Hi,
to remove 'some of the voodoo' out of it, we recently published a paper
showing a really fast_and_easy (and cheap) technique to check HA binding
on cysteines.
One of the most interesting result was that we could see binding of
mercury and gold on 1 protein, but not platinum. We didn't try to
explain why, but this result tells you not to use platinum on this
particular protein... Then it's up to you to use pre-labelling or
soaking, but you should avoid platinum to incorporate the HA (in this
particular case again).
In another case, we showed that some platinum were better than other to
yield complete labelling.
This method (FD-HAL) isn't the ultimate answer to phasing but removes
some mystery, and will save you time on the beam line by working on
samples that you know have incorporated HA.
http://www.ncbi.nlm.nih.gov/pubmed/20152903
best
vincent
Paul Smith wrote:
Hi Seema,
In theory, Ammonium Sulfate contains some small fraction of neutral ammonia
which can act as a strong nucleophile and react with many heavy metal compounds.
That being said, I recently phased two structures with mercury soaks, both of
which contained ammonium sulfate. The first was a thimerisol soak with 2M
AmSO4 in the mother liquor, and the second with a MeHgCl soak with 0.2M AmSO4.
Both were fairly routine.
I think others will agree that with heavy metals, logic and theory can go right
out the window. There is no way of knowing if it will work, you just have to
try.
One tip I can offer is to use fresh stocks of metals dissolved at saturating
concentrations in water and used on the same day. The fresher the better in my
experience, but it could just be voodoo.
Good luck!
--Paul
--- On Sun, 9/26/10, Seema Nath <[email protected]> wrote:
From: Seema Nath <[email protected]>
Subject: [ccp4bb] problem in heavy metal soaking
To: [email protected]
Date: Sunday, September 26, 2010, 9:00 AM
I'm working with a protein which
crystallizes in a mixture of PEG6K with 0.2M AmSO4,my
question is if there's any problem if I want to soak heavy
metal derivatives in this crystallizing condition? Does
AmSO4 interfere in heavy-metal soaking ? if yes, what's the
reason?
Thank you in advance.
--
Vincent Chaptal
Dept. of Physiology at UCLA
http://www.physiology.ucla.edu/Labs/Abramson/index.html
<http://www.physiology.ucla.edu/Labs/Abramson/index.html/>
Phone: 1-310-206-1399
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