Re: Selenomethionine analysis

Sibylle Wilbert (swilbert@imail.neorx.com)
Mon, 11 Oct 1999 08:08:05 GMT

Hi Andy,

thanks for pointing out our method, it indeed works well. If you would
like to speak with the author, his email address is "Robert A Croes"
<Robert.A.Croes-1@USA.dupont.com>.

Sibylle Wilbert


_______________________________________________________________
Subject: Selenomethionine analysis
Author: <POLYLC@aol.com> at IMail
Date: 10/08/1999 12:50 PM


Since my posting yesterday, several people asked for the details on analysis
of selenomethionine. The attached file (Powerpoint format) is Bob Croes'
poster from ASMS '99 on analysis of amino acids. It involves Hydrophilic
Interaction Chromatography (HILIC) with MS/MS detection with an LCQ. Several
notes on the method:

1) Since this poster was presented, Croes found that use of methanol instead
of acetonitrile (ACN) increases sensitivity 10x or more. This dramatically
increased sensitivity to methionine and threonine to the point that he can
now quantitate wild-type levels in individual seeds; in fact, all amino acids
can now be quantitated this way. His current mobile phase is 70% methanol
with 0.2% formic acid and 10 mM ammonium formate.

2) Time between injections is 6 minutes.

3) This method works for selenomethionine as well as other polar solutes (e.g.
, glyphosate). Contact Wilson Shue at Georgia Tech (Atlanta): (404)
894-4051. His group is looking at selenium-containing amino acids in urine.

4) Croes' poster doesn't specify the pore diameter of the PolyHYDROXYETHYL
Aspartamide column used. It's 100 A (not the 300 A usually used for peptides
and proteins).

5) The quality of the chromatography with methanol is inferior to that
obtained with ACN. Croes still uses 60% ACN for HILIC of lysine metabolites
in order to get baseline separation of pipecolic acid and lysine (they
interfere with each other's quantitation in MS/MS).

If you don't have access to Powerpoint, contact me to get Croes' extended
abstract in Word format.

Andy Alpert
PolyLC Inc.
9151 Rumsey Road, ste. 180
Columbia, MD 21045 USA
tel: (410) 992-5400 FAX: (410) 730-8340 e-mail: PolyLC@aol.com