1: Proc Natl Acad Sci U S A  1999 Aug 17;96(17):9602-6 

Imaging of thermal activation of actomyosin motors.

Kato H, Nishizaka T, Iga T, Kinosita K Jr, Ishiwata S.

Central Research Laboratory, Hitachi Ltd., Hatoyama, Saitama 350-0395, Japan.

We have developed temperature-pulse microscopy in which the temperature of a
microscopic sample is raised reversibly in a square-wave fashion with rise and
fall times of several ms, and locally in a region of approximately 10
micrometers in diameter with a temperature gradient up to 2 degrees
C/micrometers. Temperature distribution was imaged pixel by pixel by image
processing of the fluorescence intensity of rhodamine phalloidin attached to
(single) actin filaments. With short pulses, actomyosin motors could be
activated above physiological temperatures (higher than 60 degrees C at the
peak) before thermally induced protein damage began to occur. When a sliding
actin filament was heated to 40-45 degrees C, the sliding velocity reached 30
micrometers/s at 25 mM KCl and 50 micrometers/s at 50 mM KCl, the highest
velocities reported for skeletal myosin in usual in vitro assay systems. Both
the sliding velocity and force increased by an order of magnitude when heated
from 18 degrees C to 40-45 degrees C. Temperature-pulse microscopy is expected
to be useful for studies of biomolecules and cells requiring temporal and/or
spatial thermal modulation.

PMID: 10449739 [PubMed - indexed for MEDLINE]