Slowly modulating fluctuations as mesoscopic distortions occurring on an actin filament


Kuniyuki Hatori*, Masahiro Matsui, Yoichiro Omote


Department of Bio-System Engineering,

Graduate School of Science and Engineering,

Yamagata University

Yonezawa, 992-8510 Japan


*To whom correspondence should be made.

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An actin filament sliding on myosin molecules exhibits fluctuating or staggered movements as responding to changes in the ATP concentration. We previously observed that fluctuations in the sliding velocity enhanced in a manner being independent of the magnitude of the velocity. The present study focused upon a single actin filament bound to a glass surface through avidin-biotin bonding to examine those fluctuations inherent to the filament in the presence of heavy mero-myosin. The auto-correlation analysis revealed that the relaxation time of fluctuations in the filamental displacement obtains its maximum value at about 100 µM of the ATP concentration in the ambient, while the magnitude of the fluctuations gradually increased with an increase of the concentration. Furthermore, the measurement of the fluorescence intensity from the markers fixed on the filament demonstrated an enhancement of the negative correlation between the measured peak intensity and the spatial spreading of its intensity over the range of 0–200 µM of the ATP concentration, as indicating both development and mitigation of local distortions occurring within the filament.


Keywords; Actin filament; Fluctuations; Myosin; Sliding movement; ATP-dependence; Structural change