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Top-down grafting of xyloglucan to gold monitored by QCM-D and AFM: Enzymatic activity and interactions with cellulose

TitleTop-down grafting of xyloglucan to gold monitored by QCM-D and AFM: Enzymatic activity and interactions with cellulose
Publication TypeJournal Article
Year of Publication2008
AuthorsNordgren, N, Eklof, J, Zhou, Q, Brumer, H, Rutland, MW
JournalBIOMACROMOLECULES
Volume9
Pagination942-948
Date PublishedMAR
Type of ArticleArticle
ISSN1525-7797
Abstract

This study focuses on the manufacture and characterization of model surfaces consisting of end-grafted xyloglucan (XG), a naturally occurring polysaccharide, onto a gold substrate. The now well-established XET-technology was utilized for enzymatic incorporation of a thiol moiety at one end of the xyloglucan backbone. This functionalized macromolecule was subsequently top-down grafted to gold, forming a thiol-bonded xyloglucan brushlike layer. The grafting was monitored in situ with QCM-D, and a significant difference in the adsorbed/grafted amount between unmodified xyloglucan and the thiol-functionalized polymer was observed. The grafted surface was demonstrated to be accessible to enzyme digestion using the plant endo-xyloglucanase TmNXGI. The nanotribological properties toward cellulose of the untreated crystal, brush-modified surface, and enzyme-exposed surfaces were compared with a view to understanding the role of xyloglucan in friction reduction. Friction coefficients obtained by the AFM colloidal probe technique using a cellulose functionalized probe on the xyloglucan brush showed an increase of a factor of 2 after the enzyme digestion, and this result is interpreted in terms of surface roughness. Finally, the brush is shown to exhibit binding to cellulose despite its highly oriented nature.

DOI10.1021/bm701214e