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Analysis of glycated sodium caseinate proteins by MALDI-MS and LC-ESI-MS

AutorCorzo-Martínez, Marta ; Galindo-Iranzo, Plácido ; Lebrón-Aguilar, Rosa ; Villamiel, Mar ; Moreno, F. Javier
Fecha de publicación2010
CitaciónISC 2010
ResumenSodium caseinate (SC) is extensively used in the food industry as a functional ingredient due to its simple production, excellent nutritional value and versatile functional properties such as thickening, emulsifying and foaming properties. However, in spite of this, the food industry is moving towards the search of procedures to obtain new multifunctional ingredients. Over the past few years, there has been an increased interest in deliberately promoted Maillard reaction to obtain glycoconjugates with improved functionalities in relation to the initial proteins. Because of glycation-induced modifications in proteins can influence their functional properties, more precise and detailed information on structure of glycated proteins is essential to gain knowledge about their structure-function relationship. In this respect, the power of both matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS) and liquid chromatography coupled to electrospray ionization mass spectrometry (LC-ESI-MS) for the monitoring and characterization of protein glycation has been demonstrated. However, as far as we know, no studies on the advantages and disadvantages of both techniques for characterization of glycated SC have been carried out. Thus, the aim of this work was to compare the type of information that can be derived from the spectra of both MALDI-MS and LC-ESI-MS and determine the most suitable technique for the analysis of SC after its glycation via Maillard reaction with galactose and lactose. Following MALDI analyses, the less abundant k- and as2-caseins showed a low response, which impaired the accurate determination of the glycation degree of both proteins. Regarding the major caseins, as1- and b-casein, MALDI-MS spectra of glycated SC were characterized by an unique and broad Gaussian peak shape without good resolution, due to the great heterogeneity of the glycated forms of both caseins. LC-ESI-MS allowed the chromatographic separation of the four casein fractions, either in native or in glycated forms, within only nine minutes. ESI mass spectra were recorded in the negative ion mode due to the high content of SC in phosphorylated serine residues. As it occurred for MALDI, as2-casein also showed a low response by ESI, impairing its identification. Nevertheless, ESI-MS spectra corresponding to the unglycated and glycated forms of as1-, b- and k-casein were characterized by multiply charged molecular ions which allowed their identification, providing an accurate estimation of the number of carbohydrate molecules attached to each casein fraction. In conclusion, LC-ESI-MS was found to be a more efficient technique than MALDI-MS to determine the degree of glycation of SC.
DescripciónResumen del póster presentado al 28th International Symposium on Chromatography celebrado en Valencia (España) del 12 al 16 de septiembre de 2010.
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