Silver Staining of Proteins Separated by Polyacrylamide Gel Electrophoresis: a Mathematical Model

E. B. Okon,^1,2 V. Marjanovic,³ J. Hranisavljevic,³ and D. Vucelic⁴

¹Institute of Theoretical and Experimental Biophysics, Russian Academy of Sciences, Pushchino, Moscow Region, 142292 Russia.

²To whom correspondence should be addressed.

³Institute of General and Physical Chemistry, Akademski trg 12/16, Belgrade, 11000 Yugoslavia.

⁴Department of Physical Chemistry, Belgrade University, Akademski trg 12/16, Belgrade, 11000 Yugoslavia.

Submitted October 13, 1995; revision submitted July 16, 1996.

Silver staining of proteins separated by electrophoresis in a thin layer of polyacrylamide gel can be qualitatively measured provided that the data are statistically estimated. We propose a mathematical model taking into account the autocatalytic character of the key stage of silver staining, the reduction of protein-bound silver ions. According to the model, the reaction rate strongly depends on the instability constant of the complex of silver ions and functional groups of a protein, and the shape of the staining intensity versus protein concentration plots is determined by the ratio of concentration of silver-binding functional groups to the instability constant. Based on the model, the intricate shape of calibration curves is interpreted as the combination of autocatalysis and saturation. The high sensitivity of this reaction to experimental conditions, the contribution of complexes with different instability constants to the intensity of protein band staining, and optical effects are analyzed.

KEY WORDS: silver staining, electrophoresis, mathematical model.

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