Mechanisms of Protein Crystal Growth: An Atomic Force Microscopy Study of Canavalin Crystallization

Abstract

In situ atomic force microscopy has been used to investigate step dynamics and surface evolution during the growth of single crystals of canavalin, a protein with a well known structure. Growth occurs by step flow on complex dislocation hillocks, and involves the formation and incorporation of small, mobile molecular clusters. Defects in the form of hollow channels are observed and persist over growth times of several days. The results are used to establish a physical picture of the growth mechanism, and estimate the values of the free energy of the step edge, $\alpha$, and the kinetic coefficient, $\beta$.