Characterization of crystals of an Fab fragment of a murine monoclonal antibody

The Fab fragment of an antibody, made against an E2-specific feline infectious peritonitis virus neutralizing antibody, has been crystallized in a form suitable for X-ray diffraction analysis from PEG 4000 using vapor diffusion methods. The Fab fragment crystals diffract to about 2·9 Å resolution and are of triclinic space group P1. Unit cell dimensions, by which the reciprocal lattice can be indexed, are a = 57·16 A ̊, b = 70·85 A ̊, c = 75·81 A ̊, α = 85·11{ring operator}, β = 121·28{ring operator} and γ = 116·33{ring operator}. There are two Fab fragments comprising the asymmetric unit of the crystals. The presence of a pseudo-mirror plane in the diffraction pattern suggests the presence of at least an approximate dyad axis relating the two Fab fragments within the asymmetric unit. © 1991.