Detection of Lewis antigen structural change by FTIR spectroscopy

Mucins are a family of extensively glycosylated, high molecular weight glycoproteins. Secretion of mucins with altered terminal carbohydrate moieties alters the rheological and viscoelastic properties of mucus and observed glycosylation changes in respiratory diseases may vary with disease status. Structural modifications to the Lewis x antigen with sialic acid (sialyl-Lewis x) and sulphate (sulfo-Lewis x) in particular are associated with respiratory diseases and deemed potential biomarkers for disease diagnosis, severity and progression. The major aim of this study was to evaluate the ability of Fourier transform infrared spectroscopy (FTIR) to detect, via infrared (IR) spectra, the structural changes between the Lewis x antigen and sialylated and sulphated derivatives. Although FTIR only provides information on vibrations of chemical groups, we show that by comparing mono- and oligosaccharide specific IR spectra it is possible to determine the contribution of key sugar moieties to the altered Lewis x spectral pattern.