Dear all, I am trying to phase 172 aa protein using tantalum bromide (Ta6Br12) cluster. Data belongs to space group C2221 with 4 molecules (2 dimers) in the asymmetric unit. Phenix.xtriage indicates presence of pseudo-translation (peak height= 39). I have collected data at Ta peak (1.2550 A) to a resolution of 2.9A, Ta inflection (1.2553 A) at 2.8 A using one crystal. I also collected one high energy remote (1.059 A) data at 2.6 A using another soaked crystal. All three datasets shows presence of very good anomalous signal till the highest resolution shell.
Soaking with Tantalum bromide has changed the unit cell axes "a" and "b" by 4-5 A so it is no longer isomorphous with the native data (2.7 A). But since anomalous signal is very high in all these Ta soaked datasets, I have been trying to find a solution using SAD/MAD but without any success. Processing data in lower symmetry P21 and C2 also doesn't help. Another noticeable thing is..... "scalepack2mtz" fails when I try to run to convert my sca file into mtz (using CTRUNCATE option ON) with error saying "Anisotropic correction failed - negative eigen value". Since finding a solution has not been possible for reasons unclear to me. I guess I am having problem because of presence of pseudo-translational symmetry in my crystal. I would be grateful for any helpful advice or suggestions in this regard. Thanks in advance! Regards Dhirendra
