title: Determination of protein surface excess on a liquid/solid interface by single-molecule counting.
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 microg mL(-1)) to 3 nmol L(-1) (0.2 microg 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.
authors: Biomedical Engineering Center, Hunan University, Changsha, Hunan, 410082, China.
authors: Nan
authors: N
authors: Li
authors: Hui
authors: H
authors: Tang
authors: Hongwei
authors: H
authors: Gai
authors: Xiuling
authors: X
authors: Dong
authors: Qi
authors: Q
authors: Wang
authors: Edward S
authors: ES
authors: Yeung
mesh_terms: D000327:Adsorption; D004129:Dimethylpolysiloxanes / Q000737:chemistry*; D005898:Glass / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D057927:Hydrophobic and Hydrophilic Interactions; D008856:Microscopy, Fluorescence; D009113:Muramidase / Q000032:analysis*; D010316:Particle Size; D012710:Serum Albumin, Bovine / Q000032:analysis*; D013499:Surface Properties
chemical_list: D004129:Dimethylpolysiloxanes; D012710:Serum Albumin, Bovine; C013830:baysilon; D009113:Muramidase