A fluorescence depolarization study of the orientational distribution of crossbridges in muscle fibres |
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| Authors: | Uulke A van der Heide Olaf E Rem Hans C Gerritsen Evert L de Beer Piet Schiereck Ian P Trayer Yehudi K Levine |
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| Institution: | (1) Debye Institute, Department of Molecular Biophysics, University of Utrecht, Buys Ballot Laboratory, P.O. Box 80.000, 3508 TA Utrecht, The Netherlands;(2) Department of Medical Physiology, University of Utrecht, The Netherlands;(3) School of Biochemistry, University of Birmingham, UK |
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| Abstract: | A fluorescence depolarization study of the orientational distribution of crossbridges in dye-labelled muscle fibres is presented. The characterization of this distribution is important since the rotation of crossbridges is a key element in the theory of muscle contraction. In this study we exploited the advantages of angle-resolved experiments to characterize the principal features of the orientational distribution of the crossbridges in the muscle fibre. The directions of the transition dipole moments in the frame of the dye and the orientation and motion of the dye relative to the crossbridge determined previously were explicitly incorporated into the analysis of the experimental data. This afforded the unequivocal determination of all the second and fourth rank order parameters. Moreover, this additional information provided discrimination between different models for the orientational behaviour of the crossbridges. Our results indicate that no change of orientation takes place upon a transition from rigor to relaxation. The experiments, however, do no rule out a conformational change of the myosin S 1 during the transition.
Correspondence to: Y. K. Levine |
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| Keywords: | Fluorescence Muscle Crossbridge |
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