Glycation reactions using a model peptide of collagen and glucose or ribose resulted in detection of carboxylmethyl-lysine in the peptide; and treatment with glyoxal provided a dimer of the peptide linked with glyoxal lysine dimer (GOLD). Advanced glycation end products (AGE) are accumulated in human tissues when long-lived proteins are glycated due to hyperglycemia and/or aging. In this study, we synthesized a collagen model peptide, Ac-(Pro-Hyp-Gly) 5-Pro-Lys-Gly-(Pro-Hyp-Gly) 5-Ala-NH 2 to investigate intact AGEs in peptides. The peptide formed a stable triple helix structure, and was subjected to glycation reactions with glucose, ribose and glyoxal. Besides carboxymethyl-lysine in the peptide, a conjugated form linked with glyoxal lysine dimer (GOLD) was detected upon treatment with glyoxal. This is the first example of intact glycation-derived dimers of peptides retaining intrinsic protein structures.
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