Nonequilibrium, Single-Molecule Studies of Protein Unfolding

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***NON-TECHNICAL ABSTRACT***An accurate knowledge of the energy difference between equilibrium states of protein systems is important for biophysical and biochemical understanding of molecular processes. This award will support a project focused on developing effective techniques to study this energy difference, or protein stability, at the molecular level. The studies will aid our understanding of protein stability, and ultimately our understanding of the role of protein stability in proper functioning under physiological conditions. Atomic force spectroscopy is a technique used to measure the behavior of molecules under a stretching or twisting force. Application of this technique to important molecules such as human cardiac titin will lead to understanding of how the muscle functions in heart. A new course on molecular biophysics will be developed. Students and postdoctoral associates will have the opportunity to learn to use the state-of-the art instrument for biophysics research. This project receives support from the Division of Materials Research and the Physics Division.***TECHNICAL ABSTRACT***This individual investigator award will support single-molecule studies of protein free energy landscapes by dynamic force spectroscopy using atomic force microscopy. The goal is to obtain equilibrium information about nanoscale biomolecular systems from non-equilibrium measurements. State-of-the art atomic force microscopy capable of manipulating single molecules at the nanometer scale and detecting forces with pico-newton accuracy will be used to measure the force-extension of single proteins. The recently derived Jarzynski equality, which relates the probability distribution of nonequilibrium work values to the equilibrium free energy difference, will be used to determine the free energy changes as proteins undergo mechanical transformations. The unfolding free energy curves of titin, the giant muscle protein responsible for the passive tension of heart muscles, will be obtained using Jarzynski's equality. The broader impact of this program includes the development of a novel measurement and analysis tool for solving basic biophysical problems and the training of undergraduate students, graduate students, and postdoctoral associates in nanobiophysics. This project receives support from the Division of Materials Research and the Physics Division.