P32 vs. P33 for PCR detection

[Dima Klenchin]

mwcrepeau at hotmail.com (Marc Crepeau) wrote:
:Why do people sometimes use P33 to label PCR products for detection
:via autoradiograms?  What is the advantage over P32?  We order P32
:routinely for our Southern blot hybridizations, and I'm told it's
:cheaper than P33.  But I have some microsatellite markers that I want
:to use, and the information I have states that the developers employed
:P33 for detection, not P32 (the species in question is highly
:polyploid, so visualization with EtBr is not sufficiently sensitive). 
:Would I get the same results if I just spiked the PCR with the alpha
:labeled P32 that we already have in the lab?

P33 is "cleaner". Less energy = smaller effective angle of 
radiation scatter (see pic) = sharper bands = better resolution, 
which in many applications is more important than sheer 
sensitivity. 

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    P33           P32