The conformation of tetraalanine in water determined by polarized Raman, FT-IR, and VCD spectroscopy.
The conformation of tetraalanine in water determined by polarized Raman, FT-IR, and VCD spectroscopy.
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通过偏振拉曼、FT-IR 和 VCD 光谱测定水中四丙氨酸的构象。
DOI：
10.1021/ja039452c
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发表时间：
2004
期刊：
影响因子：
--
通讯作者：
Nafie,LaurenceA
中科院分区：
文献类型：
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作者：
Schweitzer-Stenner,Reinhard;Eker,Fatma;Griebenow,Kai;Cao,Xiaolin;Nafie,LaurenceA
本文报道了阳离子四丙氨酸在水溶液中的构象。通过分析酰胺I在各自的偏振可见拉曼光谱、傅里叶变换红外光谱和振动圆二色（VCD）光谱中的带谱，利用酰胺I最近邻和次近邻肽基之间的激子耦合，实现了两个中心氨基酸残基的二面角确定。它是最近发展的理论的延伸（Schweitzer-Stenner， R.Biophys）。J。,2002、83、523−532)。利用紫外电子圆二色性（ECD）对结构分析结果进行验证。分析得出二面角（ϕ12,ψ12） =（−70°，155°）和（ϕ23,ψ23） =（−80°，145°）。所得值与聚脯氨酸II螺旋（PPII）的拉马钱德兰坐标非常接近。数据表明，这是肽在室温下主要采用的构象。这一概念得到了相应的电子圆二色光谱的证实。四丙氨酸比三丙氨酸表现出更高的PPII倾向，从最近的光谱研究中获得了50:50的聚脯氨酸II和延长的β-链样构象的混合物(Eker等人，J。点。Chem.Soc.2002, 124、14330−14341)。CD光谱的温度依赖性排除了链的任何协同性都涉及到宏观PPII跃迁。由此得出结论，溶剂-肽的相互作用导致了PPII的稳定性。我们的结果可以用来理解为什么螺旋形成肽的变性通常产生PPII而不是异质随机构象。
The present article reports the conformation of cationic tetraalanine in aqueous solution. The determination of the dihedral angles of the two central amino acid residues was achieved by analyzing the amide I‘ band profile in the respective polarized visible Raman, Fourier transform-IR, and vibrational circular dichroism (VCD) spectra by means of a novel algorithm which utilizes the excitonic coupling between the amide I modes of nearest neighbor and second nearest peptide groups. It is an extension of a recently developed theory (Schweitzer-Stenner, R.Biophys. J.,2002,83, 523−532). UV electronic circular dichroism (ECD) spectra of the peptides were used to validate the results of the structure analysis. The analyses yielded the dihedral angles (ϕ12,ψ12) = (−70°, 155°) and (ϕ23,ψ23) = (−80°, 145°). The obtained values are very close to the Ramachandran coordinates of the polyproline II helix (PPII). The data suggest that this is the conformation predominantly adopted by the peptide at room temperature. This notion was corroborated by the corresponding electronic circular dichroism spectrum. Tetraalanine exhibits a higher propensity for PPII than trialanine for which a 50:50 mixture of polyproline II and an extended β-strand-like conformation was obtained from recent spectroscopic studies (Eker et al.,J. Am. Chem.Soc.2002,124,14330−14341).The temperature dependence of the CD spectra rule out that any cooperativity is involved in the strand ⇔PPII transition. This led to the conclusion that solvent−peptide interactions give rise to the observed PPII stability. Our result can be utilized to understand why the denaturation of helix-forming peptides generally yields a PPII rather than a heterogeneous random conformation.