Hi:
Is the resolution of the data sufficient to apply direct methods to find
only the copper atoms, then use the copper atom positions in an
old-fashioned
'heavy-atom' phasing method, combined with direct methods?
Incidentally, was the following publication of any relevance in your
efforts?
Acta Crystallogr D Biol Crystallogr. 1998 Jul 1;54(Pt 4):629-35.
Structure determination of a 16.8 kDa copper protein at 2.1 A
resolution using anomalous scattering data with direct methods.
Harvey I, Hao Q, Duke EM, Ingledew WJ, Hasnain SS.
ES
University of Madras
Yi Xue wrote:
Dear all:
We already got nice crystals of a drug-protein complex, however, MR
failed due to the huge copies (>12) of protein molecules per asu. Protein
itself is a small one, only ~70 aa.
Later on, we collected MAD data of copper (copper : protein ~ 1: 1),
Rsym of the data was around ~9%, the anomalous signals were weak, and only
good to ~6A, the data also failed to solve the phases.
Thus, basically, the Cu anomallous signal is very weak, and the
crystals are kind of sensitive to radiation, it is dying but not that fast.
I am wondering, Do we stand any chances to solve the phases by Cu MAD
or SAD?
Any suggestions or comments are highly appreciated?
Yi
