蛋白质化学讲义1

氨基酸、多肽与蛋白质

(AminoAcids,Peptides&Proteins)赵颖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蛋白质，多肽■

Nuleosides&Nucleotides核酸，核苷酸■

Polysaccharides多糖■

Lipids脂质WhyProtein?ImportanceofProteinsProtein—originatedfromGreek“Proteios”Proteinsarecrucialtoallaspectsoflifeprocess,includingenzymeswhichcatalyzebiochemicalreactionsforenergytransportationandstorage,cellmotionanddivision,etc.Pharmaceuticaluses:Insulin,Hirudin,Melittin,Bombesin,Dolastatins,etc.CyclicpeptidesandPeptidomimeticsProteinasMedicinesInsulin胰岛素Urokinase尿激酶Problem:biodegradable,unstableCyclamide环肽,peptidomimetics拟肽ProteinsasdrugtargetSARSvirusMicrotubule

微管

作业：简述1-2种你所了解的药物蛋白质靶点及作用机制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：蛋白质的基本组成单位20种基本氨基酸：由密码子编码ClassificationofAminoAcidsBasedonpolarity --Neutral(Nonpolar Polar,uncharged)中性 --Acidic酸性 --Basic碱性Basedonchemicalstructuresofsidechain --alkyl脂肪族 --Aromatic芳香族 --Heteroaromatic杂环族StructuresofAminoAcidsStructuresofAminoAcidsNewNaturalL-a-AminoAcids硒代半胱氨酸1-吡咯基赖氨酸UncommonAminoAcids—ModifiedAAinthePeptideChainsDuringPost-translationAAnotfoundinproteinsγ-氨基丁酸组织胺5-羟色胺β-丙氨酸PhysiochemicalPropertiesofAA

兼性离子pI等电点：氨基酸呈电中性的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茚三酮反应ChemicalreactionsofAA丹磺酰氯:DNS-Cl二硝基氟苯二甲氨萘磺酰-aaChemicalreactionsofAA苯异硫氰酸酯苯氨基硫甲酰-aa苯乙内酰硫脲ChemicalreactionsofAA荧光胺Separationand

PurificationMethodsExtractedwithwaterordilutedalcoholIonexchangedchromatography离子交换层析

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

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

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

PurificationStrategyPreparationofAAExtractedfrombiologicalmaterialsFermentationEnzymaticsynthesis

Chemicalsynthesis

Strecker’ssynthesis,Bucherer’ssynthesisPreparationofAAStrecker’ssynthesisBucherer’ssynthesis合成外消旋产物PreparationofAAResolution --Formationofsaltswithchiralacidsorbases --Formationofdiastereoisomericamide --Formationofdiastereoisomericshiff’sbase --SeparationonchiralHPLC --EnzymaticresolutionAsymmetricsynthesis

--Corey’sapproachmimickingVB6catalysedtransamination --TransaminationcatalysedbyaminotransferaseAsymmetricChemicalSynthesis—Corey’smethod基于氨基酸生物合成途径中α-酮酸转氨基作用，设计了模拟VB6转氨基作用的手性试剂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兼性离子性质Macromolecularproperties—diffusion扩散(centrifugation应用：离心分离),viscosity粘度,impermeability不透过性Denaturation变性—destroyofnon-covalentbondsinproteinsPrecipitation沉淀—salts,heavymetals,alkaloids,organicsolvents,heatColorfulreactions呈色反应—biuret,ninhydrin,dansylchlorideUVadsorption紫外吸收—280nmcharacteristicbandsChemicalInteractionsinPeptidesTheprimarystructureofproteinsTheprimarystructureincludes:numberofpeptidebonds;TheNandCterminalofpeptide;number,typeandsequenceofaminoacidineachpeptidechain氨基酸如何连接成肽链及在肽链中的排列顺序Thesecondarystructureofproteins:

a-helixThesecondarystructureofproteins:

b-pleatedsheetThesecondarystructureofproteinsOthers:

b-turn(richinprolines)hairpinrandomcoils

借助主链的氢键形成具有周期性的构象Super-secondarystructures,domains结构域andmotifs模体:thestructuresbetweensecondaryandtertiarystructuresThetertiarystructureofproteinsThetertiarystructureofproteinsApeptideconsistsofdifferentportionsofa-helix,b-sheet,b-turnandrandomcoil,whichfoldstoaglobalconformationNon-polarsidechainsareburiedinthehydrophobiccore,whilepolarsidechainsexposedtothesurfaceofthemoleculeHydrophobicpocketsneartothesurfaceareusuallyfound,whichservebindingsitesoractivesitesinenzymes一条肽链完整折叠形成的构象ThequarternarystructureofproteinsFourl