[Histonet] freeze or not to freeze

[Andi Kappeler]

Hi Gudrun

we generally store antibodies according to the manufacturer's 
recommendations - today for most antibodies this is between 2 and 8°C. 
However, we do aliquot antibodies that we use only very rarely.  When we 
aliquot and freeze, we make sure that there is some protein in the antibody 
solution besides the antibody (e.g. BSA, serum proteins, etc.). Further, we 
store aliquots at -80°C, not at -20°C. The reason is mainly the quality of 
the freezers: most "household-type" freezers have an automatic defrost cycle 
which results in a very dry environment in the freezer. This leads to 
"freeze drying" of the aliquots over time. With -80°C freezers the problem 
is somewhat reduced (they have no defrost cycle, however, frequent opening 
of the -80°C freezer can result in a similar effect). Nevertheless we try to 
freeze aliquots of a volume no smaller than approx. 50 ul (predilute 
antibody if necessary) and we never use Eppendorf type tubes, as their lid 
is not as tightly closed as when you use screw cap tubes with a sealing 
(e.g. Sarstedt and others).
Freezing is generally not recommended for labeled antibodies (biotin, 
fluorescent labels, etc.), as the label may be detached. If we have labeled 
antibodies that we wish to store at lower temperatures, because we need only 
very small amounts per year, then we add  glycerol up to 50% (v/v) and store 
at -20°C. The glycerol keeps the solution in liquid phase and avoids the 
mechanical stress on the label that you get when you freeze (--> liquid to 
solid phase). This has worked fine with us and we have antibodies stored 
that way for years - and when they come out of the freezer, they still work. 
Hope this helps.

Best regards
Andi Kappeler
Institute of Pathology, University of Bern, Switzerland


----- Original Message ----- 
From: "Gudrun Lang" <gu.lang <@t> gmx.at>
To: "Histonetliste (Histonetliste)" <histonet <@t> lists.utsouthwestern.edu>
Sent: Tuesday, September 05, 2006 8:05 PM
Subject: [Histonet] freeze or not to freeze


> Hi,
> I hope one of the IHC-specialists can explain to me, why some of the
> antibody-concentrats are not allowed to be stored at -20°C in aliquots. 
> What
> is the difference to the others? Must I take this information on the
> datasheet seriously?
>
> Thank you
> Gudrun Lang
>
>
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