The combination of simple MALDI matrices for the improvement of intact glycoproteins and glycans analysis

The choice of matrix has fundamental importance in matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) analysis of glycoproteins. Therefore, a set of selected matrices has been tested. The attention was focused on new binary matrices, that were a combination of matrices commonly used for carbohydrates or proteins analysis such as 2,5-dihydroxybenzoic acid (2,5-DHB), 2,5-dihydroxyacetophenone (DHAP), 2,4,6-trihydroxyacetophenone (THAP), α-cyano-4-hydroxycinnamic acid (CHCA), and sinapinic acid (SA).The binary matrices 2,5-DHB/CHCA and 2,5-DHB/SA have been proved the mass spectra with the best quality and showed an universal applicability. Application of these matrices enabled to quickly screen the microheterogeneity of glycan moieties for either intact glycoproteins, or a mixture of deglycosylated glycoproteins together with free, underivatized glycans. Moreover, these binary matrices were more tolerant to the presence of salts in studied samples. Our results suggest that a combination of two matrix compounds could be useful for an improved determination of the molecular mass values of analytes coming from complex biological samples, especially for the structural characterization of glycoproteins of pharmaceutical interest.