June 11, 2013 | David F. Coppedge

Molecular Motors Put a Spring in Your Step

When you feel in spring in your step, thank tiny molecular motors in your muscles and tissues that make it possible.

A paper in Science by researchers primarily from University of Washington, Seattle, proposed the novel idea that the molecular motors in muscle cells store elastic energy.  Observing flight muscles in moths, they deduced that the springiness of these motors provides an additional boost to the power generate by muscles:

Muscles not only generate force. They may act as springs, providing energy storage to drive locomotion. Although extensible myofilaments are implicated as sites of energy storage, we show that intramuscular temperature gradients may enable molecular motors (cross-bridges) to store elastic strain energy…. These results suggest that cross-bridges can perform functions other than contraction, acting as molecular links for elastic energy storage.

Researchers from Europe, publishing in PNAS, found that collagen and fibrin exhibit non-linear strain response upon loading.  This is another factor that provides resilience in movement.

We show that the nonlinear mechanical response of networks formed from un–cross-linked fibrin or collagen type I continually changes in response to repeated large-strain loading. We demonstrate that this dynamic evolution of the mechanical response arises from a shift of a characteristic nonlinear stress–strain relationship to higher strains. Therefore, the imposed loading does not weaken the underlying matrices but instead delays the occurrence of the strain stiffening. Using confocal microscopy, we present direct evidence that this behavior results from persistent lengthening of individual fibers caused by an interplay between fiber stretching and fiber buckling when the networks are repeatedly strained…. Thus, a fibrous architecture in combination with constituents that exhibit internal plasticity creates a material whose mechanical response adapts to external loading conditions.

This behavior is so interesting, they pass the news on to biomimetics engineers: “This design principle may be useful to engineer novel materials with this capability.”

Once again, the CEH Law is confirmed: Darwin-talk is inversely proportional to the amount of detail discussed about biological systems.




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