• Bulletin of the Korean Chemical Society
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• v.35 no.3
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• pp.798-804
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• 2014

We present calculations for diglycine - $(H_2O)_n$ (n = 0-3) to examine the effects of microsolvating water on the relative stability of the zwitterionic vs. canonical forms of the dipeptide. We calculate the structures, energies and Gibbs free energies of the conformers at wB97XD/6-311++G** and MP2/aug-cc-pvdz levels of theory level of theory. We predict that microsolvation by up to three water molecules does not give thermodynamic stability of the zwitterion relative to the canonical forms. Our calculations also suggest that zwitterionic diglycine - $(H_2O)_3$ is not stable kinetically in low temperature gas phase environment.

• Preventive Nutrition and Food Science
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• v.15 no.4
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• pp.297-303
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• 2010

The present study compared the Maillard reaction products (MRPs) derived from aqueous and ethanolic fructoseglycine and its oligomer (dimer and trimer) solutions. The pH was lower in glycine (G) than in diglycine (DG) and triglycine (TG) in both aqueous and ethanolic solutions, but the pH difference between the DG and TG was not significant. MRPs derived from the DG had a greater absorbance at 294 and 420 nm in ethanolic solution than in an aqueous solution. In particular, the loss of sugar was higher in ethanolic solution than in aqueous solution. Enolization of fructose was observed in both aqueous and ethanolic MRP solutions; however, enolization was not observed for the G in aqueous MRP solutions. The glycine oligomer content in ethanolic MRP solutions remained higher than that in aqueous MRP solutions. Furthermore, neither diglycine nor triglycine were detected in the G aqueous or ethanolic MRP solutions, while triglycine was detected in both the DG aqueous and ethanolic MRP solutions. Absorption in the ultraviolet-visible (UV-Vis) spectra was higher with MRPs derived from the ethanolic solution than with those derived from the aqueous solution. MRPs derived from the DG in an ethanolic solution showed the highest absorption intensity.