The effect of chemical modification on the solution structure of derivatives of substance P: nuclear magnetic resonance study of substituted and retro-inverso analogues

Abstract

Four derivatives of the bioactive fragment 6–11 of Substance P were characterized by means of one- and two-dimensional ¹H n.m.r. spectroscopy. Indirect evidence of backbone folding for these hexapeptides was given by temperature coefficients and paramagnetic relaxation rate enhancements of the amide protons. Chemical modifications were found to modulate the solution structure. Retro-inversion caused some conformational changes and a correlation between these structural variations and the relative biological activities was attempted.