Key Points
- To investigate the rotational Brownian motions and structural constraints of myosin heads in myofibrils under relaxing and rigor conditions.
- Selectively labeled sulfhydryl groups on myosin heads within myofibrils using the triplet probe 5-eosinylmaleimide.
- Measured rotational dynamics using flash-induced phosphorescence anisotropy decay and evaluated head mobility with a double-cone wobbling model.
- Anisotropy decay under relaxing conditions exhibited fast submicrosecond and slow microsecond components, fitting a double-cone model with semiangles of roughly 30 degrees for subfragment 1 and 50 degrees for its connecting region.
- Rotational freedom of relaxed myosin heads was only slightly restricted by the myofibril filament lattice, whereas motion completely ceased on a 10-microsecond timescale under rigor conditions.
Structured PICO
PPopulationMyofibrils with myosin heads selectively labeled with the triplet probe 5-eosinylmaleimide
IInterventionFlash-induced phosphorescence anisotropy decay measurements under relaxing and rigor conditions
OOutcomeRotational Brownian motions of myosin heads (anisotropy decay curve)
This basic science study demonstrates that the rotational freedom of myosin heads is only slightly restricted by the filament lattice space in myofibrils under relaxing conditions, but completely restricted under rigor conditions.