I. Synthesis and characterization of ester-modified surfactants. II. Membrane-bound sodium in ester-laden phospholipids. III. Characterizing the shell phase formed from amphiphilic picolinates.

摘要

This dissertation broadly includes the synthesis and characterization of unnatural surfactants and phospholipids. In part I, I have designed surfactants with esters incorporated into the traditionally all-hydrocarbon tail. While studying these surfactants, I hoped to answer a question not yet posed systematically in surfactant chemistry. How do the colloidal properties of surfactants respond to insertion of non-hydrocarbon functionalities within chains that are normally entirely hydrocarbon? In answering this question, two classes of such chain-modified surfactants were discovered. One class forms only small aggregates, while the other is much more normal and can even exceed conventional surfactants in mesitylene solubilization. Differences between the two categories of chain-modified surfactants originate from the degree of segmentation of the hydrocarbon and, in particular, upon the location of the longest segment.;In Part II of this dissertation, I synthesized seven ester-laden phospholipids in order to probe the disruptive effects of an ester inside the hydrophobic region of a vesicle. Interestingly, the new phospholipids that had shorter terminal segments caused more vesicle leakage than did those with longer terminal segments. Inserting an unnatural phospholipid with a short terminal segment into a normal POPC vesicle causes domains to form. Over time, these ester-laden domains produce either water pools or pores which span the phospholipid bilayer.;In part III of this dissertation, I explored a new phase, termed the shell phase, formed from an insoluble surfactant. Interestingly, when 3 mg of 5-(1-dodecylaminocarbamoyl) picolinic acid is sonicated and vortexed with 0.25 M NaOH and 10 mL of toluene, stable, marble-like macroscopic spheres are formed. Apparently, the spheres are encased by some sort of outer covering, or shell, that is about 600 Å thick and contains the picolinate and (very likely) toluene. The shells, stable for months, are not easily distorted but can be punctured, even skewered, with a syringe needle without destroying the sphere. Yet there is enough mobility among the molecules to repair the physical damage after the needle is removed. Structure-activity comparisons among ten newly synthesized analogs indicate that chain-chain association and intermolecular hydrogen-bonding are dominant forces in a side-by-side self-assembly of the molecules within the shells.