- for Cation-Exchange of Proteins -
PolyCAT A™ is made through a unique process for attaching poly(aspartic acid) covalently to silica. Proteins elute from this polypeptide coating in sharp peaks with little tailing. Binding capacity and recovery are high as well. Use PolyCAT A™ for:
1) Protein variants involving deamidation, PEGylation, position of attachment, desialylation, etc. It is widely used by the biotechnology industry.
2) Hemoglobin variant analysis by clinical chemistry labs.
3) Proteins with pI above 6.0 (5.0 in special cases).
Since PolyCAT A™ is a weak cation-exchange (WCX) material, it is used at pH values above 4. A gradient to unbuffered acetic acid will uncharge PolyCAT A™, permitting the elution of proteins in a volatile solvent. See our poster on this subject.
Peptides can be run on PolyCAT A™ if they contain at least two excess positive charges above pH 4. More weakly basic peptides, such as tryptic fragments, are not reliably retained and should be run on PolySULFOETHYL A™ at pH = 2.7 - 3.0
For proteins larger than 20 KDa, we recommend the use of pore diameters of at least 1000 Å for optimal selectivity and efficiency. Our 3-µm material with 1000- or 1500-Å pores is the finest cation-exchanger available for protein separations.