Matrix-Assisted Laser Desorption/Ionization-Time of Flight Mass Spectrometry Analysis for Molecular Characterization of Chitosan

Abstract

Chitosan oligosaccharides designated to COS were derived from the hydrolysis of high molecular weight chitosan (HMWC). The range of molecular weight of COS was estimated to be approximately 0.5 to 2.5 kDa after the fractionation performed through gel-filtration, followed by MALDI-TOF mass spectrometry analysis. It was confirmed through the results that significant separation or fractionation was not observed well. Also, both dialyzed COS using a 12~14 kDa molecular weight cut-off (MWCO) membrane and salting-out COS were also showed no significant difference in the molecular weight of COS by MALDI-TOF mass spectrometry analysis. These results suggested that it is difficult to separate the chitosan hydrolysates bigger than 1 kDa according to the size (6-glucosamine) due to their high affinity between molecules which may tightly be associated together by hydrophobic or van der Waals force. Therefore, further examination on chitosan hydrolysis and fractionation for the production of COS with various sizes i.e., 7 or 8 units of glucosamine in large-scale, should be carefully considered for various applications.