Dipeptide micelle polymers are a new class of polymeric surfactants of which the polysodium undecanoyl-L-leucylvalinate (poly-L-SULV) was found to be a broadly applicable chiral selector for micellar electrokinetic chromatography. This negatively charged dipeptide micelle polymer is a high molecular weight compound with large countercurrent mobility, zero critical micelle concentration, low aggregation number, and high solubility in water or water-organic solvents. In an extensive chiral screening program, enantioseparation of 75 racemic compounds was tested with poly-L-SULV as chiral pseudostationary phase in neutral pH and basic pH background electrolytes. A total of 58 out of 75 racemic compounds could be resolved after choosing an appropriate concentration of poly-L-SULV. Although anionic chiral analytes are difficult to resolve using poly-L-SULV, the percent success rate for chiral resolution of cationic (77%) and neutral (85%) racemates was very high. Aspects regarding electrostatic, steric, hydrophobic, and hydrogen-bonding interactions of this dipeptide micelle polymer with various classes of chiral analytes are discussed.
The aggregation numbers of 15 dipeptide surfactants were estimated by use of fluorescence steady-state quenching techniques. Polymerization of the surfactants with γ radiation resulted in molecular micelles with a lower number of repeat units than the corresponding monomer aggregation numbers at the concentration of monomer used for polymerization in this study. In addition, the aggregation numbers of the monomers decreased with increasing size of the N-terminal R group of the dipeptide surfactants examined in this study. The aggregation behavior of the dipeptide surfactants was further investigated using proton NMR ( 1 H NMR) spectroscopy. The proton resonances due to NH and HR were measured above and below the critical micelle concentration of the surfactants. From the differences in proton chemical shifts of the monomeric dipeptide surfactants and aggregation numbers, a model for packing of the monomeric polar head is proposed.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.