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This is not at all conclusive, but one depressing thing is that DNA-only crystals are often hexagonal (like yours are). Can you reproduce them without the protein? ++++++++++++++++++++++++++++++++++++++++++ Phoebe A. Rice Dept. of Biochemistry & Molecular Biology The University of Chicago [log in to unmask] ________________________________________ From: CCP4 bulletin board [[log in to unmask]] on behalf of Joseph Ho [[log in to unmask]] Sent: Monday, June 19, 2017 9:20 AM To: [log in to unmask] Subject: [ccp4bb] Protein or DNA crystals Dear all: I would like to seek your opinion on our crystal hits. We are working on protein/dsDNA complex. By changing different protein and DNA (14-22bp) constructs, we recently got some hits from commercial screens using sitting drop vapor diffusion (very small xtals). The precipitant is PEG and the picture of crystals are attached. In this particular condition, it is 30%PEG3350, sodium succinate pH5.5 and 100mM NaCl. The crystal seems floating and sit in the bottom. We do some test shot from other conditions and it is not salt crystals. The crystals can suck in izit dye. I do some google and it seems izit dye also turns dsDNA crystal into blue. We also do UV/Vis microscope but no Trp fluorescence (6 Trp in 256 aa). It may due to low Trp. This is our first time to work on protein/DNA complex crystals and we are not certain if this is just DNA or protein/DNA crystals. Can you provide your comments on our hits? Thank you for your help Joseph