Preliminary X-ray studies of adult turkey δ-crystallin: evidence of a space-group transition

Abstract

A new calcium-dependent crystal form of 6-crystallin grown at ambient temperatures using vapour-diffusion methods exhibits a temperature-dependent space-group transition. At lower temperatures the crystal form adopts space group P2t2~2 with Z = 2 and exhibits a diffraction pattern corresponding to the crystal form reported previously, while at 294 K the resulting space group is P2t2~2~ in which the e axis doubles to 140.2 (2)A with Z=4. A third crystal form which requires a higher concentration of calcium ions shows no such transition and appears to be remarkably stable to X-rays in comparison with the other crystal forms. These crystals diffract to at least 2-4 ~ in space group P212~2~ with Z = 4 and have the largest cell dimensions of the three crystal forms with a =88.9 (1), b = 144.8 (1) and ¢ = 152.5 (1) A.