IDENTIFICATION AND QUANTIFICATION OF QUINONES IN ENVIRONMENTAL SAMPLES
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Authors
Timilsina, Anil
Issue Date
2024
Type
Dissertation
Language
en_US
Keywords
Cysteine , Identification , Peptide , Quantification , Quinone , Tagging
Alternative Title
Abstract
Quinones represent an important class of compounds, widely recognized redox-reactive organic substances in natural organic matter (NOM). Despite their critical importance in biogeochemical cycles, degradation of pollutants, and greenhouse gas (GHG) emission, their precise structure and abundance in environmental samples have puzzled environmental geochemists for decades due to the complexity of environmental samples. To tackle the grand challenge of identifying and quantifying quinones, this study aimed to: 1. Develop a chemical tagging method for quinone identification; 2. Identify quinones in complex environmental samples by integrating chemical tagging with metabolomic analysis; 3. Screen and isolate quinones through coupling chromatography separation with redox reactivity screening; and 4. Establish a method for quantifying the total quinone concentrations in environmental samples. A selective chemical tagging method for quinones was developed by using Michael addition reactions with cysteine (Cys) and cysteine-containing peptides (CCPs), and validated by UV and mass spectra (MS) analysis using model quinones. Quinones in biochars were identified by coupling chemical tagging with Cys and/or CCPs to metabolomic analysis based on high-performance liquid chromatography-high resolution tandem mass spectrometry (HPLC-HRMS/MS) analysis. Total quinones in water extraction of environmental samples were measured by integrating specific tagging with non-aromatic CCPs with size exclusionary chromatography (SEC) analysis. Analysis of Swiss biochar shows a diverse pool of quinones (390 candidates) tagged with Cys or CCPs. Benzoquinone and methyl-p-benzoquinone were confirmed, and additional high-confidence candidates include C7H6O5, C11H10O3, C12H12O3, and C12H12O4. Redox reactivity screening-based chromatography separation isolated new quinones with two quinone functional groups, i.e., doxorubicin derivatives. From quinone quantification analysis, pyrogenic carbon from wildfires showed three times higher quinone concentration (1 – 14 μM) and reactivity than background soils. In summary, this study developed innovative methodologies for identifying quinones and quantifying their concentrations in complex environmental media. These methods identified the chemical structures of quinones in complex biochar extracts, and novel quinones were isolated. Future investigations using the methods developed herein may replace the enigmatic black box of redox-reactive NOM with compounds characterized by their structures and concentrations.