Theses and Dissertations at Montana State University (MSU)
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Item NMR characterization of unfrozen brine vein distribution and structure in frozen systems(Montana State University - Bozeman, College of Engineering, 2022) Lei, Peng; Chairperson, Graduate Committee: Sarah L. Codd; This is a manuscript style paper that includes co-authored chapters.The liquid vein network (LVN) that forms in the interface of ice crystals or particles exists in frozen porous media due to the freezing point depression. The distribution and structure of the LVNs are dynamic due to the ice recrystallization phenomenon. In ice alone, the LVNs formed by the ice crystal interfaces can be characterized as a porous medium in terms of surface to volume ratio (SV /) and the tortuosity (alpha).The presence of solid particles or ice-binding proteins (IBPs) make the frozen system much more complex. The research presented uses nuclear magnetic resonance (NMR) experimental techniques, including magnetic resonance imaging (MRI), relaxation and self-diffusion measurements, to study the development of the LVNs in complex frozen systems containing solid particles or IBPs. Poly-methyl methacrylate (PMMA) particles of diameters 0.4, 9.9, and 102.2 microns are used with brine solution concentrations of 15, 30, and 60 mM Magnesium chloride (MgCl 2) to simulate complex frozen systems. The dynamic rearrangement with time of LVNs can be studied as a function of temperature, MgCl 2 concentration, and PMMA particle size. The results indicate that small solid particles dominate the structure dynamics while in larger solid particle packed beds the solute effect dominates. This behavior is quantified by determination of SV / and alpha from NMR relaxation and diffusion data. Additionally, IBP produced from the V3519-10 organism isolated from the Vostok ice core in Antarctica is added to ice samples frozen from 30, 60 and 120 mM MgCl 2 solution to investigate its influence on LVNs over months of aging. The interplay of the solute and biological effects is complicated but it appears the biological effect is more pronounced at lower salt concentrations. The data provide a basis for eventual combination of salt, IBP and solid particulate studies. The result of MRI, relaxation and self-diffusion measurements indicate the inhibition of ice recrystallization as a function of particle size, MgCl 2 concentration and the presence of IBP. The non-invasive data presented along with calibration of the relaxation experiments with self-diffusion experiments, demonstrate the continued extension of NMR techniques developed from porous media to frozen porous media and ice LVN structure.Item Spectral signs of life in ice(Montana State University - Bozeman, College of Engineering, 2020) Messmer, Mitch Wade; Chairperson, Graduate Committee: Christine ForemanIn astrobiology, new technologies are being implemented in the search for extraterrestrial life. Interpreting results from new analytical techniques requires additional information about microbial properties. A catalogue of identifying characteristics, called biosignatures was created for bacterial and algal isolates from Greenland and Antarctica by measuring substrate utilization, UV/Vis absorbance, Fourier-Transform Infrared Spectroscopy, and Raman spectroscopy. Organisms were chosen from environments analogous to Martian glacier systems. Spectral properties of these polar isolates could serve as a reference for interpreting results from NASA's Perseverance rover. Substrate utilization was evaluated using EcoPlates on an Omnilog plate reader (Biolog, California, U.S.A.). UV/Vis absorbance spectra indicated that nine of the twenty-five bacterial isolates contained carotenoid pigments, and one contained violacein. UV/Vis analysis was effective at identifying the presence of pigments, but was insufficient for distinguishing between the types of carotenoids. FTIR analysis identified general biological features such as lipids, proteins, and carbohydrates, but did not detect pigments. Raman analysis of isolates with a 532 nm laser identified both the presence of carotenoid and violacein pigments, and the general cell features observed with FTIR. The degree of saturation of membrane lipids was evaluated for the bacterial isolates by comparing the ratio of unsaturated and saturated fatty acid peaks in the Raman spectra. Results were similar for the polar isolates and mesophiles, excluding the Bacillus subtilis spores. A principal component analysis was conducted to determine the regions of the spectra that contributed the variability between samples. The spectra of the bacterial isolates were more closely related based on colony color than phylogeny. Analysis of the algal isolates indicated that chlorophyll A and B fluoresced under exposure to the 532 nm laser, creating definitive biosignatures for algae. These analytical techniques proved effective at identifying cell properties that could serve as biosignatures for identifying microbial life. Identification of the spectral features of these cellular components may aid in narrowing the search for extraterrestrial life by highlighting specific target regions within the Raman spectra. Characteristics of these polar microbes may provide the foundation for interpreting spectral data collected from future explorations of extraterrestrial environments in the search for astrobiology.