Determination of protein surface excess on a liquid/solid interface by single-molecule counting |
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| Authors: | Nan Li Hui Tang Hongwei Gai Xiuling Dong Qi Wang Edward S Yeung |
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| Institution: | (1) Biomedical Engineering Center, Hunan University, Changsha, Hunan, 410082, China;(2) State Key Laboratory of Chemo/Biosensing and Chemometrics, Hunan University, Changsha, 410082, China;(3) Dalian the Third Municipal Hospital, Dalian, 116033, China;(4) The Second Hospital Affiliated to Dalian Medical University, Dalian, 116023, China;(5) Department of Chemistry and Ames Laboratory, Iowa State University, Ames, IA 50011, USA;(6) # A202, College of Chemistry and Chemical Engineering, Hunan University, Changsha, Hunan, 410082, China; |
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| 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 μg mL−1) to 3 nmol L−1 (0.2 μg 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.
Figure Adsorption fraction of proteins on different surfaces changed with pH. |
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| Keywords: | Single-molecule imaging Protein adsorption Hydrophilic/hydrophobic surface Surface excess |
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