Re: AAA problem

Russ Henry (rsshnry@email.unc.edu)
Fri, 06 Nov 1998 11:04:03 -0500

I recently did AAA on some peptides in DMSO. I did the normal drying step in
the speedvac followed by gas phase hydrolysis. After hydrolysis, the
samples had splattered all over the inside of the tubes. Analysis showed
recoveries lower than expected. I tried running the samples again, but with
additional drying in the speed vac. This time there was no splattering in
the tubes and recoveries were as expected. It appears that samples in DMSO
just need to be dried more thoroughly than samples in aqueous solvents.

Russ Henry

--On Fri, Nov 6, 1998 10:45 AM +0000 "Len Packman" <lcp2@mole.bio.cam.ac.uk>
wrote:

> Roger
>
> I would have thought that small volumes of DMSO would readily be removed
by
> heating under vacuum. Aldrich catalogue lists DMSO boiling point as 55C at
> 5mm Hg so using an oil pump and a heated desiccator should allow removal
> before hydrolysis. Gas phase hydrolysis on a solution of DMSO is not
> something I've come across and would recommend trying this on a standard
> peptide before proceeding with a real sample.
>
> As a footnote, AAA (ion-ex/ninhydrin, Pharmacia Alpha plus) is alive and
> kicking as a service in my Facility; AccQtag is used from time to time too
> on an as-needs basis (in-house only) and I'd recommend this as a reliable
> method. We can generally accomodate samples from UK labs (see my web
site),
> but we are unable to extend the offer outside the UK. I just don't know
how
> departments survive without this technique.
>
> Len
>
>
>
>>Hi Folks!
>>
>>Since there's been so much discussion of AAA recently, let me throw you a
>>small problem we've run into. We formulate and vial peptides for cancer
>>vaccine work and have the absolute concentration determined by
quantitative
>>AAA by an outside contractor. We've recently had to formulate some
>>peptides in pure DMSO and our contractor is having trouble doing AAA in
the
>>prescence of DMSO - they "failed to produce any reliable data" (their
>>words). This is presumably by gas phase hydrolysis, although I guess
>>there's plenty of DMSO still present as they would not be able to remove
>>easily it under vacuum.
>>
>>Any hints at an alternative approach for the hydrolysis?
>>
>>(must admit I didn't think it would create this much of a problem!)
>>
>>Cheers,
>>
>>Roger
>
> *********************************************************************
> Dr Len C. Packman
> Assistant Director of Research
> Protein and Nucleic Acid Chemistry Facility
> Department of Biochemistry
> University of Cambridge
> 80 Tennis Court Road
> Old Addenbrookes Site
> Cambridge, CB2 1GA, UK
> Tel: +44 (1223) 333639
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>
>
>