VIBRATIONAL CIRCULAR-DICHROISM IN AMINO-ACIDS AND PEPTIDES .7. AMIDE STRETCHING VIBRATIONS IN POLYPEPTIDES
VIBRATIONAL CIRCULAR-DICHROISM IN AMINO-ACIDS AND PEPTIDES .7. AMIDE STRETCHING VIBRATIONS IN POLYPEPTIDES
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DOI：
10.1002/bip.360211106
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发表时间：
1982-01-01
期刊：
影响因子：
2.9
通讯作者：
NAFIE, LA
中科院分区：
文献类型：
--
作者：
LAL, BB;NAFIE, LA
本文给出并分析了多种多肽在氯仿中的振动圆二色谱(VCD)，以及在D2O中的两个例子。聚(γ-苄基-L-谷氨酸)的结果证实了Singh和Keiderling(1981)在多肽中发现VCD的第一个也是唯一一个先前的报告。总而言之，光谱显示这两个区域的双标记VCD的意义取决于α-螺旋性的意义，而不是组成氨基酸的绝对构型。这一结论是通过获得形成左旋而不是右旋α-螺旋的两种多肽，聚(β-苄基-L-天冬氨酸)和聚(亚苄基-L-组氨酸)的VCD而建立的。一个新的酰胺带由于与N.sb.H伸缩模费米共振相互作用而具有显著的VCD强度，被确认为酰胺A带低频侧3200 cm-1附近的弱肩，被指定为酰胺I和酰胺II振动的组合带。多肽在D2O溶液中的VCD光谱虽然很弱，但在酰胺I区成功地测量到了光谱，那里的光谱似乎更复杂，因为存在溶剂化和内部氢键的酰胺基。一些多肽对酰胺A和酰胺I区域的VCD的强单号贡献表明这两个区域之间的电子性质的耦合，并通过应用转动强度的局部求和规则的概念来推导。看来，对多肽的VCD的详细理解将不仅是对二级结构的诊断，也是对引起酰胺振动中局部固有手性的更微妙的结构和振动效应的诊断。
Vibrational circular dichroism (VCD) spectra for the principal amide stretching vibrations, amide A (N.sbd.H stretch) and amide I (predominantly C.dbd.O stretch), are presented and analyzed for a variety of polypeptides dissolved in chloroform, as well as for 2 examples in D2O. Results for poly(.gamma.-benzyl-L-glutamate) confirm the first and only previous report of VCD in polypeptides carried out by Singh and Keiderling (1981). Collectively, the spectra show that the sense of the bisignate VCD in these 2 regions depends on the sense of .alpha.-helicity and not on the absolute configuration of the constituent amino acids. This conclusion is established by obtaining VCD for the 2 polypeptides, poly(.beta.-benzyl-L-asparate) and poly(im-benzyl-L-histidine), that form left-handed as opposed to right-handed .alpha.-helices. A new amide band having significant VCD intensity owing to its Fermi resonance interaction with the N.sbd.H stretching mode was identified as a weak shoulder on the low-frequency side of the amide A band near 3200 cm-1 and is assigned as a combination band of the amide I and amide II vibrations. VCD spectra of polypeptides in D2O solution, although weak, were successfully measured in the amide I region, where spectra appear to be more complicated due to the presence of solvated and internally H-bonded amide groups. Strong monosignate contributions to the VCD in the amide A and amide I regions for some of the polypeptides indicate coupling of an electronic nature between these 2 regions and is deduced by an application of the concept of local sum rules of rotational strength. It appears that a detailed undertstanding of the VCD obtained for polypeptides will not only be diagnostic of secondary structure, but also of more subtle structural and vibrational effects that give rise to local, intrinsic chirality, in the amide vibrations.