIPY dyes. The author performed preliminary work validating their computational approach by comparing excited state calculations on 26 BODIPY dyes to experimental data. Molecular dynamics simulations were carried out to sample potential energy surfaces and check for non-parallelity between time-dependent density functional theory and restricted open-shell Kohn-Sham methods. Interactions between BODIPY dyes and oxygen were modeled to study singlet oxygen generation pathways.
This document describes the synthesis and characterization of a ruthenium polypyridyl complex. Key steps include:
1) Synthesizing a bipyridine ligand functionalized with a bromomethyl group and methyl substituent.
2) Attaching this ligand to diethyl malonate using a Mitsunobu reaction to form a chelating ligand.
3) Reacting this ligand with cis-bis(bipyridine)dichlororuthenium(II) dihydrate to form the target ruthenium complex.
4) Purifying and characterizing the complex using NMR spectroscopy and mass spectrometry. The complex exhibits photophysical properties suitable for applications
Literature Seminar on Expansion of Pd chains through Beta-Carotene & Tetrapho...Nina Saraei
The document summarizes two papers on the expansion of palladium chains using β-carotene and tetraphosphine ligands. The first paper discusses the stepwise expansion of homonuclear and heteronuclear palladium chains from binuclear Pd(I) complexes supported by tetraphosphine ligands. Characterization data showed the complexes adopt linear structures with reversible metalation/demetalation. The second paper examines a bis-β-carotene ligand's ability to bind decanuclear palladium and palladium-platinum complexes into infinite π-stacked columns. Both papers demonstrate the use of multidentate ligands to control the assembly of extended metal atom chains.
Transition Metals As Spectroscopic Probes for Structure and ReactivityBrandon Alexander
Transition metals can be used as spectroscopic probes to study the structure and reactivity of biologically important metal centers that are otherwise "spectroscopically silent". Common replacements include using cobalt for zinc, manganese for magnesium, and lanthanides for calcium. NMR techniques such as using shift reagents and relaxation reagents allow the study of metal binding sites and environments through analysis of signals from nearby nuclei that are perturbed by the paramagnetic metal ion substitute.
The document provides an exam review for the AP Chemistry exam, covering six big ideas: properties of matter, stoichiometry, thermochemistry, electronic structure, bonding, and reactions. It includes learning objectives, summaries of key concepts, example problems, and videos for each big idea to help students prepare for the exam. Project contributors include chemistry teachers, AP readers, and question writers who developed the review materials.
In previous published articles, formulae-based mnemonics by counting the total number of σ bonds with a lone pair of electrons (LP), a localized negative charge (LNC), or a localized lone pair of electrons (LLP) and subtracting one (01) from this total value (TSLP, TSLNC, or TSLLP) to predict the power of the hybridization state of simple molecules or ions and organic compounds, including heterocyclic compounds have been discussed. These are the innovative and time-efficient methods of enhancing student interest. Here, in this new article, the limitations of conventional formulae in comparison to the use of innovative formulae have been discussed along with the application of the hybridization state in different fields of chemical education. This article encourages students to solve multiple choice type questions (MCQs) at different competitive examinations in a time economic ground on the prediction of hybridization state of simple molecules or ions to know their normal and subnormal geometry and prediction of hybridization state of hetero atom in different heterocyclic compounds to know the planarity of the compounds, which is very essential factor for prediction of aromaticity of heterocyclic compounds. Educators can use this comparative study in their classroom lectures to make chemistry authentic and intriguing. Because the use of mnemonics in classroom lectures is an essential tool to become a distinguished educator.
General consideration (organic chemistry- heterocycles)Taj Khan
1. The document discusses whether lone pairs should be considered part of aromatic π systems. In pyridine the lone pair is not included, in pyrrole it is included, and in furan one lone pair is included but the other is not.
2. The hybridization of the atom with the lone pair must be considered. Only electrons that can shift via resonance and contribute p-orbitals to the π system are included.
3. In pyrrole, all six π electrons shift together via resonance, but in pyridine the lone pair does not shift with the double bonds. In furan, one lone pair shifts with the double bonds while the other does not.
The document discusses bio-inspired catalysts for hydrogen production. It begins by noting the importance of hydrogen as an energy carrier and limitations of existing platinum-based catalysts. It then discusses how hydrogenase enzymes provide an efficient model but have limitations as well. Recent research has focused on developing bio-inspired catalysts that incorporate features of the hydrogenase active site and outer coordination sphere to improve catalytic efficiency. Some promising systems discussed include macrocyclic cobalt complexes and nickel bis(diphosphine) complexes containing amino acid groups to mimic the outer coordination sphere, which have shown activity under broader conditions than hydrogenases. Evaluation of catalytic performance focuses on turnover frequency and overpotential.
This document describes Michael Ludden's synthesis and characterization of various molybdenum complexes. Three complexes were synthesized - [CpMo(CO)3Me], [CpMo(CO)3Et], and [CpMo(CO)2(COMe)(PPh3)]. They were characterized using NMR and IR spectroscopy. The results confirmed the structures of the complexes and showed how changing ligands affects properties. Kinetic measurements of migratory insertion reactions will be taken using these complexes to understand reaction rate dependence on factors like solvent, temperature and ligand type.
Photosynthesis is the process by which plants, algae and some bacteria use sunlight, water and carbon dioxide to produce oxygen and energy in the form of glucose. It occurs in two phases - the light-dependent reactions and the light-independent reactions. The light-dependent reactions use energy from sunlight to produce ATP and NADPH through the process of photophosphorylation. These products are then used in the light-independent reactions, also known as the Calvin cycle, to fix carbon from carbon dioxide into organic carbon compounds like glucose.
Bio-Molecular Engineering is the Future of Molecular BiologyBob Eisenberg
Bio-Molecular Engineering is the Future of Molecular Biology: Now that we have large numbers of excellent structures, we molecular biologists must turn to studying how they work. That is the task of BioMolecular Engineering that uses almost the same tools as classical membrane biophysics. Both treat systems as devices, with inputs, outputs and power supplies, that ONLY function with flow, away from equilibrium.
Radiopharmacy involves the compounding and dispensing of radioactive materials for use in nuclear medicine procedures. Radiopharmaceuticals are radioactive drugs used for diagnostic or therapeutic purposes. They consist of radioactive isotopes attached to other molecules to allow for localization within the body. Radiopharmaceuticals are prepared following stringent quality control procedures to ensure safety, purity and sterility prior to administration. Effective shielding is also required to protect personnel from radiation exposure during preparation and handling.
This review summarizes rare earth doped apatite nanomaterials and their potential for biological applications. Rare earth doped apatite nanoparticles (REAnps) have advantages over traditional fluorophores like long fluorescence lifetimes, sharp emission peaks, and resistance to photobleaching. REAnps can be synthesized through various methods and doped with lanthanide ions like Eu3+, Tb3+, and Er3+ to emit different colors. REAnps show potential for use as biological labels due to their photostability and low toxicity. The review discusses the characteristics, synthesis, and applications of REAnps as well as future studies needed for their effective use in biology.
This document summarizes research on engineering a subcomplex of the hydrogenase enzyme from Pyrococcus furiosus that is capable of producing hydrogen. Key points:
- Researchers successfully produced a heterodimeric form of the cytoplasmic hydrogenase I from P. furiosus (SHI) containing only two of the four subunits in the native enzyme.
- The engineered heterodimer is highly active in producing hydrogen using an artificial electron donor and is thermostable.
- Unlike the native enzyme, the heterodimer directly utilizes reducing power from pyruvate ferredoxin oxidoreductase without needing an intermediate electron carrier.
- This represents a two-enzyme system
This document summarizes the rational design and generation of a catalytic antibody that selectively hydrolyzes a specific substrate. Researchers designed an antibody to bind a transition state analogue for the hydrolysis of a carbonate substrate. They generated monoclonal antibodies against a nitrophenyl phosphonate transition state analogue. One antibody was found to catalyze the hydrolysis of the carbonate substrate, displaying Michaelis-Menten kinetics. The antibody-catalyzed reaction had substrate specificity and was competitively inhibited by the corresponding phosphate transition state analogue, demonstrating the ability to rationally design catalytic antibodies.
The document is Ian Blake Cooper's PhD dissertation from the Georgia Institute of Technology. It investigates the mechanism of photosynthetic water oxidation in photosystem II (PSII) using vibrational spectroscopy techniques. PSII is the membrane protein complex that uses light energy to oxidize water and produce molecular oxygen. Key findings of the dissertation include using time-resolved infrared spectroscopy to detect protein-based intermediates involved in the oxygen-evolving cycle, investigating proton-coupled electron transfer reactions associated with a redox-active tyrosine residue, examining the identity of the chloride binding site using bromide exchange, and probing proton transfer reactions at the oxygen-evolving complex using azide.
This document summarizes the synthesis and characterization of two single-strapped 21-thia-tetraphenylporphyrins. The two adjacent phenyl groups at the meso position of 21-thia-tetraphenylporphyrin were linked by either a rigid aromatic group or a flexible alkyl chain. NMR, absorption, and fluorescence studies indicated that the rigid aromatic group induced more nonplanarity in the porphyrin ring compared to the flexible alkyl chain. The synthesis involved condensing thiophene diol, dialdehyde, and pyrrole to form a mixture of porphyrins, which were then separated via chromatography. Characterization confirmed the structures and indicated the rigid strap caused more distortion of the porph
We here introduced and elucidated the mechanism of hydrolysis reaction of Adenosine Triphosphate (ATP) molecules for generation of bio-energy in the living Systems, in which the detained reaction processes of hydrolysis of ATP molecules and its properties, The center effects and functions of ATP molecules in the life activity, AIP enzyme and production of bio-energy in the hydrolysis of ATP molecules and The formation of ATP molecules and its relation with Δ-μH+ were described and explained. From these introductions and results we understand and knew that this mechanism of generation of bio-energy is its an important form, which exists widely in the life bodies of generation of bio-energy. Therefore, to elucidate and research this mechanism and its properties have quite important meanings in biology, biochemistry and biophysics.
This document presents a theoretical study examining the effects of central metal ions (Cd2+, Hg2+, Pt2+) and substituent groups (F, I, NO2, NH2, CH3, H) on the properties of metalloporphyrin complexes for use as semiconductor materials. Density functional theory calculations were used to analyze the electronic structure, density of states, and UV-Vis absorption spectra of the complexes. The results showed that electron-donating substituents and central ions from Hg to Cd to Pt decreased the bandgap and shifted absorption peaks to longer wavelengths, indicating better semiconductor performance for light absorption. NH2 substituents gave the best results with the smallest bandgap and longest absorption peak.
This document summarizes the synthesis and characterization of a new potassium complex of phthiocol, a vitamin K3 analog. Key findings include:
1) Phthiocol binds to two potassium ions through its oxygen atoms, forming a polymeric chain structure.
2) Single crystal X-ray diffraction reveals hydrogen bonding interactions between coordinated water molecules, forming water channels along the crystal structure.
3) NMR and electrochemical studies provide evidence that the complex exists as a naphthosemiquinone, with the potential for a one-electron reduction to the catechol form.
The document summarizes a student research project investigating the design of short peptide amphiphiles that can bind transition metal ions. The student synthesized a peptide called C16-AHLHL3K3 and used various characterization techniques. Results showed the peptide formed beta-pleated sheet fibers under certain conditions and was able to bind transition metals like cobalt. This demonstrates the potential for short peptides to have transition metal binding sites and possibly enzymatic capabilities.
This document describes the synthesis and characterization of a calcium phosphonate framework material (Ca-PiPhtA) and its derivatives for proton conductivity applications. The parent framework Ca-PiPhtA-I was synthesized from calcium chloride and the ligand 5-(dihydroxyphosphoryl)isophthalic acid under acidic aqueous conditions, producing a structure with 1D channels and high water content. Upon heating or exposure to ammonia vapors, it undergoes partial dehydration or structural transformations to form new derivatives Ca-PiPhtA-II and Ca-PiPhtA-NH3 respectively, as characterized through methods such as X-ray diffraction and thermal analysis. Proton conductivity measurements found the materials conduct
This document summarizes high-resolution crystal structures of native cytochrome c peroxidase (CCP) and its oxidized reaction intermediate known as Compound I. Key findings include:
1) The 1.2 Å structure of native CCP and 1.3 Å structure of Compound I reveal subtle but important conformational changes that help stabilize the tryptophan 191 cation radical in Compound I.
2) In Compound I, the histidine-iron bond distance increases, iron moves into the porphyrin plane with shorter pyrrole-iron bonds, and the iron-oxygen bond distance is 1.87 Å, suggesting a single iron-oxygen bond.
3
Calvin's experiment used radioactive carbon-14 to track the pathway of carbon fixation in photosynthesis. Samples of algae exposed to carbon-14 were taken at intervals and the radioactive compounds identified. Glycerate-3-phosphate was found to be the first labeled compound, indicating it is the initial product of carbon fixation. Analysis of later samples revealed a range of labeled intermediate and final products, elucidating the steps of the Calvin cycle. Calvin's discoveries depended on advances in technology like the discovery of carbon-14 and the development of autoradiography.
Fluoride Recognition of Amide- and Pyrrole-Based Receptors: A Theoretical Study drboon
The novel amide-based receptors, N-(anthracen-1-yl)-1H-pyrrole-2-carboxamide (1) and N-(8-(1H-pyrrole-2-carboxamido) anthracen-1-yl)-1H-pyrrole-2-carboxamide (2) have been designed and investigated for their halide ion recognition using the density functional theory calculations in gas and solvent phases. Electronic and thermodynamic properties of halide ion binding complexes of receptors were investigated. Intermolecular interactions in all the studied complexes occurring via hydrogen bonding are found. The designed receptors 1 and 2 are found to be excellent selectivity for fluoride ion in both gas and solvent phases.
Photosynthesis is a complex, multistep process that was largely elucidated by the mid-20th century through experiments measuring photosynthetic efficiency, identifying reaction center pigments, proposing the Z-scheme of electron transport, discovering the Calvin cycle, and identifying Rubisco as the key enzyme. While historically photosynthesis research was isolated from other fields, it is now recognized that photosynthesis is closely related to other cellular processes through reactive oxygen species, redox regulation, and chloroplast signals, and plays an important role in plant stress responses, productivity, and global climate modeling. This special issue explores new concepts and unanswered questions in photosynthesis research using modern techniques.
Oxidative phosphorylation and photophosphorylation are two pathways that generate ATP through electron transport chains located in mitochondria and chloroplasts respectively. Both pathways use proton gradients generated by electron transport to power ATP synthase and produce ATP. In mitochondria, electrons from NADH and FADH2 enter the electron transport chain at Complex I and II and are passed through a series of carriers including ubiquinone, cytochromes, and Complexes III and IV until they reduce oxygen to water. This electron flow is coupled to the pumping of protons out of the mitochondrial matrix, generating a proton gradient used by ATP synthase to produce ATP.
(1) Chloroplasts contain the light-dependent reactions of photosynthesis, which capture energy from sunlight and use it to produce ATP and NADPH. (2) These reactions occur in the thylakoid membranes through two photosystems that absorb light and transfer electrons. This powers an electron transport chain that pumps protons across the membrane. (3) The resulting proton gradient drives ATP synthesis when protons diffuse back through ATP synthase. Oxygen is also released as a byproduct of splitting water.
light reaction of photosynthesis (botany)PriyanshiRaj9
(1) Chloroplasts contain the light-dependent reactions of photosynthesis, which capture energy from sunlight and use it to produce ATP and NADPH. (2) These reactions occur in the thylakoid membranes through two photosystems that absorb light and transfer electrons. This powers an electron transport chain that pumps protons across the membrane. (3) The resulting proton gradient drives ATP synthesis when protons diffuse back through ATP synthase. Oxygen is also released as a byproduct of splitting water.
A Remarkable Conflict Between Biochemical Dogma And Radical Concept :
Traditional Concept :
By the 1950s it had been clearly established that oxidative phosphorylation involved the stepwise transfer of electrons through a series of carriers to molecular oxygen. But how the energy derived from these electron transfer reactions was converted to ATP remained a mystery. The general assumption was that ADP was converted to ATP by direct transfer of high-energy phosphate groups from some other intermediate. Thus it was postulated that high-energy intermediates were produced as a result of electron transfer reactions and that these intermediates drove ATP synthesis by phosphate group transfer.
Concept Proposed By Peter Mitchell :
The fundamental proposal of the chemiosmotic hypothesis was that the “intermediate” that coupled electron transport to ATP synthesis was a proton electrochemical gradient across the membrane. Mitchell postulated that such a gradient was produced by electron transport and that the flow of protons back across the membrane in the energetically favorable direction was then coupled to ATP synthesis
This document describes the synthesis and characterization of a novel redox-based chiroptically switching polymer. The polymer was prepared by grafting electrochromic viologen groups onto the side chains of an optically active conjugated polymer backbone containing 1,1'-binaphthyl units. The resulting polymer exhibited a much larger optical rotation and intense circular dichroism signal compared to a small molecule model compound, indicating secondary chirality in the main polymer chain. The polymer undergoes distinctive and reversible color changes from light yellow to dark blue upon electrochemical or chemical reduction/oxidation of the viologen units, accompanied by changes in its circular dichroism spectrum. This allows for redox-driven chiroptical switching behavior
Similar to A Suspected Derivative Morphology for pheophytin (脫鎂葉綠素) and the Enhanced Hydrogen Decomposition It Caused (20)
Northern Engraving | Modern Metal Trim, Nameplates and Appliance PanelsNorthern Engraving
What began over 115 years ago as a supplier of precision gauges to the automotive industry has evolved into being an industry leader in the manufacture of product branding, automotive cockpit trim and decorative appliance trim. Value-added services include in-house Design, Engineering, Program Management, Test Lab and Tool Shops.
Main news related to the CCS TSI 2023 (2023/1695)Jakub Marek
An English 🇬🇧 translation of a presentation to the speech I gave about the main changes brought by CCS TSI 2023 at the biggest Czech conference on Communications and signalling systems on Railways, which was held in Clarion Hotel Olomouc from 7th to 9th November 2023 (konferenceszt.cz). Attended by around 500 participants and 200 on-line followers.
The original Czech 🇨🇿 version of the presentation can be found here: https://www.slideshare.net/slideshow/hlavni-novinky-souvisejici-s-ccs-tsi-2023-2023-1695/269688092 .
The videorecording (in Czech) from the presentation is available here: https://youtu.be/WzjJWm4IyPk?si=SImb06tuXGb30BEH .
"Scaling RAG Applications to serve millions of users", Kevin GoedeckeFwdays
How we managed to grow and scale a RAG application from zero to thousands of users in 7 months. Lessons from technical challenges around managing high load for LLMs, RAGs and Vector databases.
From Natural Language to Structured Solr Queries using LLMsSease
This talk draws on experimentation to enable AI applications with Solr. One important use case is to use AI for better accessibility and discoverability of the data: while User eXperience techniques, lexical search improvements, and data harmonization can take organizations to a good level of accessibility, a structural (or “cognitive” gap) remains between the data user needs and the data producer constraints.
That is where AI – and most importantly, Natural Language Processing and Large Language Model techniques – could make a difference. This natural language, conversational engine could facilitate access and usage of the data leveraging the semantics of any data source.
The objective of the presentation is to propose a technical approach and a way forward to achieve this goal.
The key concept is to enable users to express their search queries in natural language, which the LLM then enriches, interprets, and translates into structured queries based on the Solr index’s metadata.
This approach leverages the LLM’s ability to understand the nuances of natural language and the structure of documents within Apache Solr.
The LLM acts as an intermediary agent, offering a transparent experience to users automatically and potentially uncovering relevant documents that conventional search methods might overlook. The presentation will include the results of this experimental work, lessons learned, best practices, and the scope of future work that should improve the approach and make it production-ready.
"$10 thousand per minute of downtime: architecture, queues, streaming and fin...Fwdays
Direct losses from downtime in 1 minute = $5-$10 thousand dollars. Reputation is priceless.
As part of the talk, we will consider the architectural strategies necessary for the development of highly loaded fintech solutions. We will focus on using queues and streaming to efficiently work and manage large amounts of data in real-time and to minimize latency.
We will focus special attention on the architectural patterns used in the design of the fintech system, microservices and event-driven architecture, which ensure scalability, fault tolerance, and consistency of the entire system.
The Department of Veteran Affairs (VA) invited Taylor Paschal, Knowledge & Information Management Consultant at Enterprise Knowledge, to speak at a Knowledge Management Lunch and Learn hosted on June 12, 2024. All Office of Administration staff were invited to attend and received professional development credit for participating in the voluntary event.
The objectives of the Lunch and Learn presentation were to:
- Review what KM ‘is’ and ‘isn’t’
- Understand the value of KM and the benefits of engaging
- Define and reflect on your “what’s in it for me?”
- Share actionable ways you can participate in Knowledge - - Capture & Transfer
Discover top-tier mobile app development services, offering innovative solutions for iOS and Android. Enhance your business with custom, user-friendly mobile applications.
Connector Corner: Seamlessly power UiPath Apps, GenAI with prebuilt connectorsDianaGray10
Join us to learn how UiPath Apps can directly and easily interact with prebuilt connectors via Integration Service--including Salesforce, ServiceNow, Open GenAI, and more.
The best part is you can achieve this without building a custom workflow! Say goodbye to the hassle of using separate automations to call APIs. By seamlessly integrating within App Studio, you can now easily streamline your workflow, while gaining direct access to our Connector Catalog of popular applications.
We’ll discuss and demo the benefits of UiPath Apps and connectors including:
Creating a compelling user experience for any software, without the limitations of APIs.
Accelerating the app creation process, saving time and effort
Enjoying high-performance CRUD (create, read, update, delete) operations, for
seamless data management.
Speakers:
Russell Alfeche, Technology Leader, RPA at qBotic and UiPath MVP
Charlie Greenberg, host
Freshworks Rethinks NoSQL for Rapid Scaling & Cost-EfficiencyScyllaDB
Freshworks creates AI-boosted business software that helps employees work more efficiently and effectively. Managing data across multiple RDBMS and NoSQL databases was already a challenge at their current scale. To prepare for 10X growth, they knew it was time to rethink their database strategy. Learn how they architected a solution that would simplify scaling while keeping costs under control.
"NATO Hackathon Winner: AI-Powered Drug Search", Taras KlobaFwdays
This is a session that details how PostgreSQL's features and Azure AI Services can be effectively used to significantly enhance the search functionality in any application.
In this session, we'll share insights on how we used PostgreSQL to facilitate precise searches across multiple fields in our mobile application. The techniques include using LIKE and ILIKE operators and integrating a trigram-based search to handle potential misspellings, thereby increasing the search accuracy.
We'll also discuss how the azure_ai extension on PostgreSQL databases in Azure and Azure AI Services were utilized to create vectors from user input, a feature beneficial when users wish to find specific items based on text prompts. While our application's case study involves a drug search, the techniques and principles shared in this session can be adapted to improve search functionality in a wide range of applications. Join us to learn how PostgreSQL and Azure AI can be harnessed to enhance your application's search capability.
inQuba Webinar Mastering Customer Journey Management with Dr Graham HillLizaNolte
HERE IS YOUR WEBINAR CONTENT! 'Mastering Customer Journey Management with Dr. Graham Hill'. We hope you find the webinar recording both insightful and enjoyable.
In this webinar, we explored essential aspects of Customer Journey Management and personalization. Here’s a summary of the key insights and topics discussed:
Key Takeaways:
Understanding the Customer Journey: Dr. Hill emphasized the importance of mapping and understanding the complete customer journey to identify touchpoints and opportunities for improvement.
Personalization Strategies: We discussed how to leverage data and insights to create personalized experiences that resonate with customers.
Technology Integration: Insights were shared on how inQuba’s advanced technology can streamline customer interactions and drive operational efficiency.
Dandelion Hashtable: beyond billion requests per second on a commodity serverAntonios Katsarakis
This slide deck presents DLHT, a concurrent in-memory hashtable. Despite efforts to optimize hashtables, that go as far as sacrificing core functionality, state-of-the-art designs still incur multiple memory accesses per request and block request processing in three cases. First, most hashtables block while waiting for data to be retrieved from memory. Second, open-addressing designs, which represent the current state-of-the-art, either cannot free index slots on deletes or must block all requests to do so. Third, index resizes block every request until all objects are copied to the new index. Defying folklore wisdom, DLHT forgoes open-addressing and adopts a fully-featured and memory-aware closed-addressing design based on bounded cache-line-chaining. This design offers lock-free index operations and deletes that free slots instantly, (2) completes most requests with a single memory access, (3) utilizes software prefetching to hide memory latencies, and (4) employs a novel non-blocking and parallel resizing. In a commodity server and a memory-resident workload, DLHT surpasses 1.6B requests per second and provides 3.5x (12x) the throughput of the state-of-the-art closed-addressing (open-addressing) resizable hashtable on Gets (Deletes).
"What does it really mean for your system to be available, or how to define w...Fwdays
We will talk about system monitoring from a few different angles. We will start by covering the basics, then discuss SLOs, how to define them, and why understanding the business well is crucial for success in this exercise.
QA or the Highway - Component Testing: Bridging the gap between frontend appl...zjhamm304
These are the slides for the presentation, "Component Testing: Bridging the gap between frontend applications" that was presented at QA or the Highway 2024 in Columbus, OH by Zachary Hamm.
"Frontline Battles with DDoS: Best practices and Lessons Learned", Igor IvaniukFwdays
At this talk we will discuss DDoS protection tools and best practices, discuss network architectures and what AWS has to offer. Also, we will look into one of the largest DDoS attacks on Ukrainian infrastructure that happened in February 2022. We'll see, what techniques helped to keep the web resources available for Ukrainians and how AWS improved DDoS protection for all customers based on Ukraine experience
This talk will cover ScyllaDB Architecture from the cluster-level view and zoom in on data distribution and internal node architecture. In the process, we will learn the secret sauce used to get ScyllaDB's high availability and superior performance. We will also touch on the upcoming changes to ScyllaDB architecture, moving to strongly consistent metadata and tablets.
Introduction of Cybersecurity with OSS at Code Europe 2024Hiroshi SHIBATA
I develop the Ruby programming language, RubyGems, and Bundler, which are package managers for Ruby. Today, I will introduce how to enhance the security of your application using open-source software (OSS) examples from Ruby and RubyGems.
The first topic is CVE (Common Vulnerabilities and Exposures). I have published CVEs many times. But what exactly is a CVE? I'll provide a basic understanding of CVEs and explain how to detect and handle vulnerabilities in OSS.
Next, let's discuss package managers. Package managers play a critical role in the OSS ecosystem. I'll explain how to manage library dependencies in your application.
I'll share insights into how the Ruby and RubyGems core team works to keep our ecosystem safe. By the end of this talk, you'll have a better understanding of how to safeguard your code.
Introduction of Cybersecurity with OSS at Code Europe 2024
A Suspected Derivative Morphology for pheophytin (脫鎂葉綠素) and the Enhanced Hydrogen Decomposition It Caused
1. A Suspected Derivative Morphology for
pheophytin (脫鎂葉綠素) and
the Enhanced Hydrogen Decomposition It Caused
Jyun-Lin Huang,2 Wen-Bing Lai,2 Chungpin Liao,1,2,* Li-Shen Yeh2
(黃均霖) (賴玟柄) (廖重賓) (葉立紳)
1Graduate School of Electro-Optic and Materials Science,
National Formosa University (NFU), Huwei, Taiwan 632, ROC.
2Advanced Research & Business Laboratory (ARBL),
Taichung, Taiwan 407, ROC.
*Corresponding Author: cpliao@alum.mit.edu and Speaker
2016/8/16 1CCL Group
2. 2016/8/16 2CCL Group
Outline
• What’s the role of pheophytin (pheo) in photosynthesis?
• What might be pheo’s other structure-related roles? things we
bumped into in the original low-power chlorophyll battery
• A conjectured derivative morphology and associated
proton conduction path within pheophytins (pheo’s)
• Experimental evidence in pheo-catalyzed decomposition of
hydrogen gas
• Summary and conclusions
• Porphyrin-ring family and their uses
• Spectral comparison among: 1st-principle quantum simulation,
measurement on ethanol-extracted pheo, and existing literature
3. 2016/8/16 CCL Group 3
• What’s the role of pheophytin (pheo) in photosynthesis?
Pheo as:
-1st acceptor of light-
excited electrons
-Accelerator of such
electrons (~1.14 eV)
4. 2016/8/16 CCL Group 4
• Background and motivation
– the success of pheophytin (pheo, 脫鎂葉綠素) catalyst
Pheophytin a
(textbook)
textbook
Porphyrin ring
E ~ 1.14 eV was used in our metal-air chemical batteries, but the number wasn’t right.
?
?
6. However, the oxygen evolving complex (OEC) is far from clear morphologically and
functionally.
To get back electrons for those ionized chlorophyll antennas, OEC’s have to oxidize
water under the room temperature, i.e., H2O 2H+ + ½ O2 + 2e-
2016/8/16 6CCL Group
7. OEC morphology and function
OEC itself is already a battery….
2016/8/16 7CCL Group
8. 2016/8/16 CCL Group 8
• What might be pheo’s other structure-related roles? things we
bumped into in the original low-power chlorophyll battery
The original low-power chlorophyll (葉綠素) battery demonstrated that electricity can be
extracted from wetted chlorophyll powder which apparently had pre-stored the optical
energy from sun.
Primitive chl battery structure:
(-) Al foil | MgO powder | fiber paper | chl powder |
active carbon powder | (+) graphite paper
After the burn-out of battery, all chlorophyll became yellow brown in color, signifying
the conversion of all chlorophyll (chl) into pheophytin (pheo).
Namely, the chl-pheo chains within the wetted chlorophyll powder (i.e., electrolyte)
should have fulfilled their mission in accelerating returning electrons near the positive
electrode.
However, this scenario alone fell short of explaining the significantly more electricity
generated, as observed.
Pheo’s appeared to have shown their catalyzing capability too. See below.
9. 2016/8/16 9CCL Group
MgO + H2O Mg(OH)2
(slightly soluble
in water)
Mg2+ + 2OH-
MgO + 2OH- Mg(OH)2 + 2e-
½ O2 + 2H+ + 2e- H2O (acidic)
½ O2 + H2O + 2e- 2OH- (basic)
Catalysis by pheo?
If so, how?
10. 2016/8/16 CCL Group 10
• Porphyrin-ring family and their uses
Porphyrins are compounds composed of four modified pyrrole subunits
interconnected at their α carbon atoms via methine bridges (=CH−).
The parent porphyrin is porphin, and substituted porphines are called porphyrins.
The porphyrin ring structure is aromatic (芳香族的), with a total of 26 electrons in
the conjugated system.
Porphyrin molecules typically have very intense absorption bands in the visible
region and hence may be deeply colored.
Porphyrins have been evaluated in the context of photodynamic therapy since they
strongly absorb light, which is then converted to energy and heat in the illuminated
areas.
For example, a structurally-modified porphyrin: verteporfin
porphin
11. 2016/8/16 CCL Group 11
Verteporfin (trade name Visudyne) is a medication used as
a photosensitizer for photodynamic therapy to eliminate the
abnormal blood vessels in the eye associated with conditions
such as the wet form of macular degeneration (黃斑性病變).
* Scott, L. J.; Goa, K. L. (2000). "Verteporfin". Drugs & aging 16 (2): 139–146; discussion 146–8. and,
Adelman, R.; Adelman, R. A. (2013). "Profile of verteporfin and its potential for the treatment of central serous chorioretinopathy". Clinical
Ophthalmology 7: 1867–1875.
Verteporfin accumulates in these abnormal
blood vessels and, when stimulated by
nonthermal red light with a wavelength
of 689 nm in the presence of oxygen,
produces highly reactive
short-lived singlet oxygen and other
reactive oxygen radicals,
resulting in local damage to
the endothelium (內皮) and blockage of the
vessels.*
verteporfin
12. 2016/8/16 CCL Group 12
Also, porphyrin-based compounds are of interest in molecular electronics and
supramolecular building blocks.
Synthetic porphyrin dyes that are incorporated in prototype dye-sensitized
solar cells (DSSCs)+.
As a porphyrin derivative, phthalocyanines (酞菁)
form coordination complexes with most elements
of the periodic table. These complexes are also
intensely colored and also are used as dyes or pigments.
phthalocyanine
+ Michael G. Walter; Alexander B. Rudine; Carl C. Wamser (2010). "Porphyrins and phthalocyanines in solar photovoltaic cells". Journal of Porphyrins
and Phthalocyanines 14 (9): 759–792.
Aswani Yella; Hsuan-Wei Lee; Hoi Nok Tsao; Chenyi Yi; Aravind Kumar Chandiran; Md.Khaja Nazeeruddin; Eric Wei-Guang Diau; Chen-Yu Yeh; Shaik M
Zakeeruddin; Michael Grätzel (2011). "Porphyrin-Sensitized Solar Cells with Cobalt (II/III)–Based Redox Electrolyte Exceed 12 Percent
Efficiency". Science 334 (6056): 629–634.
13. 2016/8/16 CCL Group 13
Although never commercialized, metalloporphyrin complexes are widely
studied as catalysts for the oxidation of organic compounds.
Particularly popular for such laboratory research are complexes of meso-
tetraphenylporphyrin (H2TPP), e.g., the iron(III) chloride complex (TPPFeCl),
catalyze a variety of reactions of potential interest in organic synthesis.
H2TPP
TPPFeCl
Some other complexes emulate the action of various heme enzymes such
as cytochrome (細胞色素) P450, lignin peroxidase.#
# Zucca, Paolo; Rescigno, Antonio; Rinaldi, Andrea C.; Sanjust, Enrico (July 2014). "Biomimetic metalloporphines and metalloporphyrins as potential
tools for delignification: Molecular mechanisms and application perspectives". Journal of Molecular Catalysis A: Chemical. 388–389: 2–34.
Guilard, edited by Karl M. Kadish, Kevin M. Smith & Roger (2012). Handbook of porphyrin science. with applications to chemistry, physics, materials
science, engineering, biology and medicine. Singapore: World Scientific. ISBN 9789814335492.
14. 2016/8/16 CCL Group 14
Figure 1. N-H tautomeric equilibria in porphyrins. Nonconcerted mechanism
(ab, bc) with both N-H protons exchanging independently, and concerted
mechanism with N—H exchanging simultaneously between neighboring
(de, df), or, opposite nitrogen atoms (ef).
• A conjectured derivative morphology and associated
proton conduction path within pheophytins (pheo’s)
First of all, tautomeric (互變異構的) dynamics is believed to be constantly going on
within the porphyrin ring.
Usually, you see
only one of them
in the textbooks.
15. 2016/8/16 CCL Group 15
Figure 2. Seemingly stationery orthodox morphology of pheophytin-a (pheo-a)
It was pointed out that in order for the 1st-principle simulated chemical shift
spectra of a porphyrin-based molecule to match those of NMR (nuclear magnetic
resonance) measurements, such proton-movement-caused ring current was
necessary.&
Therefore, there is likely tautomeric dynamics taking place actively within the
porphyrin ring of pheo-a, in some way.
& Iwamoto, H.; Hori, K.; Fukazawa, Y. A model of porphyrin ring current effect. Tetrahedron Letters 2005, Vol. 46, 731–734.
16. 2016/8/16 CCL Group 16
However, a single pheo molecule in its orthodox morphology (Figure 2, below)
does NOT seem to possess any capability in transporting protons across or
around within the porphyrin ring.
Namely, how can the seemingly needed tautomeric dynamic ring current owing
to the proton movement be initiated at all?
These double
bonds make the
proton movement
very hard.
17. 2016/8/16 CCL Group 17
Figure 3. Suspected derivative morphology of pheophytin
(pheo), without showing its tail
It is suspected, therefore, that if proper electron movements can be arranged
such that all double bonds attaching to nitrogen (N) atoms become single ones
(with each associated carbon atom now carrying one positive formal charge),
and all 4 N atoms are saturated with hydrogen atoms, the situation will be
utterly different.
18. 2016/8/16 CCL Group 18
Figure 4. Proposed proton (H+) transport scenario
across, or around within, a derivative pheophytin
molecule (tail not shown)
The suspected mechanism for proton internal transport within a derivative pheo,
which leads to the tautomeric ring current:
H+
H+
H+
19. 2016/8/16 CCL Group 19
Q: Can most existing spectra for standard (orthodox)
pheo be actually those of “derivative” pheo instead?
20. 2016/8/16 CCL Group 20
Figure 5. Spectral comparison among (a) standard morphology plus 2 free protons
simulation, (b) derivative morphology with 4 N-H bonds in porphyrin ring simulation,
(c) measurement on ethanol-extracted pheo, and (d) existing data in literature
[courtesy of Milenković S. M. et al. (2012)]
• Spectral comparison among: 1st-principle quantum simulation,
measurement on ethanol-extracted pheo, and existing literature
Standard pheo
simulation
Derivative
pheo simulation
To our dismay, the
wiggly features
were not complete
still.
More structures?
Even different
weighting percent?
21. 2016/8/16 CCL Group 21
1st-principle QM simulated spectrum of orthodox morphology of pheo does NOT
show the key little features as demonstrated by measurements, existent data, and
simulated derivative morphology.
Can existing textbooks or literatures about pheo morphology
be rigorously in error? If so, so what?
What can molecular geometry optimization reveal to us further?
More importantly:
Can such derivative morphologies facilitate hydrogen oxidation reaction (i.e.,
Orienting and splitting of H2 molecule, ionization of H atoms, as a catalyst for HOR)?
What about conducting energy simulations and a battery-related experiment?
22. 2016/8/16 CCL Group 22
Figure 6. A reasonable scenario to convert the entering hydrogen molecule and form the
derivative morphology of pheo with 4 N-H bonds formed under the acidic chemical battery
action, wherein yellow spots = electron lone pair, white = H, grey = C, blue = N, red = O, and
numbers on atoms = formal charges. 1 Ha (Hartree) = 27.2116 eV.
Suspected
derivative
morphology
most stable
Energetic
DMol3 simulation
on pheo
bc = 0.18 eV
( H2 13.36 eV)
By a more rigorous
calculation wherein
H2 were
perpendicular to
the porphyrin plane.
23. 2016/8/16 CCL Group 23
Figure 7. Hydrogen production by electrolysis for the intended hydrogen-fueled
battery (after the gas transfer was completed, the connection was disabled.)
• Experimental evidence in pheo-catalyzed decomposition of
hydrogen gas
24. 2016/8/16 CCL Group 24
Figure 8. Battery discharge cases with pheo-catalyzed and reference
(without pheo) negative electrodes.
25. 2016/8/16 CCL Group 25
The 1st-principle quantum mechanical simulations following the above steps
demonstrated that such proposed scenario involving pheo derivative
morphologies was energetically favorable.
It is noted, however, that the total energy increase (0.4911 Ha, or 13.36 eV) from
step (b) to step (c) (i.e., with two H’s becoming 2H+’s) has to come from the
battery action and eventually a lowest energy state –the derivative morphology—
can be achieved.
This was only made possible by the “catalytic” presence of both the N atoms in
the new pheo derivative structure.
Otherwise, the minimum price to remove a single electron from a stand-alone H
atom is known to be as large as 13.58 eV.
Pheo-catalyzed chemical batteries (or, fuel cells) are promising for room-
temperature operation.
What’s significant?
26. 2016/8/16 CCL Group 26
0
1
2
3
4
5
6
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25
H2molenumberinthecontainer(mmol)
Time(Hr)
Hydrogen gas adsorption experiments
paper
paper with P
paper with P200
Reference Group_P Group_P200
H2 mole number after 55-min
electrolysis (mmol)
5.25392 5.05739 4.8768
H2 mole number after 24 hr. 5.23208 3.93935 3.7819
Adsorbed hydrogen amount
(mmol)
0.02184 1.11804
(22.11%)
1.0949
(22.45%)
Further related evidence: hydrogen adsorption by pheo
Though invisible for
the real situation,
this extra info
may serve as an
indirect evidence.
27. 2016/8/16 CCL Group 27
• Summary and conclusions
It was conjectured that a derivative form of pheophytin had existed all along
which may provide the internal proton conductive path to account for the
observed NMR spectral features.
Then, such derivative form was suspected to facilitate its role as a general
catalyst, particularly to hydrogen gas decomposition.
Results from spectral analyses, quantum simulations, and chemical battery
experiments all pointed to the viability of such a conjecture.
Pheo-catalyzed H2 fuel cell can be a new possibility.
H2 storage in pheo can be a new fuel transport alternative after proper tailoring
of pheo structures.
Editor's Notes
This study is more related to the pheo structure, instead of the photosynthesis.
4 pyrrols porphyrin ring;
Each N can have only 3 bonds. Mg is bonded to only two N atoms, while only under the Van der Waals force influence of the other two N atoms.
Note the tautomerism of porphyrin ring.
The known absorption spectra may not correspond to the morphologies shown, as will be elaborated in this afternoon’s talk.
ab, bc: one H at a time
de: counter-clockwise rotation, df: clockwise rotation, ef: jump across simultaneously
Note the double bonds connecting to N atoms in the orthodox morphology, which make the transport of protons hard.
The obtained (b) is still unlike the realistic (c) and (d), maybe due to having not included all tautomeric possibilities in proper proportions.
Note the energy needed to strip the two electrons from H atoms.
Note the action zone features: porphyrin ring, N atoms, nearby H bond.