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  • Separation of polypeptides by isoelectric point focusing in electrospray-friendly solution using a multiple-junction capillary fractionator.

Separation of polypeptides by isoelectric point focusing in electrospray-friendly solution using a multiple-junction capillary fractionator.

Analytical chemistry (2012-07-12)
Konstantin Chingin, Juan Astorga-Wells, Mohammad Pirmoradian Najafabadi, Thorleif Lavold, Roman A Zubarev
ABSTRACT

We introduce an online multiple-junction capillary isoelectric focusing fractionator (OMJ-CIEF) for separation of biological molecules in solution by pI. In OMJ-CIEF, the separation capillary is divided into seven equal sections joined with each other via tubular Nafion membrane insertions. Each junction is communicated with its own external electrolytic buffer which is used both to supply electrical contact and for solvent exchange. The performance of the fractionator was explored using protein and peptide samples covering broad pI range. Separation was achieved in ionic and ampholytic buffers, including ammonium formate, ammonium hydroxide, histidine, and arginine. By maintaining electric potential across upstream segments of the capillary after the focusing stage, selective release of downstream analyte fractions could be achieved. The selective release mode circumvents the problem of peak broadening during mobilization and enables convenient comprehensive sampling for orthogonal separation methods. Using single-component ampholyte buffers with well-defined pI cutoff values, controlled separation of protein mixture into basic and acidic fractions was demonstrated. The device is cheap and easy to fabricate in-house, simple in operation, and straightforward in interfacing to hyphened analytical platforms. OMJ-CIEF has a potential of becoming a practical add-on unit in a wide range of bioanalytical setups, in particular as a first-dimension separation in mass spectrometry based proteomics or as a preparative tool for analyte purification, fractionation, and preconcentration.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
Ammonium hydroxide solution, BioUltra, ~1 M NH3 in H2O (T)
Sigma-Aldrich
Ammonium hydroxide solution, puriss. p.a., reag. ISO, reag. Ph. Eur., ~25% NH3 basis
Sigma-Aldrich
Ammonium hydroxide solution, 28% NH3 in H2O, ≥99.99% trace metals basis
Sigma-Aldrich
Ammonium hydroxide solution, puriss., meets analytical specification of Ph. Eur., 25-30% NH3 basis
Sigma-Aldrich
Ammonium hydroxide solution, puriss., 30-33% NH3 in H2O
Sigma-Aldrich
Ammonium hydroxide solution, puriss. p.a. plus, ≥25% NH3 in H2O
Sigma-Aldrich
Ammonium hydroxide solution, ACS reagent, 28.0-30.0% NH3 basis