A thermodynamic and optical assessment of soluble carbon particulate effects on lipid film structure and organization
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Research described in this thesis investigates the effects of carbonaceous particulate matter on model biological membrane structure, organization, and function. Although the harmful impacts of black carbon are well-documented, researchers lack the chemically-specific, mechanistic information necessary for understanding how black carbon aerosols affect lung surfactant spreading and compression. Surface specific optical spectroscopy methods together with complementary thermodynamic methods are used to measure how carbon nanoparticles, a model for black carbon aerosols that are a component of particulate matter (PM 2.5 ), change average lipid conformation, orientation, thickness, and compressibility in monolayers, and how these changes affect overall membrane organization. Addressing these questions requires a suite of independent, but complementary, experimental techniques including Langmuir trough and surface tension measurements, surface specific nonlinear optical spectroscopy measurements including both second harmonic generation and sum frequency generation, and spectroscopic ellipsometry measurements. Work presented in this thesis discusses cooperative adsorption as a possible mechanism to explain the interactions between DPPC monolayers and PHFs at biologically-relevant aqueous - air interfaces. The experiments forthcoming represent a detailed investigation of 1) the mechanism(s) responsible for accumulation of carbon particulates at the aqueous/monolayer/air interface present in the lungs, and 2) how specific thermodynamic behavior and optical properties (i.e. structure, composition, membrane integrity, orientation, thickness, and organization) at the aqueous/monolayer/air interface change with the inclusion of non-biological, nano-sized materials. Motivating this work is a need to develop a predictive understanding of black carbon - lung surfactant interactions and how non-biological, nano-sized materials impact membrane structure and function.