At 10:43 25.08.00 -0700, you wrote:
>Bart,
> I can think of two possibilities for decreasing the amount of
>the sodium adduct in your sample. The simplest is to rinse the probe
>tip (or sample spot) with distilled water after the mixture of sample
>and matrix dries. You can either dip the probe into a solution of
>distilled water or put a droplet of water on the dried sample and
>wick it away with a Kimwipe.
> The other, and probably more effective, possibility is to
>purify the sample using reversed phase HPLC. A simplified way of
>doing this is to use a Zip tip ( made by Millipore) or a SuproTip
>(made by The Nest Group). Both have reversed phase chromatographic
>material in a pipet tip that binds proteins from an aqueous solution.
>The bound protein can be rinsed with water(or water containing 5%
>acetonitrile) to remove hydrophilic contaminants, such as salts and
>glucose, followed by eluting the bound protein onto the mass spec
>sample holder with a couple of microliters of alpha cyano matrix in
>about 50% acetonitrile with the usual 0.1% TFA.
> Best wishes,
> Dan Brune
> Dept of Chem. & Biochem.
> Arizona State Univ.
In my experience you will get even better results by using 50 mM ammonia
acetate (pH 4) for rinsing the target instead of 0.1% TFA or water because
this will exchange the alkali ions more effectively. Subsequent
recrystallization of the spot may also help.
Sincerely yours,
Marcus Macht
**************************************************************
Dr. Marcus Macht
University of Cologne
Centre for molecular medicine - Service laboratory
Joseph-Stelzmann-Str. 52
50931 Cologne, Germany
Tel.: +49 221 478-6995
Fax: +49 221 478-6977
e-mail: Marcus.Macht@uni-koeln.de
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