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Determination of protein surface excess on a liquid/solid interface by single-molecule counting

TitleDetermination of protein surface excess on a liquid/solid interface by single-molecule counting
Publication TypeJournal Article
Year of Publication2009
AuthorsLi N, Tang H, Gai HW, Dong XL, Wang Q, Yeung ES
Journal TitleAnalytical and Bioanalytical Chemistry
Volume394
Pages1879-1885
Date Published08
ISBN Number1618-2642
Accession NumberISI:000268000600018
Keywordsadsorption-kine, bovine serum-albumin, capillary-electrophoresis, fluorescence microscopy, hydrophilic/hydrophobic surface, long-range, neutron reflection, protein adsorption, silica-water interface, single-molecule imaging, solid-surfaces, surface excess
Abstract

Determination of protein surface excess is an important way of evaluating the properties of biomaterials and the characteristics of biosensors. A single-molecule counting method is presented that uses a standard fluorescence microscope to measure coverage of a liquid/solid interface by adsorbed proteins. The extremely low surface excess of lysozyme and bovine serum albumin (BSA), in a bulk concentration range from 0.3 nmol L-1 (0.02 mu g mL(-1)) to 3 nmol L-1 (0.2 mu g mL(-1)), were measured by recording the counts of spatially isolated single molecules on either hydrophilic (glass) or hydrophobic (polydimethylsiloxane, PDMS) surfaces at different pH. The differences observed in amounts of adsorbed proteins under different experimental conditions can be qualitatively explained by the combined interactions of electrostatic and hydrophobic forces. This, in turn, implies that single- molecule counting is an effective way of measuring surface coverage at a liquid/solid interface.
URL<Go to ISI>://000268000600018
DOI10.1007/S00216-009-2888-4