The structure of alanine based tripeptides in water and dimethyl sulfoxide probed by vibrational Spectroscopy
The structure of alanine based tripeptides in water and dimethyl sulfoxide probed by vibrational Spectroscopy
复制标题
DOI：
10.1021/jp026958t
复制
发表时间：
2003-01-09
影响因子：
3.3
通讯作者：
Schweitzer-Stenner, R
中科院分区：
文献类型：
--
作者：
Eker, F;Cao, XL;Schweitzer-Stenner, R
我们测量了阳离子L-丙氨基-D-丙氨基-L-丙氨酸、L-丙氨基-丙氨酸-L-丙氨酸和L-丝氨基-L-丙氨酸-L-丙氨酸在D2O中的红外、各向同性和各向异性拉曼光谱中酰胺I的谱带分布。此外，我们还记录了N-乙酰基-L-丙氨酰-L-丙氨酸在D2O和DMSO-d(6)中的光谱。两个酰胺I带的强度比依赖于两个多肽的酰胺I模式之间的激子耦合。这些强度比通过光谱分解获得，然后通过最近开发的算法(Schweitzer-Stenner，BiPhys)用于确定多肽组之间的二面角。J.，83，83,523,2002)。通过测量酰胺I带的振动圆二色性来验证所得到的结构的有效性。L-赖氨酰-L-丙氨基-L-丙氨酸、L-丝氨基-L-丙氨基-L-丙氨酸和乙酰基-L-丙氨基-L-丙氨酸采用与观察到的L-丙氨基-L-丙氨基-L-丙氨酸类似的结构。这表明N-末端残基对两个多肽之间的二面角没有显著影响。如果假设为单一优势构象，则可以得到β-螺旋构象或扩展的多聚脯氨酸II构象，而两个构象模型得到的是共存的多聚脯氨酸II和扩展的β-类型构象。DMSO-d(6)中的乙酰基-L-丙氨基-L-丙氨酸采用β-片状结构。它的酰胺I谱带比用D2O溶剂观察到的要小得多。我们的结果表明，多肽与水分子之间的氢键显著地导致了酰胺I带的不均匀展宽，并稳定了多聚脯氨酸II的构象。
We have measured the band profile of amide I in the infrared, isotropic, and anisotropic Raman spectra of cationic L-alanyl-D-alanyl-L-alanine, L-alanyl-alanine-L-alanine, and L-seryl-L-alanine-L-alanine in D2O. Additionally, we recorded spectra of N-acetyl-L-alanyl-L-alanine in D2O and in DMSO-d(6). The respective intensity ratios of the two amide I bands depend on excitonic coupling between the amide I modes of the two peptides. These intensity ratios were obtained from a spectral decomposition and then used to determine the dihedral angles between the peptide groups by means of a recently developed algorithm (Schweitzer-Stenner, Biophys. J., 83, 83, 523, 2002). The validity of the obtained structures was checked by measuring the vibrational circular dichroism of the amide I bands. L-Lysyl-L-alanyl-L-alanine, L-seryl-L-alanyl-L-alanine, and acetyl-L-alanyl-L-alanine adopt structures similar to that observed for L-alanyl-L-alanyl-L-alanine. This suggests that the N-terminal residues do not significantly influence the dihedral angles between the two peptide groups. If one assumes a single dominant conformer, one obtains beta-helix or extended polyproline II conformation, while a two-conformer model yields coexisting polyproline II and extended beta-type conformers. Acetyl-L-alanyl-L-alanine in DMSO-d(6) adopts a beta-sheet-like structure. Its amide I bands are significantly less broadened than those observed with D2O solvent. Our results show that hydrogen bonding between the peptide and water molecules contributes significantly to the inhomogeneous broadening of amide I bands and stabilizes the polyproline II conformation.