Summary: Ann. N.Y. Acad. Sci. 974: 610624 (2002). ©2002 New York Academy of Sciences.
Mathematical Model for Diffusion of a
Protein and a Precipitant about a
Growing Protein Crystal in Microgravity
ONOFRIO ANNUNZIATAa,b AND JOHN G. ALBRIGHTa
aDepartment of Chemistry, Texas Christian University, Fort Worth, Texas, USA
bDepartment of Physics, Massachusetts Institute of Technology,
Cambridge, Massachusetts, USA
ABSTRACT: Equations are presented that model diffusion of a protein to the
surface of a growing crystal in a convection-free environment. The equations
apply to crystal growth solutions that contain both a protein and a protein pre-
cipitant. The solutions are assumed ternary and the equations include all four
diffusion coefficients necessary for the full description of the diffusion process.
The four diffusion coefficients are assumed constant. Effects of crystal/solution
moving boundary and the effect of a protein adsorption barrier at the crystal
interface are included. The equations were applied to the system lysozyme
chloride + NaCl + H2O, which has served as the primary model system for the
study of crystal growth of proteins and for which there are now published ter-
nary diffusion coefficients. Calculated results with and without the inclusion of
cross-term diffusion coefficients are compared.