Preliminary x-ray analysis of single crystals of ovalbumin and plakalbumin.

Two crystal forms of hen ovalbumin have been grown and were characterized by x-ray diffraction. Crystals of ovalbumin grown at pH 5.4 are monoclinic, belonging to the space group C2 (a = 116.5 A, b = 41.8 A, c = 70.5 A, beta = 101.5 degrees). At pH 5.8 or higher ovalbumin forms triclinic crystals of space group P1 (a = 62.0 A, b = 84.3 A, c = 72.2 A, alpha = 87.4 degrees, beta = 103.9 degrees, gamma = 108.7 degrees). These crystals are usually small and difficult to grow reproducibly. Crystals of plakalbumin (a proteolytic modification of ovalbumin) are much easier to grow and appear suitable for three-dimensional structure determination. Their space group is C2 (a = 99.9 A, b = 102.0 A, c = 79.3 A, beta = 112.1 degrees) with two plakalbumin molecules in each asymmetric unit.