I think I read some phosphoproteomics papers in the late 2000s where people would quantify differences in enriched phosphopeptides using differential isotopic labeling of acids with esterification by methanol. What is the best way to quantitatively esterify a mixture of peptides, for example, with heavy and light methanol to quantify differences?
Hi,
If I recall correctly, the best way to do this is by esterification using methanolic HCl. This is prepared in situ by the dropwise addition of acetyl chloride to dry methanol, thereby generating HCl and methyl acetate.
In this way, carboxylic acid side chains (and C-termini) are esterified, which improves the specificity of IMAC, that is used to enrich phosphopeptides. It can indeed also be used to differentially quantitate two samples.
Good luck!
By the way: be careful when preparing methanolic HCl: this is quite an aggressive (sputtering) reaction!
Thank you. Do you have a citation by chance that I could show my PI? I'm specifically interested in understanding if the reaction goes to completion (>99% converted to esters).
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