A 500 MHz study of peptide T in a DMSO solution

Abstract

Peptide T, an octapeptide of sequence ASTTTNYT that binds to human T cells, was studied as a zwitterion in DMSO_d6 solution by means of proton NMR spectroscopy at 500 MHz. The unusual dispersion of the resonances of residues of the same type (T) makes it possible to assign all resonances to specific residues by means of several 2D techniques. The non‐random nature of the conformation is substantiated by the observation of sequential nuclear Overhauser enhancements (NOEs). The low value of the temperature coefficient of the chemical shift of the NH of T⁸ and a diagnostic NOE between the NHs of T⁷ and T⁸ hint that a β‐turn including T⁵, N⁶, Y⁷ and T⁸ is a prominent conformational feature in solution. The ring current high field shifts of the methyl group and of the NH of T⁸ are consistent with an interaction with the side‐chain of Y⁷, favoured by the β‐turn.