Michael,
I have had similar "GC" content or complexity problems with my PCR as
well and have tried DMSO with Taq and seen the results that you
describe. Eventually I could not even get the DMSO addition to work (GC
content = ~ 75-80%). I contacted Dr. Patricia Wehley at Clontech who
turned me onto a new product they've released called GC-Advantage. It
combines DMSO, a proofreading blend of enzymes for long PCR and a
proprietary reagent that helps with GC rich templates. I have tried it
and gotten pretty good results through regions that have been giving me
quite a lot of trouble. At best it's allowing me to amplify clones from
a library that because of GC content I would not normally be able to
select. At worst my recations seem to take fewer cycles (20-25) as
opposed to standard PCR (35-40 and sometimes a nested PCR rxnas well).
Anyway, you might want to give it a try. I'm not trying to advertise for
them, I just like several of their products. If you call Clontech ask
for Pat Wehley and tell her I sent you. [This wont hurt or help you but
might help me :-) ] Best of luck,
Matt Brown, Ph.D.
Dept. of Medicine
Univ. of Alabama at Birmingham
