# KINETICS OF ENERGY LIBERATION IN ACTIVE SKELETAL MUSCLE

> **NIH NIH R01** · STATE UNIVERSITY NEW YORK STONY BROOK · 1989 · $105,625

## Abstract

This project is a study of the kinetics of energy transformation
in active muscle using mechanical and myothermal measurements.
Gilbert & Ford (1988) found that heat is absorbed during rapid
tension recovery after quick release, indicating that the entropy
change of the crossbridge 'power stroke' is positive.  The
detached-bridge transition in which the associated protein
configurational change is reset in preparation for the next cycle
must therefore have a negative entropy change and produce heat.
One goal of the project is to quantify such thermodynamic
parameters of crossbridge transitions, by measuring precisely the
kinetics of heat changes during tension transients.  Ford & Gilbert
(1987) reported that a substantial amount of the heat produced
specifically by shortening appeared afterwards, indicating its
possible association with detached bridges and the 'power-stroke-
reset'process.  Another goal is to compare the post-shortening heat
with the extents of shortening and the 'power-stroke' and 'reset'
processes.  Ford & Gilbert also showed that heart rate continues
to rise after power becomes constant, indicating that the
crossbridge cycle does not always reach a steady state.  A third
goal is to determine whether a steady state is established at all
velocities and the kinetics with which it occurs.  Sources of the
rising heat rate are the negative entropy change of 'power-stroke-
reset' and free energy dissipation by uncoupled bridges operating
in the myosin cycle.  Contributions from the two sources will be
distinguished by the kinetics of heat production during the tran-
sition to shortening steady state and from shortening to a new
isometric steady state.  The velocity dependence of energy coupling
will also be determined.  In the steady state net entropy changes
of the contractile proteins must be zero, and most of the heat
comes from dissipation of free energy.  The ratio of power to total
energy rate is therefore a measure of coupling.  The observations
will be used to develop a kinetic scheme of energy transduction
with sufficiently specific energetic and thermodynamic properties
to provide insight into the molecular mechanism.  Motility and
chemomechanical energy transduction are fundamental properties of
living organisms, and variations of the two-protein, oarlike
molecular mechanism operating in skeletal muscle are known to
produce some of the other motile behavior at the subcellular level.
Disruptions of cell motility produce many pathological conditions,
whose etiology can be fully understood only if the underlying mole-
cular mechanisms are known.

## Key facts

- **NIH application ID:** 3158004
- **Project number:** 1R01AR037277-01A3
- **Recipient organization:** STATE UNIVERSITY NEW YORK STONY BROOK
- **SAM.gov UEI:** M746VC6XMNH9
- **Principal Investigator:** SUSAN H GILBERT
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 1989
- **Award amount:** $105,625
- **Award type:** 1
- **Project period:** 1989-03-01 → 1990-06-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/3158004

## Citation

> US National Institutes of Health, RePORTER application 3158004, KINETICS OF ENERGY LIBERATION IN ACTIVE SKELETAL MUSCLE (1R01AR037277-01A3). Retrieved via MORVS 2026-10-25 from https://api.morvs.ai/grant/nih/3158004. Licensed CC0.

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