Dear Eugene,
the dehydration of crystals is the same regardless of the precipitant -
the important thing to get right is the change in relative humidity -
and that does depend highly on the precipitant. The RH in equilibrium
with your salt concentration defines your starting point and depends on
the salt and the concentration - you can calculate this here:
http://go.esrf.eu/RH
You can then either move your crystals above solutions containing
increasingly large concentrations of the salt or directly into solutions
- the best way to do this is using a controlled humidity device as you
can monitor any changes in diffraction.
As you mention there is on at diamond but also at several EU
synchrotrons and some in USA/Canada.
You can also move above PEG solutions but the only thing you are
changing is the amount of water available so you may as well use the
salt, however you can convert RH values between salts and PEGs here as
well http://go.esrf.eu/RH.
Calculation server for mother liquor RH equilibria: http://go.esrf.eu/RH
Paper describing above:
http://scripts.iucr.org/cgi-bin/paper?S1744309111054029
Best wishes, Matt.
On 2015-08-11 20:32, Eugene Valkov wrote:
> Dear colleagues,
>
> Would some of you please be kind enough to share your experiences with
> controlled dehydration of crystals grown in conditions where inorganic
> salts are the primary precipitants to improve diffraction?
>
> The crystals in question are reasonable in size (100 microns in
> longest dimension), diffract nicely to 6-7 A and are quite easy to
> handle. We have, of course, tried a variety of cryoprotection regimes
> and are now considering more exotic options.
>
> Literature examples describe transferring the cover slip with the drop
> over increasing concentrations of PEG6k in the well reservoir. Are
> there any other tricks that have worked? Yes, I am aware there is an
> HC1 device at Diamond.
>
> Please respond on or off-list and I will subsequently post a summary.
>
> Eugene
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