Structural Elucidation by Fast Atom Bombardment Mass Spectrometry of Multisulfated Oligosaccharides Isolated from Human Respiratory Mucous Glycoproteins

Abstract

Underivatized mono- and multisulfated oligosaccharides obtained by the alkalineborohydride treatment of human respiratory mucous glycoproteins were analyzed by positive ion fast atom bombardment mass spectrometry (FAB MS). Employing three unique and structurally homologous groups, the FAB mass spectra of a mono- and a disulfated tri- and tetrasaccharide and a mono-, di- and trisulfated branched hexasaccharide were compared. Each produced mass spectra displaying molecular weight-related and structurally significant fragment ions including fragments differing in mass by multiples of 102 amu reflecting the loss of one or more sulfate esters. From these data, combined with monosaccharide composition, the carbohydrate sequence and number and location of sulfate esters can readily be determined. These findings, with other chemical and enzymatic analyses, make FAB MS a valuable tool applicable to the unambiguous structural elucidation of underivatized reduced, linear and branched, mucous glycoprotein oligosaccharides that vary in degree of sulfation.     

A model for the drying process during film formation in waterborne acrylic coatings

Establishing drying mechanisms during film formation in waterborne acrylic coatings is a technologically important problem, however complex, and still poorly understood. A model for the prediction of evaporation kinetics is proposed in this paper, where films are supposed to dry normally with respect to the film surface, and a drying front separates a top dry region from a bottom wet region. The model accounts for the competition between water evaporation and particle diffusion that determines the degree of vertical homogeneity, but also for the competition between water evaporation and particle deformation that ultimately establishes the rate-determining step in film formation processes. The model was validated by performing gravimetric water-loss experiments on latexes of acrylic polymers of various composition, various particle size and stabilizing systems, under different environmental temperatures and humidity, and various initial film thicknesses in order to evaluate the effect of the different factors that can in principle influence the film formation process.