Formation of protein charge ladders by acylation of amino groups on proteins

Ian J. Colton, Janelle R. Anderson, Jinming Gao, Robert G. Chapman, Lyle Isaacs, George M. Whitesides

Research output: Contribution to journalArticlepeer-review

29 Scopus citations


The values of charge and electrophoretic mobility of a protein are changed upon acylation of its α- and Lys ε-NH3+ groups. Partial acylation of the amino groups of a protein results in a set of derivatives that is often resolved by capillary electrophoresis into a set of distinct peaks - the 'rungs' of a protein charge ladder - that differ incrementally in the number of residues modified. Proteins that have values of MW < 50 kD usually form resolved charge ladders when allowed to react with acetic anhydride, while proteins that have values of MW > 50 kD form broad unresolved peaks. Resolved charge ladders of proteins that have values of MW > 50 kD may be formed using acylating agents that introduce several charges upon acylation of each of their Lys ε-NH3+ groups. As an example, L-lactate dehydrogenase (MW = 147 kD) does not form a resolved charge ladder when modified with acetic anhydride. When it is acylated with either 1,2,4-benzenetricarboxylic anhydride, 3, or 1,2,4,5-benzenetetra-carboxylic dianhydride, 4, however, it forms charge ladders in which each of the first several pairs of adjacent rungs are separated by approximately 3 or 4 units of charge, respectively. The procedures described in this paper were used to form resolved charge ladders from 25 proteins differing in pI and in MW.

Original languageEnglish (US)
Pages (from-to)12701-12709
Number of pages9
JournalJournal of the American Chemical Society
Issue number52
StatePublished - Dec 31 1997

ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry


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