生物化学 蛋白质(二).ppt

Protein蛋白质;（氨基酸分类） ;b. Charged amino acids（带电荷的氨基酸） Aspartic acid(D) R= CH2COOH （天冬氨酸） Glutamic acid(G) R= CH2CH2COOH （谷氨酸） Lysine(K) R= CH2CH2CH2CH2NH2 （赖氨酸） Arginine(R) R= CH2CH2CH2NHC=NH(NH2) （精氨酸） c. Polar amino acids（极性氨基酸） Serine(S) R= CH2OH （丝氨酸） Threonine(T) R= CHOHCH3 （苏氨酸） Tyrosine(Y) R= CH2C6H4OH （酪氨酸） Histidine(H) R= CH2C3H4N2 （组氨酸）;c. Polar amino acids (continued) : Cysteine(C) R= CH2SH （半胱氨酸） Asparagine(N) R= CH2CONH2 （天冬酰氨） Glutamine(Q) R= CH2CH2CONH2 （谷氨酰氨） Glycine(G) R= H （甘氨酸） ;蛋白质的高级结构Secondary, tertiary and quaternary structure;Hydrogen bonds（氢键）it is the main force to maintain the secondary structures of a protein.Hydrophobic interactions（疏水作用）formed by nonpolar side chains of amino acid residues, preferably clustering in the hydrophobic core of a protein.Van der Waals interactions（范氏作用力）are ubiquitous in proteins ;Electrostatic interactions （静电作用）;Amino acid sequence of a protein is highly informative, which contains all the information for folding the polypeptide chain into its native structure.（蛋白质如何折叠成正确的三维结构由基因编码的氨基酸序列所决定）By using database of protein structures, people are able to predict the 3d structure of a polypeptide according to its primary sequence (利用已有的序列-结构数据库，可以根据氨基酸序列预测多肽的三维结构). ;Secondary structure in protein 蛋白质的二级结构;A hydrogen bond between the amide proton and carboxyl oxygen of adjacent peptide groups. （维持蛋白质二级结构的主要作用力来自于氢键） It is the H bonds that link one peptide group to another, to constitute secondary structure for proteins: α- helices （ α-螺旋）andβ-pleated sheets （ β-折叠）;The alpha-helix α-螺旋;Alpha-helices presented as coiled ribbon drawings α-螺旋的一种表示方式;Alpha-helix has a net dipole moment (α-螺旋具有偶极矩) Some AA prefers to form alpha-helix (一些氨基酸易于形成α-螺旋);β – pleated sheets： β –折叠 ;Parallel （平行）;其他二级结构 β – turns： β – 转角;Prediction of structure of α helices by hydropathy plotting the amino acid sequence of a