核磁共振次级化学位移和蛋白质二级结构

NMR SECONDARY CHEMICAL SHIFT AND PROTEIN SECONDARY STRUCTURE

蛋白质和多肽的空间结构导致ＮＭＲ化学位移的变化．称为次级化学位移（△δ）．采用已归属的化学位移数据．分析了肽链各残基αＨ、ＮＨ、１３Ｃａ、１３ＣＯ的次级化学位移值与其所处的二级结构的关系．α－螺旋结构中．同一残基的△δａＨ和△δＮＨ波动相位相反；大多数α－螺旋片段的△δａＨ和△δＮＨ的周期约为３．６残基．与α－螺旋周期一致；△δ１１Ｃａ和△δ１３ｃｏ也发现有同样周期性．β－折叠及其它结构中这些次级化学位移值不具备周期性．肽链氢键效应可能是造成次级化学位移规律变化的主要因素．

An additive variation of NMR chemical shift related to conformation of protein and peptide is named secondary chemical shift (△δ). Based on the chemical shift data of residues, the relationship between chemical shift of αH. NH. 13Cα.13CO and the secondary structure has been surveyed. In most α-helical structures, the △δαH and △δNH of a residue show reverse phase variation and the periodicity of △δαH. and △δNH is ca.3.6 residues/Cycle, which is in accordance with that of a-helix. Furthermore, the periodic feature is also found in △δuCz to and △δnco in belieal segments. However, in the case of β-sheet and other structures, it does not imply this characteristic secondary chemical shift. The hydrogen bond effect among peptide chain probably caused the periodic variation of the secondary chemical shift is also discussed.