Mat. Res. Bull., Vol. 28, pp. 541-546, 1993. Printed in the USA. 0025-5408/93 $6.00 + .00 Copyright (c) 1993 Pergamon Press Ltd. CRYSTAL QUALITY OF LYSOZYME SINGLE CRYSTALS GROWN BY THE GEL ACUPUNCTURE METHOD J.M. Garcla-Ruiz 1, A. Moreno 1, C. Viedma 2 & M. Coil 3 1 Instituto Andaluz de Geologia Mediterrfinea. CSIC-Universidad de Granada. Av. Fuentenueva. Granada 18002. Spain. 2 Dpto. de Cristalografia y Mineralogia. Facultad de Geologia. Universidad Complutense. Madrid 28002. Spain. 3 Centro de Investigaci6n y Desarrollo del CSIC and Dpto. de Ingenieria Quimica. Universidad Polit6cnica de Catalufia. Diagonal 647. Barcelona 08028. Spain (Received March 29, 1993; Refereed) ABSTRACT Lysozyme single crystals up to 2.0 mm in size have been grown from solution into capillaries which are previously punctuated into a gel layer through which the precipitant agent diffuse. These large single crystals show an excellent optical quality and it is demonstrated by in situ X-ray diffraction that they diffract up to 1.8-1.9 A. MATERIAL INDEX: Lysozyme. Introduction It is today considered that the bottle-neck for the development of structural studies of protein crystals by diffraction techniques is the very crystallisation process (1,2). Once single crystals of a particular protein are available, the next source of problems occurs when transferring them from the growth cell to the X-ray capillaries, an operation that requires some degree of dexterity to avoid breaking, dissolution or the loss of structural order of the crystals. In order to avoid this transfer, X-ray capillary glasses have been sometimes used as growth cells. To this aim, microdyalisis devices provided of membranes (3,4) or gel plugs (5), as well as direct contact between the protein solution and the precipitation agent (6,7) have been used. However, due to the difficulties found to perform microdialisys experiments, the classical hanging drop/sitting drop technique is still the running method in most of the laboratories where protein crystals are grown. 541