TURBIDITY OF MYOFIBRIL AND ACTOMYOSIN SUSPENSIONS AND ITS CHANGE INDUCED BY ATP

Optical properties of suspensions of contractile models, myofibrils an d two actomyosins (''natural'' and ''synthetic''), have been investiga ted. The turbidity and the wavelength exponent of suspensions of the o riginal, contracted, and aggregated models have been measured at diffe rent concentrations, light wavelengths, and solid angles of the spectr ophotometer photocell. Change in the turbidity of these suspensions up on addition of MgATP is compared to changes in the particle size and g el phase volume of suspensions. The turbidity of myofibril and actomyo sin suspensions is shown to be strongly dependent on the conditions of its measurement. The extent of turbidity changes upon the contraction of myofibrils and superprecipitation of actomyosin also depends on me asurement conditions and is proportional to the difference between the densities of the original and contracted particles. It is suggested t hat the increase in suspension turbidity upon addition of MgATP is due to changes in the form of the light-scattering angular diagram rather than to the enhancement of total light scattering of suspensions. (C) 1995 Academic Press, Inc.