第二章

蛋白質(zhì)化學CHEMISTRYOFPROTEINS第一節(jié)蛋白質(zhì)在生命活動中的重要生理功能IMPORTANTROLESOFPROTEINSINLIFE第二節(jié)蛋白質(zhì)的分子組成MOLECULARCOMPOSITIONOFPROTEINS第三節(jié)蛋白質(zhì)的分子結(jié)構(gòu)MOLECULARSTRUCTUREOFPROTEINS第四節(jié)蛋白質(zhì)結(jié)構(gòu)與功能的關(guān)系RELATIONSHIPBETWEENFUNCTIONANDSTRUCTURE第五節(jié)蛋白質(zhì)的理化性質(zhì)PHYSICO-CHEMICALPROPERTIESOFPROTEINS第一節(jié)蛋白質(zhì)在生命活動中的重要功能IMPORTANTROLESOFPROTEINSINLIFE●PROTEINCONTENSOFHUMANBODY

（人體蛋白質(zhì)的含量）Carbohydrates（糖類）,Lipids（脂類）,Proteins（蛋白質(zhì)）,NucleicAcids（核酸）,Water（水）,Middle/Smallorganic&inorganicMolecules（中小分子有機化合物及無機物分子）

15~20%expressedinwholebody（全重/濕重）~45%expressedindryweight（干重）Proteome(蛋白質(zhì)組):ThecompletesetofproteinsinacellProteomics(蛋白質(zhì)組學):Thecatalogingandanalysisofproteinstodeterminewhenaproteinisexpressed,howmuchismade,andwithwhatotherproteinstheproteinmayinteract●PROTEINMULTIFUNCTIONS（蛋白質(zhì)的多功能）●EssentialCompositionofTissuesorCells

（組織或細胞的基本組成成分）

●MaintainingGrowth,RenewandRepair

（維持生長、更新和修復）●SpecificRoles（特殊功能）

Catalysis(催化):i.e.,enzymes(酶)Regulation(調(diào)節(jié)):e.g.,hormones(激素);regulatoryproteins(調(diào)節(jié)蛋白/轉(zhuǎn)錄因子)Transport(運輸)：Hb,Apoprotein(載脂蛋白),Albumin(清蛋白)Motion/Mobile(運動、移動)：Actin(肌動蛋白),Myosin(肌球蛋白),Tubulin(微管蛋白)

Signaling(信號轉(zhuǎn)導)：Gproteins,ATM/ATRStorage(儲存)：Ferritin(鐵蛋白)

Defence(防御/保護)：Immuniglobins(Igs)……●

OxidativeDegradationforProvidingEnergy（氧化降解供能）第二節(jié)蛋白質(zhì)的分子組成MOLECULARCOMPOSITIONOFPROTEINS●MOLECULARCOMPOSITIONOFPROTEINS——ChemicalElements(化學元素)

C(50~55%),H(6~8%),O(19~24%),N(13~19%,average16%),

S(0.0~4.0%),Metal/non-metalZn、Fe、Mg、Cu…,P、IProteincontentin100gsample=

Ncontentpergram×6.25×100●STRUCTURALUNIT——AMINOACIDSA.AminoAcids(氨基酸)

L-α-aminoacidB.20AminoAcidsandIts’Structure(P.16-174)L-AlanineD-Alanine(SH)(H)R●PHYSICO-CHEMICALPROPERTIESOFAMINOACIDS(氨基酸的理化性質(zhì))DipolarStateofAminoAcids(氨基酸的兩性解離):Zwitterion(兼性離子)；Isoelectricpoint(pI)(等電點)B.UVAbsorption(紫外吸收):aromaticaminoacidsW,Y,F

at280nmC.ColourReaction(呈色反應):D.NinhydrinReaction(茚三酮反應):

blue-violet,570nm;yellowP440nm;brownNE.PeptideFormation(成肽反應):residues(殘基)H3N+—HC—COO-RH3N+—HC—COO-R+—→H3N+—H

OC—

CR—N—HC—COO-R|H–H2OGlutathione(GSH)第三節(jié)蛋白質(zhì)的分子結(jié)構(gòu)MOLECULARSTRUCTUREOFPROTEINSAminoAcidSequencesinPeptides(NtoC)●PEPTIDEBOND（肽鍵），PEPTIDEPLANE（肽平面）ANDPOLYPEPTIDE（多肽）●PRIMARYSTRUCTURE（一級結(jié)構(gòu)）

φψ●SECONDARYSTRUCTURE（二級結(jié)構(gòu)）Secondarystructurereferstoalocallyspatialarrangementofacertainpeptidesegmentbyhydrogenbondingbetweenpeptidebonds（基于氫鍵所導致的肽段在局部空間的排列形式）,i.e.,therelativepositionsofbackboneatomsofthispeptidesegment（肽段骨架原子的相對位置）.Hydrogenbondsareresponsibleforstabilizingthesecondarystructure.Therearefourcommontypesofsecondarystructure:

-helix（

-螺旋）,β-pleatedsheet（β-折疊/β-片層）,-turn(

-bend)（β-轉(zhuǎn)角）,Ω-loop(Ω-環(huán))andrandomcoil（隨機卷曲）.The

-helix

structuredependsonintramolecular

hydrogenbondingbetweenthe-NHand–COgroupsofpeptidebonds.Alongtheaxisofan

-helix,theriseperaminoacidresidueis1.5?,andthereare3.6residuesperturn,whichmakesthepitchofeachturn5.4?.Most

-helicesofknownpolypeptidesareright--handed.Some(e.g.,myoglobin,Hb)haveahighpercentageof

-helicalstructures;others(chymotrypsinandCytc)havealowpercentage.Theaminoacidsequenceinfluencethedegreeofhelicalstructureinagivenpolypeptide.Theβ-pleatedsheetstructuredependsoninter-molecular(interchain)

hydrogenbonding.Oneofthesestructuresistheantiparallel

β-pleatedsheet,inwhichtheindividualpolypeptidechainisextendedandismaximallybondedtotwoneighboringpolypeptides.Inanantiparallelstructure,theneighboringpolypeptidesarealignedinanoppositeN-to-Cterminusdirection.Ifinaβ-pleatedstructure,thehydrogen-bondedneighboringpolypeptidesarealignedinthesameN-to-Cdirection,thestructureisparallelβ-pleated.SUPERSECONDARYSTRUCTURE（超二級結(jié)構(gòu)）:Adistinctfoldingpatternforelementsofsecondarystructure,observedinoneormoreproteins;alsocalledamotiforfold.(局部肽段中相連的幾個二級結(jié)構(gòu)單元在空間的折疊形式，即超二級結(jié)構(gòu)，又稱基序或模體)CD4consistsoffoursimilardomainsDOMAIN(域結(jié)構(gòu)):Adistinctstructuralunitofapeptide（肽鏈中不同的結(jié)構(gòu)單位即結(jié)構(gòu)域，或域結(jié)構(gòu)）;domainsmayhaveseparatefunctionsandmayfoldasindependent,compactunits●TERTIARYSTRUCTURE（三級結(jié)構(gòu)）HydrogenBonding,SaltingBond,HydrophobicInteraction,DisulfidebondVanderWaal’sForce●QUATERNARYSTRUCTURE（四級結(jié)構(gòu)）Subunits（亞基）ProstheticGroup/Co-factor（輔助基團/輔助因子）

第四節(jié)蛋白質(zhì)結(jié)構(gòu)與功能的關(guān)系PROTEINFUNCTIONISRELATEDTOITSSTRUCTURE●PRIMARYSTRUCTUREISTHEBASEOFHIGHSTRUCTUREANDFUNCTION(一級結(jié)構(gòu)是高級結(jié)構(gòu)、功能的基礎(chǔ))

A.ProteinswithSimilarStructuresHaveSimilarFunctionsB.ProteinswithDifferentStructuresHaveDifferentFunctionsC.PrimaryStructureDetermines2nd/3rd/4thStructureD.PrimaryStructureDeterminesFunctionsE.Moleculardiseases（分子病）C-Y-I-Q-N-C-P-L-G-NH2SSC-Y-F-Q-N-C-P-R-G-NH2SSADH加壓素Oxytocin催產(chǎn)素●PROTEINFUNCTIONRELATESTOITSCONFORMATION(蛋白質(zhì)構(gòu)象表現(xiàn)功能）A.AllostericEffect&AllostericRegulation（別位效應與別為調(diào)節(jié)）

B.Denaturation/Renaturation&Function（變性、復性與功能）C.ActivationofZymogen（酶原的激活）D.ConformationalDiseases（構(gòu)象?。゛ctiveinactiveactiveO2O2O2O2O2第五節(jié)蛋白質(zhì)的理化性質(zhì)PHYSICO-CHEMICAL