Browsing by Subject "Biological Products"
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Item Investigation of the Discoipyrroles and Other Marine Bacteria Derived Natural Products(2017-07-17) Colosimo, Dominic Andrew; Bruick, Richard K.; MacMillan, John; Ready, Joseph M.; Nijhawan, DeepakNatural products are a rich source of scientific innovation. These chemical compounds are canonically celebrated as biomedical tools or synthetic chemistry feats. Discovery of new chemical compounds has benefited from the study of natural product biosynthesis, or the methods by which they are constructed. Additionally, these studies have advanced the fields of ecology, industrial chemistry, and protein biophysics. This work will demonstrate how the discoipyrrole family of natural products inspired novel biomedical and biosynthetic discovery. In particular, their biosynthesis features unique mechanisms that are independent of protein catalysts, a growing trend found in natural products. Unrelated to the discoipyrroles, the manipulation of biosynthesis pathways using the methodology known as ribosome engineering will be discussed. This work demonstrates how the discovery and development of bioactive natural products can be enhanced by biosynthetic interrogations.Item Mangrolide A, A Novel Marine Derived Polyketide with Selective Antibiotic Activity(2013-04-08) Jamison, Matthew Thomas; Chen, Chuo; MacMillan, John; De Brabander, Jef K.; Ready, Joesph M.The ability of nature to produce complex, biologically active compounds has inspired researchers throughout history. The isolation of these molecules has been instrumental in the discovery of many medicinal compounds, especially to combat infections caused by pathogenic bacteria. Antibiotic resistance is a major challenge faced in hospitals today, and there is an urgent need for new antibiotics. The "Golden Age" of antibiotic development was spurred by compounds isolated from terrestrial bacteria. Unfortunately, the rate of discovery of new compounds has decreased and new techniques and sources are required. The marine environment contains novel natural product-producing bacteria and has yielded new compounds with potent activity. This dissertation represents work towards new antibiotic discovery from marine natural products. Chapter 1 provides an introduction to marine natural product research with a focus on new developments in the field. Chapter 2 describes the isolation and characterization of a new macrolide, mangrolide A, which was discovered though a phenotypic screen against Burkholderia cepacia. Mangrolide A has selective activity against gram negative bacteria. The determination of the absolute stereochemistry of mangrolide A is described in chapter 3. In chapter 4, a new method to increase the production of mangrolide A and activate cryptic metabolite pathways in SNA-18 is applied and results in a new mangrolide analogue. Chapter 5 finishes with the results of a screen using an efflux deficient strain of Pseudomonas aeruginosa. This experiment led to the isolation of the known natural products alldimycin A-C and new ammosamide analogues.Item Precursor-Directed Identification of Natural Product Scaffolds(2017-04-17) Brumley, David Anderson; MacMillan, JohnThe rapid generation of natural product analogs is a fundamental challenge in both the optimization of medicinal potency and exploration of novel biological activity. Previous work with Streptomyces variabilis has demonstrated that natural products that incorporate non-enzymatic transformation can be exploited for the rapid generation of analogs. Herein we demonstrate a general methodology to use fluorinated or isotopically labeled substrates to identify natural product frameworks prone to non-enzymatic pathways. As proof of principle our precursor directed methodology was used in the study of discoipyrrole A formation, the guided isolation of a novel iminoquinone and the detection of a novel ammosamide analog via incorporation of a carbon-based nucleophile.Item Synthetic Studies of the Rubellin Natural Products(2020-12-01T06:00:00.000Z) Gartman, Jackson Andrew; De Brabander, Jef K.; Ready, Joseph M.; Chen, Chuo; Tambar, UttamThe effective construction of complex bioactive molecules often requires the development of innovative chemical methods to push the boundaries of organic synthesis. As the utility of available reactions increases, the complexity of possible target molecules increases analogously. This manuscript includes a review of relevant recent natural product syntheses, our studies on the rubellin class of natural products, and our investigation of a rearrangement reaction of reactive iodonium ylide intermediates. First described are select syntheses of complex anthraquinone monomers and dimers within the past 20 years. The scientific community has found deep interest in the anthraquinone class of compounds due to their therapeutic properties and challenging structural elements. Various architecturally beautiful natural products have been successfully synthesized utilizing two main strategies: either an early-stage synthesis of the anthraquinone and further elongation of the system, or a late-stage introduction of the anthraquinone ring moiety. The retrosynthetic disconnections that shape the anthraquinone-installation strategy are emphasized. The second and major chapter describes our studies of the anthraquinone-based rubellin natural products through various synthetic routes and our stereoselective total synthesis of (+)-rubellin C. The synthesis of a rubellin family member represents a synthetic landmark in anthraquinone natural products, as successful total synthesis has evaded the synthetic community since their isolation almost forty years ago. Our synthesis has allowed for preliminary investigation of the reported biological activity of these compounds on the intracellular protein tau, a therapeutic target for Alzheimer's Disease and other neurodegenerative tauopathies. Thirdly, part of our foray into the selective rearrangements of allylic iodonium ylide species is described, in particular our utilization of ligand design to control the selectivity of these rearrangements. We examine the allylic iodonium ylide species, a reactive intermediate that can undergo many uncontrolled processes. In the presence of a metal catalyst and devised ligand, we can modulate the selectivity of this process to generate useful products.Item Using Multiple Screening Strategies to Biologically and Chemically Characterize Natural Products(2016-06-10) Oswald, Nathaniel Walter; De Brabander, Jef K.; MacMillan, John; Corey, David R.; White, Michael A.Natural products play an important role in the discovery and development of therapeutics and biological probes. However, in recent decades therapeutic screening efforts have moved away from using natural product libraries, instead opting for large synthetic molecule library. This move has corresponded with a move from phenotypic screens to target based screening approaches. The perceived incompatibility of natural product libraries with target based screening efforts is often cited for these shifts. Herein we discuss the benefits of phenotypic screens and advances in bioinformatic approaches to improve natural product discovery using phenotypic screens. We describe the development and implementation of a screen using a natural product fraction library of ~9000 fractions to screen 26 non-small cell lung cancer cell lines for selective cytotoxic compounds. A screen of this magnitude is unprecedented in academia, therefore we developed a process to rapidly identify and characterize natural products of interest. Natural product fractions with selective toxicity were filtered to ~1000 high priority natural product fractions. Using LC-MS analysis and bioinformatic approaches, Elastic Net (EN) and Functional Signatures of Ontology (FuSiOn),we further prioritized these 1000 natural product fractions based on sensitivity and mechanism of action predictions, and chemical complexity. The implementation of this prioritization process has resulted in an effective discovery pipeline. Ikarugamycin, a selective cytotoxin and endocytosis inhibitor, has been characterized for cytotoxicity and as a chemical tool for inhibiting endocytosis. Piericidin A, a known complex I inhibitor, displays extreme selective toxicity to a subset of cancer cell lines independent of its complex I inhibition, however we can predict this sensitivity using a common genetic biomarker. Other natural products have also been identified, although their biological characterization is ongoing. Using FuSiOn we effectivity identified a minor metabolite (N6,N6-dimethyladenosine) responsible for AKT inhibition. FuSiOn was implemented in conjunction with our non-small cell lung cancer cell line screen to characterize the mechanisms of action of natural product fractions. This correlation led to the rapid identification of bafilomycin among our prioritized 1000 natural product fractions. The process we outline herein effectively uses bioinformatics (EN and FuSiOn) in concert with primary screening data to select for those natural product fractions of greatest biologic and chemical significance.