Eric W. Taylor

Development of a capillary electrophoretic separation of an N-(substituted)-glycine-peptoid combinatorial mixture

Capillary electrophoresis was used for the separation of a combinatorially synthesized N-(substituted)-glycine (NSG) peptoid mixture. This mixture consisted of 24 trimeric compounds sharing a common backbone structure but differing in the side chain attached at the N-terminal residue. Standards of the individual components were unavailable so that development of the separation was based on the mixture. A variety of buffer additives were investigated to enhance the CE resolution of this diverse mixture. Ion-pairing agents, cyclodextrins and organic modifiers were all evaluated as buffer additives. The best separations were achieved using a combination of buffer additives, each serving a different purpose in the separation. Heptane sulphonic acid (HSA) was used to reduce hydrophobic intramolecular interactions. Methyl-beta-cyclodextrin was used to provide host-guest interactions in order to resolve the very hydrophobic components of the NSG-peptoid mixture. The optimized run buffer consisted of 250 mM sodium phosphate buffer, pH 2.0, with 25 mM HSA and 40 mg/ml BCD and resulted in the resolution of 21 peaks for the 24 peptoids in the combinatorial mixture.

Application of capillary electrophoresis to the separation of structurally diverse N-(substituted)-glycine–peptoid combinatorial mixtures

The capillary electrophoresis (CE)-based separation of five N-(substituted)-glycine (NSG)-peptoid mixtures with a wide range of physical and chemical properties was studied. A CE separation, initially developed using a single representative peptoid mixture, with a background electrolyte (BGE) modified by the addition of both methyl-beta-cyclodextrin and heptane sulfonic acid was found to provide good separations of most of the combinatorial mixtures investigated. For those mixtures not separated well by this procedure, the use of SDS micelles in conjunction with methyl-beta-cyclodextrin resulted in dramatic improvements in the separation. While no single set of separation conditions proved sufficient for all of the NSG-peptoid combinatorial mixtures, the two methods were able to provide separation sufficient for characterization of a set of mixtures with a wide range of physical and chemical properties. The efficiency of the CE-based separation of the combinatorial mixtures studied was compared to a reversed-phase liquid chromatographic method using gradient elution.