Crystallographic characterization of a principal non-toxic lectin from seeds of Ricinus communis

Large hexagonal crystals of ricinus lectin, present as a major component in the seeds of Ricinus communis, have been obtained at 4 °C in the presence of polyethylene glycol 6000 by vapor diffusion against media containing acetic acid. The crystals are of space group P622, with hexagonal unit cell parameters $\text{a = b = 166}\text{A}\text{?}\text{and}\text{c = 341}\text{A}\text{?}$. The asymmetric unit contains two molecules of molecular weight 125,000. The crystals are extremely unstable, both to environmental changes and to X-irradiation, and have a solvent content of approximately 55% by volume.