初二地理上冊復(fù)習(xí)題

1、二、肽（一）肽和肽鍵的結(jié)構(gòu) 肽鍵的C和N均為sp2雜化，有部分雙鍵的性質(zhì)，相關(guān)的6個原子處于共平面，稱作肽平面，肽平面內(nèi)兩個C多處于反式構(gòu)型。 The peptide bond is shown in its usual trans conformation of carbonyl O and amide H. The C atoms are the -carbons oftwo adjacent amino acids joined in peptide linkage. The dimensions and angles are the average values observed by

2、 crystallographic analysis of amino acids and small peptides. The peptide bond is the light gray bond between C and N. The partial double bond character of the peptide bond. Resonance interactionsamong the carbon, oxygen, and nitrogen atoms of the peptide group can be represented by two resonance ex

3、tremes (a and b). (a) The usual way the peptide atoms are drawn. (b) In an equally feasible form, the peptide bond is now a double bond; the amide N bears a positive charge and the carbonyl O has a negative charge. (c) The actual peptide bond is best described as a resonance hybrid of the forms in (

4、a) and (b). Significantly, all of the atoms associatedwith the peptide group are coplanar, rotation about C-N is restricted, and thepeptide is distinctly polar.The pentapeptide serylglycyltyrosylalanylleucine, or SerGlyTyrAlaLeu. Peptides are named beginning with the aminoterminal residue, which by

5、convention is placed at the left. The peptide bonds are shaded in yellow; the R groups are in red.（二） 肽的物理和化學(xué)性質(zhì) 肽的等電點計算需先分別判斷各解離基團的帶電荷情況，再統(tǒng)計凈電荷的量（P166表4-6）。 肽的化學(xué)反應(yīng)與氨基酸類似，同時，由于肽鍵的存在,肽可以進行雙縮脲反應(yīng)。Alanylglutamylglycyllysine. This tetrapeptide has one free -amino group, one free -carboxyl group, and two i

6、onizable R groups. The groups ionized at pH 7.0 are in red.（三）天然存在的活性肽 主要有：肽類激素、肽類抗生素和肽類毒素。有關(guān)內(nèi)容將在后續(xù)章節(jié)介紹。環(huán)狀八肽，真核生物環(huán)狀八肽，真核生物RNA合成的抑制劑合成的抑制劑+H3N-Tyr-Gly-Gly-Phe-Met-COO- Met-腦啡肽 +H3N-Tyr-Gly-Gly-Phe-Leu-COO- Leu-腦啡肽CysTyrILeGlnAsnCysProLeuGlyNH2SS牛催產(chǎn)素CysTyrGlnAsnCysProSSPheArgGlyNH2牛加壓素*均為9（8）肽，僅2個氨基酸有

7、差別，生理功能差別極大。 L-Leu-D-Phe-L-Pro-L-Val L-Orn L-Orn L-Val-L-Pro-D-Phe-L-Leu 短桿菌肽短桿菌肽S(S(環(huán)十肽環(huán)十肽) ) 由細菌分泌的多肽，是氧化磷酸化的解偶聯(lián)劑，由細菌分泌的多肽，是氧化磷酸化的解偶聯(lián)劑，有很強的抗菌作用，但有溶血作用，不能做注有很強的抗菌作用，但有溶血作用，不能做注射劑。含有射劑。含有D-D-氨基酸和一些不常見氨基酸，如氨基酸和一些不常見氨基酸，如鳥氨酸（鳥氨酸（Ornithine, Ornithine, 縮寫為縮寫為 OrnOrn）。）。 三、蛋白質(zhì)一級結(jié)構(gòu)的測定(一)蛋白質(zhì)測序的策略 1.確定蛋白質(zhì)的純

8、度在97%以上。2.測定多肽鏈的數(shù)目。3.拆分多肽鏈。4.分析每一條多肽鏈的氨基酸組成。5.鑒定多肽鏈的N末端和C末端氨基酸殘基。6.用兩種以上方法裂解多肽鏈成較小的肽段。7.測定各肽段的氨基酸序列。8.拼接各肽段成完整的多肽鏈。9.確定二硫鍵的位置。Protein Sequencing StrategyThe usual strategy for determining the amino acid sequence of a protein involves eight basic steps:1. If the protein contains more than one polypep

9、tide chain, the chains are separated and purified.2. Intrachain S-S (disulfide) cross-bridges between cysteine residues in the polypeptide chain are cleaved. (If these disulfides are interchain linkages,then step 2 precedes step 1.)3. The amino acid composition of each polypeptide chain is determine

10、d.4. The N-terminal and C-terminal residues are identified.5. Each polypeptide chain is cleaved into smaller fragments, and the amino acid composition and sequence of each fragment are determined.6. Step 5 is repeated, using a different cleavage procedure to generate a different and therefore overla

11、pping set of peptide fragments.7. The overall amino acid sequence of the protein is reconstructed from the sequences in overlapping fragments.8. The positions of S-S cross-bridges formed between cysteine residues are located.O2NFNO2+ H2NCHCROHNCHCROO2NNO2H+H2OO2NNO2HNCHCROOH+氨基酸DNFBN-端氨基酸DNP衍生物DNP-氨

12、基酸(二)N-末端和C-末端氨基酸殘基的鑒定 末端的測定 （1）二硝基氟苯(DNFB )法 (Sanger法):2,4-二硝基氟苯在堿性條件下，能夠與肽鏈N-端的游離氨基作用，生成二硝基苯衍生物（DNP）。在酸性條件下水解，得到黃色DNP-氨基酸。該產(chǎn)物能夠用乙醚抽提分離。不同的DNP-氨基酸可以用色譜法進行鑒定。N(CH3)2SO2ClH2NCHCROHNCHCROSO2N(CH3)2+水解N(CH3)2SO2HNCHCROOH+氨基酸丹磺酰氯多肽N-端丹磺酰N-端氨基酸丹磺酰氨基酸 （2）丹磺酰氯法:在堿性條件下，丹磺酰氯（二甲氨基萘磺酰氯）可以與N-端氨基酸的游離氨基作用，得到丹磺酰-氨

13、基酸。此法的優(yōu)點是丹磺酰-氨基酸有很強的熒光吸收，檢測靈敏度可以達到110-9mol,比DNFB法靈敏100倍。 （3）異硫氰酸苯酯(PITC)法: N末端氨基酸生成相應(yīng)的PTH（苯乙內(nèi)酰硫脲）AA，并脫離肽鏈，可連續(xù)測定N末端氨基酸，廣泛應(yīng)用于肽鏈的的氨基酸序列測定 。 （4）氨肽酶法：氨肽酶是一種肽鏈外切酶，它能從多肽鏈的N-端逐個水解肽鏈，釋放氨基酸。根據(jù)不同的反應(yīng)時間測出酶水解所釋放出的氨基酸種類和數(shù)量，按反應(yīng)時間和氨基酸殘基釋放量作動力學(xué)曲線，可以確定蛋白質(zhì)的N-末端殘基。末端的測定 （1）還原法。C末端氨基酸可用硼氫化鋰還原生成相應(yīng)的氨基醇。肽鏈水解后，再用層析法鑒定。 （2）肼解

14、法。多肽與肼在無水條件下加熱，可以斷裂所有的肽鍵，除C末端氨基酸外，其他氨基酸都轉(zhuǎn)變?yōu)橄鄳?yīng)的酰肼化合物。肼化物能夠與苯甲醛縮合成不溶于水的物質(zhì)而與C-端氨基酸分離，C末端氨基酸可用紙層析鑒定。但精氨酸會變成鳥氨酸，半胱氨酸、天冬酰胺和谷氨酰胺被破壞。 H2NCHCROHNCHCROORnCCHHNOHn-1N-端氨基酸 C-端氨基酸ORnCCHH2NOHH2NCHCRONHNH2+H+NH2NH2氨基酸酰肼C-端氨基酸 （3）羧肽酶法。將蛋白質(zhì)在pH 8.0, 30與羧肽酶一起保溫，按一定時間間隔取樣，用紙層析測定釋放出來的氨基酸，根據(jù)氨基酸的量與時間的關(guān)系，就可以知道C末端氨基酸的排列順序。

15、目前常用的羧肽酶有四種：A,B,C和Y；A和B來自胰臟；C來自柑桔葉；Y來自面包酵母。羧肽酶A能水解除Pro,Arg和Lys以外的所有C-末端氨基酸殘基；B只能水解Arg和Lys為C-末端殘基的肽鍵。通常將二者混合使用。羧肽酶Y可作用于任何氨基酸，因而，除用來測定C末端氨基酸外，還可以用來測定氨基酸的排列順序。（三）二硫橋的斷裂過甲酸氧化法過甲酸氧化法巰基化合巰基化合物還原法物還原法Breaking disulfide bonds in proteins. Two common methods are illustrated. Oxidation of a cystine residue wi

16、th performic acid produces two cysteic acid residues. Reduction by dithiothreitol to form Cys residues must be followed by further modification of the reactive -SH groups to prevent re-formation of the disulfide bond. Acetylation by iodoacetate serves this purpose. （四）氨基酸組成的分析 一般用酸水解，得到氨基酸混合物，再分離測定氨

17、基酸。目前用氨基酸自動分析儀，24小時即可完成。 蛋白質(zhì)的氨基酸組成，一般用每分子蛋白質(zhì)中所含的氨基酸分子數(shù)表示。不同種類的蛋白質(zhì)，其氨基酸組成相差很大。（五（五)多肽鏈的部分裂解和肽段混合物的分離純化多肽鏈的部分裂解和肽段混合物的分離純化 可以用酶水解法或化學(xué)水解法將蛋白質(zhì)水解成肽段。 肽段的分離純化可用層析法或電泳法。葡萄球菌蛋白酶葡萄球菌蛋白酶梭菌蛋白酶梭菌蛋白酶Trypsin is a proteolytic enzyme, or protease, that specifically cleaves only those peptide bonds in which arginine

18、 or lysine contributes the carbonyl function. The products of the reaction are a mixture of peptide fragments with C-terminal Arg or Lys residues and a single peptide derived from the polypeptides C-terminal end. 溴化氰斷裂法 羥胺斷裂法：斷裂Asn-Gly之間的肽鍵，但專一性不強，也可以斷裂Asn-Leu和Asn-Ala之間的鍵. 化學(xué)降解法: 用此原理已制成蛋白質(zhì)序列分析儀。若每次

19、循環(huán)的準確度為99%，經(jīng)60次循環(huán)，準確度為：6060(六)肽段氨基酸序列的測定N-Terminal analysis using Edmans reagent, phenylisothiocyanate. Phenylisothiocyanate combines with the N-terminus of a peptide under mildly alkaline conditions to form a phenylthiocarbamoyl substitution. Upon treatment with TFA (trifluoroacetic acid), this cyc

20、lizes to release the N-terminal amino acid residue as a thiazolinone derivative, but the other peptide bonds are not hydrolyzed. Organic extraction and treatment with aqueous acid yield the N-terminal amino acid as a phenylthiohydantoin (PTH) derivative.Steps in sequencing a polypeptide. (a) Identif

21、ication of the amino-terminal residue can be the first step in sequencing a polypeptide. Sangers method for identifying the amino-terminal residue is shown here. (b) The Edman degradation procedure reveals the entire sequence of a peptide. For shorter peptides, this method alone readily yields the e

22、ntire sequence, and step (a) is often omitted. Step (a) is useful in the case of larger polypeptides, which are often fragmented into smaller peptides for sequencing. 2.降解法：可用氨肽酶和羧肽酶，只能測出末端的幾個氨基酸。羧肽酶Y可作用于任何氨基酸，有可能以此為基礎(chǔ)開發(fā)出新的氨基酸的順序測定儀。 3.根據(jù)核苷酸序列推定法：分離mRNA，經(jīng)反轉(zhuǎn)錄測定cDNA的核苷酸序列, 再用遺傳密碼推定氨基酸序列。 4.質(zhì)譜法：可分析微量的肽

23、鏈，短肽在第一臺質(zhì)譜儀中經(jīng)電噴射電離，按荷質(zhì)比分離，依次在經(jīng)碰撞池被裂解成離子碎片，在第二臺質(zhì)譜儀中測出各個離子碎片的譜線，推算出短肽的氨基酸序列。在蛋白質(zhì)組學(xué)中應(yīng)用廣泛，但不能區(qū)分亮氨酸和異亮氨酸。 (a) Configuration used in tandem MS.(b) Schematic description of tandem MS: tandem MS involves electrospray ionization of a protein digest (IS in this figure), followed by selection of a single pepti

24、de ion mass for collision with inert gas molecules (He) and mass analysis of the fragment ions resulting from the collisions. (c) Fragmentation usually occurs at peptide bonds, as indicated.(a) After proteolytic hydrolysis, a protein solution is injected into a mass spectrometer (MS-1). The differen

25、t peptides are sorted so that only one type is selected for further analysis. The selected peptide is further fragmented in a chamber between the two mass spectrometers, and m/z for each fragment is measured in the second mass spectrometer (MS-2). Many of the ions generated during this second fragme

26、ntation result from breakage of the peptide bond, as shown. These are called b-type or y-type ions, depending on whether the charge is retained on the amino- or carboxyl-terminal side, respectively. The successive peaks differ by the mass of a particular amino acid in the original peptide. In this c

27、ase, the deduced sequence was PheProGlyGln(Ile/Leu)AsnAlaAsp(Ile/Leu)Arg. Note the ambiguity about Ile and Leu residues, because they have the same molecular mass. In this example, the set of peaks derived from y-type ions predominates, and the spectrum is greatly simplified as a result. This is bec

28、ause an Arg residue occurs at the carboxyl terminus of the peptide, and most of the positive charges are retained on this residue.(b) A typical spectrum with peaks representing the peptide fragments generated from a sample of one small peptide (10 residues). The labeled peaks are y-type ions. The la

29、rge peak next to y5 is a doubly charged ion and is not part of the y set.The three principal steps in electrospray mass spectrometry (ES-MS). (a) Small, highly charged droplets are formed by electrostatic dispersion of a protein solution through a glass capillary subjected to a high electric field;

30、(b) protein ions are desorbed from the droplets into the gas phase (assisted by evaporation of the droplets in a stream of hot N2 gas）; and (c) analysis of the protein ions in a mass spectrometer.Electrospray mass spectrometry of a protein. (a) A protein solution is dispersed into highly charged dro

31、plets by passage through a needle under the influence of a high-voltage electric field. The droplets evaporate, and the ions (with added protons in this case) enter the mass spectrometer for m/z measurement. The spectrum generated (b) is a family of peaks, with each successive peak (from right to le

32、ft) corresponding to a charged species increased by 1 in both mass and charge. A computer-generated transformation of this spectrum is shown in the inset.(七)肽段在多肽鏈中次序的決定肽段Reconstruction of the Overall Amino Acid SequenceThe sequences obtained for the sets of fragments derived from two or more cleava

33、ge procedures are now compared, with the objective being to find overlaps that establish continuity of the overall amino acid sequence of the polypeptide chain. Peptides generated from specific hydrolysis of the polypeptide can be aligned to reveal the overall amino acid sequence. Such comparisons a

34、re also useful in eliminating errors and validating the accuracy of the sequences determined for the individual fragments.Summary of the sequence analysis of catrocollastatin-C, a 23.6-kD protein found in the venom of the western diamondback rattlesnake Crotalus atrox. Sequences shown are given in t

35、he one-letter amino acid code. The overall amino acid sequence (216 amino acid residues long) for catrocollastatin-C as deduced from the overlapping sequences of peptide fragments is shown on the linesheaded CAT-C. The other lines report the various sequences used to obtain the overlaps. These seque

36、nces were obtained from (a) N-term.: Edman degradation of the intact protein in an automated Edman sequenator; (b) M: proteolytic fragments generated by CNBr cleavage, followed by Edman sequencing of the individual fragments (numbers denote fragments M1 through M5); (c) K: proteolytic fragments (K3

37、through K6) from endopeptidase Lys-C cleavage, followed by Edman sequencing; (d) E: proteolytic fragments from Staphylococcus protease (E13 through E15) digestion of catrocollastatin sequenced in the Edman sequenator. Cleaving proteins and sequencing and ordering the peptide fragments. First, the am

38、ino acid composition and aminoterminal residue of an intact sample are determined. Then any disulfide bonds are broken before fragmenting so that sequencing can proceed efficiently. In this example, there are only two Cys (C) residues and thus only one possibility for location of the disulfide bond.

39、 In polypeptides with three or more Cys residues, the position of disulfide bonds can be determined as described in the text. (八)二硫橋位置的確定用對角線電泳法Disulfide bridges typically are cleaved prior to determining the primary structure of a polypeptide. Consequently, the positions of disulfide links are not

40、obvious from the sequence data. To determine their location, a sample of the polypeptide with intact S-S bonds can be fragmented and the sites of any disulfides can be elucidated from fragments that remain linked. Diagonal electrophoresis is a technique for identifying such fragments.+-(a) A protein

41、 digest in which any disulfide bonds remain intact and link their respective Cys-containing peptides is streaked along the edge of a filter paper and (b) subjected to electrophoresis.(c) A strip cut from the edge of the paper is then exposed to performic acid fumes to oxidize any disulfide bridges.

42、(d) Then the paper strip is attached to a new filter paper so that a second electrophoresis can be run in a direction perpendicular to the first. (e) Peptides devoid of disulfides experience no mobility change, and thus their pattern of migration defines a diagonal. Peptides that had disulfides migr

43、ate off this diagonal and can be easily identified, isolated, and sequenced to reveal the location of cysteic acid residues formerly involved in disulfide bridges.(九)蛋白質(zhì)測序舉例（胰島素的序列測定）Amino acid sequence of bovine insulin. The two polypeptide chains are joined by disulfide crosslinkages. The A chain

44、is identical in human, pig, dog, rabbit, and sperm whale insulins. The B chains of the cow, pig, dog, goat, and horse are identical. （十）蛋白質(zhì)序列數(shù)據(jù)庫 1.歐洲生物信息中心研究所和瑞士生物信息研究所共同管理的SWISS-PROT有10多萬條肽鏈的信息； 2.美國國家生物醫(yī)學(xué)基金會主持的PIR有近30萬條肽鏈的信息，但多數(shù)由核酸信息翻譯而來，有些未經(jīng)嚴格檢驗。 3.美國政府支持的Gen Bank和歐洲的 EMBL有大量的基因序列信息，從其閱讀框可以得到蛋白質(zhì)序

45、列的不少信息。四、蛋白質(zhì)的氨基酸序列與生物功能（一） 同源蛋白質(zhì)的物種差異與生物進化細胞色素C的物種差異Cytochrome c is a small protein consisting of a single polypeptide chain of 104 residues in terrestrial vertebrates, 103 or 104 in fishes, 107 in insects, 107 to 109 in fungi and yeasts, and 111 or 112 in green plants. Analysis of the sequence of c

46、ytochrome c from more than 40 different species reveals that 28 residues are invariant. These invariant residues are scattered irregularly along the polypeptide chain, except for a cluster between residues 70 and 80. All cytochrome c polypeptide chains have a cysteine residue at position 17, and all

47、 but one have another Cys at position 14. These Cys residues serve to link the heme prosthetic group of cytochrome c to the protein, a role explaining their invariable presence. This phylogenetic tree depicts the evolutionary relationships among organisms as determined by the similarity of their cyt

48、ochrome c amino acid sequences. The numbers along the branches give the amino acid changes between a species and ahypothetical progenitor. Note that extant species are located only at the tips of branches. Below, the sequence of human cytochrome c is compared with an inferred ancestral sequence repr

49、esented by the base of the tree. Uncertainties are denoted by question marks. （二）同源蛋白質(zhì)具有共同的進化起源1.血紅素蛋白與肌紅蛋白This evolutionary tree is inferred from the homology between the amino acid sequences of the -globin, -globin, and myoglobin chains. Duplication of an ancestral globin gene allowed the divergen

50、ce of the myoglobin and ancestral hemoglobin genes. Another gene duplication event subsequently gave rise to ancestral and forms, as indicated. Gene duplication is an important evolutionary force in creating diversity.Inspection of the amino acid sequences of the globin chains of human hemoglobin an

51、d myoglobin reveals a strong degree of homology. The -globin and -globin chains share 64 residues of their approximately 140 residues in common. Myoglobin and the-globin chain have 38 amino acid sequence identities. This homology is further reflected in these proteins tertiary structure.3. 一些功能差異很大的

52、蛋白質(zhì):如溶菌酶和-乳清蛋白功能差異很大,但有序列同源性。蛋白質(zhì)家族的形成可能有趨同進化和趨異進化兩種機制。 2. 絲氨酸蛋白酶類:顯示明顯的序列同源性。（三）血液凝固與氨基酸序列的局部斷裂1.血液凝固中的級聯(lián)過程12中蛋白質(zhì)凝血因子有7種是絲氨酸蛋白酶*與Ca2+結(jié)合促進凝血酶原與血小板膜結(jié)合，起始凝血酶原的激活帶凈負電荷帶凈負電荷五、肽與蛋白質(zhì)的人工合成（一）肽的人工合成氨基和羧基的保護羧基的活化常用的縮合劑是O,O-二環(huán)己基碳二亞(O,O-dicyclohexyl-carbodiimide,DCC)（二）固相肽合成Solid phase synthesis of a peptide. T

53、ertiary butyloxycarbonyl chloride (tBocCl) is an excellent reagent for blocking amino groups of amino acids during organic synthesis. Dicyclohexylcarbodiimide (DCCD) is a powerful agent for activating carboxyl groups to condense with amino groups to form peptide bonds. The carboxyl group of the firs

54、t amino acid (the carboxyl-terminal amino acid of the peptide to be synthesized) is attached to an insoluble resin particle (the aminoacyl-resin particle). The next amino acid,with its amino group blocked by a tBoc group and its carboxyl group activated with DCCD, is reacted with the aminoacylresin

55、particle to form a peptide linkage, with elimination of DCCD as dicyclohexylurea. Acid treatment removes the N-terminal tBoc blocking group as the gaseous products CO2 and isobutylene, exposing the N-terminus of the dipeptide for another cycle of amino acid addition. The growing peptide chain is eas

56、ily recovered after cyclic additions of amino acids simply by filtering or centrifuging the reaction mixture. Chemical synthesis of a peptide on an insoluble polymer support. The major breakthrough in this technology was provided by R. Bruce Merrifield in 1962. His innovation involved synthesizing a

57、 peptide while keeping it attached at one end to a solid support.Reactions (1) through (4) are necessary for the formation of each peptide bond. The 9-fluorenylmethoxycarbonyl (Fmoc) group (shaded blue) prevents unwanted reactions at the -amino group of the residue (shaded red). Chemical synthesis p

58、roceeds from the carboxyl terminus to the amino terminus, the reverse of the direction of protein synthesis in vivo.9-芴甲芴甲氧羰基氧羰基 基本要求1.掌握蛋白質(zhì)的分類和功能多樣性；2.掌握肽的結(jié)構(gòu)特點和基本性質(zhì)；3.熟悉蛋白質(zhì)一級結(jié)構(gòu)的測定方法；4.掌握蛋白質(zhì)一級結(jié)構(gòu)與生物學(xué)功能的關(guān)系，熟悉有關(guān)的典型例子。5.熟悉蛋白質(zhì)人工合成的基本步驟。作業(yè)題作業(yè)題第194頁第1題；第194頁第2題；第195頁第3題；第196頁第10題；1. 習(xí)題書第66頁第10，31，32，34，35題

59、，第5章 蛋白質(zhì)的三維結(jié)構(gòu) 一、研究蛋白質(zhì)構(gòu)象的方法一、研究蛋白質(zhì)構(gòu)象的方法 (一)X射線衍射法基本規(guī)律：X射線穿過原子平面層時，當(dāng)光程差等于波長的倍數(shù)，反射波可以互相疊加形成衍射斑點。如圖5-2所示，光程差等于2dsin,上述規(guī)律可總結(jié)為Bragg方程： 2dsin=n(n=1, 2, 3)(二)研究溶液中蛋白質(zhì)構(gòu)象的光譜學(xué)方法 1.紫外差光譜 芳香族氨基酸在極性環(huán)境下吸收峰向短波長移動，稱作籃移，反之會紅移。2.熒光和熒光偏振 變性和非變性蛋白質(zhì)熒光峰和熒光偏振的位置會有特定的變化。3.圓二色性由尼科爾棱鏡產(chǎn)生由電光調(diào)制器產(chǎn)生橢圓率= 短軸/長軸 = tan 33cl(適合于小的）（ =

60、R L，c為摩爾濃度，l為光程， 為摩爾吸光系數(shù)）摩爾橢圓率=（/cl）100 = 3300 圓偏振光可看成是相位相差90o的兩個平面偏振光疊加而成，若左、右圓偏振光因被測物的吸收而振幅不同，二者疊加會形成橢圓偏振光。4.核磁共振(NMR) 二、穩(wěn)定蛋白質(zhì)三維結(jié)構(gòu)的作用力 （三）疏水作用(熵效應(yīng))（四）鹽鍵（五）二硫鍵（一）氫鍵（二）范德華力 定向效應(yīng)；誘導(dǎo)效應(yīng)；分散效應(yīng) 三、多肽主鏈折疊的空間限制（一）酰胺平面與-碳原子的二面角（和）： 規(guī)定鍵兩側(cè)基團為順式排列時為0o，從C沿鍵軸方向觀察，順時針旋轉(zhuǎn)的角度為正值。The amide or peptide bond planes are jo