[Monitoring the orientation of myosin bridges on two-dimensional maps of birefringence in a single muscle fiber].
Two-dimensional maps of birefringence in sarcomers of a single fiber of rabbit m.psoas were obtained by an automated interference microscope developed at our laboratory. The changes in birefringence of muscle fibers reflect the movement of myosin cross-bridges. The orientation of cross-bridges was modified by varying the pH (pH 7.0, 6.0, 8.0) and ionic strength (mu = 0.115, 0.085, 0.235) of the bathing rigor solution. The maximum value of total birefringence in the rigor state was observed at neutral pH. Total birefringence markedly decreased (by 40%) as pH was changed from 7.0 to both 8.0 and 6.0. No significant changes in light phase shifts were found at a 1.5 reduction of ionic strength in the rigor solution. The calculated birefringence values were 45% higher in rigor solutions of a high (mu = 0.235) ionic strength. The results observed are discussed in terms of changes in the orientation of cross-bridges due to the movement of the alpha-helical subfragment-2 away from the filament shaft (pH 8) or coming closer to it (mu = 0.235). The available data do not allow one to explain the results obtained at pH 6.0.
Skrebnitskaia
L K
LK
Institute of Theoretical and Experimental Biophysics, Russian Academy of Sciences, Pushchino, Moscow Region, 142290 Russia.
Neĭman
S A
SA
Rozhdestvenskaia
Z E
ZE
Vishniakov
G N
GN
D000818:Animals; D001718:Birefringence; D066298:In Vitro Techniques; D007368:Interferometry; D018485:Muscle Fibers, Skeletal / Q000737:chemistry* / Q000502:physiology; D009126:Muscle Relaxation; D018482:Muscle, Skeletal / Q000737:chemistry / Q000502:physiology / Q000648:ultrastructure; D009218:Myosins / Q000737:chemistry*; D011817:Rabbits; D012518:Sarcomeres / Q000737:chemistry
D009218:Myosins