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We've found that high PEG concentration seems to compete with dye binding, so I'm not surprised your didn't see good uptake. I doubt the anomalous signal is from the dye ... if you calculate the molar dye concentration you would need to have significant occupancy in the lattice, you'll probably find that the crystals would look almost black ... unless there was a color change. I recall seeing a poster at the annual ACA meeting 3-4 years ago maybe, in which somebody was using polybrominated or polyiodinated aromatics to both dye the crystals and phase the structures at once. In fact, I think we gave the poster an award for that. I don't have my past notes handy to remember, but could look it up if you're interested. Richard Gillilan MacCHESS On Nov 30, 2012, at 4:19 PM, Sarathy Karunan Partha wrote: Dear all, We did some Izit dye staining to test our crystal (salt or protein) and we observed that the crystal didn’t take up the dye well. But, showed nice protein diffraction (home source KCr 2.2909 A) and we collected a dataset (360 frames, 1o osc, 5 min exposure) on this dye stained crystal. The data collection statistics looks great and most interestingly we saw some anomalous signal for this data (see attached XSCALE.LP). This protein was crystallized in 0.2 M Ca acetate, 30 % PEG 400 pH 4.5. Izit dye is basically methylene blue which contains a sulfur atom (phenothiazine ring) and also has some basic dimethylamio groups. Our protein has many acidic residues that could enhance binding of this basic dye.We think the anomalous signal could be from this dye and the heavy atom search with autoSHARP and Phenix autosol is suggestive of 4 sulfur atoms. Did anyone come across similar situation with using this dye and also welcome any suggestions about using this data for S-SAD phasing. Thanks, Sarathy <XSCALE.INP>