Spectroscopic studies of transmembrane helical peptides and LC-MS/MS method development and validation for PFAS quantitation
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Water hydrogen bonding (H-bonding) to [alpha]-helical transmembrane (TM) peptides is fundamental to understanding the behavior and function of [alpha]-helical peptides, disease pathways, and the development of new drugs. Deep-UV resonance Raman (dUVRR) spectroscopy is a non-destructive technique amenable to both lipophilic and aqueous environments, which is an excellent and convenient approach for studying water Hbonding (or water accessibility) to [alpha]-helical TM peptides in a membrane mimicking environment. The dUVRR results indicate that water molecules can access the lipid membrane and form H-bonds with carbonyl groups along [alpha]-helical backbones. Raman bands at ~1629 and ~1672 cm-1 can be used to monitor the hydration and dehydration conditions along TM [alpha]-helices. Two bands at ~1300 and ~1340 cm-1 are also potential characteristic features of dehydration and hydration along the [alpha]-helices in a membrane environment. Per- and polyfluorinated alkyl substances (PFAS) are a class of widespread contaminants in the ecosystem, which may cause adverse health effects under high levels of exposure. HPLC-MS/MS is commonly used for accurate and reproducible PFAS quantitation in water systems. Triple quadrupole and q-ToF mass analyzers are commonly used for PFAS quantification. To the best of our knowledge, an ion trap, a cost-effective mass analyzer, has not been utilized for PFAS quantitation. Therefore, we developed and validated an SPE-HPLC-ESI-quadruple ion trap method to perform quantification of 14 different PFAS. Method LOQs for all analytes are below EPA advisory limit of 70 ppt. The calibration curves range from 0.5-140 ng/ml. The method was then applied to evaluate the effectiveness of a supercritical water oxidation (SCWO) reactor for degrading PFAS and the efficiency of resin beads for adsorbing PFAS compounds. The results indicate the SCWO rector is effective in breaking down 14 target PFAS and reducing their total level below EPA advisory limit of 70 ppt and resin beads are effective in removing more than 96 percent PFAS in water and reduce PFAS amounts close to 100 ppt.
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Ph. D.