Separation of peptides by capillary electrophoresis.

Peptides are an important class of analytes in chemistry, biochemistry, and food chemistry as well as medical and pharmaceutical sciences. As a high-resolution technique, capillary electrophoresis (CE) is well suited for the analysis of polar compounds such as peptides. In addition, CE is orthogonal to high-performance liquid chromatography, as both techniques are based on different physico-chemical separation principles.

Nonaqueous versus aqueous capillary electrophoresis of alpha-helical polypeptides: effect of secondary structure on separation selectivity.

The CE separation of alpha-helical polypeptides composed of 14-31 amino acid residues has been investigated using aqueous and nonaqueous BGEs. The running buffers were optimized with respect to pH. Generally, higher separation selectivities were observed in nonaqueous electrolytes.

Determination of enkephalin peptides by nonaqueous capillary electrophoresis with electrochemical detection.

Nonaqueous capillary electrophoresis with electrochemical detection (NACE-ED) was applied to the analysis of enkephalin peptides. The effect of different buffer compositions on the electrophoretic behavior of methionine enkephalin, leucine enkephalin, and [D-Ala2]-leucine enkephalin was studied. Separation of the protonated and the deprotonated peptides was obtained using ACN/methanol-based electrolyte systems.

Analysis of the lipophilic peptaibol alamethicin by nonaqueous capillary electrophoresis-electrospray ionization-mass spectrometry.

The microheterogeneous peptaibol alamethicin F30 isolated from the culture broth of Trichoderma viride was analyzed by nonaqueous CE-electrospray-MS using an IT and a TOF mass analyzer. Compared to aqueous buffers, higher separation selectivity was observed for methanolic BGE allowing the detection of more minor components. The low electrophoretic mobility observed for neutral analytes under nonaqueous conditions may be explained by ion-dipole interactions between the peptide analytes and electrolyte ions.

Detection of new amino acid sequences of alamethicins F30 by nonaqueous capillary electrophoresis-mass spectrometry.

The microheterogeneous alamethicin F30 (ALM F30) isolated from the fermentation of Trichoderma viride strain NRRL 3199 was analyzed by nonaqueous capillary electrophoresis coupled to electrospray ion-trap mass spectrometry (ESI-IT-MS) and electrospray time-of-flight mass spectrometry (ESI-TOF-MS). Tandem ESI-IT-MS was used for elucidation of the amino acid sequence based on the fragmentation pattern of selected parent ions. The MS/MS spectra using the [M + 3H](3+) or [M + 2H](2+) ions as precursor ions displayed the respective b- and the y-type fragments resulting from cleavage of the particularly labile Aib-Pro bond.

Peptide separations and dissociation constants in nonaqueous capillary electrophoresis: comparison of methanol and aqueous buffers.

Nonaqueous capillary electrophoresis was evaluated for its potential to separate peptides in methanolic background electrolytes in comparison to aqueous-methanol (50% v/v) and water. Isomeric aspartyl dipeptides and Leu- and Met-enkephalin served as model compounds. pK(a) values were determined in the three solvent systems based on the apparent pH scale and in the case of methanol additionally based on the conventional pH scale.