Stepwise translation of myofilaments

这种竞争性更新的目的是继续探索肌丝的逐步滑动。动力学 滑动将在PI实验室开发的两种制剂中进行探索： 肌原纤维制备，其中单个肌节中缩短和延长的动力学是 研究;和，一个制剂组成的一个单一的肌动蛋白丝滑动超过一个单一的肌球蛋白或厚 灯丝初步，在两个准备的证据表明，滑动发生在步骤和步骤的大小是一个 2.7 nm的整数倍，即n × 2.7。后续实验旨在测试这种范式是否 真的为此，将对两种制剂进行对照实验，并对各种技术方案进行比较。 将进行改进以提高分辨率。一个问题是， 缩短的步长显示相同的步进范例。另一个问题是n > 1的值是否是 有限的分辨率，以及在更高的分辨率下，所有步骤是否具有不同的值。暂停的持续时间， 也就是说，也将探讨步骤之间的时间。暂停持续时间对负载的函数依赖性将 被探索。最后，将实施若干战略，例如，单个灯丝对的重叠减少， 以减少横桥的数量，使其接近一座。这样，滑动的动力学很少 检查天桥。虽然这可能不是一个“单分子”实验，但其优点是， 与肌动蛋白相互作用的肌球蛋白分子保持其天然构型。因此，实验 应该会产生关于收缩过程的近分子性质的有价值的信息。

The aim of this competing renewal is a continued exploration of stepwise sliding of myofilaments. Dynamics of sliding will be explored in two preparations that have been developed in the laboratory of the PI: a single myofibril preparation in which the dynamics of shortening and lengthening in single sarcomeres is investigated; and, a preparation consisting of a single actin filament sliding over a single myosin or thick filament. Preliminary,evidence in both preparations indicates that sliding occurs in steps and step size is an integer multiple of 2.7 nm, i.e. n x 2.7. Followup experiments are designed to test whether this paradigm is genuine. To this end, control experiments will be carried out on both preparations, and various technical improvements will be implemented to improve resolution. One question is whether lengthening steps and shortening steps show the same stepping paradigm. Another is whether values of n > 1 are artifacts of limited resolution, and whether, with higher resolution, all steps are of a distinct value. Duration of pauses, i.e., periods between steps, will also be explored. The functional dependence of pause duration on load will be explored. Finally, several strategies will be implemented, e.g., diminished overlap of single filament pairs, to reduce the number of cross-bridges to approach one. In such a way, dynamics of sliding with very few cross-bridges will be examined. Although this may not be a "single molecule" experiment, the advantage is that myosin molecules that interact with actin remain in their natural configuration. Hence, the experiments should yield valuable information on the near-molecular nature of the contractile process.