Dear Thuy, It might be indeed a Cd2+ ion as suggested by Herman. In this sense I would process the data assuming a false Friedel law and look if there is some significant anomalous signal that superimposes to your mFo-DFc positive peaks around the His you pointed out.
Best regards, Philippe ________________________________ Philippe BENAS, Ph.D. X-ray diffraction and computing facilities manager Laboratoire de Cristallographie et RMN Biologiques, UMR 8015 CNRS E-mails: [email protected], [email protected] URLs: http://lcrbw.pharmacie.univ-paris5.fr/ , http://lcrbw.pharmacie.univ-paris5.fr/spip.php?article18 ________________________________ "We do know nothing ! But tomorrow is another day ! ;-) " ________________________________ De : "[email protected]" <[email protected]> À : [email protected] Envoyé le : Jeudi 31 octobre 2013 9h16 Objet : [ccp4bb] AW: [ccp4bb] help with strange density map Dear Thuy, I would try to model alternative conformations. E.g. blob2 looks like a lower occupancy cadmium ion coordinated to the glutamine, causing the histidine to assume an alternative conformation, also coordinating the ion. Just try to build different possibilities. If, after refinement it turns out to be incorrect, you can always reject it and try other things. Good luck! HErman Von:CCP4 bulletin board [mailto:[email protected]] Im Auftrag von thuy ngo Gesendet: Donnerstag, 31. Oktober 2013 08:41 An: [email protected] Betreff: [ccp4bb] help with strange density map Dear all, I am dealing with two strange extra density map. One is connected from Cb of Proline to Ca of glycine (blob 1) and other is positioned between two symmetric molecules which is connected from Cb of Histidine to carboxylate group of Glutamate. I checked all the crystallization and purification condition but no ligand is suitable for these blobs. Could you suggest some possible candidates? This is the structure complex between peptide deformylase and fMAS Crystallization condition: 2M Sodium acetate, 0.1 M HEPES 7.5 and 0.05M CdSO4 Thank you
