Hi all, I have got some crystals, the purified protein was in Tris buffer with 300mM NaCl for crystallization. they grew in light weight PEG, PEG400 or monomethyl ethyl PEG500, they were needle shaped, could be long (~0.2mm) but very thin all the time and sometimes grew into sea-urchin like needle cluster. What interesting is, when i gridded crystallization conditions against pH or PEG amount, the crystals sizes and shapes varied, and the crystals were fragile so i believed they were protein crystals in nature. But upon X-ray diffraction, they gave no reflection at all, not even a faint spot. I wonder, beside silly mistakes like misalignment of the crystal to the beam, not enough exposure time, what could be the reason for this mysterious crystals? Are they protein or PEG or what? Thanks very much.
Tc
