This study was to investigate the effect of molecular size and charge state of reducing sugars on the nonenzymatic glycation of β-lactoglobulin (β-lg), with emphasis on the variation in glycation extent and glycation site. Five sugars (glucose, galactose, galacturonic acid, maltose and maltotriose) were selected to react with β-lg in dry-state (aw at 0.53, 45°C) and the glycated products were analyzed by liquid chromatography-mass spectrometry (LC-MS) and data-independent acquisition LC-MS (LC-MSE). The results showed that increasing molecular size and negative charge state of reducing sugars would reduce the glycation extent. In addition, the difference of molecular size would result in the variation of glycation on the site of K 8, 70 and 75, and the negative charge state would lead to dissimilarity of glycation on K 77 of β-lg. The analysis of the glycation sites was based on the fragmentation behaviors of the reducing sugars proposed according to the deconvoluted MSE spectra. Among the five reducing sugars, glucose and galactose had the same dissociation pathway. Galacturonic acid had a distinctive dissociation behavior with a neutral loss of 98. Maltose and maltotriose were comparable to glucose but more complex.
Bibliographical noteFunding Information:
This research was supported by the National Natural Science Foundation of China ( 31071492 ), the Program for New Century Excellent Talents in University ( NCET-11-0666 ), the Fok Ying Tung Education Foundation ( 121033 ), and the 111 Project - B07029 . The authors would like to thank Davisco Foods International, Inc. for donating the β-lg sample. The authors also thank Guanjun Tao for the technical assistance on the MS analysis.
- Molecular size
- Negative charge state