Detection of Biopolymer -poly-L-lysine with Molybdosilicate Anion for Screening of Synthetic Enzymes

-Poly-L-lysine (-PL) exists as a cationic polymer in acidic solution. Yellow tetravalent 12-molybdosilicate ([SiMo₁₂O₄₀]⁴⁻) anion is formed in acidic solution containing and anions. By mixing the test -PL solution with the acidic − solution, the [SiMo₁₂O₄₀]⁴⁻ anion associates with the cationic -PL to form yellow precipitate. The yellowness of the supernatant decreased with the initial concentration of -PL in the test solution due to the residual [SiMo₁₂O₄₀]⁴⁻ anion. By addition of ascorbic acid to the supernatant, the residual [SiMo₁₂O₄₀]⁴⁻ anion was reduced to blue molybdosilicate species. Thus the concentration of -PL in sample media can also be estimated by the blueness of the reaction mixture. The present method can be applied successfully to the screening of -PL-synthetase in culture media.