The aqueous thermal polycondensation of asparagine and isoasparagine and the structure of polyaspartic acid

Summary

Both asparagine and isoasparagine were converted into polyaspartic acids by refluxing the corresponding aqueous solutions at neutral pH in the presence of a salt. The properties of the resulting polyaspartic acids were studied. The dissociation behavior of the carboxyl groups in the polypeptides were studied by the potentiometric titration. The analysis of the titrational data was performed by a modified Speakman's method. The analysis show that both polyaspartic acids prepared from asparagine and isoasparagine have α- and β-aspartyl residues and the ratio of α- and β-aspartyl residues is 75 ∶ 25∼85 ∶ 15. A possible mechanism for the formation of α- and β-aspartyl residues in the polymer was discussed.