Becker E L, Bleich H E, Day A R, Freer R J, Glasel J A, Visintainer J
Biochemistry. 1979 Oct 16;18(21):4656-68. doi: 10.1021/bi00588a029.
Previous work by several groups has shown that the combination of spin--spin coupling constants and spectral density components (derived from spin--lattice relaxation and/or nuclear Overhauser measurements) may aid in the task of conformational determination of peptides in solution. Using the peptide formyl-L-methionyl-L-leucyl-L-phenylalanine, which is a potent specific chemotactic agent for leucocytes, we show the following: (a) that 3JNHCH coupling constants are consistent with a high degree of rigidity in the peptide backbone in solution, (b) that 3H isotopic substitution in combination with relaxation data taken at different Larmor frequencies enables spectral density, and thence conformational, information to be obtained, (c) that side-chain conformations for this molecule mirror, in some aspects, those found in the solid state for other peptides containing the same residues, and (d) that temperature dependence of amide chemical shifts does not have direct implication concerning the existence of intramolecular hydrogen bonds in peptides. We are able to propose a family of conformations which appear to interchange rapidly on the NMR time scale and are characterized by a distribution of side-chain rotamers. The basic backbone conformation is, or closely approximates, a small beta antiparallel pleated sheet and as such suggests a possible mode of receptor--chemotactic peptide interaction.
几个研究小组之前的工作表明，自旋 - 自旋耦合常数与光谱密度分量（由自旋 - 晶格弛豫和/或核Overhauser测量得出）相结合，可能有助于确定溶液中肽的构象。我们使用肽甲酰 - L - 蛋氨酰 - L - 亮氨酰 - L - 苯丙氨酸（一种对白细胞有效的特异性趋化剂）进行研究，结果如下：（a）3JNHCH耦合常数与溶液中肽主链的高度刚性一致；（b）3H同位素取代与在不同拉莫尔频率下获取的弛豫数据相结合，能够获得光谱密度，进而获得构象信息；（c）该分子的侧链构象在某些方面反映了其他含有相同残基的肽在固态中的构象；（d）酰胺化学位移的温度依赖性与肽中分子内氢键的存在没有直接关联。我们能够提出一系列构象，这些构象在核磁共振时间尺度上似乎能快速互换，并以侧链旋转异构体的分布为特征。基本的主链构象是或非常接近一个小的反平行β折叠片，因此暗示了受体 - 趋化肽相互作用的一种可能模式。
