A nitroxide derivative as a probe for conformational studies of short linear peptides in solution. Spectroscopic and molecular mechanics investigation

A spectroscopic investigation was undertaken to ascertain whether the ordered structure of short linear peptides' crystal state is preserved in solution. The conformational equilibria characterizing the peptides containing tryptophan (Trp) and the nitroxide derivative, Toac, was due to the rotation of the dihedral angles of the Trp side chain. Results indicate that irrespective of the polarity of the solvents used, the peptides examined maintain the basic features of the crystal state, and exhibit poor flexibility in solution.