REASSESSMENT OF THE RANDOM COIL CONFORMATION - VIBRATIONAL CD STUDY OF PROLINE OLIGOPEPTIDES AND RELATED POLYPEPTIDES
REASSESSMENT OF THE RANDOM COIL CONFORMATION - VIBRATIONAL CD STUDY OF PROLINE OLIGOPEPTIDES AND RELATED POLYPEPTIDES
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DOI：
10.1002/bip.360311409
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发表时间：
1991-12-01
期刊：
影响因子：
2.9
通讯作者：
KEIDERLING, TA
中科院分区：
文献类型：
--
作者：
DUKOR, RK;KEIDERLING, TA
通过将各种多肽模型体系的振动CD （VCD）光谱与脯氨酸低聚物[(Pro)n]和聚（l -脯氨酸）的振动CD （VCD）光谱进行比较，研究了“随机线圈”构象问题。报道了阻断l -脯氨酸寡肽[(Pro)n, n = 2-12]在不同溶剂中的VCD， ir和uv CD光谱，并与聚（l -脯氨酸）II，聚（l -谷氨酸）和未阻断的脯氨酸寡聚物的光谱进行了比较。基于脯氨酸低聚物的VCD和电子CD （ECD）谱的链长依赖性，确定了VCD谱以短程相互作用为主。随机线圈模型多肽的VCD在形状上与聚（l -脯氨酸）II相同，但大小较小，与（Pro）n的大小相似（n = 3,4）。根据光谱证据，可以得出结论，“随机线圈”构象具有很大比例的螺旋区域，构象类似于Krimm及其同事先前提出的左旋，3]聚脯氨酸II螺旋。盐（CaCl2, LiBr, LiClO4）、温度（5-75℃）和pH对l -脯氨酸低聚物、聚（l -脯氨酸）II和聚（l -谷氨酸）VCD光谱的影响进一步支持了这一结论。这些结果表明，在每一次扰动之后，低聚物和聚合物中仍然存在显著的局部顺序，并且带电荷的多肽（如聚l -谷氨酸）比聚脯氨酸甚至l -脯氨酸低聚物更灵活。
The "random coil" conformational problem is examined by comparison of vibrational CD (VCD) spectra of various polypeptide model systems with that of proline oligomers [(Pro)n] and poly (L-proline). VCD, ir and uv CD spectra of blocked L-proline oligopeptides [(Pro)n, n = 2-12] in different solvents are reported and compared to the spectra Of poly (L-proline) II, poly(L-glutamic acid), and unblocked proline oligomers. Based on the chain-length dependence of the VCD and electronic CD (ECD) spectra of proline oligomers, it is established that VCD spectra are dominated by short-range interactions. The VCD of random coil model polypeptides is shown to be identical in shape but smaller in magnitude than poly(L-proline) II and of similar magnitude to that of (Pro)n (n = 3, 4). Based on the spectral evidence, it is concluded that the "random coil" conformation has a large fraction of helical regions, conformationally similar to the left-handed, 3] polyproline II helix, as was previously suggested by Krimm and co-workers. This conclusion is further supported by studies of effects of salt (CaCl2, LiBr, LiClO4), temperature (5-75-degrees-C), and pH on the VCD spectra of L-proline oligomers, poly (L-proline) II, and poly (L-glutamic acid). These show that, after each of these perturbations, a significant local ordering remains in the oligomers and polymers studied, and that charged polypeptides such as poly(L-glutamic acid) are more flexible than are polyproline or even L-proline oligomers.