Reversible modification of amino groups with maleic anhydride and similar reagents

Reversible modification of amino groups with maleic anhydride and similar reagents 

Solid maleic anhydride (preferably purified by sublimation or by 

The maleylated protein can be demaleylated at acid pH. Near maximal rates are obtained at pH 3.0-3.5 but in some studies a higher pH and a longer time may be preferable. Any O-maleyl groups must be removed with hydroxylamine (see above). A convenient procedure 

The removal of added substituents from amino groups, formed with these reagents, depends on the presence of a protonated carboxyl group specifically oriented to participate as an intramolecular catalyst of the hydrolytic reaction. In 3 of the reagents the specific orientation is a result of the c/s-configuration of the groups about the carbon-carbon double bond, and in the other 2 reagents the specific orientation is 

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