英文课件-氨基酸和肽.ppt

《英文课件-氨基酸和肽.ppt》由会员上传分享，免费在线阅读，更多相关内容在教育资源-天天文库。

1、BiochemistryAminoAcidsandPeptidesAminoAcidsAminoacid:acompoundthatcontainsbothanaminogroupandacarboxylgroup-Aminoacid:anaminoacidinwhichtheaminogroupisonthecarbonadjacenttothecarboxylgroupalthough-aminoacidsarecommonlywrittenintheunionizedform,theyaremoreproperl

2、ywritteninthezwitterion(internalsalt)form问题蛋白质氨基酸的构型是什么样的？ChiralityofAminoAcidsWiththeexceptionofglycine,allprotein-derivedaminoacidshaveatleastonestereocenter(the-carbon)andarechiralthevastmajorityof-aminoacidshavetheL-configurationatthe-carbonChiralityofAminoA

3、cidsComparisonofthestereochemistryofalanineandglyceraldehyde(Fischerprojectionformulas)蛋白质氨基酸分类问题1.蛋白质氨基酸有哪些非极性侧链基团？（5-8）2.蛋白质氨基酸有哪些极性侧链基团？（5-9）3.蛋白质氨基酸有哪些酸性侧链基团？（5-10）4.蛋白质氨基酸有哪些碱性侧链基团？（5-11）1.在哪些蛋白质中发现以下修饰氨基酸？-羧基谷氨酸、5-羟赖氨酸、4-羟哺氨酸、O-磷酸丝氨酸、甲状腺素？（5-13）20Protein-Der

4、ivedAA20Protein-DerivedAA20Protein-DerivedAA20Protein-DerivedAA20Protein-DerivedAANotethesestructuralfeatures1.All20are-aminoacids2.For19ofthe20,the-aminogroupisprimary;forproline,itissecondary3.Withtheexceptionofglycine,thea-carbonofeachisastereocenter4.Isoleuci

5、neandthreoninecontainasecondstereocenter5.Thesulfhydrylgroup(pKa8.3)ofcysteine,theimidazolegroup(pKa6.0)ofhistidine,andthephenolichydroxyl(pKa10.1)ofphenylalaninearepartiallyionizedatpH7.0,buttheionicformisnotthemajorformatthispHUncommonAminoAcidsEachexampleisderiv

6、edfromacommonaminoacidbythemodificationshownincolorhydroxylysineandhydroxyprolinearefoundonlyinafewconnectivetissuessuchascollagenthyroxineisfoundonlyinthethyroidglandIonizationofAminoAcidsTitrationofAminoAcidsFigure(a)TitrationofalaninewithNaOHTitrationofAminoAcid

7、sFigure(b)TitrationofhistidinewithNaOH氨基酸解离问题1.某一氨基酸的解离过程1.甘氨酸的羧基和乙酸的羧基哪一种更酸？2.如果甘氨酸的羧基更酸，解释为什么？3.丙氨酸的氨基和丙胺的氨基哪一个更碱？4.精氨酸的胍基与赖氨酸的-氨基哪一种更碱？5.如果精氨酸的胍基更碱，解释为什么？6.胍基和-氨基哪一种更适合作为质子受体？7.三种碱性侧链中哪一种既可作为质子供体又可作为质子受体？Acidity:-COOHGroupsTheaveragepKaofan-carboxylgroupis2.

8、19,whichmakesthemconsiderablystrongeracidsthanaceticacid(pKa4.76)thegreateracidityoftheaminoacidcarboxylgroupisduetotheelectron-withdrawinginduct