Aromatic side‐chain contributions to the far ultraviolet circular dichroism of peptides and proteins
Aromatic side‐chain contributions to the far ultraviolet circular dichroism of peptides and proteins
复制标题
芳香侧链对肽和蛋白质远紫外圆二色性的贡献
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发表时间：
1978
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影响因子：
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通讯作者：
R. Woody
中科院分区：
文献类型：
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作者：
R. Woody
计算了具有各种主链和侧链构象的二肽的苯丙氨酸和酪氨酸侧链中La跃迁的转动强度。对于β转角构象中的三肽也进行了类似的计算，其中芳香残基位于转角处。芳香环与邻近肽的相互作用在La跃迁中产生0.1德拜-玻尔磁子量级的旋转强度。当考虑优选的主链和侧链构象时，发现最可能的构象具有正La键。该结果解释了L-Tyr和LPhe的N-酰基氨基酸酰胺具有阳性La条带的观察结果。它还表明，尽管其他相互作用可能会影响数值甚至符号，但最近邻相互作用对球状蛋白中芳香残基的旋转强度有显著的正贡献。在最近邻水平上对已知构象的蛋白质的计算证实了Phe和Tyr残基的正La贡献趋势。即使在具有相当强的酰胺贡献的蛋白质中，这种贡献也可以是所观察到的CD的10%的量级。在一些蛋白质中，例如来自噬菌体fd的基因5蛋白和许多蛇毒毒素，来自Tyr和Trp残基的侧链贡献在225-250 nm区域表现为阳性CD带。最近邻贡献的大小和正向贡献的趋势与球状蛋白中此类CD带的观察结果一致。芳族侧链之间不需要调用特殊的堆积相互作用。
The rotational strength of the La transition in phenylalanine and tyrosine side chains has been calculated for dipeptides with various backbone and side‐chain conformations. Similar calculations have also been performed for tripeptides in the β‐turn conformation with aromatic residues at the corners of the turn. The interaction of the aromatic ring with neighboring peptides generates rotational strengths in the La transition of the order of 0.1 Debye‐Bohr magneton. When the preferred backbone and side‐chain conformations are considered, it is found that the most probable conformations have positive La bonds. This result accounts for the observation that the N‐acyl amino acid amides of L‐Tyr and LPhe have positive La bands. It also suggests that, although other interactions may affect the numerical value and even the sign, there will be a significant positive contribution to the rotational strength of aromatic residues in globular proteins from nearest‐neighbor interactions. Calculations on proteins of known conformation at the nearest‐neighbor level confirm the tendency toward positive La contributions for Phe and Tyr residues. This contribution can be of the order of 10% of the observed CD even in proteins with rather strong amide contributions. In some proteins, such as the gene 5 protein from bacteriophage fd and many snake‐venom toxins, side‐chain contributions from Tyr and Trp residues manifest themselves as positive CD bands in the 225–250‐nm region. The magnitude of the nearest‐neighbor contributions and the trend toward positive contributions are consistent with the observation of such CD bands in globular proteins. No special stacking interaction among aromatic side chains needs to be invoked.