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Chapter 4 Chemistry of Protein 第四章 蛋白质化学

Chapter 4 Chemistry of Protein 第四章 蛋白质化学. 主 要 内 容 Protein 的分子组成 Protein 的分子结构 Protein 结构与功能的关系 Protein 的理化性质. 什么是蛋白质 ( protein) ?. 自然界约 150 余万种生物体中,约有 10 10 ~ 10 12 种蛋白质 ; 人体中大约 10 5 种。. X 衍射法 -- 晶体 --10 余年。世界上最大 PDB 到 2002 年 7 月 23 日存有 18294 种蛋白质的构象数据。. 道尔顿 Dalton, Da :.

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Chapter 4 Chemistry of Protein 第四章 蛋白质化学

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  1. Chapter 4 Chemistry of Protein第四章 蛋白质化学

  2. 主 要 内 容 • Protein的分子组成 • Protein的分子结构 • Protein结构与功能的关系 • Protein的理化性质

  3. 什么是蛋白质( protein)? 自然界约 150余万种生物体中,约有1010~1012种蛋白质;人体中大约105种。 X衍射法--晶体--10余年。世界上最大PDB到2002年7月23日存有18294种蛋白质的构象数据。 道尔顿Dalton, Da:

  4. 第一节Protein的化学组成

  5. 一、Protein的元素element组成 • 元素element构成: 碳——50%-55% 氢——6%-7%       氧——13%-19% Nitrogen (N) ——13%-19% 硫——0%-4% 其他—— • The relation between N content and total protein: mgPr=mgN×6.25

  6. 二、氨基酸amino acids(AA)的化学结构 1. Configuration of AA——L- type

  7. ⒉ AA的碳原子编号——α-AA

  8. 三、Classes of AA

  9. ★ 非极性疏水R-AA

  10. ★极性不带电荷R-AA

  11. ★ 带正电荷R-AA (Basic AA)

  12. ★ 带负电荷R-AA (Acidic AA)

  13. ★ Essential AA and non-essential AA

  14. ★ Non-standard AA • 羟脯氨酸 • 羟赖氨酸 • N-甲基赖氨酸 • 硒代半胱氨酸 • 胱氨酸 • γ-羧基谷氨酸 • 鸟氨酸、瓜氨酸

  15. 四、Classes of Protein • By components: simple protein: albumin, globin conjugated protein: lipoprotein, glycoprotein, ribonucleoprotein • By source: animal/vegetable/microorganism protein • By configuration: fibrous protein, globular protein

  16. 第二节 Chemical structure of protein

  17. 一级结构primary structure • 二级结构secondary structure • 三级结构tertiary structure • 四级结构quaternary structure

  18. 基本概念: 游离氨基酸free AA, FAA 氨基酸残基AA residue 肽键peptide bond:刚性作用 肽平面/单元peptide plane/unit 寡肽oligopeptide 多肽/链polypeptide/chain N-端N-terminal/C-端C-terminal

  19. 谷胱甘肽Glutathione,GSH

  20. Two peptides

  21. N-terminal and C-terminal 多肽链

  22. Chemical bonds holding protein configuration: peptide bond disulfide bond 氢键hydrogen bond 疏水作用hydrophobic interaction 离子键ionic bond 范德华力Van der Waals interaction

  23. 一、 Primary structure • Definition: The linear sequence of amino acids is the primary structure of a protein (including disulfide bridge). • 生物学意义: 基础、病理、进化

  24. 牛胰岛素bovine insulin • Bovine insulin是第一个阐明P. S.的protein,也是第一个人工合成的protein 。它含A、B两条peptide chains,A链有21个AA residues,B链有30个AA residues,此外含6个Cys,构成3个disulfide bridges,其中2个在A、B链之间,A链内还有1个disulfide bridge。

  25. 二、 Secondary structure • Definition:Secondary structure is a local regular occuring structure in proteins and is mainly formed through hydrogen bonds between backbone atoms. • So-called random coils无规则卷曲, loops环状结构or turns转角don't have a stable secondary structure. There are two types of stable secondary structures: Alpha helix(α-螺旋)and beta-sheet (β-折叠). • Alpha-helix and beta-sheet are preferably located at the core of the protein, whereat loops prefer to reside in outer regions.

  26. α-Helix的结构模型 • right-handed • 3.6 aa per turn • hydrogen bond • N-H···O=C

  27. 同向β-Sheet

  28. 反向β-Sheet

  29. β-Turn

  30. 超二级结构super secondary structure: 又称模体/基元motif。 αα/ααα βαβ βββ α-转角-α

  31. 三、Tertiary structure • Definition: Tertiary structure describes the more compact packing of alpha-helices, beta-sheets and random coils with respect to each other on the level of one whole polypeptide chain. • 结构域domain:

  32. 肌红蛋白

  33. 肌红蛋白

  34. 四、quaternary structure • Definition: In biochemistry, quaternary structure is the arrangement of multiple folded protein molecules in a multi-subunit complex.

  35. 血红蛋白

  36. 血红蛋白

  37. 四种结构的比较:

  38. 第三节 Structure and Function of Protein

  39. Primary structure & Function • Dimensional structure & Function

  40. 第四节 Chemicophysical Properties of Protein

  41. 一般性质: 紫外吸收ultraviolet absorption 呈色反应chromogenic reaction 两性电离amphipathic ionization 等电点isoelectric point, pI

  42. Ultraviolet absorption of AA and protein

  43. 茚三酮chromogenic reaction(AA)

  44. Protein双缩脲反应: peptide bond 硫酸铜 紫色或红色 检测protein水解程度 • Protein的Lowry反应: Folin-酚试剂 蓝色复合物

  45. amphipathic ionization and pI ofAA and protein

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