In article ja9 at u.cc.utah.edu, David Stillman <stillman at bioscience.utah.edu> writes:
> In article <32aqrc$e6k at emory.mathcs.emory.edu> Abhijit Datta,
>adatta at bimcore.emory.edu writes:
> >If anyone out there is having problems with the latest lot of Sigma
> alpha aa
> >(the lot has not changed since Jan) then pl contact Sigma 'cos I have
> >toxicity problems myself and apparently so has one other person in the
> >world. I wuld appreciate hearing from anyone with a similar experience
> >suggestions regarding a reliable supplier.
>> Your posting is not specific enough.
> First, by "alpha aa" do you mean alpha amino adipate?
> Second, it would be useful if you listed the Sigma catalog number and the
> lot number. Finally, what sort of toxicity problems?
>> We tried alpha amino adipate plates to select for loss of LYS2 plasmids,
> and the method basically failed in our hands. Wild type LYS2 strains grew
> on these plates, although at slower rate than lys2 strains. I don't know
> if our problem stems from the lot of alpha amino adipate, or how we made
> the plates.
>> David Stillman
> Department of Cellular, Viral and Molecular Biology
> University of Utah Medical Center
> Salt Lake City, UT 84132
>stillman at bioscience.utah.edu> phone: 801-581-5429
> fax: 801-581-3607
Gee sorry. My posting is indeed about DL-alpha amino adipate from sigma (Sigma sells just one kind of DL alpha amino adipate and the DL kind I believe is the kind usable for lys2 selection) and as my post does indicate the most recent lot (the lot number does not change since jan, 94). My problem is that nothing grows wild type nor Lys- (opposite of the problem you mention). Even titration of alpha aa conc. did not help. But USB alpha amino adipate seems to be working in my hands. I still am not sure if the lot from sigma is the problem and was merely trying to find out if others have had any inconsistant selection problems.