Extension of separation range in capillary isoelectric focusing for resolving highly basic biomolecules

Area of Science:

• Analytical Chemistry
• Biochemistry
• Separation Science

Background:

• Commercial carrier ampholytes are unavailable for pH ranges above 11, hindering the separation of highly basic proteins and peptides.
• Capillary isoelectric focusing (cIEF) is a powerful technique for protein and peptide separation, but its range is limited by ampholyte availability.

Purpose of the Study:

• To investigate methods for extending the separation range of capillary isoelectric focusing (cIEF) beyond pH 11.
• To improve the resolution of highly basic proteins and peptides using cIEF.

Main Methods:

• Two approaches were explored: addition of N,N,N',N'-tetramethylethylenediamine (TEMED) to pharmalyte 3-10 and the use of ampholyte 9-11 in combination with pharmalyte 3-10.
• Capillary isoelectric focusing (cIEF) was performed using a sample mixture containing bradykinin (pI 12), a high-pI protein calibration kit (pI 5.2-10.3), and cytochrome c digest.

Main Results:

• The addition of TEMED to pharmalyte 3-10 extended the cIEF separation range to at least isoelectric point (pI) 12, preventing premature focusing.
• Combining ampholyte 9-11 with pharmalyte 3-10 achieved baseline resolution between bradykinin (pI 12) and cytochrome c (pI 10.3).
• Demonstrated successful cIEF separation of proteins and peptides across a wide pH range of 3.7-12.

Conclusions:

• N,N,N',N'-tetramethylethylenediamine (TEMED) and ampholyte 9-11 are effective in extending the pH separation range of capillary isoelectric focusing (cIEF).
• These methods enable the resolution of highly basic proteins and peptides, overcoming limitations of commercially available ampholytes.