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

Jinming Gao, Frank A. Gomez, Ralph Härter, George M. Whitesides

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Abstract

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 ε-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.

Original languageEnglish (US)
Pages (from-to)12027-12030
Number of pages4
JournalProceedings of the National Academy of Sciences of the United States of America
Volume91
Issue number25
DOIs
StatePublished - Dec 6 1994

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Keywords

  • protein charge ladders

ASJC Scopus subject areas

  • General

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