부산대학교 도서관

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.bpj.2008.11.032 Byline: Andre E.X. Brown (a )(a ), Alina Hategan (As.), Daniel Safer (As.), Yale E. Goldman (a )(As.)(A[paragraph]), Dennis E. Discher (a )(A[paragraph])(a) Abstract: Myosin-II's rod-like tail drives filament assembly with a head arrangement that is often considered to be a symmetric bipole that generates equal and opposite contractile forces on actin. Self-assembled myosin filaments are shown here to be asymmetric in physiological buffer based on cross-correlated images from both atomic force microscopy and total internal reflection fluorescence. Quantitative cross-correlation of these orthogonal methods produces structural information unavailable to either method alone in showing that fluorescence intensity along the filament length is proportional to height. This implies that myosin heads form a shell around the filament axis, consistent with F-actin binding. A motor density of [approximately equal to]50-100 heads/micrometer is further estimated but with an average of 32% more motors on one half of any given filament compared to the other, regardless of length. A purely entropic pyramidal lattice model is developed and mapped onto the Dyck paths problem that qualitatively captures this lack of length dependence and the distribution of filament asymmetries. Such strongly asymmetric bipoles are likely to produce an unbalanced contractile force in cells and in actin-myosin gels and thereby contribute to motility as well as cytoskeletal tension. Author Affiliation: (a ) Department of Physics and Astronomy, University of Pennsylvania, Philadelphia, Pennsylvania 19104 (a ) Nano/Bio Interface Center, University of Pennsylvania, Philadelphia, Pennsylvania 19104 (As.) Pennsylvania Muscle Institute, and Graduate Groups in, University of Pennsylvania, Philadelphia, Pennsylvania 19104 (A[paragraph]) Cell and Molecular Biology, University of Pennsylvania, Philadelphia, Pennsylvania 19104 (a) Physics, University of Pennsylvania, Philadelphia, Pennsylvania 19104 Article History: Received 10 June 2008; Accepted 21 November 2008 Article Note: (footnote) Andre E. X. Brown and Alina Hategan contributed equally to this work.