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Application of XPS to the surface analysis of yeast cells
Author(s) -
Amory D. E.,
Genet M. J.,
Rouxhet P. G.
Publication year - 1988
Publication title -
surface and interface analysis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.52
H-Index - 90
eISSN - 1096-9918
pISSN - 0142-2421
DOI - 10.1002/sia.740110904
Subject(s) - x ray photoelectron spectroscopy , yeast , distilled water , contact angle , chemistry , surface roughness , analytical chemistry (journal) , electrophoresis , materials science , chromatography , chemical engineering , biochemistry , composite material , engineering
Yeast cells, Saccharomyces cerevisiae and carlsbergensis , have been analysed by XPS. A preparation and analysis procedure was developed in order to minimize contamination and re‐arrangements of the cell surface. The use of an external standard of silica permitted the absolute surface concentrations to be estimated and the influences of sample preparation procedure on surface roughness and chemical composition of the cell surface to be evaluated separately. The selected procedure consisted of washing the cells in distilled water, freezing a pellet in liquid nitrogen, freeze‐drying at 268 K, mounting the obtained powder in a trough and pressing the surface. Repeated analyses on a given yeast strain enable the variances linked to the main steps of the preparation procedure for each surface element to be evaluated; thereby, confidence intervals can be given for any small set of XPS data. Freeze‐drying is the main source of variation and samples which have to be compared should be freeze‐dried together. The reproducibility of the surface concentration decreases in the order C, O, N, P and is much better for the N/P ratio than for N or P alone. The neutrality of the XPS preparation and analysis procedure towards the yeast cell surface is supported by the correlation obtained for ten yeast strains between the surface N/P ratio (dehydrated state) and the electrophoretic mobility at pH 4 (hydrated state). This gives confidence in the ability of XPS to investigate a biological surface. The surface specificity of XPS is illustrated by the very low O/C (0.39) and N/C (0.1) concentration ratios which denote a high proportion of lipids at the cell surface (60–70%), in contrast with the low proportion in the whole cell wall (8%).