Sulfhydryls with BMPA

BMPA is N-(3-maleimidopropionic acid (or 3-maleimidopropionic acid), which contains a thiol-reactive maleimide group at one end and a carboxylate group on the other end (Rich et al., 1975 Moroder, 1983, 1987). The compound is the acid precursor to the short, heterobifunctional crosslinker 3-maleimidopropionic acid N-hydroxysuccinimide ester (BMPS). 

Ether Bond Formation with Conversion to Carboxylate 

The use of BMPA to block a thiol and create a terminal carboxylate is illustrated in the following protocol. The protocol relates to the modification of proteins, but similar reaction conditions can be used to modify other thiol-containing molecules or surfaces. 

Dissolve BMPA in DMSO or DMF to prepare a stock solution at a higher concentration such that adding an aliquot of this solution to the protein solution will result in the desired molar excess of the maleimide over the concentration of thiols present. 

Add a quantity of BMPA to the protein solution to obtain at least a 5-fold molar excess of maleimide reagent over the amount of thiol present in the protein. The final concentration of organic solvent in the protein solution should not exceed 10 percent to prevent protein precipitation. Mix thoroughly to dissolve. 

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