At 17:10 +0000 1/2/01, michael diver wrote:
>Jonathan,
> We have stored samples in all types of tubes frozen
>for lenghthy periods of time and see no effect of
>adsorption to glass or plastic. Remember that sex hormone
>binding globulin has a very high binding affinity (nmolar)
>and there is loads of albumin around which binds steroids,
>albeit with a lower binding affinity but an almost
>limitless saturation. Certainly when steroids are extracted
>from serum and the organic solvent evaporated then they
>will 'stick' to glass. We always incubate our redisolving
>steroids (in serum) for at least 30' at 37 to take them off
>the walls of the glass tubes. One can achieve very high
>recoveries in this manner.Hope these anecdotal experiences
>might reassure you (plural).
>Yours
>Michael J. Diver.
The same phenomenon occurs with T4 and T3. These bind like glue to
glass (less so to some of the plastics we used ), but insignificantly
in the presence of serum. Glass acts as an exogenous binding protein,
and binds the hormones to an extent essentially determined by the
free concentration in the solution to which it is exposed (and the
exposed area, of course).
I have likewise often used this phenomenon (in the distant past) to
recover extracted hormones
--
Roger Ekins
Molecular Endocrinology
University College London
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