Reactions Which Retain the Positive Charge

Alkylation of the free amino group of lysine with aldehydes and ketones is possible, with a simultaneous reduction step  

This reaction is used analytically to assess the amount of biologically available e-amino groups and for measuring protein digestibility. 

Derivatization with imido esters is also possible. The reactant is readily accessible from the corresponding nitriles  

Proteins can be cross-linked with the use of a bi-functional imido ester (cf. 1.4.4.10). 

Treatment of the anuno acid residue with amino acid carboxyanhydrides yields a polycondensation reaction product  

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