A systematic comparison of sitting and hanging-drop crystallization using traditional and cross-diffusion microbatch crystallization plates

Obtaining good quality protein crystals is still desirable for high resolution structural determination of the proteins using crystallography. The crystal quality is affected by the growth environment and growth methods. As frequently used methods in practical protein crystallization, sitting and hanging-drop methods are seldom compared in terms of crystal quality in the literatures. We performed a systematic comparison on the quality of the protein crystals grown in sitting and hanging-drop methods using different crystallization plates: cross-diffusion microbatch plate (CDM SD: CDM plate, sitting drop method; CDM HD: CDM plate, hanging drop method), traditional sitting and hanging-drop vapor diffusion plates (T SD: traditional plate, sitting drop method; and T HD: traditional plate, hanging drop method). Five different proteins, proteinase K (prk), lysozyme (lys), concanavalin A VI (con), catalase (cat) and α-Chymotrypsinogen A II (chy), were used. The crystal quality was compared in terms of the resolution limit, mosaicity and Wilson plot B factor. It was found that the crystals grown in CDM plate using the hanging drop method (CDM HD) exhibited the best morphology and the best crystal quality. X-ray diffraction tests showed that the CDM plate using hanging drop method is indeed a practical and useful method for obtaining high-quality protein crystals.