Hello Jeff. I don't have a literature reference for the procedure, but here is
a protocol which I learned in grad. school and has been very reliable.
1. Speed-vac the sample to dryness.
2. Prepare 2N methanolic or ethanolic HCl by drowpise addition of 60 uL
acetyl choride to 300 uL anhydrous methanol or ethanol in a glass test tube.
Cover with parafilm and let stand 10 min. Warning: exothermic reaction - use
safety glasses, work in hood with the tube opening pointed away.
3. Add 15 uL of the reagent to each sample and let stand at room temp. for 90
min (methyl esters) or 120 min. (ethyl esters).
4. Dry the sample on a speed-vac.
5. Redissolve the modified peptides.
Esterification of each carboxylic acid group increases the mass of a peptide by
14 Da for methyl esters or 28 Da for ethyl esters.
Good luck
David
JWU388880@cs.com wrote:
> Hi,
> Does anybody know the protocol (or recipe) for the direct esterification of
> tryptic digests (convert -COOH to -COOCH3). The chemistry has been used to
> facilitate mass spec identification of peptides. Thanks a lot.
> Jeff.
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