X-Message-Number: 4442
Date: Wed, 24 May 1995 07:55:19 -0700 (PDT)
From: "Joseph J. Strout" <>
Subject: Re: Cool Flies & Chilled Mice.

> A second thought. Metals are known to exist in glass state if cooled
> at some billion degrees/s. The equivalent for cerebral tissue would
> require extremely fast contact of a tiny tissue specimen with a 
> cryofluid or a LN2fied metal block. Fluid gases will not do since
> they have Leidenfrost and low heat capacity. A supercold fluid
> (e.g. carbon tetrachloride or sumpn) is definitely better. I dimly
> recall reading in Nature about a fast freezer based on a LN2fied copper
> block and a probe guillotine bringing specimen slice into tight
> contact of the heat sink. Even if we would reach no much glass state 
> (xRay diffraction pattern as a probe), this should eliminate freeze
> artefacts considerably. Anybody care to investigate that?

Actually, techniques such as these are routinely used in cryomicroscopy.  
"Plunge freezing" involves attaching the sample (brain tissue, for 
example) to a metal screw, then plunging the screw into liquid propane or 
liquid freon (LN is not good, since it boils away to quickly -- you can 
actually stick you hand (briefly) in LN without damage -- but don't try 
this at home, kids).  "Slam freezing" involves slamming the sample into a 
metal mirror cooled to LN temperature.  Both techniques result in a 
vitreous sample, provided it's not too thick.

-- Joe

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