FIG 4.

Characterization of the antiprion activities of melanin compounds. (A) Immunoblot data for PrPres in ScN2a cells treated with nonultrafiltrated (U) or ultrafiltrated melanin samples (retentate [R]) or filtrate [F]) from 1.5 μg/ml tyr-melanin or dopa-melanin. Ultrafiltration was performed with a 100-kDa cutoff membrane. The photo on the right shows the retentates and filtrates of melanin compound solutions. (B) Immunoblot data for PrPres in ScN2a cells treated with tyr-melanin, which had been treated with the designated concentrations of NaOH with or without autoclaving. Tyr-melanin was used at a concentration of 1.5 μg/ml in culture medium. Tyr-melanin was hardly solubilized in water or 0.01 N NaOH irrespective of heating. (C) Immunoblot data for PrPres in ScN2a cells treated with 1.5 μg/ml tyr-melanin that had been decomposed and decolored by treatment with H₂O₂ or NaClO.