Analysis of Spin Label Line Shapes with Novel Inhomogeneous Broadening from Different Component Widths Application to Spatially Disconnected Domains in Membranes

4. Conclusions

Chapter 1 presents a theoretical formalism for the phenomenon of inhomogeneous broadening of spin label ESR spectra from different component widths. An internally normalized measure of the line shape, namely, the intensity ratio, is shown to be a diagnostic parameter for distinguishing between the conventional origins of line broadening, including unresolved hyperfine structure and spin label dynamics, and the novel mechanism of a statistical distribution of component lines differing in line width. The method is applied to characterize lipid domain connectivity in two-component, two-phase lipid binary mixtures and the effects of peptides on membrane in-plane domain structure. Experimental results show that intensity ratio measurements indicate the presence of disconnected domain structure in membranes, and such measurements are able to distinguish domain growth in size from growth in number.