Bulletin of the American Physical Society
Spring 2012 Meeting of the APS Ohio-Region Section
Volume 57, Number 4
Friday–Saturday, April 13–14, 2012; Columbus, Ohio
Session A1: Welcome and Biophysics Invited Session I |
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Chair: Dongping Zhong, Ohio State University Room: Physics Research Building Smith Seminar Room |
Friday, April 13, 2012 1:45PM - 2:00PM |
A1.00001: Welcome Jim Beatty |
Friday, April 13, 2012 2:00PM - 3:00PM |
A1.00002: Single-Molecule Spectroscopy and Imaging Studies of Protein Dynamics Invited Speaker: H. Peter Lu Enzymatic reactions and protein-protein interactions are traditionally studied at the ensemble level, despite significant static and dynamic inhomogeneities. Subtle conformational changes play a crucial role in protein functions, and these protein conformations are highly dynamic rather than being static. We applied AFM-enhanced single-molecule spectroscopy to study the mechanisms and dynamics of enzymatic reactions involved with kinase and lysozyme proteins. Enzymatic reaction turnovers and the associated structure changes of individual protein molecules were observed simultaneously in real-time by single-molecule FRET detections. Our single-molecule spectroscopy measurements of T4 lysozyme and HPPK enzymatic conformational dynamics have revealed time bunching effect and intermittent coherence in conformational state change dynamics involving in enzymatic reaction cycles. The coherent conformational state dynamics suggests that the enzymatic catalysis involves a multi-step conformational motion along the coordinates of substrate-enzyme complex formation and product releasing, presenting as an extreme dynamic behavior intrinsically related to the time bunching effect that we have reported previously. Our results of HPPK interaction with substrate support a multiple-conformational state model, being consistent with a complementary conformation selection and induced-fit enzymatic loop-gated conformational change mechanism in substrate-enzyme active complex formation. Our new approach is applicable to a wide range of single-molecule FRET measurements for protein conformational changes under enzymatic reactions. [Preview Abstract] |
Friday, April 13, 2012 3:00PM - 3:15PM |
A1.00003: BREAK
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Friday, April 13, 2012 3:15PM - 4:15PM |
A1.00004: Membrane disruption mechanism of antimicrobial peptides Invited Speaker: Ka Yee Lee Largely distributed among living organisms, antimicrobial peptides are a class of small ($<$100 residues) host defense peptides that induce selective membrane lytic activity against microbial pathogens. The permeabilizing behavior of these diverse peptides has been commonly attributed to the formation of pores, and such pore formation has been categorized as barrel-stave, toroidal, or carpet-like. With the continuing discovery of new peptide species, many are uncharacterized and the exact mechanism is unknown. Through the use of atomic force microscopy, the disruption of supported lipid bilayer patches by protegrin-1 is concentration-dependent. The intercalation of antimicrobial peptide into the bilayer results in structures beyond that of pore formation, but with the formation of worm-like micelles at high peptide concentration. Our results suggest that antimicrobial peptide acts to lower the interfacial energy of the bilayer in a way similar to detergents. Antimicrobial peptides with structural differences, magainin-1 and aurein 1.1, exhibit a mechanistic commonality. [Preview Abstract] |
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