Tropomyosin/troponin binding significantly increases the bending stiffness of actin filaments, providing biophysical insights into muscle mechanics.
Does not inform clinical practice; extends biophysical models of thin-filament stiffness but leaves in vivo cardiac effects open.
Quasi-elastic light scattering (QELS) is applied to investigate the effect of the tropomyosin/troponin complex (Tm/Tn) on the stiffness of actin filaments. The importance of hydrodynamic screening in semidilute solutions is demonstrated. A new concentration dependent expression for the dynamic structure factor g ( k, t ) of semiflexible polymers in semidilute solutions is used to analyze the experimental QELS data. A concentration independent value for the bending modulus κ is thus obtained. It increases by 50% as a consequence of Tm/Tn binding in a 7:1:1 molar ratio of actin/Tm/Tn. In addition a new expression for the initial slope of the dynamic structure factor of a semiflexible polymer is used to determine the effective hydrodynamic diameter of the actin filament. Our results confirm the general relevance of the concept of (intrinsic) semiflexibility to polymer dynamics.
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A 1996 study studied this question.
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