3->5 rate of Klenow

[ADVANCED TECH (CAMB)]

Does anybody know what the rate of the 3' to 5' exonuclease activity of the Klenow 
fragment is (in terms of bases/sec).  I intend to use it to end label a 100 bp probe.  
My protocol says incubate for 10min at R.T. before the polymerase reaction but I think 
this may be too long and will completely digest my probe. Does anyone have a better 
protocol, mine is not very detailed. 

Thanks

kin (kin.cheung at virgin.net)