Colorimetric quantification of amino groups in linear and dendritic structures

BACKGROUND: The aim of the work reported was to develop a procedure using 96-well microtiter plates for the easy determination of protonated groups of compounds including linear poly(amino acid)s and dendritic polymers divided into dendrigraft and dendrimeric structures. This study is a prerequisite step for the quantification of protonated groups in a macromolecule grafted onto a solid surface. RESULTS: The procedure was developed from the modified Bradford protein assay and incorporates several modifications that enable one to determine available amino groups (or even other cationic groups) present on the polyresidues backbone, all within five minutes. Based on the Atherton mathematical model, we evaluated the maximal number of Coomassie blue binding sites on linear, dendrigraft or even dendrimeric structures. CONCLUSION: The mean calculated percentage of occupied sites on a given macromolecule led us to demonstrate that one Coomassie blue molecule interacts with only one single protonated group. Consequently, the developed method using Coomassie blue binding can be used for the quantification of cationic groups in a macromolecule grafted onto a solid surface. (C) 2009 Society of Chemical Industry