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
FAX: +44 (1223) 766002
e-mail: lcp2@mole.bio.cam.ac.uk
Visit my WWW page at http://www.bio.cam.ac.uk/proj/adr/PNAC/pnac.html