Protein reversible modifying reagents

Reversible Modifying Reagents for Amino Groups in Proteins... 

The only disadvantage of the succinylation procedure (which is practical and amenable to conventional cell disruption processes) is that the final product is a succinylated protein. Succinyl groups cannot be removed from the succinylated proteins under mild conditions. This could be a problem if succinylated yeast protein was a major source of dietary proteins. Therefore we explored the feasibility of using reversible modifying reagents (citraconic anhydride and maleic anhydride) to separate proteins from NAs and subsequently remove the modifying groups under mild acidic conditions. 

Scheme III. Scheme for separating proteins and nucleic acids from a nucleoprotein complex using reversible modifying reagents of amino groups in the proteins...

Figure 47.4. Chemical modification of the protein with a water-insoluble reagent in the reverse micelles of Aerosol OT in octane. (1) Protein molecule incorporates into the inner water pool of the reverse micelle, acquiring a monolayer cover of the hydrated surfactant molecules. (2) The modifying reagent incorporates into the surfactant layer of the micelle coming into contact with the modified group of the protein. (3) Following the completion of the reaction the modified protein is precipitated and the surfactant and excess of the reagent are removed by adding cold acetone. Proteins modified with fatty acid residues with controlled and low degree of modification are obtained.

Amides and esters of haloacids have been frequently used in the synthesis of affinity labels. Like haloketones, these derivatives react with all the nucleophilic amino acids. Their advantages as modification reagents are two-fold. First, they are relatively more easy to synthetize than haloketones. Any substrate or reversible inhibitor with a free amino or hydroxyl group can be potentially converted into an affinity labelling reagent. Second upon acid hydrolysis, the modified protein yields carboxymethylated derivatives which are known and therefore readily identifiable and quantifiable. 

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