Thermodynamic and Hydrodynamic Studies Relating to the Mechanochemical Cycle in the Flagellum of Crithidia Oncopelti

The motile response of the flagellum of Crithidia oncopelti to changes in the temperature, pressure and viscosity of the environment were studied. The dependence of beat frequency on temperature and pressure can be interpreted in terms of the theory of reaction rates by making the assumption that the frequency is proportional to the rate constant of a chemical reaction within the flagellum. For viscosities below a characteristic value, which depends on the temperature, increasing the pressure causes a reduction in the beat frequency. At the characteristic value, pressure changes do not affect the frequency while above this value an increase in pressure causes an increase in the frequency. Pressure and temperature changes directly affect chemical reactions within the flagella whereas alterations in viscosity produce changes which can be attributed to a modification of the microtubule sliding rate. The time for which detergent-treated flagella remain active following addition of ATP depends upon the environmental conditions. It appears that these in vitro preparations can convert only a limited amount of chemical energy into mechanical work.