The isoelectric point (pI) is an important property of proteins. The pI is the sum of the charged groups on the surface of a protein and reflects the amino acid sequence of the protein. Small changes in pI is an excellent indicator of post-translational modifications (PTMs) to the protein.
In capillary isoelectric focusing (CIEF), the pH gradient generated by the electric field is assumed to be linear. pI markers are reference standards of a known pI; by using two pI markers as reference standards, the pI of other proteins can conveniently be determined.
As part of the CEInfinite product line, Advanced Electrophoresis Solutions Ltd. (AES) has developed a series of small molecule pI markers to enable accurate protein pI calibration and routine protein verification in quality control environments. These small molecule pI markers consist of non-peptide synthetic molecules that cover the full pH range from 3 to 10.5, allowing convenient application of pI markers in an enzymatic matrix.
CEInfinite pI markers are also available as peptides with tryptophan. Peptide pI markers offer reference standards for both ultraviolet (UV, 280 nm) and fluorescent (290 nm/340 nm) detection, but are less stable than small molecule pI markers and are prone to digestion by enzymatic buffers.
With 32 individually-packaged pI reference standards available, AES has the most comprehensive pI markers for your applications. Also available is a pI Mixture, with six different pI markers to easily confirm the linearity of your electrophoretic separation.
If you would like to purchase CEInfinite pI markers, please click here to be directed to our online store.