26,780 research outputs found

    Mechanism of unidirectional movement of kinesin motors

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    Kinesin motors have been studied extensively both experimentally and theoretically. However, the microscopic mechanism of the processive movement of kinesin is still an open question. In this paper, we propose a hand-over-hand model for the processivity of kinesin, which is based on chemical, mechanical, and electrical couplings. In the model the processive movement does not need to rely on the two heads' coordination in their ATP hydrolysis and mechanical cycles. Rather, the ATP hydrolyses at the two heads are independent. The much higher ATPase rate at the trailing head than the leading head makes the motor walk processively in a natural way, with one ATP being hydrolyzed per step. The model is consistent with the structural study of kinesin and the measured pathway of the kinesin ATPase. Using the model the estimated driving force of ~ 5.8 pN is in agreements with the experimental results (5~7.5 pN). The prediction of the moving time in one step (~10 microseconds) is also consistent with the measured values of 0~50 microseconds. The previous observation of substeps within the 8-nm step is explained. The shapes of velocity-load (both positive and negative) curves show resemblance to previous experimental results.Comment: 22 pages, 6 figure

    Control of spiral waves and turbulent states in a cardiac model by travelling-wave perturbations

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    We propose a travelling-wave perturbation method to control the spatiotemporal dynamics in a cardiac model. It is numerically demonstrated that the method can successfully suppress the wave instability (alternans in action potential duration) in the one-dimensional case and convert spiral waves and turbulent states to the normal travelling wave states in the two-dimensional case. An experimental scheme is suggested which may provide a new design for a cardiac defibrillator.Comment: 9 pages, 5 figure
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