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  • The American Society for Microbiology (ASM)  (3)
  • Cham :Springer International Publishing AG,  (2)
  • National Academy of Sciences  (1)
  • 1
    Online Resource
    Online Resource
    Cham :Springer International Publishing AG,
    Keywords: Chemistry, Organic. ; Electronic books.
    Type of Medium: Online Resource
    Pages: 1 online resource (258 pages)
    Edition: 1st ed.
    ISBN: 9783319049007
    Series Statement: Progress in the Chemistry of Organic Natural Products Series ; v.99
    DDC: 547
    Language: English
    Note: Intro -- Contents -- Contributors -- About the Authors -- Pharmacognosy of Black Cohosh: The Phytochemical and Biological Profile of a Major Botanical Dietary Supplement -- 1 Introduction -- 2 Phytochemistry -- 2.1 Cycloartane Triterpenes -- 2.1.1 Structural Diversity -- 2.1.2 Naming System -- 2.1.3 Isolation Techniques -- 2.1.4 Structural Elucidation -- 2.1.4.1 Mass Spectrometry -- 2.1.4.2 Nuclear Magnetic Resonance -- 2.1.4.3 X-Ray Diffraction -- 2.1.5 Dereplication -- 2.1.5.1 Dereplication by LC/MS and LC/ELSD -- 2.1.5.2 Dereplication by NMR -- 2.2 Cimicifugic Acids -- 2.2.1 Structural Characteristics -- 2.2.2 Naming System -- 2.2.3 Isolation Techniques -- 2.2.4 Structural Elucidation -- 2.2.5 Dereplication -- 2.3 Nitrogen-Containing Constituents -- 2.3.1 Structural Diversity -- 2.3.1.1 Primary Metabolites -- Amino Acid Derivatives -- Nucleobase Derivatives -- 2.3.1.2 Secondary Metabolites -- Aporphines -- Betaines -- β-Carbolines -- Cinnamides -- Cholines -- Guanidines -- Isoquinolines -- Protoberberines -- Protopines -- Pyridoxines -- Miscellaneous -- 2.3.2 Structural Elucidation -- 2.3.2.1 Nucleobases and Their Derivatives -- 2.3.2.2 Guanidino Alkaloids -- 2.3.2.3 Hydroxycinnamic Amides -- 2.3.2.4 Choline and Betaine Alkaloids -- 2.3.2.5 Pictet-Spengler Adducts with Tryptamine Derivatives -- 2.3.2.6 Other Alkaloids -- 3 Fingerprinting -- 4 Names and Origin -- 5 Pharmacology -- 5.1 Estrogenic Activity -- 5.2 Prevention of Bone Loss -- 5.3 Potential Anticancer Activity -- 5.4 Stress Relief -- 5.5 Hepatotoxicity -- 6 Clinical Trials -- 7 Concluding Remarks -- References -- A Colorful History: The Evolution of Indigoids -- 1 Introduction -- 1.1 Natural Dyes -- 1.2 Dyes from Plants -- 2 Indigoid Family -- 2.1 Family Presentation -- 2.2 Particular Electronic Effects: Origin of the Color -- 3 Indigo and Its Relatives. , 3.1 Sources and Extraction of Indigo Around the World -- 3.1.1 Japan, Asia -- 3.1.1.1 History -- 3.1.1.2 Extraction Process -- 3.1.2 Europe -- 3.1.2.1 History -- 3.1.2.2 Extraction Procedure -- 3.1.2.3 Chemistry -- 3.1.3 India, South America, and French West Indies -- 3.1.3.1 History -- 3.1.3.2 Extraction Process -- 3.1.3.3 Chemistry -- 3.2 Chemical Synthesis of Indigo -- 3.2.1 The First Syntheses: Baeyer, Drewsen, and BASF -- 3.2.2 New Methods and Mechanism Description -- 4 Tyrian Purple -- 4.1 Legendary History -- 4.2 Extraction -- 4.2.1 Sources -- 4.2.2 Extraction Process -- 4.2.2.1 Central America-South America-Caribbean Sea -- 4.2.2.2 Japan -- 4.2.2.3 Europe -- 4.2.3 Chemistry -- 4.2.3.1 Composition -- 4.2.3.2 Precursors and Biosynthesis -- 4.2.3.3 Chemical Process -- 4.2.3.4 The Case of Vat Dyeing -- 4.3 Chemical Synthesis of Tyrian Purple -- 5 Renewal of Interest of Indigoids in Medicinal Chemistry -- 5.1 Discovery of the Biological Potency of Indirubin -- 5.1.1 Danggui Longhui Wan -- 5.1.2 Mechanism of Action -- 5.2 Royal Purple: A Source of Therapeutic Agents -- 5.2.1 Discovery of the Potential of 6-Bromoindirubin -- 5.2.2 GSK-3β -- 5.2.3 6BIO, a Biological Tool -- 5.2.3.1 Maintenance of Stem Cell Pluripotency -- 5.2.3.2 Antiparasitic Activity -- 5.2.3.3 Anticancer Activity -- 5.2.4 Novel Analogs of 6BIO -- 5.3 Indirubin Synthesis -- 5.3.1 Baeyer Breakthrough -- 5.3.2 Activation of the 2-Position -- 5.3.2.1 The 2-Chloro-3 H -indole-3-one Pathway -- 5.3.2.2 Stabilization of the Intermediate -- 5.3.2.3 Other Isatin Derivatives -- 5.3.3 Indoxyl Pathway -- 5.3.3.1 Stabilization at the 2-Position -- 5.3.3.2 Indoxyl Acetate: The Ultimate Intermediate -- 5.3.4 Biotransformations -- 5.4 Biological Applications of Synthetic Indirubins -- 5.4.1 Creation of Compound Assemblies -- 5.4.2 Indirubin Derivatives -- 5.4.3 7-Bromo-Indirubins. , 5.4.4 New DYRK 1A Inhibitors -- 5.4.5 Other Indirubin Derivatives -- 5.4.6 Conclusion -- 5.5 Glycoside Indigoids -- 5.5.1 Glycosides of Indigos -- 5.5.1.1 The Family of Akashins -- 5.5.1.2 Synthesis of Akashins Derivatives -- 5.5.2 Glycosides of Indirubins -- 5.5.2.1 Indirubin N -Glycosides -- 5.5.2.2 N′ -Glycosylindirubins -- 5.5.2.3 O -Glycosylindirubins -- 5.6 Isoindigo: A Forgotten Family Member -- 5.6.1 Synthesis of Isoindigo -- 5.6.2 Isoindigo in Medicinal Chemistry -- 5.6.2.1 Halogenated Isoindigo -- 5.6.2.2 Glycosylisoindigo -- 5.6.2.3 N -Substituted Isoindigo -- 6 Conclusion -- References -- Bioactive Heterocyclic Natural Products from Actinomycetes Having Effects on Cancer-Related Signaling Pathways -- 1 Introduction -- 2 Collection and Preparation of Actinomycete Strains -- 2.1 Collection of Field Samples for Isolation of Actinomycete Strains Principally from the Chiba Area of Japan -- 2.2 Preparation of an Actinomycete Extract Assembly -- 3 Screening Studies Using the Actinomycete Extract Assembly -- 3.1 Chemical Screening -- 3.2 Cytotoxicity Testing -- 3.3 Screening Tests Targeting Signaling Pathways Related to Cancer Disease -- 3.3.1 TRAIL Signaling (1): Enhancement of Death-Receptor 5 Promoter Activity -- 3.3.2 TRAIL Signaling (2): TRAIL-Resistance Overcoming Activity -- 3.3.3 Wnt Signaling -- 4 Izumiphenazines and Izuminosides -- 4.1 Izumiphenazines -- 4.2 Izuminosides -- 4.3 Effects on Wnt and TRAIL Signaling -- 5 Pyranonaphthoquinones -- 5.1 Pyranonaphthoquinones -- 5.2 Yorophenazine -- 5.3 Yoropyrazone -- 5.4 Effects on TRAIL Signaling -- 6 Azaquinones -- 6.1 Katorazone -- 6.2 Utahmycin and Others -- 6.3 Effects on Wnt and TRAIL Signaling -- 7 Fuzanins -- 7.1 Fuzanins A-D -- 7.2 Fuzanins E-I -- 8 Elmonin -- 9 Actinomycete Metabolites Found in Screening Studies Targeting Cancer-Related Signaling Pathways. , 9.1 Teleocidin with Enhancing Death-Receptor 5 Promoter Activity -- 9.2 Tyrosine Derivatives with TRAIL-Resistance Overcoming Activity -- 9.3 Nonactins, Griseoviridin, and Nocardamines with Wnt Signaling Inhibitory Activity -- 10 Synthesis Aspects -- 10.1 Synthesis of Phenazines -- 10.2 Synthesis of Pyranonaphthoquinones -- References -- Genome Mining: Concept and Strategies for Natural Product Discovery -- 1 Introduction -- 2 Principles of Microbial Natural Product Biosynthesis -- 2.1 Polyketides -- 2.2 Nonribosomal Peptides -- 2.3 Ribosomally Synthesized and Post-translationally Modified Peptides -- 2.4 Terpenes -- 3 Bioinformatic Software Tools -- 4 Discovery of Natural Products from Orphan Pathways -- 4.1 Structure- and Bioactivity-Guided Strategies -- 4.1.1 UV-Based Methods -- 4.1.2 NMR-Based Methods -- 4.1.3 MS-Based Methods -- 4.1.4 Assay-Based Methods -- 4.1.5 One-Strain-Many-Compounds (OSMAC) -- 4.2 Genetic Approaches -- 4.2.1 Mutagenesis and Metabolic Profiling -- 4.2.2 Transcriptional Modulation -- 4.2.3 Heterologous Expression -- 4.2.4 In vitro Reconstitution -- 5 Conclusions and Perspectives -- References.
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  • 2
    Online Resource
    Online Resource
    Cham :Springer International Publishing AG,
    Keywords: Natural products. ; Electronic books.
    Type of Medium: Online Resource
    Pages: 1 online resource (602 pages)
    Edition: 1st ed.
    ISBN: 9783319052755
    Series Statement: Progress in the Chemistry of Organic Natural Products Series ; v.100
    DDC: 547
    Language: English
    Note: Intro -- Foreword -- Contents -- Contributors -- About the Authors -- Structure Elucidation of Natural Compoundsby X-Ray Crystallography -- 1 Introduction -- 2 History -- 3 Theoretical Background -- 3.1 Heuristic Introduction -- 3.2 Scattering Theory -- 3.3 Symmetry in Crystals -- 3.4 Crystallographic Resolution -- 3.5 Anomalous Dispersion -- 3.6 The Patterson Function -- 4 Crystal Structure Analysis -- 4.1 Crystallization -- 4.1.1 Crystallization Methodology -- 4.1.2 Crystallization of Membrane Proteins -- 4.1.3 Crystallization of Protein-DNA Complexes -- 4.2 Data Collection -- 4.2.1 X-ray Source -- 4.2.1.1 Laboratory Source -- 4.2.1.2 Synchrotrons -- 4.2.1.3 Compton Source -- 4.2.2 Crystal Mounting -- 4.2.3 Goniometer -- 4.2.4 Detectors -- 4.2.4.1 Imaging Plate Detector -- 4.2.4.2 CCD Detector -- 4.2.4.3 Solid State Detector -- 4.3 Data Reduction -- 4.3.1 Challenges in Data Reduction -- 4.4 Solving the Structure: The Phase Problem -- 4.4.1 Direct Methods -- 4.4.2 Molecular Replacement -- 4.4.2.1 The Search Model -- 4.4.2.2 The Technicalities of Molecular Replacement -- 4.4.3 Experimental Structure Solution -- 4.4.3.1 Multiple Isomorphous Replacement -- 4.4.3.2 Single Isomorphous Replacement -- 4.4.3.3 Anomalous Dispersion -- 4.4.4 Density Modification and NCS Averaging -- 4.5 Model Building and Refinement -- 4.5.1 Least-Squares Refinement -- 4.5.2 Restrained Refinement -- 4.6 Structure Validation -- 5 Results -- 5.1 Cambridge Structural Database -- 5.2 Crystallographic Open Database -- 5.3 Protein Data Bank -- 5.3.1 Nucleic Acid Data Bank -- 5.3.2 Membrane Proteins of Known Three-Dimensional Structure -- 5.3.3 Protein-DNA Complexes -- 5.4 Other Databases -- 6 Special Techniques -- 6.1 Time-Resolved Crystallography -- 6.2 Neutron Crystallography -- 6.3 Electron Crystallography -- 7 Outlook -- References. , Mass Spectrometry in Natural Product Structure Elucidation -- 1 Introduction -- 2 Mass Spectrometric Techniques -- 2.1 Ionization Techniques -- 2.2 Ion Separation Techniques -- 2.3 Analysis of Mixtures -- 2.4 High and Extremely High Masses -- 3 Pentacyclic Triterpenes -- 3.1 Saturated Triterpenes -- 3.2 Triterpenes with Double Bonds -- 3.2.1 Δ12-Oleanenes and -Ursenes -- 3.2.2 Δ12-Lupenes and -Hopenes -- 3.2.3 Δ5-Triterpenes -- 3.2.4 Δ9(11)-Triterpenes -- 3.2.5 Δ14-Taraxerenes -- 3.2.6 Δ13(18)-Oleanene -- 3.2.7 Δ11-Ursenes and -Oleanenes -- 3.2.8 Δ18-Oleanenes and -Friedelenes -- 3.2.9 Δ20- and Δ18(30)-Ursenes -- 3.3 Baueranes, Multifloranes, and Swertanes -- 3.4 Fernane and Arborane Derivatives -- 4 Alkaloids from Vertebrates -- 4.1 Amphibia -- 4.1.1 Toads and Frogs (Anura) -- 4.1.1.1 Biogenic Amines -- 4.1.1.2 Steroidal Alkaloids: Batrachotoxin and Tauromantellic Acid -- 4.1.1.3 Pyrrolidines and Piperidines -- 4.1.1.4 Histrionicotoxins -- 4.1.1.5 Decahydroquinolines -- 4.1.1.6 3,5-Disubstituted Pyrrolizidines and Indolizidines, 4,6-Disubstituted Quinolizidines, and Lehmizidines -- 4.1.1.7 Spiropyrrolizidines -- 4.1.1.8 5,8-Disubstituted Indolizidines and 1,4-Disubstituted Quinolizidines -- 4.1.1.9 Pumiliotoxins (170) and Related Compounds -- 4.1.1.10 Tricyclic Compounds -- 4.1.1.11 Pseudophrynamines -- 4.1.1.12 Epibatidine -- 4.1.1.13 Zetekitoxin AB (Atelopidtoxin) -- 4.1.1.14 Chiriquitoxin -- 4.1.1.15 Alkaloids of Plant Origin Found in Amphibians -- 4.1.1.16 Toad Venoms -- 4.1.2 Salamanders and Newts (Caudata) -- 4.2 Reptiles -- 4.3 Fishes -- 4.3.1 Tetrodotoxin -- 4.3.2 Steroids -- 4.3.3 Ichthyotoxins -- 4.4 Birds -- 4.5 Mammals and Mankind -- 5 Fatty Acids and Lipids -- 5.1 Fatty Acids -- 5.1.1 Saturated and Unsaturated Fatty Acids -- 5.1.2 Furan Fatty Acids -- 5.2 Glycerol Derivatives -- 5.2.1 Glycerol Ethers from Archaebacteria and Sediments. , 5.2.2 Triglycerides -- 5.2.3 Glycerophospholipids -- 5.3 Lipidomics -- 6 Carbohydrates -- 6.1 Monosaccharides -- 6.2 Di-, Oligo-, and Polysaccharides -- 6.3 Glycosides -- 7 Amino Acids, Peptides, and Proteins -- 7.1 Amino Acids -- 7.2 Peptides -- 7.2.1 Linear Peptides -- 7.2.2 Cyclopeptides and Cyclodepsipeptides -- 7.3 Proteomics -- 8 Nucleosides, Nucleotides, and Nucleic Acids -- 8.1 Nucleobases, Mono-Nucleosides, and Mono-Nucleotides -- 8.2 Di- and Oligo-Nucleotides -- 8.3 Polynucleotides, DNA, and RNA -- 8.4 Interaction with Other Compounds -- 9 Mass Spectra Collections -- 9.1 General -- 9.2 Alkaloids -- 9.3 Drugs, Poisons, Pesticides, and Pollutants -- 9.4 Flavors and Fragrances -- 9.5 Geo- and Petrochemicals -- 9.6 Lipids -- 9.7 Steroids -- 9.8 Terpenes -- 10 Addendum -- References -- Nuclear Magnetic Resonance in the Structural Elucidation of Natural Products -- 1 Introduction -- 2 Dereplication: Distinguishing Between New and Known Natural Products -- 3 Quantitative NMR -- 4 Using 2D NMR to Determine Skeletal Structures of Natural Products -- 5 Avoiding Getting the Wrong Skeletal Structure -- 6 Determination of Configuration and/or Conformation of Natural Products -- 7 An Example of a Solved Structure: Kauradienoic Acid -- 7.1 HSQC Data -- 7.2 COSY and TOCSY Data -- 7.3 HMBC Data -- 7.4 General Molecular Assembly Strategy -- 7.5 A Specific Molecular Assembly Procedure -- 7.6 Determination of Overall Stereochemistry and Proton Chemical Shift Assignments -- 8 Computer-Assisted Structure Elucidation -- 8.1 Guyanin -- 8.2 T-2 Toxin -- 8.3 Kauradienoic Acid -- 9 The Effect of Dynamic Processes on the Appearance of NMR Spectra of Natural Products and Other Organic Compounds -- 10 The Relative Advantages and Disadvantages of Different Pulse Sequences -- 11 Liquid-Chromatography-NMR -- 12 Probe Choices. , 12.1 Essential Probe Features for Natural Product Research -- 12.2 Ambient-Temperature Probes -- 12.3 Cryogenically Cooled Probes -- 12.4 Microprobes -- 13 A Fully Automated Setup of 2D NMR Experiments for Organic Structure Determination -- 14 Parameter Choices for Acquisition and Processing of 1D and 2D NMR Spectra -- 14.1 Basics of NMR Data Acquisition -- 14.1.1 Sampling Rate -- 14.1.2 Analog to Digital Conversion -- 14.1.3 Digital Oversampling -- 14.1.4 Quadrature Detection -- 14.1.5 Fold-in Peaks -- 14.1.6 Analog Versus Digital Filters -- 14.2 Recommended Acquisition and Processing Parameters for 1D Spectra -- 14.2.1 Spectral Widths -- 14.2.2 Number of Data Points and Acquisition Times -- 14.2.3 Number of Scans (Transients) -- 14.2.4 Zero Filling and Data Point Resolution -- 14.2.5 Pulse Widths and Delay Times -- 14.2.6 Apodization (Weighting) Functions -- 14.2.7 13C Spectral Editing -- 14.3 Basics of 2D NMR -- 14.3.1 General Features of 2D NMR Sequences -- 14.3.2 Homonuclear and Heteronuclear 2D NMR Spectra -- 14.3.3 Absolute-Value Versus Phase-Sensitive Spectra -- 14.3.4 Phase Cycling Versus Gradient Selection -- 14.3.5 Acquisition Times and Relaxation Delays -- 14.3.6 Number of Time Increments, Forward Linear Prediction, and Zero Filling -- 14.3.7 Number of Scans -- 14.3.8 Apodization Functions -- 14.3.9 Data Point Resolution in 2D NMR Spectra -- 14.3.10 Shaped Pulses and Selective 1D Analogues of 2D NMR Spectra -- 14.4 Recommended Acquisition and Processing Parameters for Commonly Used 2D Experiments and Selective 1D Experiments -- 14.4.1 COSY and TOCSY Experiments -- 14.4.1.1 Gradient-Selected COSY (Absolute-Value Mode) -- 14.4.1.2 Gradient-Selected Double Quantum Filtered COSY (Phase Sensitive) -- 14.4.1.3 TOCSY or Z-TOCSY* (Phase-Sensitive) -- 14.4.2 NOESY and ROESY Experiments -- 14.4.2.1 NOESY (Phase-Sensitive). , 14.4.2.2 ROESY *(Phase-Sensitive) -- 14.4.3 HMQC, HSQC, HMBC, and H2BC Experiments -- 14.4.3.1 Gradient-Selected HMQC (Absolute-Value) -- 14.4.3.2 Gradient-Selected HSQC* (With or Without 13C Spectral Editing) -- 14.4.3.3 Gradient-Selected HMBC (Absolute-Value) -- 14.4.3.4 Gradient-Selected HMBC (Mixed-Mode Processing)* -- 14.4.3.5 Gradient-Selected H2BC (Phase-Sensitive) -- 14.4.4 Selective 1D Experiments -- 14.4.4.1 1D TOCSY* -- 14.4.4.2 1D NOESY or ROESY* -- 15 Conclusions -- References -- Vibrational Circular Dichroism Absolute Configuration Determination of Natural Products -- 1 Introduction -- 2 A Brief History -- 3 Experimental Considerations -- 3.1 VCD-FT Spectrophotometer -- 4 Theoretical Calculations -- 4.1 Fundamental Parameters -- 4.1.1 Dipolar and Rotational Strengths in VCD Transitions -- 4.1.2 Computational Calculations of Dipolar and Rotational Strengths -- 4.2 Density Functional Theory -- 4.2.1 Hybrid Functionals and Basis Set -- 4.3 Conformational Optimization and Graphical VCD Methods for Absolute Configuration Assignment -- 5 Studies of Natural Products and Some Chiral Structurally Related Molecules -- 5.1 Fundamentals in the Interpretation of VCD Spectra -- 5.1.1 The Local Model -- 5.1.2 Normal Versus Local Mode Assignment -- 5.1.3 H-bonding and Solvent Effects. The Robust Mode Concept -- 5.1.4 Symmetry and Conformation -- 5.2 Assignment of Absolute Configurations of Terpenes, Aromatic Molecules, and other Natural Compounds -- 5.2.1 Monoterpenes -- 5.2.2 Sesquiterpenes -- 5.2.3 Diterpenes and Meroterpenoids -- 5.2.4 Triterpenes -- 5.2.5 Aromatic Molecules -- 5.2.6 Other Natural Products -- 6 Concluding Remarks -- References -- The Series "Progress in the Chemistry of Organic Natural Products": 75 Years of Service in the Development of Natural Product Chemistry -- 1 Introduction -- 2 László Zechmeister: Editor from 1938 to 1969. , 2.1 Previous History: Phytochemistry in Hungary.
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  • 3
    Publication Date: 2013-02-20
    Description: Double-stranded DNA (dsDNA) derived from pathogen- or host-damaged cells triggers innate immune responses when exposed to cytoplasm. However, the machinery underlying the primary recognition of intracellular dsDNA is obscure. Here we show that the DNA damage sensor, meiotic recombination 11 homolog A (MRE11), serves as a cytosolic sensor for dsDNA....
    Print ISSN: 0027-8424
    Electronic ISSN: 1091-6490
    Topics: Biology , Medicine , Natural Sciences in General
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  • 4
    Publication Date: 2014-12-12
    Description: Thermostability is an important property of enzymes utilized for practical applications because it allows long-term storage and use as catalysts. In this study, we constructed an error-prone strain of the thermophile Geobacillus kaustophilus HTA426 and investigated thermoadaptation-directed enzyme evolution using the strain. A mutation frequency assay using the antibiotics rifampin and streptomycin revealed that G. kaustophilus had substantially higher mutability than Escherichia coli and Bacillus subtilis . The predominant mutations in G. kaustophilus were A · T-〉G · C and C · G-〉T · A transitions, implying that the high mutability of G. kaustophilus was attributable in part to high-temperature-associated DNA damage during growth. Among the genes that may be involved in DNA repair in G. kaustophilus , deletions of the mutSL , mutY , ung , and mfd genes markedly enhanced mutability. These genes were subsequently deleted to construct an error-prone thermophile that showed much higher (700- to 9,000-fold) mutability than the parent strain. The error-prone strain was auxotrophic for uracil owing to the fact that the strain was deficient in the intrinsic pyrF gene. Although the strain harboring Bacillus subtilis pyrF was also essentially auxotrophic, cells became prototrophic after 2 days of culture under uracil starvation, generating B. subtilis PyrF variants with an enhanced half-denaturation temperature of 〉10°C. These data suggest that this error-prone strain is a promising host for thermoadaptation-directed evolution to generate thermostable variants from thermolabile enzymes.
    Print ISSN: 0099-2240
    Electronic ISSN: 1098-5336
    Topics: Biology
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  • 5
    Publication Date: 2015-10-03
    Description: The plasmid pGKE75- cat A138T , which comprises pUC18 and the cat A138T gene encoding thermostable chloramphenicol acetyltransferase with an A138T amino acid replacement (CAT A138T ), serves as an Escherichia coli-Geobacillus kaustophilus shuttle plasmid that confers moderate chloramphenicol resistance on G. kaustophilus HTA426. The present study examined the thermoadaptation-directed mutagenesis of pGKE75- cat A138T in an error-prone thermophile, generating the mutant plasmid pGKE75 αβ - cat A138T responsible for substantial chloramphenicol resistance at 65°C. pGKE75 αβ - cat A138T contained no mutation in the cat A138T gene but had two mutations in the pUC replicon, even though the replicon has no apparent role in G. kaustophilus . Biochemical characterization suggested that the efficient chloramphenicol resistance conferred by pGKE75 αβ - cat A138T is attributable to increases in intracellular CAT A138T and acetyl-coenzyme A following a decrease in incomplete forms of pGKE75 αβ - cat A138T . The decrease in incomplete plasmids may be due to optimization of plasmid replication by RNA species transcribed from the mutant pUC replicon, which were actually produced in G. kaustophilus . It is noteworthy that G. kaustophilus was transformed with pGKE75 αβ - cat A138T using chloramphenicol selection at 60°C. In addition, a pUC18 derivative with the two mutations propagated in E. coli at a high copy number independently of the culture temperature and high plasmid stability. Since these properties have not been observed in known plasmids, the outcomes extend the genetic toolboxes for G. kaustophilus and E. coli .
    Print ISSN: 0099-2240
    Electronic ISSN: 1098-5336
    Topics: Biology
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  • 6
    Publication Date: 2016-05-24
    Description: The emergence and spread of artemisinin-resistant Plasmodium falciparum is of huge concern for the global effort toward malaria control and elimination. Artemisinin resistance, defined as a delayed time to parasite clearance following administration of artemisinin, is associated with mutations in the Pfkelch13 gene of resistant parasites. To date, as many as 60 nonsynonymous mutations have been identified in this gene, but whether these mutations have been selected by artemisinin usage or merely reflect natural polymorphism independent of selection is currently unknown. To clarify this, we sequenced the Pfkelch13 propeller domain in 581 isolates collected before (420 isolates) and after (161 isolates) the implementation of artemisinin combination therapies (ACTs), from various regions of endemicity worldwide. Nonsynonymous mutations were observed in 1% of parasites isolated prior to the introduction of ACTs. Frequencies of mutant isolates, nucleotide diversity, and haplotype diversity were significantly higher in the parasites isolated from populations exposed to artemisinin than in those from populations that had not been exposed to the drug. In the artemisinin-exposed population, a significant excess of dN compared to dS was observed, suggesting the presence of positive selection. In contrast, pairwise comparison of dN and dS and the McDonald and Kreitman test indicate that purifying selection acts on the Pfkelch13 propeller domain in populations not exposed to ACTs. These population genetic analyses reveal a low baseline of Pfkelch13 polymorphism, probably due to purifying selection in the absence of artemisinin selection. In contrast, various Pfkelch13 mutations have been selected under artemisinin pressure.
    Print ISSN: 0066-4804
    Electronic ISSN: 1098-6596
    Topics: Biology , Medicine
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