| Budget Amount *help |
¥3,300,000 (Direct Cost: ¥3,300,000)
Fiscal Year 1999: ¥1,500,000 (Direct Cost: ¥1,500,000)
Fiscal Year 1998: ¥1,800,000 (Direct Cost: ¥1,800,000)
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| Research Abstract |
In order to study the FENN effect of actomyosin motor, we have been studying the nucleotide exchange rate constants between the bound nucleotide and ATP on flash photolysis of caged ATP during shortening of rabbit psoas myofibrils, and shown the strain-dependent rate constant during the shortening(chaen et al. 1997, Biophys. J). To ascertain the above result, we have measured the rate constant of soleus myofibrils, which is expected to be better preparation to our method limited by video rate (30 Hz). When the myofibril was allowed to shorten, the rate constant was increased with increasing shortening velocity, while the rate constant was not significantly affected by stretch. These results suggest that the cross-bridge kinetics are not significantly affected at higher strain during lengthening but depend on the lower strain during shortening. Moreover, to extend this study from myofibril to actomyosin motor, we have constructed an apparatus to examine if the lifetime of nucleotide bound state depends on the strain of the cross-bridge. The apparatus consists of total internal reflection fluorescence microscopy, dual view imaging unit, and image-intensified CCD camera. By tracing the image of the fluorescent nucleotide on a video frame with scanning mirror, we have succeeded in measuring the shorter life time than 1/30 sec in the ordinary video system (30 frames /sec).
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