Jens
Here is a list to start (there are many many more).
A problem with moderate sized peptides is that the detection limits MAY not
be as low as RIA in biological matrices.
One method I have observed with peptides is to tune the source conditions to
promote multiply charged ions and then use the multiply charged ion(s) as
the parent ion, collide that gently, and then monitor a lower charge state.
This one is 3465 MW and so even a +3 would be around 1100 and the +2 even
higher. This is in the region where quads have less transmission (maybe a
poor method-I assume you have a quad inst).
I would say that is one reason why many of these methods use tryptic
digestion prior to analysis (to reduce MW). This may be a TOF/sector
application for the best data, but that is pure speculation on my part and a
digestion step may allow it to be nicely run on an LC/MS system that is not
a sector/TOF.
One other way would be to simply monitor one or more of the multiply charged
ions in a single quad SIM mode. At the higher mass they occur at, the
chemical background is fairly low and you'd get more ions to the detector
than in MS/MS.
Ok... the bottom line-
Try LC-ESI with selected ion monitoring of the +4/+3/+2 ion(s). Leave TFA
out of the mobile phase if at all possible (it kills signal). Perhaps
borrow a sample prep method from one of the papers below.
Matt Sweeney
mattsweeney@earthlink.net
Mass Spec Consulting
Training/Operations/Consulting/Method Development
LC/MS Pharmacokinetics, Peptides, Proteins, Metabolism,
Maintenance Classes, Specialist in Finnigan Equipment and Software
Desiderio DM.
Mass spectrometric analysis of neuropeptidergic systems in the human
pituitary and cerebrospinal fluid.
J Chromatogr B Biomed Sci App. 1999 Aug 6;731(1):3-22. Review.
PMID: 10491985; UI: 99419734.
Desiderio DM.
Mass spectrometric quantification of neuropeptides.
Methods Mol Biol. 1996;61:57-65.
PMID: 8930865; UI: 97084522.
Desiderio DM.
Quantitative analytical mass spectrometry of endogenous neuropeptides in
human pituitaries.
Life Sci. 1992;51(3):169-76. Review.
PMID: 1614283; UI: 92310110.
Desiderio DM, et al.
Quantitative analysis of methionine enkephalin and beta-endorphin in the
pituitary by liquid secondary ion mass spectrometry and tandem mass
spectrometry.
J Chromatogr A. 1998 Jan 23;794(1-2):85-96. Review.
PMID: 9491558; UI: 98152258.
Nilsson CL, et al.
Mass spectrometry of peptides in neuroscience.
Peptides. 1998;19(4):781-9. Review.
PMID: 9622036; UI: 98283355.
Yan L, et al.
Evidence of an intermediate-size beta-endorphin-containing precursor
molecule in bovine pituitary by mass spectrometry.
Biochem Biophys Res Commun. 1993 Oct 29;196(2):521-6.
PMID: 8240323; UI: 94059068.
Desiderio DM, et al
Measurement of enkephalin peptides in canine brain regions, teeth, and
cerebrospinal fluid with high-performance liquid chromatography and mass
spectrometry.
J Chromatogr. 1984 Aug 3;297:245-60.
PMID: 6490759; UI: 85030720.
Brudel M, et al.
Liquid chromatographic-mass spectrometric studies on the enzymatic
degradation of beta-endorphin by endothelial cells.
J Chromatogr A. 1995 Sep 29;712(1):169-75.
PMID: 8556149; UI: 96039611.
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