The influence of sugars on the U.V. absorption spectrum of proteins

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Abstract
N‐Glycosidic coupling of aldoses and the free amino groups of protein is accompanied by profound modification of the ultraviolet absorption spectrum of the protein partner in the Maillard reaction. The increased extinction coefficient at 250 mμ of protein‐carbohydrate complexes incorporating sites of N‐glycosidic linkage is largely attributable to effects of denaturation, while absorbancy changes at 325 and 350 mμ are accounted for by side reactions involving the sugar partner only. Specifically, the Maillard reaction between protein and sugar results in the formation of a chromophor at the site of coupling absorbing at 305 mμ. The identification of this chromophor as the 1,2‐enol form of an N‐substituted 1‐amino‐1‐deoxy‐2‐ketose is substantiated by studies of ultraviolet absorption in model systems containing low‐molecular weight primary amines and aldoses.