title: A novel method to measure self-association of small amphipathic molecules: temperature profiling in reversed-phase chromatography.
abstract: Biophysical techniques such as size-exclusion chromatography, sedimentation equilibrium analytical ultracentrifugation, and non-denaturing gel electrophoresis are the classical methods for determining the self-association of molecules into dimers, trimers, or other higher order species. However, these techniques usually require high (mg/ml) loading concentrations to detect self-association and also possess a lower size limit that is dependent on the ability of the technique to resolve monomeric from higher order species. Here we describe a novel, sensitive method with no upper or lower molecular size limits that indicates self-association of molecules driven together by the hydrophobic effect under aqueous conditions. "Temperature profiling in reversed-phase chromatography" analyzes the retention behavior of a sample over the temperature range of 5-80 degrees C during gradient elution reversed-phase high-performance liquid chromatography. Because this technique greatly increases the effective concentration of analyte upon adsorption to the column, it is extremely sensitive, requiring very small sample quantities (microgram or less). In contrast, the classical techniques mentioned above decrease the effective analyte concentration during analysis, decreasing sensitivity by requiring larger amounts of analyte to detect molecular self-association. We demonstrate the utility of this technique with 14-residue cyclic and linear cationic peptides (<2000 Da) based on the sequence of the de novo-designed cytolytic peptide, GS14. The only requirements for the analyte molecule when using this technique are its ability to be retained on the reversed-phase column and to be subsequently removed from the column during gradient elution.
authors.affiliation: Department of Biochemistry, University of Alberta, Edmonton, Alberta T6G 2H7, Canada.
authors.forename: Darin L
authors.initials: DL
authors.lastname: Lee
authors.forename: Colin T
authors.initials: CT
authors.lastname: Mant
authors.forename: Robert S
authors.initials: RS
authors.lastname: Hodges
mesh_terms: D000595:Amino Acid Sequence; D001665:Binding Sites; D002851:Chromatography, High Pressure Liquid; D007700:Kinetics; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D010456:Peptides, Cyclic / Q000138:chemical synthesis / Q000737:chemistry*; D011487:Protein Conformation; D013329:Structure-Activity Relationship; D013816:Thermodynamics
chemical_list: D010456:Peptides, Cyclic