1: J Biol Chem  1987 Jun 15;262(17):8314-7 

Rotational motions of myosin heads in myofibril studied by phosphorescence
anisotropy decay measurements.

Ishiwata S, Kinosita K Jr, Yoshimura H, Ikegami A.

We studied the rotational Brownian motions of myosin heads, of which the
sulfhydryl group was selectively labeled with the triplet probe
5-eosinylmaleimide, in myofibril by using flash-induced phosphorescence
anisotropy decay measurements. The anisotropy decay curve under relaxing
conditions consisted of a fast (submicrosecond) and a slow (a few microseconds)
component and a small constant part as in the synthetic myosin filaments in
solution. The decay curves could be analyzed by assuming that a head part, i.e.
subfragment 1 (S1), wobbles in the first cone and a part connecting S1 and the
tail of a myosin molecule of which the length is shorter than subfragment 2 (S2)
wobbles in the second cone (a double-cone model); the semiangles of the former
and the latter cones were about 30 degrees and 50 degrees, respectively. The
rotational freedom of myosin heads was only slightly restricted by the limited
space of the filament lattice in myofibrils. Under rigor conditions, no motion
of myosin heads was observed in the 10-microseconds time scale.

PMID: 2439498 [PubMed - indexed for MEDLINE]