NMR spectroscopy is a technique that detects atomic nuclei and probes their magnetic properties. It works by applying a strong magnetic field to align nuclear magnetic moments, and a second magnetic field to excite the nuclei and cause them to emit radio signals. The emitted signals are analyzed to yield information about the nuclei undergoing NMR. NMR is widely used in fields such as chemistry, medicine, materials science, and biology.
The postulates of quantum mechanics have been successfully used for deriving exact solutions to Schrodinger equation for problems like A particle in 1 Dimensional box Harmonic oscillator Rigid rotator Hydrogen atom • However for a multielectron system, the SWE cannot be solved exactly due to inter-electronic repulsion terms.
The SWE is solved by method of seperation of variables.
• However, the inter-electronic repulsion term cannot be solved because the variables cannot be seperated and the SWE cannot be solved. • Approximate methods have helped to generate solutions for such and even more complex real quantum systems. • Approximate methods have been developed for solving Schrodinger equation to find wave function and energy of the complex system under consideration. • Two widely used approximate methods are, 1. Perturbation theory 2. Variation method
Perturbation theory is an approximate method that describes a complex quantum system in terms of a simpler system for which the exact solution is known. • Perturbation theory has been categorized into, i. Time independent perturbation theory, proposed by Erwin Schrodinger, where the perturbation Hamiltonian is static. ii. Time dependent perturbation theory, proposed by Paul Dirac, which studies the effect of time dependent perturbation on a time independent Hamiltonian H0.
PERTURBATION THEOREM
FIRST ORDER PERTURBATION THEORY
FIRST ORDER ENERGY CORRECTION
FIRST ORDER WAVE FUNCTION CORRECTION
APPLICATIONS OF PERTURBATION METHOD
SIGNIFICANCE OF PERTURBATION METHOD
Nmr nuclear magnetic resonance spectroscopyJoel Cornelio
Basics of NMR. Suitable for UG and PG courses.
Includes principle, instrumentation, solvents. chemical shift and factors affecting it. Some problems. resolving agents, coupling constant and much more
The postulates of quantum mechanics have been successfully used for deriving exact solutions to Schrodinger equation for problems like A particle in 1 Dimensional box Harmonic oscillator Rigid rotator Hydrogen atom • However for a multielectron system, the SWE cannot be solved exactly due to inter-electronic repulsion terms.
The SWE is solved by method of seperation of variables.
• However, the inter-electronic repulsion term cannot be solved because the variables cannot be seperated and the SWE cannot be solved. • Approximate methods have helped to generate solutions for such and even more complex real quantum systems. • Approximate methods have been developed for solving Schrodinger equation to find wave function and energy of the complex system under consideration. • Two widely used approximate methods are, 1. Perturbation theory 2. Variation method
Perturbation theory is an approximate method that describes a complex quantum system in terms of a simpler system for which the exact solution is known. • Perturbation theory has been categorized into, i. Time independent perturbation theory, proposed by Erwin Schrodinger, where the perturbation Hamiltonian is static. ii. Time dependent perturbation theory, proposed by Paul Dirac, which studies the effect of time dependent perturbation on a time independent Hamiltonian H0.
PERTURBATION THEOREM
FIRST ORDER PERTURBATION THEORY
FIRST ORDER ENERGY CORRECTION
FIRST ORDER WAVE FUNCTION CORRECTION
APPLICATIONS OF PERTURBATION METHOD
SIGNIFICANCE OF PERTURBATION METHOD
Nmr nuclear magnetic resonance spectroscopyJoel Cornelio
Basics of NMR. Suitable for UG and PG courses.
Includes principle, instrumentation, solvents. chemical shift and factors affecting it. Some problems. resolving agents, coupling constant and much more
This presentation shows a technique of how to solve for the approximate ground state energy using Schrodinger Equation in which the solution for wave function is not on hand
Lecture 8: Introduction to Quantum Chemical Simulation graduate course taught at MIT in Fall 2014 by Heather Kulik. This course covers: wavefunction theory, density functional theory, force fields and molecular dynamics and sampling.
This presentation shows a technique of how to solve for the approximate ground state energy using Schrodinger Equation in which the solution for wave function is not on hand
Lecture 8: Introduction to Quantum Chemical Simulation graduate course taught at MIT in Fall 2014 by Heather Kulik. This course covers: wavefunction theory, density functional theory, force fields and molecular dynamics and sampling.
It is spectroscopy technique to determine number of hydrogen atoms present in the molecules and atoms.It is useful method for separation of molecules and compounds from mixtures components highly recommended in pharmaceutical and chemical engineering fields.
NMR, principle, chemical shift , valu,13 C, applicationTripura University
Nuclear magnetic resonance (NMR) is a physical phenomenon in which nuclei in a strong, constant magnetic field are perturbed by a weak oscillating magnetic field (in the near field [1]) and respond by producing an electromagnetic signal with a frequency characteristic of the magnetic field at the nucleus. This process occurs near resonance, when the oscillation frequency matches the intrinsic frequency of the nuclei, which depends on the strength of the static magnetic field, the chemical environment, and the magnetic properties of the isotope involved; in practical applications with static magnetic fields up to ca. 20 tesla, the frequency is similar to VHF and UHF television broadcasts (60–1000 MHz). NMR results from the specific magnetic properties of certain atomic nuclei. Nuclear magnetic resonance spectroscopy is widely used to determine the structure of organic molecules in solution and study molecular physics and crystals as well as non-crystalline materials. NMR is also routinely used in advanced medical imaging techniques, such as magnetic resonance imaging (MRI). The original application of NMR to condensed matter physics is nowadays mostly devoted to strongly correlated electron systems. It reveals large many-body couplings by fast broadband detection, and it should not be confused with solid-state NMR, which aims at removing the effect of the same couplings by magic angle spinning techniques.
NMR - Nuclear magnetic resonance (NMR).pptxmuskaangandhi1
Nuclear magnetic resonance (NMR) spectroscopy is the study of molecules by recording the interaction of radiofrequency (Rf) electromagnetic radiations with the nuclei of molecules placed in a strong magnetic field.
It is concerned with absorption of certain amount of energy
by spinning nuclei in a magnetic field when irradiated with
radiofrequency radiation (RFR) of equivalent energy.
NMR gives the information about the number and configuration of
magnetically active atoms, like positions of different types
of Hydrogen over the C- skeleton of an organic molecule.
Absorption of RFR occurs when the nucleus undergoes
transition from one alignment in the applied magnetic field
to the opposite alignment, i.e. from parallel (ground state)
orientation to anti-parallel (excited state) orientation.
When the frequency of the oscillating electric field of the
incoming RFR just matches the frequency of the electric field
generated by the precising nucleus, then the 2 fields can
couple, and the energy can be transferred from the
incoming radiation to the nucleus, thus causing a spin change
(clock-wise to anti-clock-wise).
This condition is called "resonance", and the nucleus is said to
have resonance with the incoming electromagnetic wave
(RFR).
In NMR technique, the frequency of the RFR is kept constant
(60MHz) and the strength of magnetic field is varied.
At certain value of the applied field strength, depending
upon the nature of proton or nucleus, the energy required to
flip the proton matches the energy of radiation.
As a result, absorption takes place and a signal is observed
in the spectrum. Such a signal or peak is called an NMR
Spectrum.
NMR spectrum is graphical plot of relative intensity
(Y axis) and the δ value (x axis).
The nucleus of a hydrogen atom (proton) behaves as a spinning bar magnet because it possesses both electric and magnetic spin.
Like any other spinning charged body, the nucleus of hydrogen atom also generates a magnetic field.
Nuclear magnetic resonance Involves the interaction between an oscillating magnetic field of electromagnetic radiation and the magnetic energy of the hydrogen nucleus or some other type of nuclei when these are placed in an external static magnetic field.
The sample absorbs electromagnetic radiations in radio wave region at different frequencies since absorption depends upon the type of protons or certain nuclei contained in the sample)
Consider a spinning top. It also performs a slower waltz like motion,
in which the spinning axis of the top moves slowly around
the vertical.
This is processional motion & the top is said to be processing around the vertical axis of earth's gravitational field.
The precession arises from the interaction of spin with earth's gravity acting vertically downwards.
It is called Gyroscopic motion.
Proton will be showing processional motion due to interaction of Spin &
Gravitational force of Earth
CHEMICAL SHIFT AND ITS FACTOR EFFECTS, COUPLING CONSTANT, FIRST ORDER TO NON FIRST ORDER, SPIN SYSTEMS, CHEMICAL EQUIVALENCE AND NON EQUIVALENCE, TIRUMALA SANTHOSHKUMAR S
Slide 1: Title Slide
Extrachromosomal Inheritance
Slide 2: Introduction to Extrachromosomal Inheritance
Definition: Extrachromosomal inheritance refers to the transmission of genetic material that is not found within the nucleus.
Key Components: Involves genes located in mitochondria, chloroplasts, and plasmids.
Slide 3: Mitochondrial Inheritance
Mitochondria: Organelles responsible for energy production.
Mitochondrial DNA (mtDNA): Circular DNA molecule found in mitochondria.
Inheritance Pattern: Maternally inherited, meaning it is passed from mothers to all their offspring.
Diseases: Examples include Leber’s hereditary optic neuropathy (LHON) and mitochondrial myopathy.
Slide 4: Chloroplast Inheritance
Chloroplasts: Organelles responsible for photosynthesis in plants.
Chloroplast DNA (cpDNA): Circular DNA molecule found in chloroplasts.
Inheritance Pattern: Often maternally inherited in most plants, but can vary in some species.
Examples: Variegation in plants, where leaf color patterns are determined by chloroplast DNA.
Slide 5: Plasmid Inheritance
Plasmids: Small, circular DNA molecules found in bacteria and some eukaryotes.
Features: Can carry antibiotic resistance genes and can be transferred between cells through processes like conjugation.
Significance: Important in biotechnology for gene cloning and genetic engineering.
Slide 6: Mechanisms of Extrachromosomal Inheritance
Non-Mendelian Patterns: Do not follow Mendel’s laws of inheritance.
Cytoplasmic Segregation: During cell division, organelles like mitochondria and chloroplasts are randomly distributed to daughter cells.
Heteroplasmy: Presence of more than one type of organellar genome within a cell, leading to variation in expression.
Slide 7: Examples of Extrachromosomal Inheritance
Four O’clock Plant (Mirabilis jalapa): Shows variegated leaves due to different cpDNA in leaf cells.
Petite Mutants in Yeast: Result from mutations in mitochondrial DNA affecting respiration.
Slide 8: Importance of Extrachromosomal Inheritance
Evolution: Provides insight into the evolution of eukaryotic cells.
Medicine: Understanding mitochondrial inheritance helps in diagnosing and treating mitochondrial diseases.
Agriculture: Chloroplast inheritance can be used in plant breeding and genetic modification.
Slide 9: Recent Research and Advances
Gene Editing: Techniques like CRISPR-Cas9 are being used to edit mitochondrial and chloroplast DNA.
Therapies: Development of mitochondrial replacement therapy (MRT) for preventing mitochondrial diseases.
Slide 10: Conclusion
Summary: Extrachromosomal inheritance involves the transmission of genetic material outside the nucleus and plays a crucial role in genetics, medicine, and biotechnology.
Future Directions: Continued research and technological advancements hold promise for new treatments and applications.
Slide 11: Questions and Discussion
Invite Audience: Open the floor for any questions or further discussion on the topic.
Richard's aventures in two entangled wonderlandsRichard Gill
Since the loophole-free Bell experiments of 2020 and the Nobel prizes in physics of 2022, critics of Bell's work have retreated to the fortress of super-determinism. Now, super-determinism is a derogatory word - it just means "determinism". Palmer, Hance and Hossenfelder argue that quantum mechanics and determinism are not incompatible, using a sophisticated mathematical construction based on a subtle thinning of allowed states and measurements in quantum mechanics, such that what is left appears to make Bell's argument fail, without altering the empirical predictions of quantum mechanics. I think however that it is a smoke screen, and the slogan "lost in math" comes to my mind. I will discuss some other recent disproofs of Bell's theorem using the language of causality based on causal graphs. Causal thinking is also central to law and justice. I will mention surprising connections to my work on serial killer nurse cases, in particular the Dutch case of Lucia de Berk and the current UK case of Lucy Letby.
A brief information about the SCOP protein database used in bioinformatics.
The Structural Classification of Proteins (SCOP) database is a comprehensive and authoritative resource for the structural and evolutionary relationships of proteins. It provides a detailed and curated classification of protein structures, grouping them into families, superfamilies, and folds based on their structural and sequence similarities.
THE IMPORTANCE OF MARTIAN ATMOSPHERE SAMPLE RETURN.Sérgio Sacani
The return of a sample of near-surface atmosphere from Mars would facilitate answers to several first-order science questions surrounding the formation and evolution of the planet. One of the important aspects of terrestrial planet formation in general is the role that primary atmospheres played in influencing the chemistry and structure of the planets and their antecedents. Studies of the martian atmosphere can be used to investigate the role of a primary atmosphere in its history. Atmosphere samples would also inform our understanding of the near-surface chemistry of the planet, and ultimately the prospects for life. High-precision isotopic analyses of constituent gases are needed to address these questions, requiring that the analyses are made on returned samples rather than in situ.
The increased availability of biomedical data, particularly in the public domain, offers the opportunity to better understand human health and to develop effective therapeutics for a wide range of unmet medical needs. However, data scientists remain stymied by the fact that data remain hard to find and to productively reuse because data and their metadata i) are wholly inaccessible, ii) are in non-standard or incompatible representations, iii) do not conform to community standards, and iv) have unclear or highly restricted terms and conditions that preclude legitimate reuse. These limitations require a rethink on data can be made machine and AI-ready - the key motivation behind the FAIR Guiding Principles. Concurrently, while recent efforts have explored the use of deep learning to fuse disparate data into predictive models for a wide range of biomedical applications, these models often fail even when the correct answer is already known, and fail to explain individual predictions in terms that data scientists can appreciate. These limitations suggest that new methods to produce practical artificial intelligence are still needed.
In this talk, I will discuss our work in (1) building an integrative knowledge infrastructure to prepare FAIR and "AI-ready" data and services along with (2) neurosymbolic AI methods to improve the quality of predictions and to generate plausible explanations. Attention is given to standards, platforms, and methods to wrangle knowledge into simple, but effective semantic and latent representations, and to make these available into standards-compliant and discoverable interfaces that can be used in model building, validation, and explanation. Our work, and those of others in the field, creates a baseline for building trustworthy and easy to deploy AI models in biomedicine.
Bio
Dr. Michel Dumontier is the Distinguished Professor of Data Science at Maastricht University, founder and executive director of the Institute of Data Science, and co-founder of the FAIR (Findable, Accessible, Interoperable and Reusable) data principles. His research explores socio-technological approaches for responsible discovery science, which includes collaborative multi-modal knowledge graphs, privacy-preserving distributed data mining, and AI methods for drug discovery and personalized medicine. His work is supported through the Dutch National Research Agenda, the Netherlands Organisation for Scientific Research, Horizon Europe, the European Open Science Cloud, the US National Institutes of Health, and a Marie-Curie Innovative Training Network. He is the editor-in-chief for the journal Data Science and is internationally recognized for his contributions in bioinformatics, biomedical informatics, and semantic technologies including ontologies and linked data.
Multi-source connectivity as the driver of solar wind variability in the heli...Sérgio Sacani
The ambient solar wind that flls the heliosphere originates from multiple
sources in the solar corona and is highly structured. It is often described
as high-speed, relatively homogeneous, plasma streams from coronal
holes and slow-speed, highly variable, streams whose source regions are
under debate. A key goal of ESA/NASA’s Solar Orbiter mission is to identify
solar wind sources and understand what drives the complexity seen in the
heliosphere. By combining magnetic feld modelling and spectroscopic
techniques with high-resolution observations and measurements, we show
that the solar wind variability detected in situ by Solar Orbiter in March
2022 is driven by spatio-temporal changes in the magnetic connectivity to
multiple sources in the solar atmosphere. The magnetic feld footpoints
connected to the spacecraft moved from the boundaries of a coronal hole
to one active region (12961) and then across to another region (12957). This
is refected in the in situ measurements, which show the transition from fast
to highly Alfvénic then to slow solar wind that is disrupted by the arrival of
a coronal mass ejection. Our results describe solar wind variability at 0.5 au
but are applicable to near-Earth observatories.
(May 29th, 2024) Advancements in Intravital Microscopy- Insights for Preclini...Scintica Instrumentation
Intravital microscopy (IVM) is a powerful tool utilized to study cellular behavior over time and space in vivo. Much of our understanding of cell biology has been accomplished using various in vitro and ex vivo methods; however, these studies do not necessarily reflect the natural dynamics of biological processes. Unlike traditional cell culture or fixed tissue imaging, IVM allows for the ultra-fast high-resolution imaging of cellular processes over time and space and were studied in its natural environment. Real-time visualization of biological processes in the context of an intact organism helps maintain physiological relevance and provide insights into the progression of disease, response to treatments or developmental processes.
In this webinar we give an overview of advanced applications of the IVM system in preclinical research. IVIM technology is a provider of all-in-one intravital microscopy systems and solutions optimized for in vivo imaging of live animal models at sub-micron resolution. The system’s unique features and user-friendly software enables researchers to probe fast dynamic biological processes such as immune cell tracking, cell-cell interaction as well as vascularization and tumor metastasis with exceptional detail. This webinar will also give an overview of IVM being utilized in drug development, offering a view into the intricate interaction between drugs/nanoparticles and tissues in vivo and allows for the evaluation of therapeutic intervention in a variety of tissues and organs. This interdisciplinary collaboration continues to drive the advancements of novel therapeutic strategies.
Professional air quality monitoring systems provide immediate, on-site data for analysis, compliance, and decision-making.
Monitor common gases, weather parameters, particulates.
1. 1
Introductory to NMR Spectroscopy
Ref:
1. NMR Spectroscopy, Basic Principles and Applications, by Roger S. Macomber
2. http://www.cis.rit.edu/htbooks/nmr/ by Joseph P. Hornak
3. Some figures copy from the web page by Guillermo Moyna, University of the
Sciences in Philadelphia
4. Wüthrich, K. “NMR of Proteins and Nucleic Acids”, Wiley, 1986. 科儀新知1994
年六月份
5. Cavanagh, J. et al., “Protein NMR Spectroscopy-Principles and Practice”,
Academic Press, 1996.
6. Van de Ven, F.J. (1995), “Multi-dimensional NMR in Liquid-Basic Principles &
Experimental Methods”. VCH Publishing
2. 2
1nm 10 102 103 104 105 106 107
(the wave) X-ray UV/VIS Infrared Microwave Radio
Frequency
(the transition) electronic Vibration Rotation Nuclear
(spectrometer) X-ray UV/VIS Infrared/Raman NMR
Fluorescence
NMR Spectroscopy
Where is it?
3. 3
NMR Historic Review
1924 Pauli proposed the presence of nuclear magnetic moment to explain the
hyperfine structure in atomic spectral lines.
1930 Nuclear magnetic moment was detected using refined Stern-Gerlach
experiment by Estermann.
1939 Rabi et al. First detected unclear magnetic resonance phenomenon by
applying r.f. energy to a beam of hydrogen molecules in the Stern-Gerach
set up and observed measurable deflection of the beam.
1946 Purcell et al. at Harvard reported nuclear resonance absorption in paraffin
wax.
Bloch et al. at Stanford found nuclear resonance in liquid water.
1949 Chemical shift phenomenon was observed.
1952 Nobel prize in Physics was awarded to Purcell and Bloch.
1966 Ernst and Anderson first introduce the Fourier Transform technique into
NMR.
Late in the 1960s:
Solid State NMR was revived due to the effort of Waugh.
and associates at MIT.
NMR Historic Review
4. 4
1966 Ernst and Anderson first introduce the Fourier Transform technique into
NMR.
Late in the 1960s:
Solid State NMR was revived due to the effort of Waugh.
and associates at MIT.
Biological application become possible due to the introduction
superconducting magnets.
NMR imaging was demonstrated.
1970 2D NMR was introduced.
1980s Macromolecular structure determination in solution by NMR was
achieved.
1991 Nobel prize in Chemistry was awarded to Richard Ernst.
1990s Continuing development of heteronuclear multi-dimensional NMR permit
the determination of protein structure up to 50 KDa.
MRI become a major radiological tool in medical diagnostic.
NMR Applications
(One of themost, if not the most, important analytical spectroscopic tool.)
1. Biomedical applications:
2002 Nobel prize in Chemistry was awarded to Kurt Wuthrich
NMR is a versatile tool and it has applications in wide varieties of subjects
in addition to its chemical and biomedical applications, including material
and quantum computing.
7. 7
The problem the we want to solve by NMR
What we “really”
see
What we want to “see”
NMR
8. 8
Before using NMR
What are N, M, and R ?
Properties of the Nucleus
Nuclear spin
Nuclear magnetic moments
The Nucleus in a Magnetic Field
Precession and the Larmor frequency
Nuclear Zeeman effect & Boltzmann distribution
When the Nucleus Meet the right Magnet and radio wave
Nuclear Magnetic Resonance
9. 9
Nuclear spin
Nuclear spin is the total nuclear angular momentum quantum number.
This is characterized by a quantum number I, which may be integral,
half-integral or 0.
Only nuclei with spin number I 0 can absorb/emit electromagnetic
radiation. The magnetic quantum number mI has values of –I, -I+1, …..+I .
( e.g. for I=3/2, mI=-3/2, -1/2, 1/2, 3/2 )
1. A nucleus with an even mass A and even charge Z nuclear spin I is
zero
Example: 12C, 16O, 32S No NMR signal
2. A nucleus with an even mass A and odd charge Z integer value I
Example: 2H, 10B, 14N NMR detectable
3. A nucleus with odd mass A I=n/2, where n is an odd integer
Example: 1H, 13C, 15N, 31P NMR detectable
Properties of the Nucleus
10. 10
Nuclear magnetic moments
Magnetic moment is another important parameter for a nuclei
= I (h/2)
I: spin number; h: Plank constant;
: gyromagnetic ratio (property of a nuclei)
1H: I=1/2 , = 267.512 *106 rad T-1S-1
13C: I=1/2 , = 67.264*106
15N: I=1/2 , = 27.107*106
11. 11
Table 1.1 Nuclei of Major Interest to NMR Spectroscopists
Iostope
Abundance
(%)
Ζ Spin μ2
γ ×10-8b Relativec
sensitivity
ν0 at
1T(MHz)
At 7.04T
1
H 99.9844 1 1/2 2.7927 2.6752 1.000 42.577 300
2
H 0.0156 1 1 0.8574 0.4107 0.00964 6.536 46
10
B 18.83 5 3 1.8006 0.2875 0.0199 4.575
11
B 81.17 5 3/2 2.6880 0.8583 0.165 13.660
13
C 1.108 6 1/2 0.7022 0.6726 0.0159 10.705 75.4
14
N 99.635 7 1 0.4036 0.1933 0.00101 3.076
15
N 0.365 7 1/2 -0.2830 -0.2711 0.00104 4.315 30.4
19
F 100 9 1/2 2.6273 2.5167 0.834 40.055 282.3
29
Si 4.70 14 1/2 -0.5548 -0.5316 0.0785 8.460
31
P 100 15 1/2 1.1305 1.0829 0.0664 17.235 121.4
a Magnetic moment in units of the nuclear magneton, eh/(ΔμMp c)
b Magnetogyric ratio in SI units
c For equal numbers of nuclei at constant field
12. 12
The Nucleus in a Magnetic Field
Precession and the Larmor frequency
• The magnetic moment of a spinning nucleus processes with a characteristic
angular frequency called the Larmor frequency w, which is a function of r and B0
Remember = I (h/2) ?
Angular momentum dJ/dt= x B0
Larmor frequency w=rB0
Linear precession frequency v=w/2= rB0/2
Example: At what field strength do 1H process at a frequency of 600.13MHz? What would be the
process frequency for 13C at the same field?
J
13. 13
Nuclear Zeeman effect
• Zeeman effect: when an atom is placed in an external magnetic field,
the energy levels of the atom are split into several states.
• The energy of a give spin sate (Ei) is directly proportional to the value
of mI and the magnetic field strength B0
Spin State Energy EI=- . B0 =-mIB0 r(h/2p)
• Notice that, the difference in energy will always be an integer multiple
of B0r(h/2p). For a nucleus with I=1/2, the energy difference between
two states is
ΔE=E-1/2-E+1/2 = B0 r(h/2p)
m=–1/2
m=+1/2
The Zeeman splitting is proportional to the strength of the magnetic
field
14. 14
Boltzmann distribution
Quantum mechanics tells us that, for net absorption of radiation to occur,
there must be more particles in the lower-energy state than in the higher
one. If no net absorption is possible, a condition called saturation.
When it’s saturated, Boltzmann distribution comes to rescue:
Pm=-1/2 / Pm=+1/2 = e -DE/kT
where P is the fraction of the particle population in each state,
T is the absolute temperature,
k is Boltzmann constant 1.381*10-28 JK-1
Example: At 298K, what fraction of 1H nuclei in 2.35 T field are in the upper and
lower states? (m=-1/2 : 0.4999959 ; m=1/2 : 0.5000041 )
The difference in populations of the two states is only on the order of
few parts per million. However, this difference is sufficient to generate
NMR signal.
Anything that increases the population difference will give rise to a more
intense NMR signal.
15. 15
•For a particle to absorb a photon of electromagnetic radiation, the particle must
first be in some sort of uniform periodic motion
• If the particle “uniformly periodic moves” (i.e. precession)
at vprecession, and absorb erengy. The energy is E=hvprecession
•For I=1/2 nuclei in B0 field, the energy gap between two spin states:
DE=rhB0/2
• The radiation frequency must exactly match the precession frequency
Ephoton=hvprecession=hvphoton=DE=rhB0/2
This is the so called “ Nuclear Magnetic RESONANCE”!!!!!!!!!
v
DE =hvphoton
When the Nucleus Meet the Magnet
Nuclear Magnetic Resonance
17. 17
Magnet B0 and irradiation energy B1
B0 ( the magnet of machine)
(1) Provide energy for the nuclei to spin
Ei=-miB0 (rh/2)
Larmor frequency w=rB0
(2) Induce energy level separation (Boltzmann distribution)
The stronger the magnetic field B0, the greater separation
between different nuclei in the spectra
Dv =v1-v2=(r1-r2)B0/2
(3) The nuclei in both spin states are randomly oriented around the z axis.
M z=M, Mxy=0
( where M is the net
nuclear magnetization)
18. 18
What happen before irradiation
• Before irradiation, the nuclei in both spin states are processing with
characteristic frequency, but they are completely out of phase, i.e., randomly
oriented around the z axis. The net nuclear magnetization M is aligned statically
along the z axis (M=Mz, Mxy=0)
19. 19
What happen during irradiation
When irradiation begins, all of the individual nuclear magnetic moments become
phase coherent, and this phase coherence forces the net magnetization vector M
to process around the z axis. As such, M has a component in the x, y plan,
Mxy=Msina. a is the tip angle which is determined by the power and duration of
the electromagnetic irradiation.
a
Mo
z
x
B1
y
wo
x
Mxy
y
90 deg pulsea deg pulse
20. 20
What happen after irradiation ceases
•After irradiation ceases, not only do the population of the states revert to a
Boltzmann distribution, but also the individual nuclear magnetic moments begin to
lose their phase coherence and return to a random arrangement around the z axis.
(NMR spectroscopy record this process!!)
•This process is called “relaxation process”
•There are two types of relaxation process : T1(spin-lattice relaxation) & T2(spin-
spin relaxation)
21. 21
B1(the irradiation magnet, current induced)
(1) Induce energy for nuclei to absorb, but still spin at w or vprecession
Ephoton=hvphoton=DE=rhB0/2=hvprecession
And now, the spin jump to the higher energy ( from m=1/2m= – 1/2)
(2) All of the individual nuclear magnetic moments become phase
coherent, and the net M process around the z axis at a angel
M z=Mcosa
Mxy=Msina.
m= 1/2
m= –1/2
22. 22
T1 (the spin lattice relaxation)
• How long after immersion in a external field does it take for a collection of nuclei
to reach Boltzmann distribution is controlled by T1, the spin lattice relaxation time.
(major Boltzmann distribution effect)
•Lost of energy in system to surrounding (lattice) as heat
( release extra energy)
•It’s a time dependence exponential decay process of Mz components
dMz/dt=-(Mz-Mz,eq)/T1
23. 23
T2 (the spin –spin relaxation)
•This process for nuclei begin to lose their phase coherence and return to a random
arrangement around the z axis is called spin-spin relaxation.
•The decay of Mxy is at a rate controlled by the spin-spin relaxation time T2.
dMx/dt=-Mx/T2
dMy/dt=-My/T2
dephasing
25. 25
Collecting NMR signals
•The detection of NMR signal is on the xy plane. The oscillation of Mxy generate a
current in a coil , which is the NMR signal.
•Due to the “relaxation process”, the time dependent spectrum of nuclei can be
obtained. This time dependent spectrum is called “free induction decay” (FID)
Mxy
time
(if there’s no relaxation ) (the real case with T1 &T2)
26. 26
•In addition, most molecules examined by NMR have several sets of nuclei, each
with a different precession frequency.
•The FID (free induction decay) is then Fourier transform to frequency domain
to obtain each vpression ( chemical shift) for different nuclei.
Time (sec)
frequency (Hz)
28. 28
AT 71000 GAUSS (7.1 TELSLA)
(1T = 10,000G)
Hz) 0 30 75 121 280 300 320
s 15
N 13
C
31
P 19
F 1
H 3
H
Table 1.1 Nuclei of Major Interest to NMR Spectroscopists
e
Abundance
(%)
Ζ Spin μ
2
γ ×10-8b Relativec
sensitivity
ν 0 at
1T(MHz)
At 7.04T
29. 29
NMR signals
• We have immersed our collection of nuclei in a magnetic field, each is processing with
a characteristic frequency, To observe resonance, all we have to do is irradiate them
with electromagnetic radiation of the appropriate frequency.
•It’s easy to understand that different nucleus “type” will give different NMR signal.
(remember v =w/2= B0/2 ? Thus, different cause different v !! )
•However, it is very important to know that for same “nucleus type”, but “different
nucleus” could generate different signal. This is also what make NMR useful and
interesting.
•Depending on the chemical environment, there are variations on the magnetic field
that the nuclei feels, even for the same type of nuclei.
•The main reason for this is, each nuclei could be surrounded by different electron
environment, which make the nuclei “feel” different net magnetic field , Beffect
31. 31
NMR Parameters
Chemical Shift
• The chemical shift of a nucleus is the difference between the resonance frequency
of the nucleus and a standard, relative to the standard. This quantity is reported
in ppm and given the symbol delta,
= (n - nREF) x106 / nREF
• In NMR spectroscopy, this standard is often tetramethylsilane, Si(CH3)4,
abbreviated TMS, or 2,2-dimethyl-2-silapentane-5-sulfonate, DSS, in
biomolecular NMR.
• The good thing is that since it is a relative scale, the for a sample in a 100 MHz
magnet (2.35 T) is the same as that obtained in a 600 MHz magnet (14.1 T).
0
TMS
ppm
210 7 515
Aliphatic
Alcohols, protons a
to ketones
Olefins
Aromatics
AmidesAcids
Aldehydes Shielded
(up field)
Deshielded
(low field)
32. 32
Electron surrounding each nucleus in a molecule serves to shield that
nucleus from the applied magnetic field. This shielding effect cause the
DE difference, thus, different v will be obtained in the spectrum
Beff=B0-Bi where Bi induced by cloud electron
Bi = sB0 where s is the shielding constant
Beff=(1-s) B0
vprecession= (rB0/2p) (1-s)
s=0 naked nuclei
s >0 nuclei is shielded by electron cloud
s <0 electron around this nuclei is withdraw , i.e.
deshielded
Example: Calculate the chemical shifts of a sample that contains two signals
( 140Hz & 430 Hz using 60MHz instrument; 187Hz & 573 Hz using 80MHz
instrument). (2.33ppm & 7.17ppm)
Example: The 60MHz 1H spectrum of CH3Li shows a signal at 126 Hz upfield of
TMS. What is its chemical shift? (-2.10ppm)
35. 35
J-coupling
•Nuclei which are close to one another could cause an influence on each other's
effective magnetic field. If the distance between non-equivalent nuclei is less than or
equal to three bond lengths, this effect is observable. This is called spin-spin coupling
or J coupling.
13
C
1
H 1
H 1
H
one-bond
three-bond
•Each spin now seems to has two energy ‘sub-levels’ depending on the state of the spin it
is coupled to:
The magnitude of the separation is called coupling constant (J) and has units of Hz.
aa
ab ba
bb
I SS
S
I
I
J (Hz)
36. 36
Single spin:
One neighboring spins: - CH – CH -
Two neighboring spins: - CH2 – CH -
•N neighboring spins: split into N + 1 lines
• From coupling constant (J) information, dihedral angles can be derived ( Karplus
equation)
8.1cos6.1cos5.9
8.1)120cos(6.1)120(cos5.9
9.1)60cos(4.1)60(cos4.6
11
2
2
3
11
2
1
3
23
ab
ab
a
J
J
JNH
ψ Ψ
Cα
Cβ
Cγ
ω
N
χ1
χ2
C’
N
37. 37
Nuclear Overhauser Effect (NOE)
•The NOE is one of the ways in which the system (a certain spin) can release energy.
Therefore, it is profoundly related to relaxation processes. In particular, the NOE is
related to exchange of energy between two spins that are not scalarly coupled (JIS = 0),
but have dipolar coupling.
• The NOE is evidenced by enhancement of certain signals in the spectrum when the
equilibrium (or populations) of other nearby are altered. For a two spin system, the
energy diagram is as follwing:
aa
ab
bb
W1S
W1S
W1I
W1I
ba
W2IS
W0IS
•W represents a transition probability, or the rate at which certain transition can take
place. For example, the system in equilibrium, there would be W1I and W1S transitions,
which represents single quantum transitions.
38. 38
• NOE could provide information of distance between two atoms:
NOE / NOEstd = rstd
6 / r 6
• Thus, NOE is very important parameter for structure determination of
macromolecules
39. 39
Relaxation Rates
•The Bloch Equations:
dMx(t) / dt = [ My(t) * Bz - Mz(t) * By ] - Mx(t) / T2
dMy(t) / dt = [ Mz(t) * Bx - Mx(t) * Bz ] - My(t) / T2
dMz(t) / dt = [ Mx(t) * By - My(t) * Bx ] - ( Mz(t) - Mo ) / T1
•The relaxation rates of the longitudinal magnetization, T1, determine the
length of the recycle delay needed between acquisitions, and the relaxation rates
T2 determine the line width of the signal.
•Relaxation could also provide experimental information on the physical
processes governing relaxation, including molecular motions (dynamics).
40. 40
1. Chemical Shift Indices: Determining secondary structure.
2. J-coupling: Determine dihedral angles.
(Karplus equation)
.
3. Nuclear Overhauser Effect (NOE):
Determine inter-atomic distances (NOE R-6)
.
4. Residual dipolar coupling:
Determine bond orientations.
.
5. Relaxation rates (T1, T2 etc):
Determine macromolecular dynamics.
NMR Parameters employed for determining protein structure
R 1H1H
15N
1H
BO
I
t
42. 42
1. Sample preparation (準備適當之樣品條件)
Which buffer to choose? Isotopic labeling?
Best temperature?
Sample Position ?
Preparation for NMR Experiment
N S
2. What’s the nucleus or prohead? (選擇合適之探頭)
A nucleus with an even mass A and even charge Z nuclear spin I is zero
Example: 12C, 16O, 32S No NMR signal
A nucleus with an even mass A and odd charge Z integer value I
Example: 2H, 10B, 14N NMR detectable
A nucleus with odd mass A I=n/2, where n is an odd integer
Example: 1H, 13C, 15N, 31P NMR detectable
43. 43
3. The best condition for NMR Spectrometer? (調整硬體狀態)
Wobble : Tune & Match & Shimming
RCVR
Tune
Match
Absorption
0%
100% Frequency
4. What’s the goal? Which type of experiment you need? (選擇合適之實驗方法)
Different experiments will result in different useful information
44. 44
The FID (free induction decay) is then Fourier transform to frequency domain to
obtain vpression ( chemical shift) for each different nuclei.
frequency (Hz)
5. NMR Data Processing
Time (sec)
45. 45
1D one pulse 1H
Ca CON
R1
H H
Ca CON
R2
H H
AliphaticAromatic & Amide
………………..
Types of NMR Experiments
Homo Nuclear 1D NMR