Abstract

The molecular weight of myosin has been determined in 0.5 M KCl and 5 M guanidine · HCl. 1. The molecular weight, using the Archibald approach to equilibrium method is strongly dependent on protein concentration in both solvents giving infinite dilution values of 6.19·105 in 0.5 M KCl and 2.06·105 in 5 M guanidine·HCl. 2. Sedimentation, diffusion and viscosity studies on myosin in 5 M guanidine·HCl provide estimates of the molecular weight in reasonable agreement with the Archibald studies. 3. Preferential binding of guanidine·HCl by myosin has been determined and shown to be of the order of 5% or less. 4. Utilizing these molecular weight determinations and available X-ray diffraction, light scattering and optical rotatory data, a model for the myosin molecule is proposed, based on three equal weight polypeptide chains in the form of a three-stranded α rope.