蛋白質(zhì)化學(xué)講義1

氨基酸、多肽與蛋白質(zhì)

(AminoAcids,Peptides&Proteins)趙穎2012.9.18R:W334Tel:63165211E-mail:zhaoying@ContentsIntroductionCompositionofProteins－AminoAcidsClassificationofProteinsPhysio-chemicalPropertiesofProteinsMolecularStructuresofProteinsStructure&FunctionRelationshipofProteinsIsolation,purificationandidentificationofProteins&PeptidesDeterminationofPrimaryStructuresofProteinsDeterminationofStereoStructuresofProteinsChemicalsynthesisandBiosynthesisofPeptides&ProteinsIntroductionProteios—Protein首要，第一Biomacromolecules生物大分子■

Proteinsandpeptides蛋白質(zhì)，多肽■

Nuleosides&Nucleotides核酸，核苷酸■

Polysaccharides多糖■

Lipids脂質(zhì)WhyProtein?ImportanceofProteinsProtein—originatedfromGreek“Proteios”Proteinsarecrucialtoallaspectsoflifeprocess,includingenzymeswhichcatalyzebiochemicalreactionsforenergytransportationandstorage,cellmotionanddivision,etc.Pharmaceuticaluses:Insulin,Hirudin,Melittin,Bombesin,Dolastatins,etc.CyclicpeptidesandPeptidomimeticsProteinasMedicinesInsulin胰島素Urokinase尿激酶Problem:biodegradable,unstableCyclamide環(huán)肽,peptidomimetics擬肽ProteinsasdrugtargetSARSvirusMicrotubule

微管

作業(yè)：簡(jiǎn)述1-2種你所了解的藥物蛋白質(zhì)靶點(diǎn)及作用機(jī)制Peptides,Proteins:

Structures&FunctionsStructuresStructures 1.Primarystructures 2.AdvancedstructuresMethods

1.

Extraction&purification 2.StructuredeterminationFunctionsFunctions Structuralproteins Enzymes,etc.Methods

Spectroscopy

StructuresofAminoAcidsAminoacidsarethebuildingblocksofnaturallyoccurringproteins.Itiswidelyrecognizedthatonly20L-a-aminoacidsconstituteallproteins.氨基酸：蛋白質(zhì)的基本組成單位20種基本氨基酸：由密碼子編碼ClassificationofAminoAcidsBasedonpolarity --Neutral(Nonpolar Polar,uncharged)中性 --Acidic酸性 --Basic堿性Basedonchemicalstructuresofsidechain --alkyl脂肪族 --Aromatic芳香族 --Heteroaromatic雜環(huán)族StructuresofAminoAcidsStructuresofAminoAcidsNewNaturalL-a-AminoAcids硒代半胱氨酸1-吡咯基賴氨酸UncommonAminoAcids—ModifiedAAinthePeptideChainsDuringPost-translationAAnotfoundinproteinsγ-氨基丁酸組織胺5-羥色胺β-丙氨酸PhysiochemicalPropertiesofAA

兼性離子pI等電點(diǎn)：氨基酸呈電中性的pHPhysiochemicalPropertiesofAA(2)Ionizationofsidechain: --Acidic:Glu,Asp(COOH),Tyr(phenol),Cys(thiol) forAsp:pKa(β-COOH)>pKa(α-COOH) --Basic: ForLys:pKa(ε-NH2)>pKa(α-NH2)ChemicalreactionsofAA茚三酮反應(yīng)ChemicalreactionsofAA丹磺酰氯:DNS-Cl二硝基氟苯二甲氨萘磺酰-aaChemicalreactionsofAA苯異硫氰酸酯苯氨基硫甲酰-aa苯乙內(nèi)酰硫脲ChemicalreactionsofAA熒光胺Separationand

PurificationMethodsExtractedwithwaterordilutedalcoholIonexchangedchromatography離子交換層析

stronglyacidic—sulphopropyl(SP)Sepharose weaklyacidic—carboxymethyl(CM)cellulose

stronglybasic—quaternaryammonium(Q)Sepharose weaklybasic—dimethylaminoethyl(DEAE)cellulose

--ninhydrin,OPA(o-phthaldehyde鄰苯二甲醛),fluorescaminederivativesGCandHPLC GC:PTH-aa→TMS三甲基硅derivatives HPLC:DNFB,OPA,DNS,PITC,fluorescaminederivativesSeparationand

PurificationStrategyPreparationofAAExtractedfrombiologicalmaterialsFermentationEnzymaticsynthesis

Chemicalsynthesis

Strecker’ssynthesis,Bucherer’ssynthesisPreparationofAAStrecker’ssynthesisBucherer’ssynthesis合成外消旋產(chǎn)物PreparationofAAResolution --Formationofsaltswithchiralacidsorbases --Formationofdiastereoisomericamide --Formationofdiastereoisomericshiff’sbase --SeparationonchiralHPLC --EnzymaticresolutionAsymmetricsynthesis

--Corey’sapproachmimickingVB6catalysedtransamination --TransaminationcatalysedbyaminotransferaseAsymmetricChemicalSynthesis—Corey’smethod基于氨基酸生物合成途徑中α-酮酸轉(zhuǎn)氨基作用，設(shè)計(jì)了模擬VB6轉(zhuǎn)氨基作用的手性試劑EnzymeMediatedAsymmetricSynthesisEnzymaticsynthesisofunusualaminoacidsfromnaturallyabundantones.BiosynthesisofaminoacidsEssentialaminoacids必需氨基酸:--Cannotbeself-synthesized--Inhuman:Phe,Lys,Leu,Ile,Met,Thr,Trp,Val,HisandArgNonessentialaminoacids非必需氨基酸: --Canbeself-synthesized--PlantscansynthesizeallkindsofaminoacidsBiosynthesisofaminoacidsoriginatesfromkeyintermediateproductsofmetabolicpathwaysBiosynthesisofaminoacidsDegradationofAminoAcidtoa-KetoacidVB6ClassificationofProteinsShapeofthemoleculesCompositionSolubilityFunctionGlycoprotein—Glycansiscovalentlyboundtoproteinsorpeptides.GlycoproteinsVersatilefunctions—enzymes,hormones,interferons,lectins,memberaneblocks,bloodtyperecognitionStructurecharacteristics—openorbranchedchainsofsugarmoietiescomposedofseveraltypeofsugars,includingpentose(D-xylose),hexose(D-galactose),hexosederivatives(N-acetyl-D-glucosamine),sialicacid,etc.C-1ofsugarcovalentlyboundtoOHinaminoacidsidechains,oramideofasparagine.Solubility—mostofthemarewatersoluble.Physio-chemicalPropertiesofPeptidesandProteinsZwitterionizationandisoelectricpoint—leastsolubleatisoelectricpoint兼性離子性質(zhì)Macromolecularproperties—diffusion擴(kuò)散(centrifugation應(yīng)用：離心分離),viscosity粘度,impermeability不透過性Denaturation變性—destroyofnon-covalentbondsinproteinsPrecipitation沉淀—salts,heavymetals,alkaloids,organicsolvents,heatColorfulreactions呈色反應(yīng)—biuret,ninhydrin,dansylchlorideUVadsorption紫外吸收—280nmcharacteristicbandsChemicalInteractionsinPeptidesTheprimarystructureofproteinsTheprimarystructureincludes:numberofpeptidebonds;TheNandCterminalofpeptide;number,typeandsequenceofaminoacidineachpeptidechain氨基酸如何連接成肽鏈及在肽鏈中的排列順序Thesecondarystructureofproteins:

a-helixThesecondarystructureofproteins:

b-pleatedsheetThesecondarystructureofproteinsOthers:

b-turn(richinprolines)hairpinrandomcoils

借助主鏈的氫鍵形成具有周期性的構(gòu)象Super-secondarystructures,domains結(jié)構(gòu)域andmotifs模體:thestructuresbetweensecondaryandtertiarystructuresThetertiarystructureofproteinsThetertiarystructureofproteinsApeptideconsistsofdifferentportionsofa-helix,b-sheet,b-turnandrandomcoil,whichfoldstoaglobalconformationNon-polarsidechainsareburiedinthehydrophobiccore,whilepolarsidechainsexposedtothesurfaceofthemoleculeHydrophobicpocketsneartothesurfaceareusuallyfound,whichservebindingsitesoractivesitesinenzymes一條肽鏈完整折疊形成的構(gòu)象ThequarternarystructureofproteinsFourl