Protein glycation reactions

The reactions of the early and intermediate stages of protein glycation were studied using bovine serum albumin and hen egg white lysozyme as model proteins, and D-glucose and D-fructose as model reducing sugars. The reactions were studied under low moisture and limiting sugar conditions in the presence and absence of oxygen in a closed system. Several analytical methods, including the fluorescamine assay, total Maillard fluorescence and solubility measurement, size exclusion chromatography, and electrospray ionization mass spectrometry were used to follow the glycation reaction. The effect of glycation on the structure of proteins was also studied by electrospray ionization mass spectrometric peptide mapping. The results showed that under low moisture conditions, the initial rate of glucation was 5 to 6 times higher than the initial rate of fructation, both in the presence and in the absence of oxygen. The presence of oxygen in the reaction system induced selectivity of the glycation of the protein amino groups during the initial stages of the reaction, due to competition between glycation and glycoxidation. The reaction, however, occurred at a higher rate in the presence of oxygen than in its absence, especially during the latter stages of the reaction. The more reactive glycoxidation products, formed during the initial stages of the reaction also participated in the glycation reaction and increased the involvement of arginine residues in the glycation reaction. The glycation reaction also resulted in a heterogeneous mixture of protein glycoforms with varying degrees and extent of glycation. The heterogeneity of the glycated species was further complicated by the involvement of glycoxidation products in the glycation reaction, resulting in a distribution of different classes of glycoconjugates. Limited glycation improved protein solubility and increased solvent accessibility into the interior of the protein, thereby, increasing protein digestibility. Electrosp

Characterization of tryptic hydrolysates of protein isolates of Phaseolus beans

This study was directed at elucidating the structural and functional characteristics of legume protein isolates with different microstructures.Protein isolates with different microstructures (crystalline and amorphous) were prepared from four varieties of Phaseolus beans; white kidney bean and navy bean (P. vulgaris), and large lima and baby lima beans (P. lunatus). The protein isolates were subjected to tryptic hydrolysis at various time intervals, and the effect of hydrolysis on the functional properties of the protein isolates was studied, using bovine casein as control. Reversed phase HPLC with UV detection was used to generate peptide maps of the tryptic hydrolysates, and electrospray mass spectrometry was used to characterize the peptide profile of the protein hydrolysates.There was no difference between the susceptibility of the crystalline and amorphous protein isolates to tryptic hydrolysis, however, the hydrolytic products of the crystalline isolates showed higher solubility and functional properties compared with those of the amorphous isolates. Limited hydrolysis markedly improved the functional properties of both crystalline and amorphous protein isolates. The effect of hydrolysis on the functionality of the bean protein isolates was higher compared with casein. In general the hydrolysates of the bean protein isolates showed higher functional properties than casein and its hydrolysates.Reversed phase HPLC peptide mapping of the tryptic digests and ESI/MS of the RP-HPLC fractions showed structural and compositional difference between crystalline and amorphous protein isolates prepared from the same bean variety. The results also showed that off-line ESI/MS, and ESI/MS/MS of RP-HPLC fractions of the tryptic hydrolysates could be used for the structural characterization of the protein isolates

Mass Spectrometry of biomolecules: Functional foods, nutraceuticals, and natural health products

200404NRC publication: Ye

Mass Spectrometry of biomolecules: Functional foods, nutraceuticals, and natural health products

200404NRC publication: Ye

Detection and partial structure elucidation of basic taxoids from Taxus wallichiana by electrospray ionization tandem mass spectrometry

NRC publication: Ye

Detection and partial structure elucidation of basic taxoids from Taxus wallichiana by electrospray ionization tandem mass spectrometry

NRC publication: Ye

Monitoring glycation of lysozyme by electrospray ionization mass spectrometry

NRC publication: Ye

Monitoring glycation of lysozyme by electrospray ionization mass spectrometry

NRC publication: Ye