Monitoring the effect of glucosamine and glyceraldehyde glycation on the secondary structure of human serum albumin and immunoglobulin G: An analysis based on circular dichroism, thermal melting profiles and UV–fluorescence spectroscopy

Glucosamine and glyceraldehyde can nonenzymatically interact with proteins to form advanced glycation endproducts (AGEs). The objective of this investigation was to determine the effects of nonenzymatic glycation by glucosamine and glyceraldehyde on the secondary structure of human serum albumin (HSA) and human IgG and to also demonstrate the in vitro formation of AGEs by these two sugars under different conditions. The formation of AGEs was monitored by capillary electrophoresis, UV and fluorescence spectroscopy. The changes in the secondary structure of HSA and IgG were determined by circular dichroism (CD) and thermal melting (Tm) profiles of the native and glycated proteins. CD and Tm studies revealed that at 40 mM sugar concentration, glucosamine had a stabilizing effect on HSA and destabilized IgG whereas glyceraldehyde destabilized both the α-helical and β-pleated conformations of HSA and IgG, respectively. HSA and IgG structures were also negatively impacted with 40 mM glucose.