. Why do biomolecules retain activity when attached to some surfaces (e.g., the cell membrane) and yet almost invariably unfold and inactivate when attached to others (e.g., many artificial surfaces)? And how can we recreate the former effect to produce artificial surfaces on which attached biomolecules similarly retain their function? To date our ability to address these important questions has been hampered by an acute lack of quantitative experimental methods for measuring the thermodynamics of biomolecule-surface interactions. That is, despite a large body of qualitative literature describing how adsorption alters biomolecular structure, and a large number of empirical studies searching for adsorption- resistant surfaces, quantitative, experimentally testable insights into how and why this occurs have proven elusive. Thus motivated, we propose here the development and validation of a novel experimental (electrochemical) approach to measuring the folding free energy of biomolecules site-specifically attached to well-defined macroscopic surfaces. Comparison with the folding free energy in bulk solution then informs on the thermodynamics -and thus mechanisms- underlying biopolymer-surface interactions. To date we have employed this approach to characterize the easily modeled folding of a surface-confined DNA stem-loop in studies that have, for the first time, defined experimentally the extent to which, and mechanisms by which a specific biomolecule interacts with a range of well-defined, macroscopic surfaces. Here we propose a two-year research program aimed at adapting this quantitative experimental tool to the study of protein-surface interactions.

Public Health Relevance

Biopolymers interact with surfaces in many and varied ways, and the rich behavior that results from such interactions is interesting from both a scientific and increasingly, practical standpoint. Many important biotechnologies, for example, including biosensors, protein microarrays, drug targeting nanoparticles, biocompatible materials, and tissue engineering scaffolds exploit -or, more often, are limited by- such interactions. Despite the importance of these effects, however, our understanding of the means by which biomolecules interact with surfaces remains inadequate. That is, while empirical studies have mapped out a handful of artificial surfaces upon which biomolecules generally maintain their function, key questions about why biomolecules frequently unfold on and adhere to artificial surfaces, but rarely do so on, for example, the cell membrane remain unanswered. By producing quantitative, predictive models of how biomolecules interact with surfaces the successful conclusion of our research will greatly augment current, empirical efforts to design functional, biomolecule-modified and biomolecule-resistant surfaces and materials.

National Institute of Health (NIH)
National Institute of Biomedical Imaging and Bioengineering (NIBIB)
Exploratory/Developmental Grants (R21)
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Macromolecular Structure and Function B Study Section (MSFB)
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Hunziker, Rosemarie
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University of California Santa Barbara
Schools of Arts and Sciences
Santa Barbara
United States
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Watkins, Herschel M; Simon, Anna J; Ricci, Francesco et al. (2014) Effects of crowding on the stability of a surface-tethered biopolymer: an experimental study of folding in a highly crowded regime. J Am Chem Soc 136:8923-7