In a study of the force-generating mechanism in muscle, Goldman et al. [Nature 300:701 (19...

In a study of the force-generating mechanism in muscle, Goldman et al. [Nature 300:701 (1982)] first soaked rabbit skeletal muscle fibers in a solution containing an analog of ATP, P3-1-(2-nitro)phenylethyladenosine 5-triphosphate, which has no effect on muscle contraction or relaxation. When the muscle fibers equilibrated with this analog are irradiated with a pulse of intense 347-nm UV light from a frequency-doubled ruby laser, photolysis of the analog occurs and ATP is suddenly generated:

It has been observed that in the presence of excess Mg2+ this generation of ATP leads to relaxation of the muscle fiber according to first-order kinetics. By varying the intensity of the laser beam, different concentrations of ATP can be generated, and the first-order relaxation time t has been measured as a function of ATP concentration:

a. From the data given, obtain the best second-order rate coefficient for the relaxation of the muscle.

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b. Describe briefly why it is important to use a short pulse of light in this experiment.