Self-diffusion of zinc in cross-linked crystalline carboxypeptidase A

Abstract

The technique of measuring self-diffusion rates of metal ions in zeolitic ion-exchangers using radioactive tracers has been extended to the measurement of the self-diffusion of zinc in crystalline cross-linked carboxypeptidase A_γ, which may be regarded as a porous crystal of low ion-exchange capacity. Values for thermodynamic parameters of self-diffusion have been determined, which indicate that water structuring in the protein is an important factor in influencing the mobility of the zinc ion. The results obtained show that an analogy can be drawn between certain zeolitic ion-exchangers and a crystalline protein such as carboxypeptidase A.