Результаты поиска по 'fragmentation':
Найдено статей: 22
  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. Abdullatypov A.V., Tsygankov A.A.
    Homology modeling of the spatial structure of HydSL hydrogenase from purple sulphur bacterium Thiocapsa roseopersicina BBS
    Computer Research and Modeling, 2013, v. 5, no. 4, pp. 737-747

    The results of homology modeling of HydSL, a NiFe-hydrogenase from purple sulphur bacterium Thiocapsa roseopersicina BBS are presented in this work. It is shown that the models have larger confidence level than earlier published ones; a full-size model of HydSL hydrogenase is presented for the first time. The C-end fragment of the enzyme is shown to have random orientation in relation to the main protein globule. The obtain models have a large number of ion pairs, as well as thermostable HydSL hydrogenase from Allochromatium vinosum, in contrast to thermolabile HydAB hydrogenase from Desulfovibrio vulgaris.

    Keywords: homology modeling, hydrogenases, Thiocapsa roseopersicina.
    Views (last year): 2. Citations: 5 (RSCI).
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