Date on Master's Thesis/Doctoral Dissertation

5-2016

Document Type

Doctoral Dissertation

Degree Name

Ph. D.

Department

Chemistry

Degree Program

Chemistry, PhD

Committee Chair

Nantz, Michael

Committee Co-Chair (if applicable)

Hammond, Gerald

Committee Member

Hammond, Gerald

Committee Member

Zhang, Xiang

Committee Member

Fu, Xiao-An

Author's Keywords

Metabolomics; Boron; FT-ICR-MS; Xylose; Transesterification; Hypotaurine

Abstract

Chemoselectivity is the preferential reaction of a reagent with a select functional group among other plausible reactions. This dissertation describes chemoselective reagents and methods explored to develop more accurate, efficient and high-throughput means to quantify metabolites containing either thiol, carboxylic acid or 1,2-diol moieties directly from biological mixtures. Chapter 1 discusses how dysregulation of thiol- or carboxylic acid-containing metabolites is either the cause or effect of cellular dysfunction. Quantifying such metabolites is important in discovery of pathways to understand etiology of diseases. Chapter 1 also discusses the need for sustainable syntheses using renewable resources and describes the traditional methods for isolation of sugars from biomass hydrolyzates. Chapter 2 describes the design, synthesis and use of the iodoacetamide-based reagents QDE and *QDE for selective capture and analysis of thiol metabolites. The identification of major thiol metabolites and quantification of glutathione in A549 cells were realized using this technology. Total concentrations of [GSH] and [GSSG] in cultured cells of a human lung adenocarcinoma cell line (A549) were determined at 34.4 ± 11.5 nmole/mg protein and 10.1 ± 4.0 nmole/mg protein, respectively. Chapter 3 presents attempts to prepare a bis(boron halide) reagent for capture of carboxylic acids via formation of a six-member cationic N,B,C,O heteroaromatic ring. Although the reagent proved to be impractical for use in metabolite analysis due to air/moisture sensitivity, we isolated a novel oxygen bridged bicyclic boron fluoride complex with potential applications in electroluminescent devices. Chapter 4 outlines a method for chemoselective isolation of C5 sugars from dried distillers’ grains hydrolyzate that exploits the phenylboronic acid chelation of cis-1,2-diols followed by a transesterification protocol on the resultant diol-boronate adducts. A large scale demonstration of the process delivered crystalline xylose from hydrolyzate in 48% yield with recovery of >80% of all reagents/solvents used. Chapter 5 describes the experimental protocols for the syntheses and use of the aforementioned chemoselective reagents. To summarize, the present research illustrates how application of chemoselective reactions can lead to superior methods for isolation and identification of targeted metabolites in complex mixtures. The high reaction rate, selectivity and adduct stability afforded by chemoselective derivatization can be employed in a myriad of other research disciplines.

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