Single actomyosin motor interactions in skeletal muscle |
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Authors: | Zeno Földes-Papp Shih-Chu Jeff LiaoBen Barbieri Karol Gryczynski Jr Rafal LuchowskiZygmunt Gryczynski Ignacy GryczynskiJulian Borejdo Tiefeng You |
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Affiliation: | a Department of Molecular Biology and Immunology, University of North Texas Health Science Center, 3500 Camp Bowie Boulevard, Fort Worth, TX 76107, USAb ISS, 1602 Newton Drive, Champaign, IL 61822, USAc Medical University of Graz, Department of Internal Medicine, Division of Clinical Angiology, A-8036 Graz, Austriad Department of Physics, University of North Texas, Denton, TX, USA |
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Abstract: | We present a study of intramuscular motion during contraction of skeletal muscle myofibrils. Myofibrillar actin was labeled with fluorescent dye so that the ratio of fluorescently labeled to unlabeled protein was 1:105. Such sparse labeling assured that there was on average only one actin-marker present in the focus at a given time. From the intensity signal in the two orthogonal detection channels, significant fluctuations, similar to fluorescent burst in diffusion-based single-molecule detection schemes, were identified via a threshold algorithm and analyzed with respect to their intensity and polarization. When only rigor complexes were formed, the fluctuations of polarized intensity were characterized by unimodal Gaussian photon distributions. During contraction, in contrast, bimodal Gaussian photon distributions were observed above the rigor background threshold. This suggests that the bimodal Gaussian photon distributions represent pre- and post-power stroke conformations. Clusters of polarized photons indicated an anisotropy decay of single actomyosin motors of ~ 9 s during muscle contraction. |
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Keywords: | Single actomyosin Live skeletal muscle cell Polarization dependent fluorescence fluctuations Time-dependent photon distributions Molecular orientations |
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