SELF-DIFFUSION OF MYOGLOBIN AND WATER-MOL ECULES IN SOLUTIONS

Variations of the self-diffusion coefficients of myoglobin and water w ere studied within a wide range of concentrations and temperatures by NMR method with pulsed field gradient. An analysis shows that there is a critical concentration phi(2) at which the character of the concen tration dependence of the self-diffusion coefficient of myoglobin chan ges. At this concentration, the distance between the centers of mass o f myoglobin molecules coincides with the maximum dimension of the mole cule. A comparison of the concentration dependences of the self-diffus ion coefficient of myoglobin with the generalized concentration curve for the flexible-chain polymers and with the concentration dependence of the self-diffusion coefficient of hard spheres was performed. It wa s found that the activation energy of the self-diffusion of myoglobin molecules within the interval 10-35 degrees C exceeds the activation e nergy for the self-diffusion of water molecules.