Dear Tiancen,
I would look to the coordination of the Mn. In other words to the
geometry and distances from the Mn to it's potential ligands. The most
stable oxidation state of Mn is +2, with a octahedral (6-fold)
coordination sphere and bond lengths (e.g. Mn-O) of 2.1-2.4 Å. For Mn3+
one would expect somewhat longer bonds. But Mn3+ is probably not stable
in the environment of a protein. Even if the Mn2+ was oxidized and
stayed like that, during data collection (at least at a high dose like
at a synchrotron) one could expect reduction through X-ray radiation.
Greetings,
Klaus
TC Hu wrote:
Dear all,
Sorry for the non-topic question. We are working on an enzyme with two Mn2+
in its active center. The Mn2+-coordinated water molecules are responsible
for binding and nucleophillic attack of the substrate. We soaked the protein
crystal with an inhibitor and determined the structure, in which we did not
find the inhibitor. However, from the Fsoaked_crystal - Funsoaked_crystal
map constructed with the refined phases, we discovered two strong (>4 sigma)
difference signal near the two Mn2+, one for each. Both two datasets were
collected to 2.2A and of good quality. Considering the strong effect of the
inhibitor (IC50 ~75nM), we doubt that the manganese ions might be oxidized
and the catalytic water molecules are replaced. But since there are several
oxidation states of manganese, how can we verify which one occurred in our
crystal?
Another minor question: is there any movie-making software that can produce
the animation of bond formation and breakage (like that during catalysis)?
Thanks for your input!
Tiancen Hu
Shanghai Institute of Materia Medica
Chinese Academy of Sciences
--
Dr. Klaus Piontek
Albert-Ludwigs-University Freiburg
Institute of Organic Chemistry and Biochemistry, Room 401 H
Albertstrasse 21
D-79104 Freiburg
Germany
Phone: ++49-761-203-6036
Fax: ++49-761-203-8714
Email: [EMAIL PROTECTED]
Web: http://www.chemie.uni-freiburg.de/orgbio/w3platt/
