Analysis of carbohydrates and glycoconjugates by matrix-assisted laser desorption/ionization mass spectrometry (CAT#: STEM-ST-0317-LJX)

Introduction

Unlike proteins and nucleic acids that are linear polymers of amino acids and nucleotides respectively, with linkages at only one position, carbohydrates can adopt complex branched structures with individual monomeric units linked at one of several sites. Furthermore, each monomer can adopt different ring sizes and conformation or can sometimes appear in a linear form. Thus, for a carbohydrate of a given mass, it is possible to produce very large numbers of isomeric structures. For example, it has been calculated that, for a simple hexasaccharide, there are approximately 1.05×1012 possible isomers. Such structural complexities present major problems for the analyst, particularly as many compounds are available in only trace quantities. Fortunately, however, only a few of the possible structures are found in nature because of the limit in the number of glycosyltransferases involved in their biosynthesis. Knowledge of the activity of such enzymes often plays an important role in structural determination. Mass spectrometry is used extensively in this work particularly as the techniques of fast atom bombardment (FAB) and, more recently, matrix-assisted laser desorption/ionization (MALDI) and electrospray ionization (ESI) have enabled spectra of the larger and more polar molecules to be examined directly.