Undergraduate Honors Theses

Thesis Defended

Spring 2015

Document Type


Type of Thesis

Departmental Honors



First Advisor

Veronica Vaida


While modern cell membranes are composed of phospholipids, primitive membranes were probably made from simpler fatty acids. Due to the prebiotic availability of fatty acids, fatty acid vesicles are a popular model for proto-cell membranes in origin-of-life studies. Vesicles of one such fatty acid, decanoic acid, are often used to model early membranes, but the mechanism by which decanoic acid forms vesicles is not clear. Monolayer studies of the stability of decanoic acid on water surfaces may help illuminate the key molecular interactions that result in vesicle formation. To this end, consistent amounts of decanoic acid were deposited on the surface of aqueous salt and buffer solutions, and a variety of isotherms were collected with a Langmuir trough and Wilhelmy balance. Time versus surface pressure isotherms were analyzed and it was found that there was no statistical difference in the isotherms collected on 50 mM and 500 mM NaCl, indicating that the effects of salt on the phase behavior of decanoic acid might plateau at a lower concentration. However, the isotherms run on a Tris buffer substrate were statistically different from the isotherms at both salt concentrations. These preliminary results suggest that pH and buffer type are influential on decanoic acid surface partitioning and stability, and that the speed of equilibration increases at higher bulk ionic strength.