Scholarship & Research
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Item A thermodynamic and optical assessment of soluble carbon particulate effects on lipid film structure and organization(Montana State University - Bozeman, College of Letters & Science, 2022) Shaikh, Nida; Chairperson, Graduate Committee: Robert Walker; This is a manuscript style paper that includes co-authored chapters.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.Item Solute partitioning into model biological membranes studied with time-resolved emission spectroscopy and calorimetry(Montana State University - Bozeman, College of Letters & Science, 2022) Duncan, Katelyn Marie; Chairperson, Graduate Committee: Robert Walker; This is a manuscript style paper that includes co-authored chapters.Bioaccumulation and bioconcentration are terms used to quantify the concentration of the solute in an organism with respect to the source of exposure. Empirical values are commonly used to predict a solutes tendency for bioconcentration. While they are useful zeroth order indicators, empirical values lack the chemical specificity required to fully understand the exact solute-solute and solute-lipid chemical interactions that occur when a solute is introduced to a biological membrane. The work described here uses fluorescence spectroscopy and thermoanalytical techniques to quantify solute partitioning into model biological membranes. The model membranes used in this study are lipid bilayer vesicles that are analyzed as a function of temperature from the rigid gel-phase through the transition temperature and into the fluid liquid-crystalline phase. Studies described in this work seek to create a quantitative, mechanistic description of solute behavior in heterogeneous chemical environments. Each body of work either altered the solute used for partitioning or altered the membrane to add chemical complexity. The first body of work describes a proof-of-concept study analyzing the change in partitioning behavior from small structural changes in the solute. This study found that small changes to the solute affects membrane permeability in a way that is not accounted for in empirical models. The subsequent study sought to understand how the addition of amino acids to the membrane changes partitioning tendencies. Further analysis was done to study the partitioning behavior of amino acid L-Phenylalanine. Studies showed L-Phenylalanine integrates into the membrane and experiences a conformationally restricted environment. Additional studies were done on a pharmaceutical candidate and found membrane permeability does not correlate with drug activity. The drug was predicted to interact with the target-protein directly. Furthermore, analysis on the herbicide Dicamba has shown some indication of membrane interaction; however, more studies are required to fully understand the partitioning behavior.Item The molecular spring model for docosahexaenoic acid (22:6w3) function in biological membranes(Montana State University - Bozeman, College of Letters & Science, 1992) Holte, Laura LeeItem Cloning, sequencing and expression of cDNA encoding two lysosomal membrane proteins, and generation of monoclonal antibodies against them(Montana State University - Bozeman, College of Agriculture, 1993) Selvanayagam, Uthayakumar