Huxley’s model

Huxley s model (1957) for muscle contraction states that the mechanical and enzymatic characteristics can be described by the overall apparent attachment and detachment rates of the cross-bridge. Contraction was described as a transition between free and attached states (Huxley, 1957). This simple yet elegant two-state model produces several specific predictions about the relationships between force production, ATPase rates, and shortening as a function of these two rate constants. Although this model is somewhat oversimplified given the actual number of biochemical states, and several of its assumptions may not strictly hold in... 

Huxley s Model for Muscle Contraction Revisited The Importance of Microscopic Reversibility... 

The basic idea of Huxley s model is that the myosin filament has a subgroup (termed a head) attached to the main filament by a spring-like element. This subgroup fluctoates back and forth because of thermal noise and can form temporary interactions and attach to sites on the adjacent actin filament with a rate, denoted by /(x), which depends on its position x. The temporary interactions can be broken by a free-energy releasing process (ATP hydrolysis) that detaches the myosin from actin with a rate g(x) that also depends on position. These two... 

F. 1 Huxley s model for how a eyelie binding of myosin to actin (with rale/ (jc)) and release of actin (with rate g(x)) can cause net translatirai of the actin, and ultimately leads to contractirai of the actin-myosin fiber bundle... 

Despite excellent success in fitting kinetic data, however, Huxley s model is not thermodynamically complete because there is no explicit dependence of the velocity or average force on the free-energy released by ATP hydrolysis (Ay =... 

A model that is consistent with the constraint on the transition rates expressed in (3) is essential for understanding the thermodynamics of energy coupling - stoichiometry, thermodynamic efficiency, stopping force, ratio of forward to backward steps, etc. Further, to address what is perhaps the most basic question about muscle - why does ATP hydrolysis drive myosin to move actin one way and not the other the velocity must be an output of the theory rather than an input as it is in Huxley s model. We can better understand this question in terms of a mechanistic description... 

Huxley s Model for Musele Contraction Revisited The Importanee of... 

---