多肽和蛋白质NMR预饱和实验中饱和转移效应的研究

通过改变预饱和照射时间研究了一些多肽和蛋白质分子在水溶液中的饱和转移效应.定量分析了在照射60s之后大分子中绝大多数酰胺质子仍不受影响的原因.结果表明:具有稳定的三维溶液结构的蛋白质(如溶菌酶)中,活泼氢的信号基本上不受饱和转移影响;对于溶液结构比较稳定的多肽和蛋白质(如胰岛素),只有少部分酰胺质子信号强度受到影响;小分子六肽因为溶液中不存在稳定的构象,饱和转移效应十分显著.因此对于溶液中多肽与蛋白质构象的NMR研究,预饱和仍不失为一种简便而有效的溶剂峰压制技术.

ON THE SATURATION TRANSFER EFFECTS IN PRESATURATION NMR EXPERIMENTS OF PEPTIDE AND PROTEINS

Saturation transfer effect in NMR experiments on peptide and proteins in aqueous solutions has been investigated using presaturation method with varied irradiation time. The reason why most amide protons are not affected by 60s irradiation has been quantitatively analyzed. It has been shown that the labile protons in lysozyme, which is a macromolecule with stable secondary and tertiary structure, are almost not affected by saturation transfer. Very few amide protons in insulin, whose tertiary structure is less stable than lysozyme, have lost intensity due to saturation transfer. As for the peptide with six amino acid residues, because it dose not have secondary structure in solution, saturation transfer effect is severe. It is thus concluded that for the purpose of three dimensional structure study using NMR, presaturation is still a powerful and practical technique for solvent suppression.