Direct Observation of Sugar-Protein, Sugar-Sugar, and Sugar-Water Complexes by Cold-Spray Ionization Time-of-Flight Mass Spectrometry

摘要

The direct observation of noncovalent and specific intermolecular-recognition events such as enzyme-substrate, antigen-antibody, receptor-ligand, carbohydrate-protein, and carbohydrate-carbohydrate interactions is important for understanding the mechanisms behind these biological processes. Electrospray ionization mass spectrometry (ESI MS) is an important tool for investigations of the sensitivity, specificity, and speed of noncovalent complex formation.[1] The advantages of MS over traditional methods such as UV/Vis spectroscopy, fluorescence spectroscopy, surface plasmon resonance (SPR), isothermal titration microcalorimetry, NMR spectroscopy, and X ray crystallographic analysis include the accuracy of mass measurement, speed of analysis, and small sample quantities. However, the harsh conditions of the ionization process in MS are often detrimental to the survival of noncovalent and unstable biomolecular interactions such as those of sugar-protein, sugar-sugar, and sugar-water complexes. Recently, Yamaguchi and co-workers developed cold-spray ionization mass spectrometry (CSI MS), which allows facile and precise characterization of labile self-assembling nanostructures and unstable organometallic complexes in solution.[2] CSI MS may become one of the most promising and versatile tools for characterizing a variety of weak but specific biomolecular interactions, as the ionization at low temperature (-20 °C) allows direct observation of unstable large-scale aggregates of amino acids or nucleosides in organic solvents with magnetic-sector-equipped instruments.