1、§2Amino Acidsand Proteins§2.1Amino Acids (aa)§2.2Peptides and Proteins1中山大學生物化學一+細胞生物學詳見：網學天地（，）；咨詢、考點、命題規律獨家講解§2.1Amino Acids2.Class: Standard AAs Nonstandard AAsChemical properties: Titration Curves Characteristic Reactions3.2中山大學生物化學一+細胞生物學詳見：網學天地（，）；咨詢、考點、命題規律獨家講解1. Structura

2、l Features1.Structural Features (1)General formulaEach has a different side chain R( R=“Remainder of the molecule”)3中山大學生物化學一+細胞生物學詳見：網學天地（，）；咨詢、考點、命題規律獨家講解1.Structural Features (2)hybridhybrid4中山大學生物化學一+細胞生物學詳見：網學天地（，）；咨詢、考點、命題規律獨家講解1.Structural Features (3)ChiralityEnantiomer(對映異構體)5中山大學生物化學一+細胞生物

3、學，、考點、命題規律獨家講解詳見：網學天地（）；咨詢1.Structural Features (4)TheDextrorotary-andLevorotary-formsofAAsarenamed in reference to the absolute configuration of D-and L- glyceraldehydesGo6perspective formulas1.Structural Features (5) projection formulas 爾(Fischer)投影式 Perspective formulasThe horizontal bonds projec

4、t out of the plane of the paper, the vertical behind.7中山大學生物化學一+細胞生物學詳見：網學天地（，）；咨詢、考點、命題規律獨家講解1.Structural Features (6)l About AA chirality1. Normally, the a-carbon is the only chiral center with several exceptions.2. OnlytheL-AAshavebeenfoundinproteins(D-isomers have been found only in small peptid

5、es of bacteria cell walls and in some peptide antibiotics).3. The correlation of structure with optical rotation isvery complex and has not beensuccessful to date! tell anything about(i.e., the D- and L-signs their optical rotation!)donot8中山大學生物化學一+細胞生物學詳見：網學天地（，）；咨詢、考點、命題規律獨家講解§2.1Amino Acids1

6、.Structural Features Standard AAs Nonstandard AAsChemical properties: Titration Curves Characteristic Reactions3.9中山大學生物化學一+細胞生物學詳見：網學天地（，）；咨詢、考點、命題規律獨家講解2. Class:2.Class (1)Standard AAs:L-enantomerdirectly incorporated into a proteinNonstandard AAs:Derivative from Standard AAs10中山大學生物化學一+細胞生物學詳見：網學

7、天地（，）；、考點、命題規律獨家26講解2.Class (2)All the AAs were given a trivial (common) nameAsparagine from asparagus (1st, in 1806)Glutamate from wheat gluten (sticky)Tyrosine from cheese (“tyros” in Greek)EachAAisgivenathree-letterabbreviationand a one-letter symbol. They often use the firstthreeletterandthefirs

8、tletter.Whenthereisconfusion, an alternative is used.11中山大學生物化學一+細胞生物學詳見：網學天地（，）；咨詢、考點、命題規律獨家講解List of Amino Acids and Their Abbreviations12中山大學生物化學一+細胞生物學詳見：網學天地（，）；咨詢、考點、命題規律獨家講解AspartateAspDGlutamateGluEYellow amino acids contain sulfur. Green amino acids can be phosphorylated.Electrically Charge

9、d (negative and hydrophilic)Electrically Charged (positive and hydrophilic)lysineLysKarginineArgRhistidineHisHPolar AAs (hydrophilic)serineSerSthreonineThrTcysteineCysCtyrosineTyrYasparagineAsnNglutamineGlnQNonpolar AAs (hydrophobic)amino acid3 letter code1 letter codeglycineGlyGalanineAlaAvalineVal

10、VleucineLeuLisoleucineIleImethionineMetMphenylalaninePheFtryptophanTrpWprolineProP2.Class (3)甘氨酸丙氨酸脯氨酸纈氨酸異亮氨酸甲硫氨酸亮氨酸132.Class (4)苯丙氨酸F絡氨酸色氨酸W14中山大學生物化學一+細胞生物學詳見：網學天地（，）；咨詢、考點、命題規律獨家講解15中山大學生物化學一+細胞生物學詳見：網學天地（，）；咨詢、考點、命題規律獨家講解Lambert-Beers law:A=Log Io/I = ecle, extinction coefficient; c, concentrati

11、on;l, optical length2.Class (5)絲氨酸蘇氨酸半胱氨酸天冬酰胺谷氨酰胺16Cystine is dimer of cysteine17中山大學生物化學一+細胞生物學詳見：網學天地（，）；咨詢、考點、命題規律獨家講解2.Class (6)K 賴氨酸組氨酸精氨酸18中山大學生物化學一+細胞生物學詳見：網學天地（，）；咨詢、考點、命題規律獨家講解2.Class (7)D 天冬氨酸E 谷氨酸19中山大學生物化學一+細胞生物學詳見：網學天地（，）；咨詢、考點、命題規律獨家講解2.Class (8)Two additional AAs (rare) have been iden

12、tified and are standard AAs.Selenocysteine: encoded by the RNAnucleotidetripletUGAfoundinArchaea,eubacteriaandanimals including mammals.Pyrrolysine:encodedbytheRNAnucleotidetriplet UAG, found in Archaea, and eubacteria Science (2002) vol. 296, 1409; 1459; 1462Nature may yet surprise us with more dir

13、ectly encoded amino acids.20中山大學生物化學一+細胞生物學詳見：網學天地（，）；咨詢、考點、命題規律獨家講解Two rare standard AAs21中山大學生物化學一+細胞生物學詳見：網學天地（，）；咨詢、考點、命題規律獨家講解2.Class (9)Nonstandard AAs are found in certain proteinsandaremadeafterthestandardaminoacidshave been incorporated into proteins.Some 300 additional nonstandard AAs are

14、found in cells, but not in proteins (e.g., ornithine 鳥氨酸 and citrulline 瓜氨酸, intermediates in aminoacid metabolism).22中山大學生物化學一+細胞生物學詳見：網學天地（，）；咨詢、考點、命題規律獨家講解in prothrombin (凝血酶原）in collagen (膠原)in collagen (膠原)in myosin(肌球蛋白)中山大學生物化學一+細胞生物學詳見：網學天地（in elastin (彈性蛋白).23，）；咨詢、考點、命題規律獨家講解鳥氨酸瓜氨酸24中山大學生物

15、化學一+細胞生物學詳見：網學天地（，）；咨詢、考點、命題規律獨家講解§2.1Amino Acids1.2.Structural FeaturesClass: Standard AAs Nonstandard AAs Titration Curves Characteristic Reactions25中山大學生物化學一+細胞生物學詳見：網學天地（，）；咨詢、考點、命題規律獨家講解3. Chemical properties:3.Chemical properties: acid-base26中山大學生物化學一+細胞生物學詳見：網學天地（，）；咨詢、考點、命題規律獨家講解3.Chemi

16、cal properties: isoelectric pointApHatwhichanAAhasequalpositiveandnegative charge-isoelectric point (PI).273.Chemical properties: titration curves (1)28中山大學生物化學一+細胞生物學詳見：網學天地（，）；咨詢、考點、命題規律獨家講解3.Chemicalproperties: titration curves (2)29中山大學生物化學一+細胞生物學詳見：網學天地（，）；咨詢、考點、命題規律獨家講解3.Chemicalproperties: ti

17、tration curves (3)303.Chemical properties:Characteristic Reactions32中山大學生物化學一+細胞生物學詳見：網學天地（，）；咨詢、考點、命題規律獨家講解(水合)茚三酮二硝基氟苯熒光胺丹磺酰氯34§2Amino Acidsand Proteins§2.1Amino Acids§ 2.2Peptides and Proteins35中山大學生物化學一+細胞生物學詳見：網學天地（，）；咨詢、考點、命題規律獨家講解§2.2Peptides and Proteins 1. Chains of AAs

18、2. Vast Range of Sizes3.4.Other Chemical GroupsCharacteristic AA Compositions361. Chains of AAs (1)D G: not 5 beingkcal/mol,lifetimeofapeptideabletobond: 1000 years in H2O without catalyst.occur spontaneously37The condensation reaction can occur repeatedly to form oligopeptides (less than 50 aa), po

19、lypeptides (btw 50-100 aa), and proteins (longer).1. Chains of AAs (2)An amino acid unit in a peptide chain is called a residue.Although the M of 20 AAs is 138, the M of AAs in proteins is about 128 because the small AAs predominate in most proteins.The M of residues in proteins can be: 128-18=1101.

20、 Chains of AAs (3)C-terminalN-terminalBiosynthesis starts from the N-terminal. By convention, the N-terminal is put at the left (C-terminal at the right).40Each peptide has a characteristic titration curve and an isoelectric point (pI).§2.2Peptides and Proteins1. Chains of AAs 2. Vast Range of

21、Sizes 3.4.Other Chemical GroupsCharacteristic AA Compositions5. Homology among Species41中山大學生物化學一+細胞生物學詳見：網學天地（，）；咨詢、考點、命題規律獨家講解2. Vast Range of Sizes (1)Some short peptides aNeurotransmitters/neuromodulatorsHormonesSome short peptides aantibiotics42中山大學生物化學一+細胞生物學詳見：網學天地（，）；咨詢、考點、命題規律獨家講解2. Vast Ra

22、nge of Sizes (2)43§2.2Peptides and Proteins1. Chains of AAs2. Vast Range of Sizes 3. Other Chemical Groups 4.Characteristic AA Compositions44中山大學生物化學一+細胞生物學詳見：網學天地（，）；咨詢、考點、命題規律獨家講解3. Other chemical groups45中山大學生物化學一+細胞生物學詳見：網學天地（，）；咨詢、考點、命題規律獨家講解These proteins are referred as conjugated protei

23、ns while the amino acid part alone is called apoprotein.§2.2Peptides and Proteins1. Chains of AAs2. Vast Range of Sizes3.Other Chemical Groups 4. Characteristic AA Compositions46中山大學生物化學一+細胞生物學詳見：網學天地（，）；咨詢、考點、命題規律獨家講解47TheEnd中山大學生物化學一+細胞生物學詳見：網學天地（48，）；咨詢、考點、命題規律獨家講解光 (電磁波) 是橫波YXEOMAZ電場矢量E, 磁場矢量B, 偏振面YZ，波長l=OA，波數n1/l，頻率 f1/T，波速c = f l49中山大學生物化學一+細胞生物學詳見：網學天地（，）；咨詢、考點、命題規律獨家講解自然光與平面偏振光偏振片（器）自然光電場矢量E的方向是平面