Quantitative Proteinbestimmung in Einzelzellen mit Amidschwarz

In aqueous solution Amido Black B (ASB) forms stable and well-defined complexes with bovine serum albumin (RSA) at pH 5.5. The complexes can be separated by column chromatography. The formation of the complexes consists in a fast reaction during which, after 3 to 5 h approximately, 3 molecules of ASB have been bound per molecule RSA, and of a much slower reaction which, even after a laps of 24 h, is still far from approaching its final stage. With solid films of RSA, after denaturation with ethanol, fast reaction is found to approach its final stage after 10 min reaction time. With these model protein preparations, the molar extinction coefficient of the ASB-protein complexes can be determined: the soluble ASB-RSA complexes can be brought to complete dissociation at pH 12.3. After the additivity of the specific absorptions of both RSA and ASB had been proven, it was possible to determine the content of the solution of ASB and RSA, and therefrom the molar extinction coefficient of the ASB-RSA-complex at pH 5.5: e₆₂₀=110,000. ASB-stained ethanolfixed RSA films show an e₆₂₀ of approximately 96,000, if their thickness and specific weight are known.