NMR Investigation of Micelle Formation by a Dipeptide Surfactant — Presentation Detail — Celebration of Scholars

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Jun Wang
Kim Instenes
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James Ripley

NMR Investigation of Micelle Formation by a Dipeptide Surfactant

Name: Tyler Witzleb
Major: Chemistry
Hometown: Rock Falls
Faculty Sponsor: Kevin Morris
Other Sponsors:
Type of research: SURE
Funding: National Science Foundation

Abstract

NMR spectroscopy was used to investigate how a chiral surfactant molecule formed aggregates known as micelles. Micelles have an oily hydrocarbon core and a polar or charged surface. The surfactant contained a hydrocarbon tail attached to a leucine-valine dipeptide. Micelles formed by this surfactant have been used to separate the enantiomers or mirror image forms of drugs. NMR diffusion experiments showed that in the pH range 7.0 to 11.5, the micelles had radii of approximately 25 Angstroms. These radii agreed well with measurements from small angle neutron scattering. Below pH nine, lysine and arginine amino acids were found to bind to the anionic micelles. At higher pH’s, though, both amino acid dissociated from the micelles. Finally, the dipeptide NH protons were observed to exchange with solvent protons. The rate of this exchange reaction was investigated along with the conformation of the surfactant’s dipeptide headgroup. Studying the properties of the micelles formed by unique surfactant molecules, like UND-LV, can aid to improve the chiral separation experiments that utilize them.

Poster file