Результаты поиска по 'mechanical structure':
Найдено статей: 52
  1. Zhmurov A.A., Alekseenko A.E., Barsegov V.A., Kononova O.G., Kholodov Y.A.
    Phase transition from α-helices to β-sheets in supercoils of fibrillar proteins
    Computer Research and Modeling, 2013, v. 5, no. 4, pp. 705-725

    The transition from α-helices to β-strands under external mechanical force in fibrin molecule containing coiled-coils is studied and free energy landscape is resolved. The detailed theoretical modeling of each stage of coiled-coils fragment pulling process was performed. The plots of force (F) as a function of molecule expansion (X) for two symmetrical fibrin coiled-coils (each ∼17 nm in length) show three distinct modes of mechanical behaviour: (1) linear (elastic) mode when coiled-coils behave like entropic springs (F<100−125 pN and X<7−8 nm), (2) viscous (plastic) mode when molecule resistance force does not increase with increase in elongation length (F≈150 pN and X≈10−35 nm) and (3) nonlinear mode (F>175−200 pN and X>40−50 nm). In linear mode the coiled-coils unwind at 2π radian angle, but no structural transition occurs. Viscous mode is characterized by the phase transition from the triple α-spirals to three-stranded parallel β-sheet. The critical tension of α-helices is 0.25 nm per turn, and the characteristic energy change is equal to 4.9 kcal/mol. Changes in internal energy Δu, entropy Δs and force capacity cf per one helical turn for phase transition were also computed. The observed dynamic behavior of α-helices and phase transition from α-helices to β-sheets under tension might represent a universal mechanism of regulation of fibrillar protein structures subject to mechanical stresses due to biological forces.

    Keywords: phase transition from α-helices to β-sheets, thermodynamics of transition from α-helices to β-sheets, molecular modeling, fibrinogen, fibrin fibers, Molecular Dynamics, GPU.
    Views (last year): 6. Citations: 1 (RSCI).
  2. Lihachev I.V., Galzitskaya O.V., Balabaev N.K.
    Investigation of C-Cadherin mechanical properties by Molecular Dynamics
    Computer Research and Modeling, 2013, v. 5, no. 4, pp. 727-735

    The mechanical stability of cell adhesion protein Cadherin with explicit model of water is studied by the method of molecular dynamics. The protein in apo-form and with the ions of different types (Ca2+, Mg2+, Na+, K+) was unfolding with a constant speed by applying the force to the ends. Eight independent experiments were done for each form of the protein. It was shown that univalent ions stabilize the structure less than bivalent one under mechanical unfolding of the protein. A model system composed of two amino acids and the metal ion between them demonstrates properties similar to that of the cadherin in the stretching experiments. The systems with potassium and sodium ions have less mechanical stability then the systems with calcium and magnesium ions.

    Keywords: C-Cadherin, molecular dynamics, bivalent and univalent ions.
    Views (last year): 5.
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