Loxdale H D, Tregear R T
J Muscle Res Cell Motil. 1985 Apr;6(2):163-75. doi: 10.1007/BF00713058.
A method for the continuous measurement of ATP hydrolysis (ATPase) by demembranated muscle fibres has been applied to isometrically held, glycerol-extracted flight muscle fibres from the water-bug Lethocerus, under conditions of high MgATP, neutral pH, and varying ionic strength, Ca2+ and extension. These variables caused parallel changes in isometric tension and ATPase. The slope of ATPase upon tension (delta ATPase/delta Tension; incremental tension cost) remained the same upon extension at either different Ca2+ concentrations or different ionic strength. Isometric activation by Ca2+ gave a higher incremental tension cost. The calculated mechanical rate constant of the work-producing process, measured by the small-amplitude behaviour, was increased by either Ca2+ or ionic strength, and little changed by extension; there was therefore a dissociation between its value and that of the incremental tension cost. The results appear to exclude a two-state crossbridge model for fibrillar insect flight muscle.
一种通过去膜肌纤维连续测量ATP水解（ATP酶）的方法，已应用于在高MgATP、中性pH值以及不同离子强度、Ca2+和拉伸条件下，对来自水蝽Lethocerus的等长保持的甘油提取飞行肌纤维进行研究。这些变量导致等长张力和ATP酶发生平行变化。在不同Ca2+浓度或不同离子强度下进行拉伸时，ATP酶随张力的斜率（δATP酶/δ张力；增量张力成本）保持不变。Ca2+引起的等长激活产生了更高的增量张力成本。通过小振幅行为测量的产生功过程的计算机械速率常数，会因Ca2+或离子强度而增加，而拉伸对其影响不大；因此，其值与增量张力成本的值之间存在解离。结果似乎排除了纤维状昆虫飞行肌的双态横桥模型。
