Ishimoto B, Tonan K, Ikawa S
Division of Chemistry, Graduate School of Science, Hokkaido University, Sapporo, Japan.
Spectrochim Acta A Mol Biomol Spectrosc. 2000 Jan;56A(1):201-9. doi: 10.1016/s1386-1425(99)00219-x.
A relationship between intramolecular hydrogen bonding and the cis-trans isomerization of a proline imide bond for proline-containing short peptides were studied by proton NMR and infrared spectroscopy using DMSO-d6/CDCl3 mixed solvents. The percentage of the trans form increases with increasing fraction of CDCl3 in the mixed solvents except for compounds without possibility of intramolecular hydrogen bonding. Chemical shift variations of amide protons with solvent mixing ratios were found to be useful for judging whether the amide protons take part in the intramolecular hydrogen bonding to a considerable degree or not. These results and infrared spectra were used to specify intramolecularly hydrogen bonded structures of the peptides. Formation of the 10-membered or 13-membered hydrogen bonded ring which includes the carbonyl group precedent to the prolyl residue facilitates the cis-to-trans isomerization and these hydrogen bonded rings are strong enough to restrict the proline imide bond to the trans form in CDCl3 solution. On the other hand, a 7-membered hydrogen bonded ring is not so effective in restricting the proline imide bond.
利用 DMSO-d6/CDCl3 混合溶剂，通过质子核磁共振（NMR）和红外光谱法研究了含脯氨酸的短肽分子内氢键与脯氨酸亚胺键顺反异构化之间的关系。除了不可能形成分子内氢键的化合物外，反式构象的百分比随混合溶剂中 CDCl3 比例的增加而增加。发现酰胺质子的化学位移随溶剂混合比例的变化有助于判断酰胺质子是否在相当程度上参与了分子内氢键的形成。这些结果和红外光谱被用于确定肽的分子内氢键结构。包含脯氨酰残基之前的羰基的 10 元或 13 元氢键环的形成促进了顺式到反式的异构化，并且这些氢键环足够强大，能够在 CDCl3 溶液中将脯氨酸亚胺键限制为反式构象。另一方面，7 元氢键环在限制脯氨酸亚胺键方面效果不那么显著。
