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Chapter24碳水化合物
- 2. PhotosynthesisPhotosynthesis: Energy storage: Energy storage 6 CO2 + 6 H2O C6(H2O)6 + 6 O2 Sun, chlorophyll Metabolism GlucoseGlucose
- 3. Universal Land plants ChlorophyllChlorophyll 3% to 6% of the total incident solar radiation is used for chemical conversion of H2O (oxidation to O2) and CO2 (reduction to glucose).
- 4. Carbohydrate =Carbohydrate = CCnn(H(H22O)O)nn Carbohydrates occur inCarbohydrates occur in nature in nucleic acids, fats,nature in nucleic acids, fats, cellulose, fibers, starch,cellulose, fibers, starch, “table sugar,” antibiotics,“table sugar,” antibiotics, and other biologicaland other biological molecules.molecules. Hydrated carbonHydrated carbon A pentahydroxyaldehydeA pentahydroxyaldehyde
- 5. NamingNaming The simplest carbohydrates are theThe simplest carbohydrates are the sugarssugars oror saccharidessaccharides. They constitute polyhydroxy-. They constitute polyhydroxy- aldehydesaldehydes ((aldosesaldoses) or) or -ketones-ketones ((ketosesketoses); they); they formform oligomersoligomers byby ether bridgesether bridges (hence(hence di-di-,, tri-tri-,, tetrasaccharidetetrasaccharide, etc.)., etc.). The simplestThe simplest sugars, bothsugars, both CC33(H(H22O)O)33:: 2,3-Dihydroxypropanal2,3-Dihydroxypropanal (Glyceraldehyde)(Glyceraldehyde) AnAn aldotriosealdotriose 1,3-Dihydroxyacetone1,3-Dihydroxyacetone AA ketotrioseketotriose ChainChain lengthlength:: TriTriose,ose, tetrtetrose,ose, pentpentose, etc.ose, etc. ChiralChiral
- 6. Fischer projections: Review chapter 5Fischer projections: Review chapter 5 Some importantSome important monomonosaccharides:saccharides: Dextrose, blood sugar, grape sugar Sweetest natural sugar; fruits Ribonucleic acids 4 Stereo-4 Stereo- centerscenters 3 Stereo-3 Stereo- centerscenters ** ** ** ** ** ** ** ** ** **
- 7. Fischer Projection:Fischer Projection: A flat stencilA flat stencil CCHH33 CCHH22CCHH33 HH BrBr Eyes in theEyes in the plane of theplane of the boardboard Depending on your starting dashed-wedged lineDepending on your starting dashed-wedged line structure,structure, severalseveral Fischer projections are possibleFischer projections are possible for thefor the samesame molecule.molecule. BrBr HH CCCCHH33 CCHH22CCHH33 HH BrBr Rules reminder:Rules reminder: 180 º turn or double180 º turn or double exchangeexchange leavesleaves stereochemistrystereochemistry intactintact
- 8. Most sugars are chiral and occur enantiomericallyMost sugars are chiral and occur enantiomerically pure. Simplest case, one stereocenter:pure. Simplest case, one stereocenter: Almost allAlmost all natural sugarsnatural sugars have stereocenterhave stereocenter furthest awayfurthest away from carbonyl (drawn at the bottom) with thefrom carbonyl (drawn at the bottom) with the samesame absolute configuration asabsolute configuration as D-glyceraldehydeD-glyceraldehyde:: “D-sugars”“D-sugars” DD andand LL is an older nomenclature (predates the knowledge of theis an older nomenclature (predates the knowledge of the absolute configuration of glyceraldehyde). The dextrorotatoryabsolute configuration of glyceraldehyde). The dextrorotatory enantiomer was called D, the other L. Later, D was found to beenantiomer was called D, the other L. Later, D was found to be RR, L therefore, L therefore SS..
- 9. Natural UnnaturalNatural Unnatural D-Threose L-ThreoseD-Erythrose L-Erythrose RulesRules for arrangingfor arranging the Fischer stencil:the Fischer stencil: CarbonylCarbonyl onon toptop,, places bottom C*places bottom C*OHOH on theon the rightright in the Din the D sugars.sugars.
- 10. The Family of Natural AldosesThe Family of Natural Aldoses
- 11. The Family of Natural KetosesThe Family of Natural Ketoses
- 12. Fischer Projections and Dashed-Wedged Line StructuresFischer Projections and Dashed-Wedged Line Structures Recall: FischerRecall: Fischer projectionsprojections represent anrepresent an unrealisticunrealistic modelmodel of the molecule: Allof the molecule: All eclipsedeclipsed; carbon; carbon chain “chain “curvescurves”. It’s”. It’s usefulness is inusefulness is in stereochemicalstereochemical bookkeeping.bookkeeping. D-GlucoseD-Glucose
- 15. Haworth StructuresHaworth Structures Groups that lie on the right in the Fischer projection point downward in the Haworth projection. At the anomeric carbon: OH down is called theAt the anomeric carbon: OH down is called the αα-anomer, OH up is-anomer, OH up is called thecalled the ββ-anomer.-anomer.
- 16. Other ways of drawing cyclic structures:Other ways of drawing cyclic structures: Not a carbon atom
- 17. Best are conformational pictures:Best are conformational pictures: MutarotationMutarotation: Change in observed optical: Change in observed optical rotation when a sugar molecule equilibratesrotation when a sugar molecule equilibrates with its anomer.with its anomer. Anomeric carbon Anomeric carbon OH down:OH down: αα-Anomer;-Anomer; crystallizescrystallizes OH up:OH up: ββ-Anomer;-Anomer; more stable becausemore stable because all-equatorialall-equatorial
- 18. Reactions of SugarsReactions of Sugars 1.1. OxidationOxidation a. CHOa. CHO COOH (aldoseCOOH (aldose aldonic acidaldonic acid)) b.b. αα-Hydroxy group of ketoses-Hydroxy group of ketoses αα-dicarbonyl-dicarbonyl Tests for “reducing” sugars; all ordinary saccharides are reducing.Tests for “reducing” sugars; all ordinary saccharides are reducing.
- 19. Large scale preparation of aldonic acids: BrLarge scale preparation of aldonic acids: Br22, H, H22OO Dehydration gives lactones, typically five-membered (Dehydration gives lactones, typically five-membered (γγ- lactones).- lactones). MechanismMechanism of bromine oxidation:of bromine oxidation: R C O OH H H O H H : : Br BrRCH O H2O, H+ R C OH OH H Br2 RCHOH O
- 20. c. Oxidation of both ends of aldosesc. Oxidation of both ends of aldoses →→ aldaric acidaldaric acid NoteNote selectivityselectivity of nitricof nitric acid: Picks onacid: Picks on primary OHprimary OH function (after oxidizingfunction (after oxidizing the formyl group):the formyl group): LessLess hindered.hindered. RCH O H2O, HO-NO2 H C OO R N O O H :: : RCOH + HO-NO O Mechanism:Mechanism: Nitrous acidNitrous acid
- 21. For some sugars, this oxidation may giveFor some sugars, this oxidation may give mesomeso (achiral)(achiral) aldaric acid. Can be used for proof of stereochemistry.aldaric acid. Can be used for proof of stereochemistry. D-(+)-AlloseD-(+)-Allose Allaric acid (meso)Allaric acid (meso) CHO OHH OHH OHH OHH CH2OH COOH OHH OHH OHH OHH COOH HNO3 Mirror planeMirror plane Symmetry becomes obvious also in NMR, e.g.Symmetry becomes obvious also in NMR, e.g. 1313 C NMR:C NMR: 6 peaks6 peaks 3 peaks3 peaks
- 22. d. Oxidative cleavage: HIOd. Oxidative cleavage: HIO44 This reagent causesThis reagent causes thethe rupturerupture ofof vicinal diols tovicinal diols to dialdehydes.dialdehydes. How?How?
- 23. Does this ring a bell? Remember OsODoes this ring a bell? Remember OsO44 oxidation of alkenesoxidation of alkenes to vicinal diols: Cleaves “half” a double bond.to vicinal diols: Cleaves “half” a double bond. HIOHIO44 does the same to adoes the same to a singlesingle bond (bearing OHs).bond (bearing OHs). Similarly: Remember benzylic oxidation of alkylbenzenesSimilarly: Remember benzylic oxidation of alkylbenzenes to benzenecarboxylic acids by basic KMnOto benzenecarboxylic acids by basic KMnO44.. O Mn O O:: : O K
- 24. • C-C bond broken via:C-C bond broken via: OH O OH KMnOKMnO44 doesdoes bothboth the OsOthe OsO44-type and HIO-type and HIO44-type-type oxidations sequentially in the same reaction step.oxidations sequentially in the same reaction step.
- 25. How does this work for sugars? Leads toHow does this work for sugars? Leads to complete degradationcomplete degradation of the carbon chain.of the carbon chain. Note: Each carbon fragment retains the same number of attached hydrogen atoms as were present in the original sugar. CHO OHH OHH HOH C OHH OHH H HO OH HIO4 C OH OHH H HO O I OH O O C H HO O OH OHH
- 26. Note: Each carbon fragment retains the same number of attached hydrogen atoms as were present in the original sugar. Another way to think about this isAnother way to think about this is as a “dihydroxylative” cleavage ofas a “dihydroxylative” cleavage of each chain C-C bond, e.g. fructose:each chain C-C bond, e.g. fructose: OHOH OHOH OHOH OHOH OHOH OHOH OHOH OHOH OHOH OHOH Add OHs to each sideAdd OHs to each side of the bond brokenof the bond broken
- 27. 2. Reduction to2. Reduction to alditolsalditols Sorbitol (“sugar alcohol”) is used as artificial sweetener in diet foods: 2.6 cal/g per versus 4 cal/g for normal sugar. Sorbitol also occurs naturally in many stone fruits. Note: Just as in the oxidation to aldaric acids, reduction mayNote: Just as in the oxidation to aldaric acids, reduction may symmetrizesymmetrize the sugar.the sugar.
- 28. 3. Esters and Ethers:3. Esters and Ethers: ProtectionProtection AcetalAcetalHemiacetalHemiacetal Acetal functionAcetal function can be deprotectedcan be deprotected selectivelyselectively
- 29. Protection of anomeric carbonProtection of anomeric carbon no mutarotationno mutarotation, no aldehyde, no aldehyde oxidation (i.e. does not behave as reducing sugar), no reduction.oxidation (i.e. does not behave as reducing sugar), no reduction. Mild, does not touch normal ether Alternative exploitation of the special reactivity of the (hemi)acetal function:Alternative exploitation of the special reactivity of the (hemi)acetal function: Turn it into anTurn it into an acetalacetal, called, called glycosideglycoside for sugars.for sugars.
- 30. Protection asProtection as cyclic acetalscyclic acetals Recall:Recall: ββ-D-Altrose-D-Altrose ββ-D-Altrose bisacetonide-D-Altrose bisacetonide O H HO OH H HO H HH OH OH O H O O H O H HH O OH H3C H3C H3C CH3 O , H+ -CH2OH often not engaged: Flexibility makes entropy of acetal formation worse
- 31. 4. Kiliani-Fischer Extension (Modified)4. Kiliani-Fischer Extension (Modified) Lindlar type Heinrich Kiliani 1855 - 1945 Emil Fischer 1852-1919
- 32. Example:Example: D-LyxoseD-Lyxose D-TaloseD-Talose D-GalactoseD-Galactose + 1. HCN 2. H2, Pd-BaSO4, H2O, H+ CHO HHO HHO HHO OHH CH2OH CHO OHH HHO HHO OHH CH2OH CHO HHO HHO OHH CH2OH
- 33. 5. Ruff Degradation5. Ruff Degradation Note: BothNote: Both diastereomersdiastereomers ((RR oror SS at the top stereocenter)at the top stereocenter) degrade to thedegrade to the samesame lower sugar.lower sugar. FeFe3+3+ FeFe2+2+ FeFe3+3+ FeFe2+2+
- 34. Structure DeterminationStructure Determination of Sugars-of Sugars- The FischerThe Fischer ProofProof Logical combination ofLogical combination of 1.1. Sugar extensionSugar extension →→ 2 diastereomers2 diastereomers 2.2. Sugar degradation: 2 Diastereomers giveSugar degradation: 2 Diastereomers give same sugar)same sugar) 3.3. Sugar symmetrization via aldaric acids orSugar symmetrization via aldaric acids or alditolsalditols 4.4. Recognition of intricate stereochemicalRecognition of intricate stereochemical relationshipsrelationships
- 35. A glimpse at the logic:A glimpse at the logic: ExtExt.. ExtExt.. Oxn. orOxn. or Redn.Redn. Oxn. orOxn. or Redn.Redn. AchiralAchiral ChiralChiral EtcEtc.. EtcEtc.. Oxn. or Redn. Oxn. or Redn. Same compound
- 36. CHO HHO HHO OHH CH2OH CHO HHO OHH OHH CH2OH CH2OH HHO OHH OHH CH2OH CH2OH HHO HHO OHH CH2OH Same!Same!D-ArabinoseD-Arabinose D-LyxoseD-Lyxose D-Glucaric acidD-Glucaric acid D-Gularic acidD-Gularic acid EnantiomersEnantiomers CHO OHH HHO OHH OHH CH2OH CHO OHH OHH HHO OHH CH2OH COOH OHH HHO OHH OHH COOH COOH OHH OHH HHO OHH COOH
- 37. D-Ketoses correlate with alditols by reductionD-Ketoses correlate with alditols by reduction Alditols of erythrose and threose Alditols of glucose and mannose E.g.,E.g., Again, potentialAgain, potential symmetrizationsymmetrization helps inhelps in structuralstructural assignmentassignment
- 38. Di- and HigherDi- and Higher SaccharidesSaccharides Sucrose:Sucrose: Disaccharide derived fromDisaccharide derived from glucose and fructoseglucose and fructose Ether bridge between respective anomeric centers: Nonreducing ““Table sugar”Table sugar” 150 lb/150 lb/ person/person/ yearyear
- 39. [α]D = +66.5 [α]D = -20
- 40. Lactose (milk sugar)Lactose (milk sugar) Ether bridge between anomeric C and CEther bridge between anomeric C and C44 CC44 αα ββ ReducingReducing
- 41. Cellulose: Sugar PolymerCellulose: Sugar Polymer Molecular weight 500,000 (~3000 units)Molecular weight 500,000 (~3000 units) 1 unit = 178 molecular weight. Used in1 unit = 178 molecular weight. Used in cell wall material: Rigid structure due tocell wall material: Rigid structure due to multiple hydrogen bonds.multiple hydrogen bonds.
- 42. Nitrocellulose: ExplosiveNitrocellulose: Explosive Major component of smokeless gunpowder (guncotton); used in photographic film. Christian F. Schönbein 1799-1868 Henri Braconnot:Henri Braconnot: 1832: HNO1832: HNO33 ++ starchstarch Théophile-JulesThéophile-Jules Pelouze:Pelouze: 1838: HNO1838: HNO33 ++ paperpaper
- 43. Starch: Polyglucose withStarch: Polyglucose with αα–acetal links–acetal links AmyloseAmylose Constitutes fuel reserve in plants: Corn,Constitutes fuel reserve in plants: Corn, potatoes, wheat (bread), rice.potatoes, wheat (bread), rice. Hydrolyzes to glucose (sweat taste ofHydrolyzes to glucose (sweat taste of bread in mouth). Two major components:bread in mouth). Two major components:
- 44. Amylopectin (has branches)Amylopectin (has branches)
- 45. Human Fuel Tank: GlycogenHuman Fuel Tank: Glycogen Provides immediate glucose during strainProvides immediate glucose during strain MW = 100MW = 100 millionmillion
- 46. Sugars as water solubilizing groups in nature:Sugars as water solubilizing groups in nature: Anthracycline anticancer agents and antibioticsAnthracycline anticancer agents and antibiotics AnthracyclineAnthracycline intercalates intointercalates into DNA: Kills (tumor)DNA: Kills (tumor) cellscells StreptomycinStreptomycin binds to thebinds to the ribosome, causesribosome, causes misreading ofmisreading of geneticgenetic informationinformation
Editor's Notes
- Chlorophyll and photosynthesis In plant photosynthesis, incoming light is absorbed by chlorophyll and other accessory pigments in the antenna complexes of photosystem I and photosystem II. The antenna pigments are predominantly chlorophyll a, chlorophyll b and carotenoids; their absorption spectra are non-overlapping, this serves to broaden the specific bandwidths of light these individual compounds absorb during the process of photosynthesis. The carotenoids also play a role as antioxidants, and serve to reduce photo-oxidative damage to chlorophyll molecules. Each antenna complex has between 250 and 400 pigment molecules, and the energy they absorb is shuttled by resonance energy transfer to a specialized chlorophyll a at the reaction center of each photosystem. When either of the two chorophyll a molecules at the reaction center absorb energy, an electron is excited and transferred to an electron-acceptor molecule, leaving an electron hole in the donor chlorophyll. In a poorly-understood reaction, electrons from water molecules participate in an oxidiation reaction, where the hole from the donor chlorophyll is filled (recombined with another electron), and diatomic oxygen is produced. Resulting chemical energy originating from the initial excited electron is eventually captured in the form of ATP and NADPH, and is then ultimately used to convert carbon dioxide (CO2) to carbohydrates. This CO2 fixation process results in the conversion (or an integrated external quantum efficiency) of 3% to 6% of the total incident solar radiation, with a theoretical maximum efficiency of 11%. [1] [edit] Special pair The photosystem reaction centers consist of a "special pair" of chlorophyll a molecules that are characterised by their specific absorption maximum. The special pair in photosystem I are designated P700, and those from photosystem II are designated P680. The P is short for pigment, and the number is the specific absorption peak in nanometers for the chlorophyll molecules in each reaction center. Chlorophyll a is common to all eukaryotic photosynthetic organisms, and, due to its central role in the reaction center, is essential for photosynthesis. The accessory pigments such as chlorophyll b and carotenoids are not essential. Some algae, such as brown algae and diatoms, use chlorophyll c as a substitute for chlorophyll b. Historically, red algae have been assumed to have chlorophyll d, although it could not be isolated from all species. This puzzle has recently been resolved, since the chlorophyll d is actually from an epiphytic cyanobacterium (Acaryochloris marina) that lives on the red algae. These cyanobacteria have a ratio of chlorophyll d: chlorophyll a of approximately 30:1, and represent a rare example of a photosystem with chlorophyll d at the reaction center of the photosystem. All other known eukaryotes and cyanobacteria use chlorophyll a. Other chemical variations of chlorophyll are found in photosynthetic bacteria, other than cyanobacteria. Purple bacteria use bacteriochlorophyll, which absorbs infrared light between 800nm - 1000nm, and the green sulphur bacteria chlorobium chlorophyll.
- Nitrocellulose From Wikipedia, the free encyclopedia Jump to: navigation, search Nitrocellulose (Cellulose nitrate, guncotton, flash paper) is a highly flammable compound formed by nitrating cellulose (e.g. through exposure to nitric acid or powerful nitrating agent). This compound, when used as a propellant or low order explosive, was known as guncotton. Contents [hide] 1 Uses 1.1 Guncotton 1.2 Nitrate Film 1.3 Other uses 2 See also 3 External links [edit] Uses Nitrocellulose is a major component of smokeless gunpowder (also see the section on guncotton below). Photographic film Nitrocellulose membrane or nitrocellulose paper is a sticky membrane used for Western blots and immobilizing DNA. It is also used for immobilization of proteins, due to its non-specific affinity for amino acids. Nitrocellulose is widely used as support in diagnostic tests where antigen-antibody binding occur, e.g. pregnancy tests, U-Albumin tests and CRP. When dissolved in ether or other organic solvents, the solution is called collodion, which has been used as a wound dressing and carrier of topical medications since the U.S. Civil War. To this day it is used in Compound W Wart Remover as a carrier of salicylic acid, the active ingredient. Collodion was also used as the carrier for silver salts in some very early photographic emulsions, particularly spread in thin layers on glass plates. Magician's "flash paper", sheets of paper or cloth made from nitrocellulose, which burn almost instantly, with a bright flash, and leave no ash. Nail polish Radon tests for alpha track etches [edit] Guncotton Henri Braconnot, a French chemist, discovered in 1832 that nitric acid, when combined with starch or wood fibers, would produce a lightweight combustible explosive material which he named Xyloïdine. A few years later in 1838 another French chemist Théophile-Jules Pelouze (teacher of Ascanio Sobrero and Alfred Nobel) treated paper and cardboard in the same way. He obtained a similar material he called Nitramidine . Both of these substances were highly unstable, and were not practical explosives. However, Christian Friedrich Schönbein, a German-Swiss chemist, discovered a more practical solution around 1846. He was working in the kitchen at his home in Basle when he spilled a bottle of concentrated nitric acid on the kitchen table. Immediately he reached for the nearest cloth, a cotton apron, and wiped it up. He hung the apron on the stove door to dry, and as soon as it dried there was a flash as the apron exploded. His preparation method was the first to be widely imitated - one part of fine cotton wool to be immersed in fifteen parts of an equal mix of sulfuric and nitric acids. After two minutes the cotton was removed and placed in cold water and washed to set the esterification level and remove all acid residue. It was then slowly dried at a temperature of less than 100°C. The process uses the nitric acid to convert the cellulose into cellulose nitrate and water: HNO3+ C6H10O5 ---> C6H8(NO2)2O5 + H2O. The sulfuric acid is present to prevent the water produced in the reaction from diluting the concentrated nitric acid. The power of guncotton meant that it was adopted for blasting. As a projectile force, it has around six times the gas generation of an equal volume of black powder and produces less smoke and less heating. However the sensitivity of the material during production led to the British, Prussians and French discontinuing manufacture within a year. Jules Verne viewed the development of guncotton with optimism. He referred to the substance several times in his novels including From the Earth to the Moon where guncotton was used to launch a projectile into space. Further research indicated that the key was the very careful preparation of the cotton: unless it was very well cleaned and dried it was liable to explode spontaneously. The British, led by Frederick Augustus Abel, also developed a much lengthier manufacturing process, with the washing and drying times each extended to 48 hours and repeated eight times over. The acid mixture was also changed to two parts sulfuric acid to one part nitric acid. Guncotton remained useful only for limited applications. For firearms, a more stable and slower burning mixture would be needed. Guncotton-like preparations were eventually prepared for this role, known at the time as smokeless powder. Guncotton, dissolved at approximately 25% in acetone, forms a lacquer used in preliminary stages of wood finishing to develop a hard finish with a deep lustre. It is normally the first coat applied, sanded, and followed by other coatings that bond to it. [edit] Nitrate Film Nitrocellulose was used as the first flexible film base, beginning with Eastman Kodak products in August, 1889. Camphor is used as plasticizer for nitrocellulose film. It was used until 1933 for X-ray films (where its flammability hazard was most acute) and for motion picture film until 1951. It was replaced by safety film with an acetate base. The use of nitrocellulose film for motion pictures led to a widespread requirement for fireproof projection rooms with wall coverings made of asbestos. Famously, the US Navy shot a training film for projectionists which included footage of a controlled ignition of a reel of nitrate film which continued to burn even when fully submerged in water. Due to public safety precautions, the London Underground forbade transport of nitrate films on its system until well past the introduction of safety film. A cinema fire caused by ignition of nitrocellulose film stock (foreshadowed by an earlier small fire) was a central plot element in the Italian film Cinema Paradiso. Today nitrate film projection is usually highly regulated and requires extensive precautionary measures including extra projectionist health and safety training. Additionally, projectors certified to run nitrate films have many containment stategies in effect. Among them, this includes the chambering of both the feed and takeup reels in thick metal covers with small slits to allow the film to run through. Furthermore, the projector is modified to accommodate several fire extinguishers with nozzles all aimed directly at the film gate; the extinguishers automatically trigger if a piece of flammable fabric placed near the gate starts to burn. While this triggering would likely damage or destroy a significant portion of the projection components, it would prevent a devastating fire which almost certainly would cause far greater damage. It was discovered decades later that nitrocellulose gradually decomposes, releasing nitric acid which further catalyses the decomposition (usually into a still-flammable powder or goo). Low temperatures can delay these reactions indefinitely. It is estimated that the great majority of films produced during the early twentieth century were lost forever either through this accelerating, self-catalysed disintegration or studio warehouse fires. Salvaging old films is a major problem for film archivists (see film preservation). Nitrocellulose film base manufactured by Kodak can be identified by the presence of the word Nitrate dark letters between the perforations. Acetate film manufactured during the era when nitrate films were still in use was marked Safety or Safety Film between the perforations dark letters. Letters in white or light colors are print-through from the negative. Color negative film was never manufactured with a nitrate base, nor were 8mm or 16mm motion picture film stocks. [edit] Other uses Depending on the manufacturing process, nitrocellulose is esterified to varying degrees. Table tennis balls and some photographic films have a fairly low esterification level and burn comparatively slowly with some charred residue.
- Streptomycin: Streptomycin is effective against gram-negative bacteria, although it is also used in the treatment of tuberculosis. Streptomycin binds to the 30S ribosome and changes its shape so that it and inhibits protein synthesis by causing a misreading of messenger RNA information.