Confused about the different principles to freeze & thaw cells and purified protein

[Zhonglin Chai]

My personal view on this is that for cells, we tried to avoid formation of ice crystals which break cell membrane to kill your cells. This is achieved by the protocol you described with slow freezing (in DMSO) and fast thawing in 37oC degree water bath. For proteins, particularly for enzymes, or other bioactive samples, they may be sensitive to high temperatures, the best way to thaw is on ice to avoid exposing them to an undesirable higher temperature such as room temperature.

Z Chai

-----Original Message-----
From: methods-bounces from oat.bio.indiana.edu [mailto:methods-bounces from oat.bio.indiana.edu] On Behalf Of Xuan Yang
Sent: Friday, 24 July 2009 12:25 PM
To: methods from magpie.bio.indiana.edu
Subject: Confused about the different principles to freeze & thaw cells and purified protein

Dear Sir or Madam,

When we store cells (especially eukaryotic cells), storage box filled with isopropyl alcohol was used to prevent the temperature from dropping too fast. While thawing the cells from liquid nitrogen, we put the tube immediately into 37ºC water bath. Freezing slowly, thawing fast. This strategy was totally contrary to the way we deal with purified proteins, namely freezing rapidly (favorablely in liquid nitrogen), but thawing slowly (favorablely on ice). It was quite confusing and I was wondering whether anyone would be so kind to offer me some explanations.

Sincerely,

Xuan Yang

National Laboratory of Biomacromolecules and Center for Infection and Immunity, Institute of Biophysics, Chinese Academy of Sciences, Room 1617, 15 DaTun Road,Chaoyang District, Beijing, China, 100101
Tel: 86-10-64884329
We will either find a way or make one.
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