The Role of Surface Physics in Motility

Abstract

Nearly all research in motility has focused sole attention to the solid active elements in the cell while regarding the fluid components (the cytoplasmic and myoplasmic fluids) as primarily passive elements in force generation and movement. The release of the products of hydrolysis has a major effect on the surface energy in the fluid boundary making the fluid proteophobic directly producing force and movement of the structure it is interfaced with. Considering the fluid surface physics elucidates the following: 1. In muscle a change in surface tension at the fluid-filament boundary of only 6 dynes/cm will producing an increase in proteophobicity resulting in a contractile force equal to the maximum that striated muscle can produce. 2. The optimum position for hydrolysis of ATP to most effectively produce the force on a cargo attached to a microtubule at the 12 o'clock position will be shown to be at the 5 or 7 o'clock position. 3. The viral packing motor function is explained by the release of phosphate ions in the hydrolysis of ATP around the DNA outside the capsid. The free surface energy at the fluid-DNA boundary becomes elevated by the ions which forces the DNA inside where the DNA-DNA interface (as it folds) is less.