关键词: 次级化学位移, 二级结构, 周期性, 氢键效应

Abstract: 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 △δ_αH and △δ_NH of a residue show reverse phase variation and the periodicity of △δ_αH. and △δ_NH is ca.3.6 residues/Cycle, which is in accordance with that of a-helix. Furthermore, the periodic feature is also found in △δ_{¹¹Ca and △δ¹³co 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.}

Key words: Secondary chemical shift, Secondary structure, Periodicity, Hydrogen bond effect