But only if the solvent channels are small and you thus don’t need a 
penetrating cryoprotectant…
Good luck!
Elspeth
----------------------------------------------------
Elspeth F. Garman,
Professor of Molecular Biophysics (Emerita),
E-mail: [email protected]<mailto:[email protected]>
https://www.bioch.ox.ac.uk/garmangroup
New undergraduate textbook out May 2025:
MATHEMATICS FOR BIOSCIENCES:
From Theory to Worked Examples and Applications
Elspeth F Garman and Nicola Laurieri
World Scientific Publishing Co.https://doi.org/10.1142/q0473

From: CCP4 bulletin board <[email protected]> On Behalf Of Sarah Bowman
Sent: 04 December 2025 18:13
To: [email protected]
Subject: Re: [ccp4bb] Skin around crystal

Another advantage of microbatch-under-oil is that the oil *can* also serve as 
cryoprotectant if you are doing cryocrystallography…

Sarah EJ Bowman PhD
Associate Professor | Department of Biochemistry | Jacobs School of Medicine 
and Biomedical Sciences | University at Buffalo
Director | National Crystallization Center | UB Hauptman Woodward Institute 
(www.getacrystal.org<http://www.getacrystal.org>)

From: CCP4 bulletin board <[email protected]<mailto:[email protected]>> 
on behalf of Patrick Shaw Stewart 
<[email protected]<mailto:[email protected]>>
Date: Thursday, December 4, 2025 at 3:01 AM
To: [email protected]<mailto:[email protected]> 
<[email protected]<mailto:[email protected]>>
Subject: Re: [ccp4bb] Skin around crystal
You don't often get email from 
[email protected]<mailto:[email protected]>.
 Learn why this is important<https://aka.ms/LearnAboutSenderIdentification>
Another approach is to use the microbatch-under-oil crystallization method - 
you very rarely get skins with that.  Harvesting crystals from under oil is 
roughly as easy as from vapor diffusion drops.  You have to make sure that the 
crystal fits the loop well, because it can be pulled off by the oil.  On the 
other hand, you can take your time because you don't need to worry about 
evaporation, which makes it easier.

On Thu, Dec 4, 2025 at 7:22 AM Cesar Luna-Chavez 
<[email protected]<mailto:[email protected]>>
 wrote:
BTW. How come nobody has asked about the crystallization conditions?
I spent nearly four years nailing down the conditions to crystallize Fumarate 
Reductase from E coli.  Certainly, I came across "skins" but managed to let the 
improvements lead me to a more conclusive protocol.

1) 
https://www.ucsf.edu/news/1999/06/97513/sfvamc-ucsf-scientists-solve-key-protein-structure
2) https://www.sciencedirect.com/science/article/abs/pii/S1046592800912385
3) https://journals.iucr.org/paper?cy0109

Feel free to reach out to start optimizing YOUR conditions to avoid skins.

On Mon, Oct 6, 2025 at 5:19 AM Nichols, Charlie 
<[email protected]<mailto:[email protected]>>
 wrote:
Hi, I have been offline for medical reasons for a few weeks…

Trawling through my ~1000 emails and saw this thread…

Have faced this problem many times, some crystals seem to like to grow from the 
interface of skin and solution phase and are therefore inherently adherent to 
the skin.

Adding additives to stop skin formation changes the dynamics of vapour 
equilibration and may be removing the preferred nucleation surface, which can 
then reduce crystal quality rather than improving it e.g. either no crystals or 
a tendency to obtain showers of smaller crystals. You may be able to ameliorate 
this by using larger drops with lower surface area : volume ratio and serial 
dilution of seeds, you may then find conditions that give more good crystals 
not entrained with the skin.

Re-solubilising the skin after crystal growth is however often the simplest 
approach. For this I can recommend testing the Cryosol screen from Molecular 
Dimensions, these multi-component organic solvent mixtures are both excellent 
for cryoprotection and also very good at resolubilising skin from PEG system 
crystallisations.
https://moleculardimensions.com/en/category/cryoprotectant-screens

Good luck, take care,
Dr Charlie Nichols
Charles River Laboratories

From: CCP4 bulletin board <[email protected]<mailto:[email protected]>> 
On Behalf Of amit gaur
Sent: 16 September 2025 21:58
To: [email protected]<mailto:[email protected]>
Subject: [ccp4bb] Skin around crystal

WARNING: This message was sent by an external party. Report suspicious messages 
via the “Report Phishing” button in Outlook.

Hi everyone,

I am facing a problem during crystal freezing. My crystals are surrounded by 
skin and not separating from skin during crystal mounting. It seems that 
crystals are embedded in the skin. Has anyone experienced a similar situation 
and handled this situation?

Dr. Amit Gaur,
Department of Biomedical Science,
College of Medicine,
Florida State University,
1115 W Call St, Tallahassee, FL,32304




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