Alternatively, you can try soaking with Ln complexes, such as
Tantalum-Br clusters (http://www.mitegen.com/mic_catalog.php?c=jenPhasingTantalum)
Ln chelated in EDTA-like molecules. It does not bind covalently.
Better used for soaking at high concentration (http://www.natx-ray.com/products/catalogue_consum_CSM002.html)
Ln-(DPA)3 is a special case, that has to be used in
co-crystallization, with new crystal forms with 3-fold axis
JL
On 05/18/2015 11:51 PM, Jurgen Bosch
wrote:
Also you can treat your SeMET as heavy atom derivative with
your native dataset.
Jürgen
......................
Hi Isa,
don't discard SeMet too rapidly if there are few Mets,
modern beamlines, high-redundancy data collection
techniques, and processing and phasing programs can extract
and use small anomalous signal to get structures even if
there are less SeMets than generally accepted by the "rule
of thumb". Especially if you can rotate around more than one
axis or merge data from different crystals. And even if the
signal is not good enough and you then need additional
phasing, the SeMet anomalous maps may be useful in tracing.
If you have Cys, try Hg compounds, my favourite is
methylmercury chloride. As it binds covalently, even if it
precipitates in your drop, you may just get just enough
soluble to react. We usually add a few grains of the mercury
compound to the reservoir, mix, cover and let equilibrate
with the drop for a few hours or overnight, then add a ul of
the reservoir to the drop and fish crystals after different
incubation times.
Greetings,
Mark
Mark J van Raaij
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
On 18 May 2015, at 11:42, isabelle Lucet wrote:
Hi All,
We recently obtained a native
data set to 2.8A. With no molecular replacement available
we are now moving to heavy atom (not enough methionine
coverage for seleno-met). Unfortunately crystals grow is
in 1.4 Na/K H phosphate pH 8 and we do not have much room
for improvement.
Any literature you could point
to or experience with for example gadolinium complexes,
co-crystallization, soaking in phosphate buffer? Are we
better off just focusing on class B metals?
Thanks for your advise.
Kind Regards,
Isa
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