35S contamination while cycle sequencing

[Johannes Winkler]

Black, Michael wrote:
> 
> Hello Everyone,
>    I run between 3 or 4 sets of cycle-sequencing reactions per week in a
> Cetus cycler (the model which pre-dated the 480 - just called DNA Thermo
> Cycler I think), using 35S-ATP as label.  Given the warnings about
> volatility of 35S which have been out for several years now, I set up the
> reactions in a hood but had thought that by the time the reactions were
> sealed in their tubes with an oil overlay the risk of air-borne
> contamination would be eliminated.  Recently our technician was doing a
> wipe test while I had a reaction running, and he lifted the lid on the
> cycler and wiped the underside - sure enough, the count was disturbingly
> high (the previous week he had wiped the block itself and it was clean).
>    My question is, does anyone have any further information about the risk
> of contamination from air-borne 35S while a cycler is running?

Hello Michael,

I'm not quite sure it's airborne contamination. At least one
manufacturer of 
plasticware claims that 0.05 to 0.1 ul of a given reaction volume will
be lost
during one cycle in a thermal cycler, regardless of the absolute volume.
The loss is said to take place by diffusion through the reaction tube's
walls.

Johannes 


--------------------------------------------------------------------------------
Johannes Winkler
Institut fuer Zoologie
Abt.Immunbiologie
Roemerstr. 164
53117 Bonn, Germany

Tel. +49-228-734338
FAX. +49-228-734555