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Membrane-confined analytical electrophoresis

Culvette and sample holder

The MCE apparatus is a unique instrument, developed at CAMIS, that provides a means of determining the charge of macromolecules under a variety of solution conditions. The charge of a molecule is a fundamental property that is inextricably linked to its structure, solubility and interactions. MCE is a primary method for measuring this charge directly and routinely, without comparison to standards.

The MCE has a sample chamber sealed with a semi-permeable membrane which permits the establishment of an electric field along the cuvette’s length while retaining macroions in the field of view of the imaging spectrophotometer. A concentration gradient is set up where the electrophoretic flow is exactly balanced by the diffusional counterflow. The resulting concentration distribution is exponential and the exponent is directly proportional to the net apparent charge.

Presentation (pdf): The importance of accurately measuring protein valence.


  • Quality control and analysis
  • Cataloging and characterization of charge on macromolecules
  • Determining the size, shape and hydration of macromolecules
  • Academic and industrial uses
    1. Detecting isozyme variants
    2. Measuring effects of different buffer conditions on ion binding
    3. Investigating charge variations of DNA
    4. Studying of drug-DNA and protein-protein interactions

Key features of the MCE:

  • Small sample sizes (2-100 µg)
  • Does not require a standard
  • Buffer can be changed without disrupting the sample

There are 2 MCE instruments at CAMIS for collaborative or fee-for-service measurements of the charge on macromolecules. For more information please contact us or visit services. Alternatively, capillary electrophoresis instruments can be used for measuring charge.