minimum radioactive probe size

WS via (by novalidaddress from
Wed Sep 26 15:50:26 EST 2007

Hi Ed,

when your probe is half size compared to a reference probe then you'll
need to double (at least) the specific activity of the probe in order
to get the same signal, assuming the probe binds in the same way. This
is achieved by increasing the specific activity in the labeling
reaction. As you normally will dilute the radioactive molecule with
cold compund, just.dilute less. The bigger problem might be to obtain
the right stringency for a small probe, so you'll need some fiddling
with conditions maybe. HTH


On Sep 26, 5:06 pm, Ed Siefker <ebs15... from> wrote:
> I'm considering doing a lambda plaque hybridization with a very small
> probe.   The unique sequence I'm looking for is 43bp long.  I'm lucky to
> have that much really.  We do our colony hybridizations exactly like we
> would do a southern.
> So has anyone done a hybridization (plaque or southern) with a tiny
> probe like this? I imagine it might be hard to get a high enough
> specific activity, but I think it's worth a shot.

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