Abstract：
:The rotation of the lever arm of myosin cross-bridges is believed to be responsible for muscle contraction. To resolve details of this rotation, it is necessary to observe a single cross-bridge. It is still impossible to do so in muscle fiber, but it is possible to investigate a small population of cross-bridges by simultaneously activating myosin in a femtoliter volume by rapid release of caged ATP. In earlier work, in which the number of observed cross-bridges was limited to approximately 600 by confocal microscopy, we were able to measure the rates of cross-bridge detachment and rebinding. However, we were unable to resolve the power stroke. We speculated that the reason for this was that the number of observed cross-bridges was too large. In an attempt to decrease this number, we used two-photon microscopy which permitted observation of approximately 1/2 as many cross-bridges as before with the same signal/noise ratio. With the two-photon excitation, the number of cross-bridges was small enough to resolve the beginning of the power stroke. The results indicated that the power stroke begins approximately 170 ms after the rigor cross-bridge first binds ATP.
journal_name
Biophys Jjournal_title
Biophysical journalauthors
Borejdo J,Shepard A,Akopova I,Grudzinski W,Malicka Jdoi
10.1529/biophysj.104.045450subject
Has Abstractpub_date
2004-12-01 00:00:00pages
3912-21issue
6eissn
0006-3495issn
1542-0086pii
S0006-3495(04)73857-6journal_volume
87pub_type
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