Enkephalins: Raman spectral analysis and comparison as function of pH 1-13.

Raman spectral studies are carried out on Leu- and Met-enkephalin as a function of the pH value in the range of 1-13. The molecules are dissolved in KCl solvent and the pH is controlled at each value. Spectral analyses reveal the dependence of the structural conformation on the pH, and a comparison of the two molecules is made in three frequency regions: the tyrosine Fermi doublet (850-830 cm(-1)), aromatic side chains (1650-1550 cm(-1)), and carboxylate (1430-1400 cm(-1)). All regions and frequencies are presented, discussed, and compared for the two molecules.