The X-ray Crystallography Core Laboratory utilizes 18 commercial screens containing 96 crystallization reagents. In a “full screen,” each commercial screen is set up at two temperatures (22°C and 4°C) with proteins of interest to identify initial crystallization conditions. X-ray Core Users will typically provide 750 microliters of a 5-20 mg/ml protein preparation to complete a full screen. It is recommended to avoid phosphate buffer in order to reduce false positives. HEPES, MES, MOPS, PIPES, CHES, Tris, acetate, citrate and bicine are suitable protein buffers for crystallization. NaCl or KCl up to 150 mM concentration is acceptable. Reducing agents DTT, BME, and TCEP are also compatible with most of the crystallization reagents.