Portal de Periódicos da CAPES

Determination of the effective charge of a protein in solution by capillary electrophoresis.

1994; National Academy of Sciences; Volume: 91; Issue: 25 Linguagem: Inglês

10.1073/pnas.91.25.12027

1091-6490

Jinming Gao, Frank A. Gomez, Ronald L. Harter, George M. Whitesides,

Mass Spectrometry Techniques and Applications

This paper describes two methods to estimate the effective charge of a protein in solution by capillary electrophoresis and demonstrates these methods by using representative proteins. In one method, a "charge ladder"--a series of derivatives of a protein differing by known increments of charge but differing only minimally in hydrodynamic drag--is generated by covalent modification of the epsilon-amino groups of lysines with 4-sulfophenyl isothiocyanate or acetic anhydride. In the second method, the equivalent of a charge ladder is produced by noncovalent association of a protein with differently charged ligands. Analysis of the electrophoretic mobilities of the protein and its derivatives as a function of added charge allows the effective charge to be estimated for the unmodified protein. This type of analysis permits estimation of the effective charge of a protein without knowing its composition, structure, or amino acid sequence.