Browsing by Author "Minto, Robert"
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Item Chemometrics applied to the discrimination of synthetic fibers by microspectrophotometry(2014-01-03) Reichard, Eric Jonathan; Goodpaster, John V. (John Vincent); Minto, Robert; Sardar, Rajesh; Siegel, Jay A.; Picard, ChristineMicrospectrophotometry is a quick, accurate, and reproducible method to compare colored fibers for forensic purposes. The use of chemometric techniques applied to spectroscopic data can provide valuable discriminatory information especially when looking at a complex dataset. Differentiating a group of samples by employing chemometric analysis increases the evidential value of fiber comparisons by decreasing the probability of false association. The aims of this research were to (1) evaluate the chemometric procedure on a data set consisting of blue acrylic fibers and (2) accurately discriminate between yellow polyester fibers with the same dye composition but different dye loadings along with introducing a multivariate calibration approach to determine the dye concentration of fibers. In the first study, background subtracted and normalized visible spectra from eleven blue acrylic exemplars dyed with varying compositions of dyes were discriminated from one another using agglomerative hierarchical clustering (AHC), principal component analysis (PCA), and discriminant analysis (DA). AHC and PCA results agreed showing similar spectra clustering close to one another. DA analysis indicated a total classification accuracy of approximately 93% with only two of the eleven exemplars confused with one another. This was expected because two exemplars consisted of the same dye compositions. An external validation of the data set was performed and showed consistent results, which validated the model produced from the training set. In the second study, background subtracted and normalized visible spectra from ten yellow polyester exemplars dyed with different concentrations of the same dye ranging from 0.1-3.5% (w/w), were analyzed by the same techniques. Three classes of fibers with a classification accuracy of approximately 96% were found representing low, medium, and high dye loadings. Exemplars with similar dye loadings were able to be readily discriminated in some cases based on a classification accuracy of 90% or higher and a receiver operating characteristic area under the curve score of 0.9 or greater. Calibration curves based upon a proximity matrix of dye loadings between 0.1-0.75% (w/w) were developed that provided better accuracy and precision to that of a traditional approach.Item Design, Synthesis and Study of DNA-Targeted Benzimidazole-Amino Acid Conjugates(2013-07-12) Garner, Matthew L.; Long, Eric C. (Eric Charles); Minto, Robert; O'Donnell, Martin J.The DNA minor groove continues to be an important biological target in the development of anticancer, antiviral, and antimicrobial compounds. Among agents that target the minor groove, studies of well-established benzimidazole-based DNA binders such as Hoechst 33258 have made it clear that the benzimidazole-amidine portion of these molecules promotes an efficient, site-selective DNA association. Building on the beneficial attributes of existing benzimidazole-based DNA binding agents, a series of benzimidazole-amino acid conjugates was synthesized to investigate their DNA recognition and binding properties. In this series of compounds, the benzimidazole-amidine moiety was utilized as a core DNA “anchoring” element accompanied by different amino acids to provide structural diversity that may influence DNA binding affinity and site-selectivity. Single amino acid conjugates of benzimidazole-amidines were synthesized, as well as a series of conjugates containing 20 dipeptides with the general structure Xaa-Gly. These conjugates were synthesized through a solid-phase synthetic route building from a resin-bound amino acid (or dipeptide). The synthetic steps involved: (1) the coupling of 4-formylbenzoic acid to the resin-bound amino acid (via diisopropylcarbodiimide and hydroxybenzotriazole); followed by (2) introduction of a 3,4-diaminobenzamidoxime in the presence of 1,4-benzoquinone to construct the benzimidazole ring; and, finally, (3) reduction of the resin-bound amidoxime functionality to an amidine via treatment with 1M SnCl2•2H2O in DMF before cleavage of final product from the resin. The synthetic route developed and employed was simple and straightforward except for the final reduction that proved to be very arduous. All target compounds were obtained in good yield (based upon weight), averaging 73% mono-amino acid and 78% di-amino acid final compound upon cleavage from resin. Ultimately, the DNA binding activities of the amino acid-benzimidazole-amidine conjugates were analyzed using a fluorescent intercalator displacement (FID) assay and calf thymus DNA as a substrate. The relative DNA binding affinities of both the mono- and di-amino acid-benzimidazole-amidine conjugates were generally weaker than that of netropsin and distamycin with the dipeptide conjugates showing stronger binding affinities than the mono-amino acid conjugates. The dipeptide conjugates containing amino acids with positively charged side chains, Lys-Gly-BI-(+) and Arg-Gly-BI-(+), showed the strongest DNA binding affinities amongst all our synthesized conjugates.Item Greener Photoredox-Catalyzed Phosphonations of Aryl Halides(2024-05) Kelley, Alexandra S.; Laulhe, Sébastien; Minto, Robert; Deng, YongmingAromatic phosphonates and phosphine oxides are highly desirable synthetic targets used in pharmaceuticals, natural products, agrichemicals, catalysis, and materials science. While a variety of aromatic precursors have been used to access these motifs, aryl halides remain one of the most desirable coupling partners owing to their low cost, commercial availability, and regioselective reactivity. Traditional phosphonation often requires the use of harsh reductants in the presence of liquid ammonia, which are caustic and pose incredible environmental concerns. Milder, transition metal-catalyzed approaches have been developed, but can be limited by air sensitivity, cost, low reaction selectivity, and low functional group compatibility. Photoredox catalysis has been significantly advanced in the past decade in the pursuit of greener, more sustainable avenues to facilitate desirable reaction transformations under mild conditions. These methods most commonly use a dual catalytic strategy in which a metal is paired with an organocatalyst. While these approaches enable facile phosphonation of a variety of aromatic precursors, the metals and organocatalysts used are often expensive and toxic. Indeed, there remains unexplored chemical space for transition metal-free photoredox-catalyzed aryl C-P bond formations. Herein, we present a series of transition metal-free, photoredox-catalyzed approaches to the phosphonation of aryl halides. The approaches and mechanistic works will be discussed in the following order: First, the discovery that 10H-phenothiazine (PTZ) enables the transition metal-free phosphonation of aryl halides using trialkyl phosphites will be presented. PTZ serves as a photocatalyst capable of reducing the aryl halide to access aryl radicals, which readily couple with phosphite esters. This transformation exhibits broad functional group tolerance in good to excellent yields. Then, photoredox catalysis by PTZ enables the formation of unsymmetrical aromatic phosphine oxides using triphenylphosphine (PPh3) and aryl halides. This is the first work in which PPh3 has been used as the starting material, and the reaction proceeds via the alkaline hydrolysis of quaternary phosphonium salts. The final work exhibits novel photocatalytic activity of N-heterocyclic carbenes (NHC) to activate aryl halides, form aryl radicals, and enable phosphonation. This method displays broad functional group tolerance under mild conditions and highlights its untapped synthetic utility as a photocatalyst.Item Identification of Tobacco-Related Compounds in Tobacco Products and Human Hair(2014-09-04) Rainey, Christina; Goodpaster, John V. (John Vincent); Minto, Robert; Shepson, Paul; Kissinger, Peter T., 1944-; Long, Eric C. (Eric Charles)Analyses of tobacco products and their usage are well-researched and have implications in analytical chemistry, forensic science, toxicology, and medicine. As such, analytical methods must be developed to extract compounds of interest from tobacco products and biological specimens in order to determine tobacco exposure. In 2009, R.J. Reynolds Tobacco Co. released a line of dissolvable tobacco products that are marketed as a smoking alternative. The dissolvables were extracted and prepared by ultrasonic extractions, derivatization, and headspace solid phase microextraction (SPME) with analysis by gas chromatography-mass spectrometry (GC-MS). The results show that the compounds present are nicotine, flavoring compounds, humectants and binders. Humectant concentrations vary among different tobacco types depending on the intended use. Humectants were quantified in various tobacco types by GC and “splitting” the column flow between a flame ionization detector (FID) and an MS using a microfluidic splitter in order to gain advantage from the MS’s selectivity. The results demonstrated excellent correlation between FID and MS and show that MS provides a higher level of selectivity and ensures peak purity. Chemometrics was also used to distinguish products by tobacco type. Hair is a common type of evidence in forensic investigations, and it is often subjected to mitochondrial DNA (mtDNA) analysis. Preliminary data was gathered on potential “lifestyle” markers for smoking status as well as any indications of subject age, gender, or race by investigating the organic “waste” produced during a mtDNA extraction procedure. The normally discarded organic fractions were analyzed by GC-MS and various lipids and fatty acids were detected. At this point, a total vaporization-SPME (TV-SPME) method was theorized, developed, and optimized for the specific determination of nicotine and its metabolite, cotinine. The theory of TV-SPME is to completely vaporize an organic extract which will eliminate the partitioning between the sample and the headspace, thereby simplifying the thermodynamic equilibrium. Parameters such as sample volume, incubation temperature, and extraction time were optimized to achieve the maximum analyte signal. Response surface methodology (RSM) is a statistical model that is very useful in predicting and determining optimum values for variables to ensure the ideal response. RSM was used to optimize the technique of TV-SPME for the analysis of nicotine and cotinine. Lastly, quantitation of nicotine and cotinine in human hair typically requires large sample sizes and extensive extraction procedures. Hence, a method using small sample sizes and a simple alkaline digestion followed by TV-SPME-GC-MS has been developed. Hair samples were collected from anonymous volunteers and nicotine and cotinine were identified and quantitated in the hair of tobacco users.Item Identifying Metabolic Pathways Producing Alkamides in Echinacea purpurea(Office of the Vice Chancellor for Research, 2016-04-08) Williams, Jermell; Teitgen, Alicen; Minto, RobertEchinacea purpurea is a widely used herbal supplement that is frequently taken to relieve cold symptoms. Alkamides are a secondary metabolite found throughout the Echinacea genus that contain fatty acid chains incorporated into amides and are believed to be the bioactive agent in Echinacea. Our goal is to identify and understand the specific metabolic processes by which E. purpurea produces alkamides. In our experiment, Echinacea seedlings were grown to where the first true leaf emerged and unfurled which is when alkamide production is known to be most active. Alkamides were then extracted and taken to the GC/MS and LC/MS for analysis. Extracted alkamides were analyzed by triplequadrupole chromatography to investigate 13C labeling by glucose. Solid phase extractions were also performed to better observe fragmentation patterns. Fatty acids were also extracted to determine if fatty acids and alkamides were affected the same way by light or the lack of light, which would indicate that they are being synthesized in the same place. It was determined that neither compound experienced a synthesis decrease in the dark significant enough to support a model where acyl chains are newly created in the chloroplasts. Therefore alkamides are more likely to be made in the mitochondria. We are currently in the process of examining the spectra in order to determine the structures of the alkamides as well as any metabolic relationships.Item Immunomodulatory Effects of Oxylipin 10-HOME Produced by Biofilm Results in Host-Biofilm Interaction in Breast Implant Illness(Wolters Kluwer, 2022) Khan Mohammed, Imran; Minto, Robert; Kelley-Patteson, Christine; Timsina, Lava; Singh, Kanhaiya; Van Natta, Bruce W.; Mohan, Ganesh; Chauhan, Ruvi; Lester, Mary; Hassanein, Al; Gordillo, Gayle M.; Sen, Chandan; Kadin, Marshall; Sinha, Mithun; Surgery, School of MedicinePURPOSE: The spread of biofilms on medical implants represents one of the principal triggers of persistent and chronic infections in clinical settings. Nearly 300,000 women annually have breast implant surgery in the United States, for reasons including post-mastectomy breast reconstruction, revision of prior augmentation/ reconstruction, cosmetic augmentation, and gender affirmation. There has been increased identification of patients experiencing a constellation of symptoms related to their implants termed as breast implant illness (BII). In this work, we report that bacterial biofilm associated with breast implant, metabolize fatty acid oleic acid present in the breast tissue milieu to oxylipins, one such oxylipin identified from this study is (E)-10-hydroxy-8-octadecenoic acid (10-HOME). We hypothesize that immunomodulatory effects of oxylipin 10-HOME produced by biofilm present on the implant could be a possible etiology for BII pathogenesis. METHOD: Implants, peri-prosthetic tissues and blood was collected from BII subjects (n=46) and two control groups, group I, (non-BII, n=34) patients with breast implants, no BII symptoms. Group II (normal tissue, n = 20), patients without an implant, whose breast tissue was removed due to surgical procedures. A questionnaire developed based on epidemiological studies on BII screened for the commonly reported symptoms associated with BII. Predictive variables included age, diabetes status, co-morbidities, type (smooth/textured) and duration of implant. Scanning electron microscopy (SEM), 16S rRNA (genomic) next generation sequencing (NGS) were used for bacterial biofilm identification. 10-HOME was quantitated through targeted and untargeted lipidomic analyses using LC-MS-MS. RNA-Seq analysis was performed on peri-prosthetic breast tissues. Flow cytometry and mass cytometry (CyToF) were conducted to investigate the role of immune cells. RESULTS: Bacterial biofilm was detected through SEM and 16SrRNA NGS. Bivariate analysis using cross-tabulation was performed between presence of biofilm and the study groups. Using the two-sample test of proportions with z-tests, Staphylococcus epidermidis colonization was observed to be higher in the BII group (73.33%) compared to non-BII group (16.67%, p=0.018) and the normal group (10%, p=0.036). The BII group was 2.4 times more likely to have S. epidermidis colonization compared to the non-BII group (Odds Ratio=2.4). Similarly, when comparing with normal group, the BII group was 3.4 times more likely to have S. epidermidis. Elevated levels of 10-HOME in BII compared to non-BII samples, (p<0.0001) were observed through mass spectrometry. Positive correlation was observed between bacterial abundance and concentration of 10-HOME in BII subjects (R2=0.88). RNA-Seq analysis on peri-prosthetic tissue and flow/ mass cytometry analyses from peripheral blood derived lymphocytes showed increased abundance of CD4+ Th1 cells. Th1 cells have been reported to be activated in auto-immune diseases. No significant difference was observed in the abundance of other Th subtypes (Th2, Th9 and Th22). Oxylipin 10-HOME polarized CD4+ naïve T cells to Th1 subtype in vitro. CONCLUSION: This study investigated the biofilm hypothesis of BII through a biofilm derived immunogenic metabolite. Through a systematic cause-effect based studies, the work shows activation of Th1 cells in presence of 10-HOME. The study provides the first evidence of a possible etiology of BII mediated via bacterial biofilm derived 10-HOME.Item Investigating the Biosynthetic Pathways to Polyacetylenic Natural Products in Fistulina hepatica and Echinacea purpurea(2013-08-20) Ransdell, Anthony S.; Minto, Robert; Long, Eric C. (Eric Charles); Li, LeiPolyacetylenic natural products, compounds containing multiple carbon-carbon triple bonds, have been found in a large collection of organisms. Radiochemical tracer studies have indicated that these bioactive metabolites are synthesized from fatty acid precursors through a series of uncharacterized desaturation and acetylenation steps. To date, there are three main pathways believed to be involved in acetylenic natural product biosynthesis. However, it is apparent that the crepenynic acid pathway is the origin of a vast majority of the known plant and fungal acetylenic products. This investigation provides concrete evidence that the polyacetylenic natural products found in the fungus Fistulina hepatica and the medicinal plant species Echinacea purpurea are biosynthesized from crepenynic acid. Through heterologous expression in Yarrowia lipolytica, two acetylenases capable of producing crepenynic acid were identified from E. purpurea. Furthermore, heterologous expression of two diverged desaturases isolated from F. hepatica, uncovered a ∆12-acetylenase and the first multifunctional enzyme capable of ∆14-/∆16- desaturation and ∆14-acetylenation.Item Investigations of lipid metabolism in Yarrowia lipolytica(2014-07-31) Blocher-Smith, Ethan Charles; Minto, Robert; Long, Eric C. (Eric Charles); Jones, LisaAn investigation of the lipid metabolism pathway in the yeast Yarrowia lipolytica was conducted. Yarrowia is an oleaginous ascomycete that is capable of growing on many different substrates, which derives its name from its high efficiency of growth on lipids. Once the exogenous lipids are converted into free fatty acids and internalized by the yeast, the primary mode of degradation is through β-oxidation mediated by the peroxisomal oxidases, or POX genes. These enzymes catalyze the formation of a trans double bond, producing the trans-2-enoyl product. Our study looked at the comparison of the Y. lipolytica prototrophic strain against a knockout of the Pox2 gene on the uptake, incorporation, and degradation of relevant fatty acids. To construct this gene knockout, a novel gene deletion method using a combination of Cre recombinase and the AHAS* gene was synthesized, developed, and tested successfully. This knockout system allows for serial deletion of genes with the use of only one resistance marker, with excision of the marker after selection.Item LIPIDOMIC PROFILING OF DICTYOSTELIUM DISCOIDEUM(2012-08-27) Birch, Garrison L.; Minto, Robert; Blacklock, Brenda J.; McLeish, Michael J.The lipid profile of Dictyostelium discoideum, a cellular slime mold found evolutionarily between plants and animals, has never been clearly defined. To address this, the fatty acid content of vegetative cells was analyzed by gas chromatography-mass spectrometry of fatty acid methyl esters and their identities verified with synthesized authentic standards. The synthetic scheme developed to produce the unusual fatty acids found in D. discoideum was engineered to afford the labeling of compounds (2H) for use in feeding studies to elucidate the fatty acid elongation and desaturation pathways present in D. discoideum. After establishing the fatty acid profile and acyl metabolic pathway, an initial understanding the complex lipids present in D. discoideum, chiefly sphingolipids, was sought. Triple quadrupole and quadrupole time-of flight mass spectrometers equipped with electrospray ionization sources were used to identify these complex lipids.Item The modification of brucine derivatives as chiral ligands and its application in the asymmetric synthesis(2014) Li, Jian-yuan; Minto, Robert; Ge, Haibo; Abu-Omar, Mahdi; Wilker, Jonathan; Long, Eric C. (Eric Charles)The modification of brucine derivatives as chiral ligands and the use of a multifaceted chiral ligand, brucine diol, under different reaction conditions to produce various optical isomers is described. In Chapter 1, the generation of a number of brucine derivatives is described. Taking the advantage of brucine-diol’s excellent molecular recognition capability for multiple organic functional groups, we focused on the synthetic modifications of brucine-diol and the synthesis of brucine N-oxide. We also produced various brucine derivatives with different functional moieties in good yields and selectivities. In Chapter 2, we described the investigation of brucine N-oxide catalyzed Morita-Baylis-Hillman (MBH) reaction of alkyl/aryl ketones. Brucine N-oxide was used as a nucleophilic organic catalyst in the MBH reaction of alkyl vinyl ketone. In addition, asymmetric MBH reactions of alkyl vinyl ketones with aldehydes were investigated using a dual catalysis of brucine N-oxide and proline. In this dual catalyst system, proline was found to form iminium intermediates with electron-deficient aryl aldehydes, while the N-oxide activated vinyl ketones provided enolates through the conjugate addition. Our dual catalysis approach also allowed the development of MBH reaction of aryl vinyl ketones. In Chapter 3, brucine diol-copper complex catalyzed asymmetric conjugate addition of glycine (ket)imines to nitroalkenes is discussed. Stereodivergent catalytic asymmetric conjugate reactions for glycine (ket)imines with nitroalkenes were achieved using various chiral catalysts derived from a single chiral source, brucine diol. Both syn- and anti-conjugate addition products were obtained with high diastereoselectivity and enantioselectivity. In Chapter 4, enantiodivergent production of endo-pyrrolidines from glycine (ket)imines using brucine diol-copper complex is described. The [3+2] cycloaddition reaction of glycine imines and activated alkenes was performed to produce endo-pyrrolidines. The reversal of enantioselectivity was observed for endo-pyrrolidines between concerted and stepwise reaction pathways. The three new brucine derivatives produced in this study would potentially work as organocatalysts and chiral ligands with metal ion in asymmetric synthesis. The brucine diol-metal complex catalyzed reactions laid a good foundation for catalytic asymmetric reactions, where a single chiral source was used to control the absolute and the relative stereochemical outcomes of reactions. Understanding the molecular-level interactions between catalyst and substrates will provide insightful mechanistic details for the stereodivergent approaches in asymmetric catalysis.