Cacodylate, being an arsenic compound, is moderately toxic. You do have
to ingest it, however, for it to be toxic. Normal lab protection should
be sufficient. It is any more concerning to me than lithium salts,
mercury, acrylamide, ethidium bromide, etc.
Having said that, we usually abandon it as a buffer when optimizing
conditions that include it. Typically, substituting 0.1 M MES pH 6.5 for
cacodylate, pH 6.5, is inconsequential for crystallization for most
proteins, but of course there are always going to be exceptions.
Cacodylate will react with thiols, and this can complicate
crystallization from solutions that contain high concentrations of DTT
or beta-ME. Cacodylate can also bind to thiol groups on proteins. (This
may be a plus or a minus, depending on your point of view.)
Cheers,
_______________________________________
Roger S. Rowlett
Gordon & Dorothy Kline Professor
Department of Chemistry
Colgate University
13 Oak Drive
Hamilton, NY 13346
tel: (315)-228-7245
ofc: (315)-228-7395
fax: (315)-228-7935
email: rrowl...@colgate.edu
On 11/9/2012 7:26 AM, Frank von Delft wrote:
Hi all -
Anybody know
a) how hazardous is cacodylate?
b) does it really matter for crystallization screens?
It seems by far the most hazardous component of the standard screens;
this 2011 paper seems to think so (bizarrely, I can't access it from
Oxford):
http://onlinelibrary.wiley.com/doi/10.1111/j.1365-2818.1977.tb01136.x/abstract
and this is site says lethal dose is 0.5-5g/kg:
http://cameochemicals.noaa.gov/chemical/4468
meaning 2ml of a 0.1M solution contains 1/10th lethal dose...?
(Someone should check my maths...) [Coarse screens come mixed 2ml per
condition.]
Has anybody done careful experiments that showed it really mattered
for a given crystal -- or even an entire screen?
So I'm inclined to toss it out entirely rather than make
crystallization screening a "hazardous activity". (We're being
subjected to a safety review.)
Thoughts welcome.
phx
