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

研究了肌肉收缩的机械和生化过程之间的相关性，以及溶剂对它们的影响。将僵硬状态下的带皮肌纤维置于含有P^3-1（2-硝基）苯基乙基-ATP、“笼状ATP”（ATP的惰性光不稳定前体）和游离Ca^&lt;2+&gt;浓度&lt;10 μ M或-30 μ M的溶液中孵育<-8>。在松弛过程中记录纤维的机械响应，以及在主动收缩过程中，通过从倍频红宝石激光器中释放347 nm光脉冲来启动ATP。当溶液中含有10%的乙二醇时，Goldman，Hierarchy和Trentham（1984）报道的松弛过程中张力的瞬时升高明显受到抑制。在光解之前拉伸纤维改变了张力瞬变的早期部分的时间过程，但对后期阶段或stifficity.The张力记录从拉伸和等距试验收敛到最终的共同时间过程的松弛的影响相对较小。张力记录的收敛性分析提供了一种测量跨桥分离率的方法，作为ATP浓度的函数。在20 ℃时，脱附的表观二级速率常数至少为5 × 10 ^5 M^<-1>s^<-1>，在乙二醇中也是如此。当培养基中含有Ca^&lt;2+&gt;时，产生主动张力.根据连续分离和再附着反应分析张力记录，提供了跨桥再附着率的测量方法和分离率的替代测量方法。在乙二醇中，导致力产生的跨桥再附着率以及稳定的主动张力降低至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.