There are many excellent review articles about cryocrystallography and
cryoprotectants. Do labs generally have these articles handy in a methods
folder? Do lab heads help their colleagues by making them read them?
Mineral oil is generally not a good oil to use because it changes volume
too much upon freezing. Have you tried other oils like Paratone-N,
perfluoropolyether oil (also known as fomblin or turbomolecular pump oil),
olive oil, etc?
Also have you tried sugars? Have you tried growing the crystals in the
presence of a little cryoprotectant? Even a little bit in the growth may
help your crystals to survive a transfer or swish into a higher
concentration for flash-cooling.
Jim
On Wed, 27 Feb 2008, wu donghui wrote:
Dear Lokesh,
Actually I have tried to dip my crytal directly into mineral oil, no ice
ring, but also no diffraction, which might indicate crystal packing under
mineral oil is not stable. Anyway, thanks a lot for your valuable
information. Other friends mention the use of LiCl or Lithium formate as
cryoprotectant, I will try these immediately and will let you know if it
works.
Best regards,
Donghui
On 2/27/08, Lokesh Gakhar <[EMAIL PROTECTED]> wrote:
Hi Donghui,
Have you tried mineral oil? That has sometimes worked for us when other
cryoprotectants have given problems.
-Lokesh
On Tue, Feb 26, 2008 at 9:30 PM, wu donghui <[EMAIL PROTECTED]> wrote:
Dear all,
Recently, I got a crystallization condition as 0.1 M Bis tris ph 6.5,
1.3M lithium sulfate, 0.1M NaCl, the shape of crystals is needle
cluster, very difficult to grow bigger, microseeding does not work, then I
tried macroseeding, and found crystal can grow bigger and rod like.
However as for the cryoprotectant, crystal will dissolve in
glycerol, ethylene glycol, MPD and PEG, even in the very low concentration
about 5%. I found my crystal can grow under the additive 2-propanol in
addition to the above mentioned crystallization condition. I also noticed
that Hampton cryoprotectant kit has the 2-propanol as cryoprotectant. I want
to know if anyone have ever used 2-propanol as the cryoprotectant and what
effect it might be. By the way Hampton also mention lithium sulfate can be
used as cryoprotectant, the recommended maxium concentration is 2M, I tried
and found ice ring is severe and it is very easily to form lithium sulfate
salt crystal at this high concentration, I also tried sodium malonate, the
diffraction gave me few spots, resolution is only about 6--7 angstrom.
Does anyone encounter such problem by lithium sulfate?
Welcome to any replies. Thanks a lot in advance.
Donghui
