[Study of bradykinin conformation in a dimethylsulfoxide solution by two-dimensional 1H-NMR spectroscopy]

The role of charged groups of the nonapeptide bradykinin in stabilization of its spatial structure in dimethyl sulfoxide solution was investigated. The signal assignment in the 1H-NMR spectra was achieved by means of two dimensional correlated spectroscopy (COSY) and nuclear Overhauser enhancement spectroscopy (NOESY). The changes in the NH and C alpha H proton chemical shifts of the Arg1 and Arg9 residues, variations both in temperature coefficients of chemical shifts of NH-resonances and coupling constants, as well as the appearance of additional NOE cross-peaks in NOESY spectra for d alpha N and d beta N 1H-1H distances were revealed by comparing the NMR spectra for two states--with the protonated C-terminal carboxyl group and deprotonated one. The experimental results are in agreement with the assumption that the conformation of the peptide in (CD3)2SO is stabilized by electrostatic interaction between the oppositely charged N- and C-terminal groups. The conformation with deprotonated alpha-carboxyl group is characterized by two beta-turns in the sequences Pro2-Pro-Gly-Phe5 and Ser6-Pro-Phe-Arg9.