Circular dichroism of the non-enzymatic browning products of poly-L-lysine and albumin.

Poly-L-lysine (PLL) and bovine serum albumin were used as models in the investigation of non-enzymatic glycation and browning reaction by circular dichroism measurements. Different sugars (glucose, glucose-6-P and ribose) induced different extents of reaction and produced different chromophores that absorbed light in the near u.v. region. All glycated samples gave a common spectral feature in absorption and blue fluorescence, but they gave distinctly different near u.v. c.d. features, indicating that the browning products containing yellow chromophores are different for glycated samples and may have rigid moieties. The ribocated PLL (at pH 11.0, alpha-helix) and albumin were unable to convert completely to beta-conformation upon heating, indicating that browning reaction may have changed the tertiary structure.