Understanding biomolecule-surface interaction mechanisms is essential for optimal design of sensor devices, biocompatible materials for biomedical engineering, antifouling coatings and many other applications. Biomolecule-surface adsorption free energy is a key physical parameter that can be used to characterize peptide-surface interactions.  Single molecule force spectroscopy (SMFS) is used to directly measure biomolecular adsorption free energy at the single-molecule level whereas surface plasmon resonance spectroscopy (SPR) is used to measure biomolecular adsorption free energy at the macroscopic level. Here, using A3 peptide (AYSSGAPPMPPF) adsorption on a gold surface as an example,  we show that, in contrast to the previously proposed linear relationship between SPR measured free energy and SMFS measured rupture forces, the measured adsorption free energy from SPR at dilute solution is equal to that obtained from SMFS within statistical error.  Further, the measured results are compared with that obtained from all-atom molecular dynamics simulation using the adaptive biasing force (ABF) algorithm and Golp-CHARMM force fields. The three different approaches yield comparable adsorption free energy of A3 on gold with an average of -9.44 ñ 0.21 kcal/mol. Our results validate a basic thermodynamic principle that a physical quantity can be obtained by averaging a large number of single molecule microstates and provide a route to estimate peptide adsorption free energy on substrates that are not suitable for SPR measurements.

Approaching peptide-surface adsorption free energy from macro and microscopic perspectives

2019 Spring National Meeting

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