The hidden ingenuity in titin structure

Titin is a giant protein that functions as a shock absorber in sarcomeres-the basic contractile unit of muscles. When stretched, thermal disturbances are expected to make titin follow the Maxwell path (global minimizer) of its energy. This path involves neither energy dissipation nor hysteresis. Therefore, a basic question is how does titin releases energy so efficiently? By adopting a simple mechanical model of a chain comprised from bistable elements, we show that dissipation depends on both system size and the height of the energy barrier separating equilibrium configurations. In this sense, titin is an optimal product of evolution. (C) 2011 American Institute of Physics. [doi:10.1063/1.3558901]