Freezing crystal (Liquid Propane Crystal Prep)

From: Steven Herron
Date: 7 February 2012 18:28

Jürgen Quote: "Propane for whatever reason has gone extinct in certain areas of the world :-) ."


I went to SSRL (Stanford) with a colleague who wanted to use liquid propane.  We had to go through a mound of paper work to get permission bring propane on site and set up the experiments.  I don't blame SSRL for their safety policy, but I can clearly understand why liquid propane is not commonly used. 

If you don't think it is much of a danger, you might enjoy: http://www.stupidvideos.com/video/stunts/propane_tank/#2974
You might also enjoy:  http://www.stupidvideos.com/video/stunts/C4_Propane_Explosion/#175408
     Note:  We did not bring any C-4 to SSRL    :)

Steve



On 2/7/2012 10:50 AM, Bosch, Juergen wrote:

Hi Dirk,

I remember a neat paper don't recall who wrote it. I think it was in Acta D where the authors made a tiny probe the size of an elongated crystal glued to a [/Advertisement on] Hampton loop [/Advertisement off]. The probe was a temperature sensor and they recorded the cooling rate under different methods. The winner as far as I recall was freezing in liquid propane for the lack of the missing gas layer, but the second best method was LN2. Propane for whatever reason has gone extinct in certain areas of the world :-) . I'll try to find that reference but perhaps somebody else on this highly educated board knows which paper I'm referring to. I want to say it was published around 2004-2006.

Jürgen

On Feb 7, 2012, at 11:12 AM, Dirk Kostrewa wrote:

Dear Jürgen,

Am 07.02.12 16:58, schrieb Bosch, Juergen:
<snip>

Then one last remark, LN2 versus cryo-stream freeze. Dipping in LN2

leads to a quicker freeze of your material.

</snip>

Are you sure? There was a publication by Warkentin et al. [1] about a
cold gas layer above liquid nitrogen that reduces the expected cooling
rate a lot!
My very personal experience is, that cryo-cooling in the N2-stream
worked better for me than in LN2 in a variety of projects - but the
reason could just be me ;-)

Best regards,

Dirk.

[1] Matthew Warkentin, Viatcheslav Berejnov, Naji S Husseini, and Robert
E Thorne: "Hyperquenching for protein cryocrystallography", J. Appl.
Crystallogr., 39, 805-811 (2006)

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Dirk Kostrewa

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Jürgen Bosch