Date of Award
1994
Degree Type
Dissertation
Degree Name
Doctor of Philosophy
Abstract
This research project is directed towards establishing the relationship between the surface areas of intermediately sized molecules (50-300A{dollar}\sp2{dollar}) and their lateral diffusion coefficients in lipid bilayer membranes. Synthetic methods were developed to allow for the preparation of two series of macrocyclic polyamide amphiphiles, with and without fluorescent nitrobenzoxadiazole (NBD) labels, using macrocyclic polyamine aza-crown ethers as starting materials.;The geometry of the macrocyclic polyamides were determined using variable temperature NMR, which has indicated that both the C(O)-N bond and NBD-N bond in the smallest, labelled macrocyclic polyamide exhibit partial double bond character. As a consequence of this restricted bond rotation, both the amide groups and the NBD-N groups of macrocyclic polyamides can be considered as rigid planar moieties.;The surface areas occupied by the macrocyclic polyamides at the air-water interface were determined using a Langmuir film balance, and were found to be in agreement with surface area measurements of computer molecular models based on the assumption that the amide and NBD-N groups are rigid and planar. Both monolayer and computer experiments have shown that there is a systematic trend of increasing surface area throughout the two series of macrocyclic polyamides.;Finally, the lateral diffusion coefficients of labelled macrocyclic polyamides were determined using Fluorescence Photobleaching Recovery (FPR), and the lateral diffusion coefficients of the amphiphiles were correlated with their surface areas. This correlation has shown that there is a significant dependence of lateral diffusion on the size of amphiphiles with surface areas between 30-250A{dollar}\sp2{dollar}, and is the first demonstrated dependence of lateral diffusion on surface area for amphiphiles in this size regime.;Analysis of the dependence of lateral diffusion on surface area has indicated that the lateral diffusion of macrocyclic polyamides which have surface areas smaller than or equal to that of the phospholipids which comprise the bilayer are best modelled using Free Area theory, which states that amphiphiles which are smaller than phospholipids will diffuse at the rate of lipid self diffusion. In contrast, the lateral diffusion of amphiphiles which have surface areas which are larger than that of phospholipids are best modelled using Sackman-Evans Continuum theory applied to a diffusant which does not span the bilayer membrane. This novel finding suggests that Continuum theory can be applied to the diffusion of molecules which are only slightly larger than the molecules which form the continuum.
Recommended Citation
Paprica, Patricia Alison, "Evidence For A Continuum Model Of Diffusion In Lipid Bilayer Membranes: Synthesis And Studies Of Macrocyclic Polyamides In Monolayer And Lipid Bilayer Systems" (1994). Digitized Theses. 2362.
https://ir.lib.uwo.ca/digitizedtheses/2362