Why 3H-GTP in GTP-binding assay?
klenchin at facstaff.wisc.edu
Wed Jul 2 18:28:07 EST 1997
In article <5p90l3$lsl at falcon.le.ac.uk>, "Dr E. Buxbaum" <EB15 at le.ac.uk> wrote:
:klenchin at facstaff.REMOVE_TO_REPLY.wisc.edu (Dima Klenchin) wrote:
:>I am not sure why not 14C-GTP but probably due to even
:>lower specific radioactivity and still lower counting efficiency.
:The counting efficiency of 14C is usually around 80-90% (compared to
:about 20% with 3H). The biggest problem with 14C is its price tag. The
:reason for this is that 14C compounds can only be isolated from organisms
:grown on a 14C carbon source. Tritium labeled compounds can be prepared
:in many cases by exchanging 1H against 3H essentially by sealing your
:compound with 3H water into an ampoule, keeping it warm for a week or so
:and then separating it from the water. Note that this process is
:reversible, one of the reasons why 3H compounds do not keep as well as
:the half life of 3H would suggest.
I stand corrected - counting efficiency of 14C is indeed extremely high.
It is VERY low specific radioactivity and high price that makes it
unusable for G-protein research.
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