2019/04/28 by Julie A. Cass, Cass, Julie A, Chelsea Williams +11
Medicine · Physics and Astronomy · #Advanced MRI Techniques and Applications #Cardiomyopathy and Myosin Studies #FOS: Biological sciences #Micro and Nano Robotics #Subcellular Processes (q-bio.SC) #Tissues and Organs (q-bio.TO)
paper · pdf · doi:10.48550/arxiv.1904.12420
openalex publication_date 2019/04/28 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
During muscle contraction, myosin motors anchored to thick filaments bind to\nand slide actin thin filaments. These motors rely on energy derived from ATP,\nsupplied, in part, by diffusion from the sarcoplasm to the interior of the\nlattice of actin and myosin filaments. The radial spacing of filaments in this\nlattice may change or remain constant during contraction. If the lattice is\nisovolumetric, it must expand when the muscle shortens. If, however, the\nspacing is constant or has a different pattern of axial and radial motion, then\nthe lattice changes volume during contraction, driving fluid motion and\nassisting in the transport of molecules between the contractile lattice and the\nsurrounding intracellular space. We first create an\nadvective-diffusive-reaction flow model and show that the flow into and out of\nthe sarcomere lattice would be significant in the absence of lattice expansion.\nAdvective transport coupled to diffusion has the potential to substantially\nenhance metabolite exchange within the crowded sarcomere. Using time-resolved\nx-ray diffraction of contracting muscle, we next show that the contractile\nlattice is neither isovolumetric nor constant in spacing. Instead, lattice\nspacing is time-varying, depends on activation, and can manifest as an\neffective time-varying Poisson ratio. The resulting fluid flow in the sarcomere\nlattice of synchronous insect flight muscles is greater than expected for\nconstant lattice spacing conditions. Lattice spacing depends on a variety of\nfactors that produce radial force, including crossbridges, titin-like\nmolecules, and other structural proteins. Volume change and advective transport\nvaries with the phase of muscle stimulation but remains significant at all\nconditions. Akin to "breathing," advective-diffusive transport in sarcomeres is\nsufficient to promote metabolite exchange and may play a role in the regulation\nof contraction itself.\n