Hi Sarathy, Are you sure your anomalous scatterers are not the Ca in the crystallisation buffer? These would also bind to the acidic residues in your protein, and Ca has a greater f'' (~2.5e compared to less than 1.5e for S) at the wavelength you used.
Just another possibility - unless you already solved the structures and see density for the izit in your density, of course! Cheers, Dave ============================ David C. Briggs PhD http://about.me/david_briggs On 30 November 2012 21:19, Sarathy Karunan Partha <[email protected]>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 >
