Research
The Role of Surface and Interface Science in
Muscle Contraction
A Testable Model
Abstract: (Download full text)
Few people have paid much attention to the role of surface and interface science of the
liquid myoplasm in the contraction process. But in 1970, Albert Szent-Györgyi, in an
opening address to a symposium on Muscle, said
“the greatest experience of my scientific life” was the moment I saw “
…motion produced for the first time in vitro by constituents of muscle …”
He had earlier succeeded in extracting actomyosin which “ … forms a
resilient gel. It is excessively hydrophillic.” He went on to say, “…Under
influence of ATP actomyosin loses hydrophillity. The hydrophillic colloid
becomes entirely hydrophobic, the most striking change I ever saw.”
Szent-Györgyi recognized in 1940-43 that contraction is triggered by a dramatic change
in the surface physics at the fluid filament boundary. Sadly, he abandoned work in
muscle when he was unable to reconcile this critical observation with the sliding filament
theory.
During contraction the chemical structure of the filaments don’t significantly change, but
the chemistry of the myoplasmic fluid changes dramatically. Thus, reinterpreting Szent-
Györgyi’s observations, rather than the filaments changing from hydrophilic to
hydrophobic, it is the fluid that changes from being proteophilic to becoming
proteophobic.
This paper presents an innovative fluid surface energy contraction model. This accounts
for force generation, filament sliding, filament shortening, contraction beyond overlap
and heat of shortening. The filaments define the fluid/filament boundary. The crossbridges
participate in the hydrolysis of the ATP changing the chemistry of the fluid thus
changing the surface energy. A surface energy gradient is set up between the overlap and
non-overlap region due to the thin film effect in the overlap region which produces force
and movement. A meaningful theoretical model must be testable. This paper suggests
experiments to confirm this theory.
The full article is found here.