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Nonaqueous versus aqueous capillary electrophoresis of α‐helical polypeptides: Effect of secondary structure on separation selectivity
Author(s) -
Psurek Arndt,
Feuerstein Sophie,
Willbold Dieter,
Scriba Gerhard K. E.
Publication year - 2006
Publication title -
electrophoresis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.666
H-Index - 158
eISSN - 1522-2683
pISSN - 0173-0835
DOI - 10.1002/elps.200500673
Subject(s) - chemistry , aqueous solution , protein secondary structure , circular dichroism , selectivity , solvent , amino acid , chromatography , capillary electrophoresis , methanol , crystallography , organic chemistry , biochemistry , catalysis
The CE separation of α‐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. This may be explained by a change in the secondary structure when changing from water to organic solvents. Circular dichroism spectra revealed a significant increase in helical structures in methanol‐based buffers compared to aqueous buffers. This change in secondary structure of the polypeptides contributed primarily to the different separation selectivity observed in aqueous CE and NACE. For small oligopeptides of two to five amino acid residues no significant effect of the solvent was observed in some cases while in other cases a reversal of the migration order occurred when changing from aqueous to nonaqueous buffers. As these peptides cannot adopt secondary structures the effect may be attributed to a shift of the p K a values in organic solvents compared to water.