13C nuclear magnetic resonance and circular dichroism studies of the tuftsin conformation in water.

13C-NMR and circular dichroic (CD) spectra of tuftsin and its analogues are discussed in connection with our hypothesis that the beta-turn is the biologically active conformation of tuftsin. The changes in CD spectra evoked by an increase in pH are interpreted as a demonstration of the increasing amount of beta-turn conformers in solution. Configurational changes in successive residues of tuftsin showed that residues 2 and 3 of the peptide chain are important for the tuftsin conformation.