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 将在PI实验室中开发的两种制备方法中探索滑动：一种单一的 肌原纤维制剂，其中单个肌节的缩短和延长的动力学是 被研究的；以及，由单个肌动蛋白细丝滑动在单个肌球蛋白上或厚的制剂 灯丝。初步，两种制剂中的证据都表明滑动是分步骤进行的，而步长是一种 2.7 nm的整数倍，即n x 2.7。后续实验旨在测试这一范式是否 真的。为此，将对制剂和各种技术进行对照试验 将实施改进以提高分辨率。一个问题是，延长步幅和 缩短步长显示出相同的步进模式。另一个问题是n&gt；1的值是否为 分辨率有限，以及分辨率较高时，是否所有步骤都具有不同的价值。暂停的持续时间， 也将探索步骤之间的时间段。暂停时间与负载的函数依赖关系将 被探索。最后，将实施几种策略，例如，减少单丝对的重叠， 将跨桥的数量减少到接近一座。在这样的方式下，滑动的动力学很少 将对跨桥进行检查。尽管这可能不是一个“单分子”实验，但它的优势是 与肌动蛋白相互作用的肌球蛋白分子保持其自然构型。因此，这些实验 应该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.