Distribution of myosin attachment times predicted from viscoelastic mechanics of striated muscle

Abstract

We demonstrate that viscoelastic mechanics of striated muscle, measured as elastic and viscous moduli, emerge directly from the myosin crossbridge attachment time, t att, also called time-on. The distribution of t att was modeled using a gamma distribution with shape parameter, p, and scale parameter, . At 5mM MgATP, was similar between mouse -MyHC (16.0 3.7 ms) and -MyHC (17.9 2.0 ms), and p was higher (P 0.05) for -MyHC (5.6 0.4 no units) compared to -MyHC (3.2 0.9). At 1mM MgATP, p approached a value of 10 in both isoforms, but rose only in the -MyHC (34.8 5.8 ms). The estimated mean t att (i.e., p product) was longer in the -MyHC compared to -MyHC, and became prolonged in both isoforms as MgATP was reduced as expected. The application of our viscoelastic model to these isoforms and varying MgATP conditions suggest that t att is better modeled as a gamma distribution due to its representing multiple temporal events occurring within t att compared to a single exponential distribution which assumes only one temporal event within t att. © 2011 Bradley M. Palmer et al.