Correlations between the mechanical and biochemical processes of muscle contraction by photogeneration of ATP.

研究了肌肉收缩的机械过程和生化过程之间的关系，以及溶剂对它们的影响。在严格状态下剥皮的肌肉纤维在含有P^3-1（2-硝基）苯乙基ATP的溶液中孵育，“笼状ATP”是ATP的惰性光稳定性前体，游离Ca^<2+>浓度<lO^<-8>M或-30 uM。在弛豫和主动收缩期间，纤维的机械响应被记录下来。主动收缩是由来自倍频红宝石激光器的347 nm光脉冲释放ATP引起的。当溶液中加入10%的乙二醇时，Goldman, Hiberd & Trentham（1984）报道的松弛过程中张力的短暂上升被明显抑制。光解前拉伸纤维改变了张力瞬态早期阶段的时间过程，但对后期阶段或刚度的影响相对较小。拉伸和等距试验的张力记录趋同于松弛的最后共同时间过程。张力记录的收敛性分析提供了一种方法来测量作为ATP浓度函数的过桥脱离率。在20oc条件下，分离的二级速率常数至少为5xlO^5 M^<-1> s^<-1>，在乙二醇条件下也是如此。当Ca^<2+>加入介质时，产生主动张力。根据顺序分离和再附着反应的张力记录分析，提供了跨桥再附着率的测量和分离率的替代测量。在乙二醇中，导致力产生的桥桥再附着率以及稳定的主动张力降低到70%。这些结果表明溶剂-蛋白质相互作用参与了跨桥再附着和力的产生。

Correlations between the mechanical and biochemical processes of muscle contraction, and the effect of the solvent on them, have been studied.Skinned muscle fibers in the rigor state were incubated in a solution containing P^3-1(2-nitro)pherlethyl-ATP, 'caged ATP' an inert photolabile precursor of ATP, and free Ca^<2+> concentration of either <lO^<-8>M of -30 uM. The mechanical response of the fibers was recorded during relaxation, as well as during the active contraction, initiated by liberating ATP with a pulse of 347 nm light from a frequency-doubled ruby laser. When ethylene glycol was included in the solution to 10%, the transient rise of tension during relaxation reported by Goldman, Hiberd & Trentham (1984) was markedly suppressed. Stretching fibers before photolysis changed the time course of the early parts of the tension transients but with relatively less effect on the later phases or on stiffness.The tension records from stretch and isometric trials converged to a final common time course of relaxation. Analysis of the convergence of tension records provided a means for measuring the cross-bridge detachment rate from the thin filament as a function of ATP concentration. The apparent second-order rate constant for detachment was at least 5xlO^5 M^<-1> s^<-1> at 20ﾟC, and this rate was the same in ethylene glycol. When Ca^<2+> was included the medium, active tension was produced. Analysis of the tension records in terms of sequential detachment and reattachment reactions, provided a measure of cross-bridge reattachment rate and an alternate measure of the detachment rate. The rate of cross-bridge reattachment leading to force production, as well as the steady active tension, was reduced to 70% in ethylene glycol. These results indicated that a solvent-protein interaction is involved in the cross-bridge reattachment and force generation.