Tension generation by isolated myofibrils

The technique for mechanical dissection of microscopic myofibrilar bundles containing few myofibrils is described. A sensitive electrooptical tension transducer capable of resolving the tension generated by such myofibrilar bundles to within a fraction of a percent is used to study the response of the preparations to low ATP concentrations. The rate of tension development decreased with a decrease in ATP concentration. Below 10^-6 M ATP the myofibrils did not demonstrate any mechanical activity at all. These findings are discussed in terms of the kinetics of the crossbridge cycle.