Terminal effect of chiral residue on helical screw sense in achiral peptides
Terminal effect of chiral residue on helical screw sense in achiral peptides
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手性残基对非手性肽螺旋方向的末端效应
DOI：
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发表时间：
1999
期刊：
影响因子：
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通讯作者：
T. Hirabayashi
中科院分区：
文献类型：
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作者：
Y. Inai;Y. Kurokawa;T. Hirabayashi
为了理解手性残基的末端效应以确定螺旋旋向，我们采用了五种含有N-和/或C-末端手性Leu残基的肽I-V：Boc-L-Leu-（Aib-Δ Phe）2-Aib-OMe（I），Boc-（Aib-Δ Phe）2-L-Leu-OMe（II）、Boc-L-Leu-（Aib-Δ Phe）2-L-Leu-OMe（III）、Boc-D-Leu-（Aib-Δ Phe）2-L-Leu-OMe（IV）和Boc-D-Leu-（Aib-Δ Phe）2-Aib-OMe（V）。片段-（Aib-Δ Phe）2-用于由两个"对映体"（左手/右手）螺旋组成的主链。实际上，这可以通过Boc-（Aib-Δ Phe）2-Aib-OMe的1H-nmr [nuclear Overhauser effect（NOE）and solvent accessibility of NH resonances]和CD光谱来证实，其具有左/右手310-螺旋。肽I-V也被发现采取310型螺旋构象在CDCl 3中，从不同的NOE测量和NH共振的溶剂可及性。氯仿、乙腈、甲醇和四氢呋喃用于CD测量。在所有溶剂中的肽I-III的CD光谱显示出显着的激子对，在较长的波长处具有正峰，这表明它们的主链更喜欢左手螺旋感而不是右手螺旋感。在所有溶剂中的肽V显示激子对，在较长波长处具有负峰，表明它更喜欢右手螺旋感。氯仿中的肽IV显示非分裂型CD图案，仅在280 nm附近具有小的负信号，这意味着左手和右手螺旋应该以几乎相同的含量存在。在其他溶剂中，肽IV显示激子对在较长波长处具有负峰，对应于右手螺旋感。从构象能计算和上述1H-nmr研究，在最低能量的左手310-螺旋构象中的N-或C-末端L-Leu残基被发现采取偏离左手螺旋的不规则构象。根据肽I-V和Boc-（L-Leu-Δ Phe）n-L-Leu-OMe（n = 2和3）的圆二色性数据，讨论了L-残基的位置对螺旋旋向的影响。© 1999 John Wiley & Sons，Inc. Biopoly 49：551 - 564，1999年
To understand the terminal effect of chiral residue for determining a helical screw sense, we adopted five kinds of peptides I–V containing N- and/or C-terminal chiral Leu residue(s): Boc–L-Leu–(Aib–ΔPhe)2–Aib–OMe (I), Boc–(Aib–ΔPhe)2–L-Leu–OMe (II), Boc–L-Leu–(Aib–ΔPhe)2–L-Leu–OMe (III), Boc–D-Leu–(Aib–ΔPhe)2–L-Leu–OMe (IV), and Boc–D-Leu–(Aib–ΔPhe)2–Aib–OMe (V). The segment –(Aib–ΔPhe)2– was used for a backbone composed of two “enantiomeric” (left-/right-handed) helices. Actually, this could be confirmed by 1H-nmr [nuclear Overhauser effect (NOE) and solvent accessibility of NH resonances] and CD spectroscopy on Boc–(Aib–ΔPhe)2–Aib–OMe, which took a left-/right-handed 310-helix. Peptides I–V were also found to take 310-type helical conformations in CDCl3, from difference NOE measurement and solvent accessibility of NH resonances. Chloroform, acetonitrile, methanol, and tetrahydrofuran were used for CD measurement. The CD spectra of peptides I–III in all solvents showed marked exciton couplets with a positive peak at longer wavelengths, indicating that their main chains prefer a left-handed screw sense over a right-handed one. Peptide V in all solvents showed exciton couplets with a negative peak at longer wavelengths, indicating it prefers a right-handed screw sense. Peptide IV in chloroform showed a nonsplit type CD pattern having only a small negative signal around 280 nm, meaning that left- and right-handed helices should exist with almost the same content. In the other solvents, peptide IV showed exciton couplets with a negative peak at longer wavelengths, corresponding to a right-handed screw sense. From conformational energy calculation and the above 1H-nmr studies, an N- or C-terminal L-Leu residue in the lowest energy left-handed 310-helical conformation was found to take an irregular conformation that deviates from a left-handed helix. The positional effect of the L-residue on helical screw sense was discussed based on CD data of peptides I–V and of Boc–(L-Leu–ΔPhe)n–L-Leu–OMe (n = 2 and 3). © 1999 John Wiley & Sons, Inc. Biopoly 49: 551–564, 1999