Hi Charles,

Date: Thu, 28 Aug 2014 09:59:30 -0400 From: CPMAS Chen To: Gabor Bunkoczi Cc: "PHENIX user mailing list \([email protected]\)" Subject: Re: [phenixbb] following on the anomalous map Message-ID: Content-Type: text/plain; charset="utf-8"

HI, Gabor,

Thanks for you suggestion.

I tried this method, it did not give out NO sites for Br.

why there is apparent anomalous signal and I cannot identify any Br sites?

are you sure that your data processing used the correct parameters? E.g. in XDS you should definitively be using "FRIEDEL'S_LAW=FALSE". If you use XSCALE after XDS, it automagically picks up this setting from XDS_ASCII.HKL i.e. you don't have to specify this again. If you, by mistake, use FRIEDEL'S_LAW=TRUE, then the large intensity differences of Friedel pairs will be judged as outliers by XDS, and these reflections will be rejected - that might lead to featureless maps. If the anomalous signal is very strong, and the multiplicity is high, and the Chi^2 values are >1.5, you may also want to use (additionally) "STRICT_ABSORPTION_CORRECTION=TRUE" . But this is rarely necessary. There are similar options in other data processing programs. If you mix and match data processing programs (e.g. XDS integration and aimless scaling) you have to be careful to have the right settings in all programs. best, Kay

As Nat pointed out, other atoms should have very weak anomalous signal diffracted at Br absorption peak (3.8e- for Br, versus 0.2e- for the sulfurs). In the difference map, I can clearly see some peaks at high sigma (> 6), but the anomalous difference map(they are all generated by phenix.refine or phenix.maps) is almost featureless, or the peaks has no overlaps. The anomalous difference gives the possible place of Br while the difference map gives the possible place of the whole ligand, and I assume there should be some overlaps between them. Am I right?

Charles