Browsing by Author "Minto, Robert E."
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Item Advances in Gas Chromatography, Thermolysis, Mass Spectrometry, and Vacuum Ultraviolet Spectrometry(2021-05) Rael, Ashur; Goodpaster, John V.; Manicke, Nicholas E.; Naumann, Christoph A.; Minto, Robert E.In the area of forensic chemistry, improved or new analysis methods are continually being investigated. One common and powerful technique used in forensic chemistry is wall-coated open-tubular column (WCOT) gas chromatography with electron ionization single quadrupole mass spectrometry (GC-MS). Improvements to and effectiveness of alternatives to this instrumental platform were explored in an array of parallel inquiries. The areas studied included the column for the chromatographic separation, the universal detection method employed, and the fragmentation method used to enhance molecular identification. Superfine-micropacked capillary (SFµPC) columns may provide an alternative to commercial packed GC columns and WCOT GC columns that combines the benefits of the larger sample capacity of packed columns and the benefits of the excellent separation capabilities and mass spectrometry (MS) flow rate compatibility of WCOT columns. SFµPC columns suffer from high inlet pressure requirements and prior reported work has required specialized instrumentation for their use. Fabrication of and chromatography with SFµPC GC columns was successfully achieved with typical GC-MS instrumentation and within the flow rate limit of a MS. Additionally, the use of higher viscosity carrier gasses was demonstrated to reduce the required inlet pressure for SFµPC GC columns. Recently, a new vacuum ultraviolet spectrometer (VUV) universal detector has been commercialized for GC. The ability of VUV detectors to acquire absorbance spectra from 125 nm to 430 nm poses a potential alternative to MS. As such, GC-VUV provides an exciting potential alternative approach to achieving excellent quantitative and qualitative analysis across a wide range of analytes. The performance of VUV and MS detectors for forensic analysis in terms of quantitative and qualitative analysis was compared. Analysis of alkylbenzenes in ignitable liquids was explored, which can be important evidence from suspected arson fires and are difficult to differentiate with MS. The VUV detector was found to have superior specificity and comparable sensitivity to the MS detector in scan mode. Addition of thermolysis (Th) as an orthogonal fragmentation pathway provides the opportunity to increase the differences between MS fragmentation patterns. Fragmentation has been widely established to aid in identification of molecules with MS by providing characteristic fragments at characteristic relative abundances. However, molecules with very similar structures do not result in sizable spectral differences in all cases with typical MS fragmentation techniques. A series of Th units were fabricated and integrated into GC-Th-MS instruments. Th-MS was conducted with the thermally labile nitrate esters across a range of instrumentation and thermal conditions.Item Biofilm Derived Oxylipin Mediated Autoimmune Response in Breast Implant Subjects(medRxiv, 2020-11-20) Khan, Imran; Minto, Robert E.; Kelley-Patteson, Christine; Natta, Bruce W. Van; Neumann, Colby R.; Suh, Lily J.; Singh, Kanhaiya; Lester, Mary; VonDerHaar, R. Jason; Gordillo, Gayle M.; Hassanein, Aladdin H.; Sen, Chandan K.; Kadin, Marshall E.; Sinha, Mithun; Chemistry and Chemical Biology, School of ScienceOver 10 million women worldwide have breast implants for breast cancer/prophylactic reconstruction or cosmetic augmentation. In recent years, a number of patients have described a constellation of symptoms that are believed to be related to their breast implants. This constellation of symptoms has been named Breast Implant Illness (BII). The symptoms described include chronic fatigue, joint pain, muscle pain and a host of other manifestations often associated with autoimmune illnesses. In this work, we report that bacterial biofilm is associated with BII. We postulate that the pathogenesis of BII is mediated via a host-pathogen interaction whereby the biofilm bacteria Staphylococcus epidermidis interacts with breast lipids to form the oxylipin 10-HOME. The oxylipin 10-HOME was found to activate CD4+ T cells to Th1 subtype. An increased abundance of CD4+Th1 was observed in the breast tissue of BII subjects. The identification of a mechanism of immune activation associated with BII via a biofilm enabled pathway provides insight into the pathogenesis for implant-associated autoimmune symptoms.Item Biofilm-derived oxylipin 10-HOME–mediated immune response in women with breast implants(The American Society for Clinical Investigation, 2023-11-30) Khan, Imran; Minto, Robert E.; Kelley-Patteson, Christine; Singh, Kanhaiya; Timsina, Lava; Suh, Lily J.; Rinne, Ethan; Van Natta, Bruce W.; Neumann, Colby R.; Mohan, Ganesh; Lester, Mary; VonDerHaar, R. Jason; German, Rana; Marino, Natascia; Hassanein, Aladdin H.; Gordillo, Gayle M.; Kaplan, Mark H.; Sen, Chandan K.; Kadin, Marshall E.; Sinha, Mithun; Surgery, School of MedicineThis study investigates a mechanistic link of bacterial biofilm–mediated host-pathogen interaction leading to immunological complications associated with breast implant illness (BII). Over 10 million women worldwide have breast implants. In recent years, women have described a constellation of immunological symptoms believed to be related to their breast implants. We report that periprosthetic breast tissue of participants with symptoms associated with BII had increased abundance of biofilm and biofilm-derived oxylipin 10-HOME compared with participants with implants who are without symptoms (non-BII) and participants without implants. S. epidermidis biofilm was observed to be higher in the BII group compared with the non-BII group and the normal tissue group. Oxylipin 10-HOME was found to be immunogenically capable of polarizing naive CD4+ T cells with a resulting Th1 subtype in vitro and in vivo. Consistently, an abundance of CD4+Th1 subtype was observed in the periprosthetic breast tissue and blood of people in the BII group. Mice injected with 10-HOME also had increased Th1 subtype in their blood, akin to patients with BII, and demonstrated fatigue-like symptoms. The identification of an oxylipin-mediated mechanism of immune activation induced by local bacterial biofilm provides insight into the possible pathogenesis of the implant-associated immune symptoms of BII.Item Biofilm-derived oxylipin 10-HOME–mediated immune response in women with breast implants(ASCI, 2024-02) Khan, Imran; Minto, Robert E.; Kelley-Patteson, Christine; Singh, Kanhaiya; Timsina, Lava; Suh, Lily J.; Rinne, Ethan; Van Natta, Bruce W.; Neumann, Colby R.; Mohan, Ganesh; Lester, Mary; VonDerHaar, R. Jason; German, Rana; Marino, Natascia; Hassanein, Aladdin H.; Gordillo, Gayle M.; Kaplan, Mark H.; Sen, Chandan K.; Kadin, Marshall E.; Sinha, Mithun; Chemistry, School of ScienceThis study investigates a mechanistic link of bacterial biofilm–mediated host-pathogen interaction leading to immunological complications associated with breast implant illness (BII). Over 10 million women worldwide have breast implants. In recent years, women have described a constellation of immunological symptoms believed to be related to their breast implants. We report that periprosthetic breast tissue of participants with symptoms associated with BII had increased abundance of biofilm and biofilm-derived oxylipin 10-HOME compared with participants with implants who are without symptoms (non-BII) and participants without implants. S. epidermidis biofilm was observed to be higher in the BII group compared with the non-BII group and the normal tissue group. Oxylipin 10-HOME was found to be immunogenically capable of polarizing naive CD4+ T cells with a resulting Th1 subtype in vitro and in vivo. Consistently, an abundance of CD4+Th1 subtype was observed in the periprosthetic breast tissue and blood of people in the BII group. Mice injected with 10-HOME also had increased Th1 subtype in their blood, akin to patients with BII, and demonstrated fatigue-like symptoms. The identification of an oxylipin-mediated mechanism of immune activation induced by local bacterial biofilm provides insight into the possible pathogenesis of the implant-associated immune symptoms of BII.Item Combination therapy in a xenograft model of glioblastoma: enhancement of the antitumor activity of temozolomide by an MDM2 antagonist(American Association of Neurological Surgeons, 2017-02) Wang, Haiyan; Cai, Shanbao; Bailey, Barbara J.; Saadatzadeh, M. Reza; Ding, Jixin; Tonsing-Carter, Eva; Georgiadis, Taxiarchis M.; Gunter, T. Zachary; Long, Eric C.; Minto, Robert E.; Gordon, Kevin R.; Sen, Stephanie E.; Cai, Wenjing; Eitel, Jacob A.; Waning, David L.; Bringman, Lauren R.; Wells, Clark D.; Murray, Mary E.; Sarkaria, Jann N.; Gelbert, Lawrence M.; Jones, David R.; Cohen-Gadol, Aaron A.; Mayo, Lindsey D.; Shannon, Harlan E.; Pollok, Karen E.; Pediatrics, School of MedicineOBJECTIVE Improvement in treatment outcome for patients with glioblastoma multiforme (GBM) requires a multifaceted approach due to dysregulation of numerous signaling pathways. The murine double minute 2 (MDM2) protein may fulfill this requirement because it is involved in the regulation of growth, survival, and invasion. The objective of this study was to investigate the impact of modulating MDM2 function in combination with front-line temozolomide (TMZ) therapy in GBM. METHODS The combination of TMZ with the MDM2 protein-protein interaction inhibitor nutlin3a was evaluated for effects on cell growth, p53 pathway activation, expression of DNA repair proteins, and invasive properties. In vivo efficacy was assessed in xenograft models of human GBM. RESULTS In combination, TMZ/nutlin3a was additive to synergistic in decreasing growth of wild-type p53 GBM cells. Pharmacodynamic studies demonstrated that inhibition of cell growth following exposure to TMZ/nutlin3a correlated with: 1) activation of the p53 pathway, 2) downregulation of DNA repair proteins, 3) persistence of DNA damage, and 4) decreased invasion. Pharmacokinetic studies indicated that nutlin3a was detected in human intracranial tumor xenografts. To assess therapeutic potential, efficacy studies were conducted in a xenograft model of intracranial GBM by using GBM cells derived from a recurrent wild-type p53 GBM that is highly TMZ resistant (GBM10). Three 5-day cycles of TMZ/nutlin3a resulted in a significant increase in the survival of mice with GBM10 intracranial tumors compared with single-agent therapy. CONCLUSIONS Modulation of MDM2/p53-associated signaling pathways is a novel approach for decreasing TMZ resistance in GBM. To the authors' knowledge, this is the first study in a humanized intracranial patient-derived xenograft model to demonstrate the efficacy of combining front-line TMZ therapy and an inhibitor of MDM2 protein-protein interactions.Item A conserved amino acid residue critical for product and substrate specificity in plant triterpene synthases(PNAS Online, 2016-07-26) Salmon, Melissa; Thimmappa, Ramesha B.; Minto, Robert E.; Melton, Rachel E.; Hughes, Richard K.; O’Maille, Paul E.; Hemmings, Andrew M.; Osbourn, Anne; Department of Chemistry & Chemical Biology, School of ScienceTriterpenes are structurally complex plant natural products with numerous medicinal applications. They are synthesized through an origami-like process that involves cyclization of the linear 30 carbon precursor 2,3-oxidosqualene into different triterpene scaffolds. Here, through a forward genetic screen in planta, we identify a conserved amino acid residue that determines product specificity in triterpene synthases from diverse plant species. Mutation of this residue results in a major change in triterpene cyclization, with production of tetracyclic rather than pentacyclic products. The mutated enzymes also use the more highly oxygenated substrate dioxidosqualene in preference to 2,3-oxidosqualene when expressed in yeast. Our discoveries provide new insights into triterpene cyclization, revealing hidden functional diversity within triterpene synthases. They further open up opportunities to engineer novel oxygenated triterpene scaffolds by manipulating the precursor supply.Item Formation of the Acyl Chain within the Alkamides(Office of the Vice Chancellor for Research, 2013-04-05) Nawlthang, Ngun H.; Shepard, Michael R.; Minto, Robert E.Echinacea, a coneflower species that is native to North America, are the most consumed medicinal plants in the United States and Europe. Their medicinal usage focuses on the treatment and prevention of colds, influenza, and other upper respiratory tract infections. In part, the traditional medicinal uses of Echinacea are attributed to their alkamide content. Structurally alkamides consist of an amine moiety acylated with a variety of fatty acids. To better describe the biosynthetic process leading to the formation of acyl chains within alkamides of Echinacea purpurea, stable isotope labeling experiments with analysis via LC/MS and NMR was undertaken. As previously reported from our lab, the acyl chains of alkamides are synthesized from fatty acid synthesis via HSQC NMR analysis of a tetraenoic isobutyl amide alkamide. As part of our continuing efforts to probe the acyl chain biosynthesis within E. purpurea, we herein report the HSQC NMR analysis of a proposed dienoic isobutyl amide alkamide that was labeled with a 70/30 [U-12C6]/[U-13C6]glucose mixture. The magnitude of 13C-13C one-bond coupling observed by NMR will allow for incorporation patterns to be determined and will help to elucidate the structure and biogenesis of this dienoic isobutyl amide alkamide.Item Generation of Alkyl Radicals Via C-H Functionalization and Halogen Atom Transfer Processes(2022-12) Niu, Ben; Laulhé, Sébastien; Long, Eric; Minto, Robert E.; Pu, JingzhiAlkyl radicals are powerful intermediates for the generation of carbon-carbon bonds, which play an indispensable role in the synthesis of natural products, pharmaceuticals, and pesticides. Traditionally, there are two main methods for the generation of alkyl radicals. The first is C-H bond functionalization via hydrogen-atom-transfer (HAT). HAT processes have been used as an effective approach for selectively activating C-H bonds via radical pathways. The other strategy to explore the generation of alkyl radicals is C-X bond functionalization via halogen-atom-transfer (XAT). Alkyl halides are one of the largest classes of building blocks in synthesis and they can be obtained from the corresponding alcohols. The most straightforward and effective way to form such alkyl radicals is the direct homolytic cleavage of C-X bonds. In past decades, photoredox catalysis has emerged as a powerful and greener tool for the synthesis of radicals under mild reaction conditions, which has brought tremendous attention. Although remarkable success has been made in this field, some methods still require costly transition metal catalysts or toxic reagents. Herein, we display a series of visible light-induced approaches under transition-metal free conditions or using earth-abundant metals. These novel photo-induced transformations and corresponding mechanistic work will be discussed in the following order: We will first present our work on metal-free visible-light-promoted C(sp3)-H functionalization of aliphatic cyclic ethers using trace O2. This reaction uses a trace amount of aerobic oxygen as the sole green oxidant under blue light at room temperature to achieve the synthesis of sulfone and phosphate derivatives in good to excellent yields using cyclic ethers and vinyl sulfones. Then, we report on a photo-induced C(sp3)-H chalcogenation of amide derivatives and ethers via a ligand-to-metal charge-transfer. This reaction converts secondary and tertiary amides, sulfonamides, and carbamates into the corresponding amido-N,S-acetal derivatives in good yields, using an earth abundant metal catalyst under mild conditions. Finally, we present a photoredox polyfluoroarylation of alkyl halides via halogen atom transfer. This method converts primary, secondary, and tertiary unactivated abundant alkyl halides into the corresponding polyfluoroaryl compounds in good yields and has good functional group compatibility.Item Identifying Metabolic Pathways Producing Alkamides in Echinacea purpurea(Office of the Vice Chancellor for Research, 2015-04-17) Williams, Jermell; Teitgen, Alicen; Minto, Robert E.Echinacea purpurea is a widely used herbal supplement that is frequently taken to relieve cold symptoms; alkamides are believed to be the bioactive agent. Alkamides are natural products found throughout the Echinacea genus that contain fatty acid chains incorporated into amides. 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 the point where the first true leaf started to grow and alkamide production is known to be active. Alkamides were then extracted and taken to the GC/MS for analysis. Extracted alkamides were analyzed by triple-quadrupole chromatography to investigate 13C labeling by glucose. 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 and if these are altered by a lack of light.Item Nature-Guided Synthesis of Advanced Bio-Lubricants(Springer Nature, 2019-08-12) Romsdahl, Trevor; Shirani, Asghar; Minto, Robert E.; Zhang, Chunyu; Cahoon, Edgar B.; Chapman, Kent D.; Berman, Diana; Chemistry and Chemical Biology, School of ScienceDesign of environmentally friendly lubricants derived from renewable resources is highly desirable for many practical applications. Here, Orychophragmus violaceus (Ov) seed oil is found to have superior lubrication properties, and this is based on the unusual structural features of the major lipid species-triacylglycerol (TAG) estolides. Ov TAG estolides contain two non-hydroxylated, glycerol-bound fatty acids (FAs) and one dihydroxylated FA with an estolide branch. Estolide branch chains vary in composition and length, leading to their thermal stability and functional properties. Using this concept, nature-guided estolides of castor oil were synthesized. As predicted, they showed improved lubrication properties similar to Ov seed oil. Our results demonstrate a structure-based design of novel lubricants inspired by natural materials.