The effect of nonenzymatic glycation on the stability and conformation of two deoxyoligonucleotide duplexes: A spectroscopic analysis by circular dichroism

Advanced glycation end products (AGEs) play a significant role in the pathophysiology of diabetes leading to such conditions as atherosclerosis, cataract formation, and renal dysfunction. While the formation of nucleoside AGEs was previously demonstrated, no extensive studies have been performed to assess the effect of AGEs on DNA structure and folding. The objective of this study was to investigate the nonenzymatic glycation of two DNA oligonucleotide duplexes with one duplex consisting of deoxy-poly(A)15 and deoxy-poly(T)15 and the other consisting of deoxy-poly(GA)15 and deoxy-poly(CT)15. With d-glucose, d-galactose, d/l-glyceraldehyde, and d-glucosamine serving as the model glycating carbohydrates, d-glucosamine was found to exhibit the greatest effect on the stability and structure of the oligonucleotide duplexes, a finding that was confirmed by circular dichroism. The nonenzymatic glycation of deoxy-poly(AT) by d-glucosamine destabilized the deoxy-poly(AT) structure and changed its conformation from A form to X form. d-Glucosamine also altered the conformation of deoxy-poly(GA)15 and deoxy-poly(CT)15 from A form to B form. Capillary electrophoresis and ultraviolet and fluorescence spectroscopy revealed that, of the various purines and pyrimidines, 2′-deoxyguanosine and guanine were most reactive with d-glucosamine. The nonenzymatic modification of nucleic acids warrants further investigation because this phenomenon may occur in vivo, altering DNA structure and/or function.