CIEF Reference Standards

Separation of pI Marker Mixture Hhowing pI Markers Covering pH 3 to 10
Separation of pI Marker Mixture Hhowing pI Markers Covering pH 3 to 10

The isoelectric point (pI) of proteins is an important property that related to their surface charge (or primary structure when proteins are fully denatured). The pI of a protein can be calibrated conveniently with two pI markers in capillary isoelectric focusing (CIEF), when the pH gradient is assumed to be linear.

There are two types of pI markers for CIEF applications, protein pI markers and synthetic small molecule pI markers. Protein pI markers are from particular proteins with commonly accepted pI values. The drawback of using protein pI markers includes stringent storage conditions, poor stability and the possibility of multiple peaks in CIEF. Synthetic small molecules are generally more stable during storage and will focus to a single peak in CIEF. Nevertheless, there is need for small molecule pI markers to be consistent with each other and with protein pI markers. As these pI markers are sometimes used in enzymatic buffers, and non-peptide markers are preferred to resist enzyme digestion.

AES (Advanced Electrophoresis Solutions Ltd.) has developed a series of small molecule pI markers to enable accurate protein pI calibration and routine protein verification in quality control environments. The values of pI markers were determined with a proprietary comprehensive method. The values of some pI markers were directly obtained from their thermodynamic pKas, which represent the theoretical pI value of these markers. The values of some other pI markers are indirectly obtained by calibration with common protein pI makers. These pI values were further validated in CIEF, so that they are accurate and consistent when applied in pI calibration and protein verification. 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.

AES has the most comprehensive pI markers for your applications.

The main benefits with CEInfinite pI Markers

PropertiesBenefits
At least one marker within each 0.5 pH unitImproved accuracy for pI calibration
Ready to mix with samplesEasy to use
Long shelf lifeReduce the time and financial burden of recurrent replacement
Peptides and non-peptides are both availableSelection of enzyme digestion resistant pI markers

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