Problems with Promega Taq

[Vivian Miao]

In article <C80ptq.JE8 at ccu.umanitoba.ca>, hamel at ccu.umanitoba.ca (Andre
Hamel) wrote:
> 
(stuff deleted from original osting)
> >>of a batch of Taq from Promega is faulty: The lot number is 28330A
> >>and the expiry is 02/95. Has anyone else experienced any problems

> We too "suffered" from experiences of Taq quality from Promega and others
> (BioCan is another that comes to mind).
> 
(more stuff deleted)
> Have you tried Deep Vent exo- from New England Biolabs?

So far we are satisfied with Taq from Promega (ours comes
 by way of Fisher also, but we haven't come across the batches
 that been mentioned as suspect).

By the way .....

I've tried side by side tests with NEB's Vent (neither Deep nor
Exo-) and it seems that for my setup, Taq makes a lot more
product than Vent.  Before I elicit a host of questions from
Andre  :-) .... the reactions are made up as a cocktail minus
enzyme and its conc'd buffer stock which are added later, the
same no. of units of enzyme are used, and reactions were run
at the same time in the thermocycler;  I ran similar volumes of
the reactions  on a gel and by inspection estimate that the product
band from Taq is probably 3-4X brighter than that from Vent.  Is
this within the range of variation, or is there something about 
error correction by Vent that has a cost in yield?  I'm not knocking
 Vent (for some applications, like templates that require very high
 temperature denaturation, Vent is the only thing we've tried that
 works), but it seems that for routine work, (e.g. at 92-94C 
denaturation, 45-55C annealing, 72C extension, 25-28 cycles)
you get more product with Taq.  Comments?