sure, "whether the structure can be solved" is a good criterion. but often, when trying different heavy atoms, the structure can NOT be solved, and then some criterion to judge whether to continue to try and solve it with that data, or whether to focus on other datasets, other derivatives, another crystal form, another construct or even another protein, is useful. CCanom in scala/aimless is one of these criteria.
Fluorescence signal is obtained also if you have disordered metal, so even if you get it, it does not mean you have a good derivative, because the metal may be in the solvent or bound to a disordered region. If you have an isomorphous native, Patterson diff maps are a way to judge the number of heavy atoms, for SAD perhaps the anomalous Patterson map, but that may be less clear (more noisy). In the Hg-case, the number of Cys can be a first guess of the number of Hg sites. On 16 Jan 2015, at 17:18, Keller, Jacob wrote: > How about “whether the structure can be solved” as a criterion, i.e, maybe > just put it into your favorite software and see whether it works, trying > various parameters? Depends on your goals, I guess―most people just want to > solve the structure and move on. > > JPK > > From: CCP4 bulletin board [mailto:CCP4BB@JISCMAIL.AC.UK] On Behalf Of luzuok > Sent: Friday, January 16, 2015 9:33 AM > To: CCP4BB@JISCMAIL.AC.UK > Subject: [ccp4bb] Assess anomalous signal? > > > Dear all, > I'm doing Hg SAD phasing for the first time, and I met some problem: > 1. How to assess the anomalous signal after I process the data and get my mtz > file? > My labmate doesn't scan the fluorescence signal. Actually, I don't quite > understand why we use fluorescence to detect anomalous signal. > 2. How to estimate the number of heave atom in one unit cell? by soaking > heavy atom derivatives. > > Best! > > Lu Zuokun > Nankai University > > -- > 卢作�j > 南开大学新生物站A202 > > Mark J van Raaij Lab 20B Dpto de Estructura de Macromoleculas Centro Nacional de Biotecnologia - CSIC c/Darwin 3 E-28049 Madrid, Spain tel. (+34) 91 585 4616 http://www.cnb.csic.es/~mjvanraaij
