Correlations Between the Charge of Proteins and the Number of Ionizable Groups They Incorporate: Studies Using Protein Charge Ladders, Capillary Electrophoresis, and Debye-Hückel Theory
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- 作者：Jeffrey D. Carbeck ; Ian J. Colton ; Janelle R. Anderson ; John M. Deutch ; and George M. Whitesides
- 刊名：Journal of the American Chemical Society
- 出版年：1999
- 出版时间：November 24, 1999
- 年：1999
- 卷：121
- 期：46
- 页码：10671 - 10679
- 全文大小：134K
- 年卷期：v.121,no.46(November 24, 1999)
- ISSN：1520-5126
文摘
The values of electrophoretic mobility, 
electro, of bovine carbonic anhydrase II, human carbonicanhydrase II, cytochrome c, lysozyme, superoxide dismutase, ovalbumin, and derivatives of these proteinsproduced by partial neutralization of Lys 
-NH3+ and/or Asp and Glu carboxyl groups were measured usingcapillary electrophoresis (CE). For derivatives of these proteins with the lowest overall values of net charge(either positive or negative), the values of electro and the values of charge measured by CE, ZCE, demonstratea linear correlation with the number of charged groups, n, converted to neutral derivatives. For derivatives ofthese proteins with larger values of net charge, the values of electro and ZCE demonstrate a nonlinear correlationwith n. Several observations made in this work suggest that shifts in the values of pka of the ionizable groupson these proteins likely contribute to the observed nonlinear correlation. Debye-Hückel theory was used tocalculate values of electrostatic potential at the surface of the derivatives of all six proteins from the measuredvalues of electro. These values were plotted against the values of electrostatic potential calculated by assigninga charge to each protein in direct proportion to n. The data for all six proteins fell along a single commoncurve, regardless of the concentration of monovalent cations in the electrophoresis buffer.
electro, of bovine carbonic anhydrase II, human carbonicanhydrase II, cytochrome c, lysozyme, superoxide dismutase, ovalbumin, and derivatives of these proteinsproduced by partial neutralization of Lys -NH3+ and/or Asp and Glu carboxyl groups were measured usingcapillary electrophoresis (CE). For derivatives of these proteins with the lowest overall values of net charge(either positive or negative), the values of electro and the values of charge measured by CE, ZCE, demonstratea linear correlation with the number of charged groups, n, converted to neutral derivatives. For derivatives ofthese proteins with larger values of net charge, the values of electro and ZCE demonstrate a nonlinear correlationwith n. Several observations made in this work suggest that shifts in the values of pka of the ionizable groupson these proteins likely contribute to the observed nonlinear correlation. Debye-Hückel theory was used tocalculate values of electrostatic potential at the surface of the derivatives of all six proteins from the measuredvalues of electro. These values were plotted against the values of electrostatic potential calculated by assigninga charge to each protein in direct proportion to n. The data for all six proteins fell along a single commoncurve, regardless of the concentration of monovalent cations in the electrophoresis buffer.