DOCSLIB.ORG

Biosynthesis of Cyclic Peptide Natural Products in Mushrooms

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Biosynthesis of Cyclic Peptide Natural Products in Mushrooms BIOSYNTHESIS OF CYCLIC PEPTIDE NATURAL PRODUCTS IN MUSHROOMS By Robert Michael Sgambelluri A DISSERTATION Submitted to Michigan State University in partial fulfillment of the requirements for the degree of Biochemistry & Molecular Biology – Doctor of Philosophy 2017 ABSTRACT BIOSYNTHESIS OF CYCLIC PEPTIDE NATURAL PRODUCTS IN MUSHROOMS By Robert Michael Sgambelluri Cyclic peptide compounds possess properties that make them attractive candidates in the development of new drugs and therapeutics. Mushrooms in the genera Amanita and Galerina produce cyclic peptides using a biosynthetic pathway that is combinatorial by nature, and involves an unidentified, core set of tailoring enzymes that synthesize cyclic peptides from precursor peptides encoded in the genome. The products of this pathway are collectively referred to as cycloamanides, and include amatoxins, phallotoxins, peptides with immunosuppressant activities, and many other uncharacterized compounds. This work aims to describe cycloamanide biosynthesis and its capacity for cyclic peptide production, and to harness the pathway as a means to design and synthesize bioactive peptides and novel compounds. The genomes of Amanita bisporigera and A. phalloides were sequenced and genes encoding cycloamanides were identified. Based on the number of genes identified and their sequences, the two species are shown to have a combined capacity to synthesize at least 51 unique cycloamanides. Using these genomic data to predict the structures of uncharacterized cycloamanides, two new cyclic peptides, CylE and CylF, were identified in A. phalloides by mass spectrometry. Two species of Lepiota mushrooms, previously not known to produce cycloamanides, were also analyzed and shown to contain amatoxins, the toxic cycloamanides responsible for fatal mushroom poisonings. The mushroom Galerina marginata, which also produces amatoxins, was used as a model orgasnism for studying cycloamanide biosynthesis due to its culturability. Three enzymes involved in the biosynthesis of cycloamanides were identified in gene knockout studies: a predicted flavin-containing monooxygenase (FMO), P450 monooxygenase, and prolyl oligopeptidase (POP). The gene encoding a specific predicted prolyl oligopeptidase (POPB) was cloned and expressed in Saccharomyces cerevisiae for further characterization, and in vitro studies revealed that the enzyme is bifunctional, catalyzing both a hydrolysis reaction and the key cyclization step in cycloamanide biosynthesis. The utility of POPB as a general catalyst for peptide cyclization was explored by defining its subtrate preferences and limitations. POPB was shown to be highly versatile, catalyzing cyclization of diverse peptide sequences ranging from 8-16 residues in length and sequences containing modified amino acids in addition to the proteinogenic twenty. A method for the use of POPB for the production of combinatorial cyclic peptide libraries is also presented. A total of 100 cyclic peptides, including both novel compounds and bioactive cycloamanides, were produced in these studies and demonstrate the applications of POPB in biotechnology. Copyright by ROBERT MICHAEL SGAMBELLURI 2017 TABLE OF CONTENTS LIST OF TABLES ........................................................................................................... viii LIST OF FIGURES ........................................................................................................... ix KEY TO ABBREVIATIONS .......................................................................................... xiii CHAPTER 1 INTRODUCTION ........................................................................................1 1.1 Cyclic Peptides ................................................................................................2 1.2 Cycloamanides ................................................................................................5 1.3 Ribosomal Biosynthesis of Cycloamanides ....................................................8 WORKS CITED ...................................................................................................11 CHAPTER 2 DETECTION AND PROFILING OF AMATOXINS IN LEPIOTA MUSHROOMS ..................................................................................................................16 2.1 Abstract .........................................................................................................17 2.2 Introduction ...................................................................................................18 2.3 Methods .........................................................................................................21 2.3.1 Mushroom Collection and Identification .........................................21 2.3.2 Toxin Extraction and LCMS ............................................................22 2.4 Results ...........................................................................................................23 2.4.1 Toxins in Amanita and Galerina Mushrooms .................................23 2.4.2 Toxins in Lepiota Mushrooms .........................................................24 2.5 Discussion .....................................................................................................27 APPENDIX ..........................................................................................................28 WORKS CITED ...................................................................................................31 CHAPTER 3 GENOMIC CAPACITY FOR CYCLOAMANIDE BIOSYNTHESIS IN AMANITA MUSHROOMS .........................................................................................34 3.1 Abstract .........................................................................................................35 3.2 Introduction ...................................................................................................36 3.3 Methods .........................................................................................................37 3.3.1 Genomics and Transcriptomics........................................................37 3.3.2 LC/MS/MS of Predicted Cycloamanides.........................................37 3.4 Results ...........................................................................................................39 3.4.1 MSDIN Genes in Amanita bisporigera and A. phalloides ..............39 3.4.2 New Cycloamanides in Amanita phalloides ....................................39 3.5 Discussion .....................................................................................................43 APPENDIX ..........................................................................................................45 WORKS CITED ...................................................................................................49 v CHAPTER 4 CHARACTERIZATION OF AMANITIN BIOSYNTHESIS IN GALERINA MARGINATA ..............................................................................................52 4.1 Abstract .........................................................................................................53 4.2 Introduction ...................................................................................................54 4.3 Methods .........................................................................................................57 4.3.1 Galerina Growth and Toxin Analysis ..............................................57 4.3.2 Galerina Transformation and Gene Knockouts ...............................58 4.3.3 Purification of an Amanitin Intermediate and NMR .......................58 4.3.4 Analysis of Gene Expression by RT-PCR .......................................59 4.4 Results ...........................................................................................................60 4.4.1 Time Course of Amanitin Production ..............................................60 4.4.2 Genes Involved in Amanitin Biosynthesis .......................................61 4.4.3 Role of a P450 Monooxygenase in Amanitin Biosynthesis.............64 4.4.4 Regulation of Biosynthetic Genes ...................................................66 4.5 Discussion .....................................................................................................68 APPENDIX ..........................................................................................................70 WORKS CITED ...................................................................................................78 CHAPTER 5 BIOCHEMICAL CHARACTERIZATION OF PROLYL OLIGOPEPTIDASE B AS A PEPTIDE MACROCYCLASE .........................................81 5.1 Abstract .........................................................................................................82 5.2 Introduction ...................................................................................................83 5.3 Methods .........................................................................................................85 5.3.1 Protein Expression and Purification.................................................85 5.3.2 Enzyme Assays ................................................................................86 5.3.3 Product Purification and NMR Spectroscopy ..................................86 5.4 Results ...........................................................................................................88 5.4.1 Preparation of Recombinant GmPOPB ...........................................88 5.4.2 GmPOPB Catalyzes Peptide Macrocyclization ...............................89
Load more

Recommended publications
  • Relationship Between the Conformation of the Cyclopeptides Isolated from the Fungus Amanita Phalloides (Vaill. Ex Fr.) Secr. and Its Toxicity
    Molecules 2000, 5 489 Relationship Between the Conformation of the Cyclopeptides Isolated from the Fungus Amanita Phalloides (Vaill. Ex Fr.) Secr. and Its Toxicity M.E. Battista, A.A. Vitale and A.B. Pomilio PROPLAME-CONICET, Departamento de Química Orgánica, Facultad de Ciencias Exactas y Natu- rales, Universidad de Buenos Aires, Pabellón 2, Ciudad Universitaria, 1428 Buenos Aires, Argentina E-mail: [email protected] Abstract: The electronic structures and conformational studies of the cyclopeptides, O- methyl-α-amanitin, phalloidin and antamanide, were obtained from molecular parameters on the basis of semiempiric and ab initio methods. Introduction During this century Amanita phalloides - the most toxic fungus known up to now - has been studied from different points of view. This basidiomycete biosynthesizes mono- and bicyclic peptides com- posed of rare amino acids. In order to determine the structure/activity relationships chemical modifica- tions were carried out and the properties of these compounds were evaluated. These results were con- firmed by studying the conformations of three selected compounds representative of the major groups of the macroconstituents of this fungus. Experimental Hyperchem package (HyperCube, version 5.2) was used for semiempirical studies, the molecular geometry being optimized by STO-631G. Net charges were calculated with HyperCube PM3 and the Polack-Ribiere algoritm. GAUSSIAN 98 was used for ab initio studies. Results and Discussion We were interested in obtaining information on the conformations that the cyclic peptides may adopt and about the potential energy maps in order to locate the regions related to the binding to pro- tein molecules, such as F-actin and RNA-polymerase.
    [Show full text]
  • Toxic Fungi of Western North America
    Toxic Fungi of Western North America by Thomas J. Duffy, MD Published by MykoWeb (www.mykoweb.com) March, 2008 (Web) August, 2008 (PDF) 2 Toxic Fungi of Western North America Copyright © 2008 by Thomas J. Duffy & Michael G. Wood Toxic Fungi of Western North America 3 Contents Introductory Material ........................................................................................... 7 Dedication ............................................................................................................... 7 Preface .................................................................................................................... 7 Acknowledgements ................................................................................................. 7 An Introduction to Mushrooms & Mushroom Poisoning .............................. 9 Introduction and collection of specimens .............................................................. 9 General overview of mushroom poisonings ......................................................... 10 Ecology and general anatomy of fungi ................................................................ 11 Description and habitat of Amanita phalloides and Amanita ocreata .............. 14 History of Amanita ocreata and Amanita phalloides in the West ..................... 18 The classical history of Amanita phalloides and related species ....................... 20 Mushroom poisoning case registry ...................................................................... 21 “Look-Alike” mushrooms .....................................................................................
    [Show full text]
  • Sequencing Abstracts Msa Annual Meeting Berkeley, California 7-11 August 2016
    M S A 2 0 1 6 SEQUENCING ABSTRACTS MSA ANNUAL MEETING BERKELEY, CALIFORNIA 7-11 AUGUST 2016 MSA Special Addresses Presidential Address Kerry O’Donnell MSA President 2015–2016 Who do you love? Karling Lecture Arturo Casadevall Johns Hopkins Bloomberg School of Public Health Thoughts on virulence, melanin and the rise of mammals Workshops Nomenclature UNITE Student Workshop on Professional Development Abstracts for Symposia, Contributed formats for downloading and using locally or in a Talks, and Poster Sessions arranged by range of applications (e.g. QIIME, Mothur, SCATA). 4. Analysis tools - UNITE provides variety of analysis last name of primary author. Presenting tools including, for example, massBLASTer for author in *bold. blasting hundreds of sequences in one batch, ITSx for detecting and extracting ITS1 and ITS2 regions of ITS 1. UNITE - Unified system for the DNA based sequences from environmental communities, or fungal species linked to the classification ATOSH for assigning your unknown sequences to *Abarenkov, Kessy (1), Kõljalg, Urmas (1,2), SHs. 5. Custom search functions and unique views to Nilsson, R. Henrik (3), Taylor, Andy F. S. (4), fungal barcode sequences - these include extended Larsson, Karl-Hnerik (5), UNITE Community (6) search filters (e.g. source, locality, habitat, traits) for 1.Natural History Museum, University of Tartu, sequences and SHs, interactive maps and graphs, and Vanemuise 46, Tartu 51014; 2.Institute of Ecology views to the largest unidentified sequence clusters and Earth Sciences, University of Tartu, Lai 40, Tartu formed by sequences from multiple independent 51005, Estonia; 3.Department of Biological and ecological studies, and for which no metadata Environmental Sciences, University of Gothenburg, currently exists.
    [Show full text]
  • A Report on Mushrooms Poisonings in 2018 at the Apulian Regional Poison Center
    Scientific Foundation SPIROSKI, Skopje, Republic of Macedonia Open Access Macedonian Journal of Medical Sciences. 2020 Sep 03; 8(E):616-622. https://doi.org/10.3889/oamjms.2020.4208 eISSN: 1857-9655 Category: E - Public Health Section: Public Health Disease Control A Report on Mushrooms Poisonings in 2018 at the Apulian Regional Poison Center Leonardo Pennisi1, Anna Lepore1, Roberto Gagliano-Candela2*, Luigi Santacroce3, Ioannis Alexandros Charitos1 1Department of Emergency/Urgent, National Poison Center, Azienda Ospedaliero Universitaria Ospedali Riuniti, Foggia, Italy; 2Department of Interdisciplinary Medicine, Forensic Medicine, University of Bari, Bari, Italy; 3Ionian Department, Microbiology and Virology Lab, University of Bari, Bari, Italy Abstract Edited by: Sasho Stoleski BACKGROUND: The “Ospedali Riuniti’s Poison Center” (Foggia, Italy) provides a 24 h telephone consultation in Citation: Pennisi L, Lepore A, Gagliano-Candela R, Santacroce L, Charitos IA. A Report on Mushrooms clinical toxicology to the general public and health-care professionals, including drug information and assessment of Poisonings in 2018 at the Apulian Regional Poison Center. the effects of commercial and industrial chemical substances, toxins but also plants and mushrooms. It participates Open Access Maced J Med Sci. 2020 Sep 03; 8(E):616-622. in diagnosis and treatment of the exposure to toxins and toxicants, also throughout its ambulatory activity. https://doi.org/10.3889/oamjms.2020.4208 Keywords: Poisoning; Intoxication; Epidemiology; Poison center; Mushroom poisoning METHODS: To report data on the epidemiology of mushroom poisoning in people contacting our Poison Center we *Correspondence: Roberto Gagliano-Candela, made computerized queries and descriptive analyses of the medical records database of the mushroom poisoning Department of Interdisciplinary Medicine, Forensic in the poison center of Foggia from January 2018 to December 2018.
    [Show full text]
  • Expansion and Diversification of the MSDIN Family of Cyclic Peptide Genes in the Poisonous Agarics Amanita Phalloides and A
    Pulman et al. BMC Genomics (2016) 17:1038 DOI 10.1186/s12864-016-3378-7 RESEARCHARTICLE Open Access Expansion and diversification of the MSDIN family of cyclic peptide genes in the poisonous agarics Amanita phalloides and A. bisporigera Jane A. Pulman1,2, Kevin L. Childs1,2, R. Michael Sgambelluri3,4 and Jonathan D. Walton1,4* Abstract Background: The cyclic peptide toxins of Amanita mushrooms, such as α-amanitin and phalloidin, are encoded by the “MSDIN” gene family and ribosomally biosynthesized. Based on partial genome sequence and PCR analysis, some members of the MSDIN family were previously identified in Amanita bisporigera, and several other members are known from other species of Amanita. However, the complete complement in any one species, and hence the genetic capacity for these fungi to make cyclic peptides, remains unknown. Results: Draft genome sequences of two cyclic peptide-producing mushrooms, the “Death Cap” A. phalloides and the “Destroying Angel” A. bisporigera, were obtained. Each species has ~30 MSDIN genes, most of which are predicted to encode unknown cyclic peptides. Some MSDIN genes were duplicated in one or the other species, but only three were common to both species. A gene encoding cycloamanide B, a previously described nontoxic cyclic heptapeptide, was also present in A. phalloides, but genes for antamanide and cycloamanides A, C, and D were not. In A. bisporigera, RNA expression was observed for 20 of the MSDIN family members. Based on their predicted sequences, novel cyclic peptides were searched for by LC/MS/MS in extracts of A. phalloides. The presence of two cyclic peptides, named cycloamanides E and F with structures cyclo(SFFFPVP) and cyclo(IVGILGLP), was thereby demonstrated.
    [Show full text]
  • Poisoning Associated with the Use of Mushrooms a Review of the Global
    Food and Chemical Toxicology 128 (2019) 267–279 Contents lists available at ScienceDirect Food and Chemical Toxicology journal homepage: www.elsevier.com/locate/foodchemtox Review Poisoning associated with the use of mushrooms: A review of the global T pattern and main characteristics ∗ Sergey Govorushkoa,b, , Ramin Rezaeec,d,e,f, Josef Dumanovg, Aristidis Tsatsakish a Pacific Geographical Institute, 7 Radio St., Vladivostok, 690041, Russia b Far Eastern Federal University, 8 Sukhanova St, Vladivostok, 690950, Russia c Clinical Research Unit, Faculty of Medicine, Mashhad University of Medical Sciences, Mashhad, Iran d Neurogenic Inflammation Research Center, Mashhad University of Medical Sciences, Mashhad, Iran e Aristotle University of Thessaloniki, Department of Chemical Engineering, Environmental Engineering Laboratory, University Campus, Thessaloniki, 54124, Greece f HERACLES Research Center on the Exposome and Health, Center for Interdisciplinary Research and Innovation, Balkan Center, Bldg. B, 10th km Thessaloniki-Thermi Road, 57001, Greece g Mycological Institute USA EU, SubClinical Research Group, Sparta, NJ, 07871, United States h Laboratory of Toxicology, University of Crete, Voutes, Heraklion, Crete, 71003, Greece ARTICLE INFO ABSTRACT Keywords: Worldwide, special attention has been paid to wild mushrooms-induced poisoning. This review article provides a Mushroom consumption report on the global pattern and characteristics of mushroom poisoning and identifies the magnitude of mortality Globe induced by mushroom poisoning. In this work, reasons underlying mushrooms-induced poisoning, and con- Mortality tamination of edible mushrooms by heavy metals and radionuclides, are provided. Moreover, a perspective of Mushrooms factors affecting the clinical signs of such toxicities (e.g. consumed species, the amount of eaten mushroom, Poisoning season, geographical location, method of preparation, and individual response to toxins) as well as mushroom Toxins toxins and approaches suggested to protect humans against mushroom poisoning, are presented.
    [Show full text]
  • Mushroom Toxicosis in Dogs
    ASK THE EXPERT > EMERGENCY MEDICINE > PEER REVIEWED Mushroom Toxicosis in Dogs Justine A. Lee, DVM, DACVECC, DABT VETgirl Saint Paul, Minnesota You have asked… Mushroom species are difficult to How should mushroom toxicosis be treated in dogs when the identify, so treatment—especially in mushroom can rarely be identified? dogs that scavenge—is based on the presumption that the mushroom is toxic. The expert says… There are thousands of mushroom species in North America, but fewer than 100 are poisonous.1 Mushroom species can be difficult to identify, so treatment, espe- cially in dogs that scavenge, is based on the presumption that the mushroom is 2 toxic. The following focuses on types of mushrooms that can result in poisoning Mushroom Toxicity Cases in dogs (Tables 1 and 2, next page). In the past 10 years, the ASPCA Animal Hepatotoxic Cyclopeptides Poison Control Center had almost The most dangerous type of mushrooms contain hepatotoxic cyclopeptides, includ- 5000 mushroom cases reported, ing amatoxins (most toxic), phallotoxins, and virotoxins. These include Amanita involving 4561 dogs, 77 cats, 7 birds, 7 phalloides (death cap or death angel), A ocreata (angel of death), Galerina spp, and goats, 3 ferrets, 3 rabbits, 1 marsupial, Lepiota spp. This class of mushroom results in 95% of mushroom-related fatalities and 1 pig.3 Death was reported in 23 5 in humans and the most fatalities worldwide. When ingested, amatoxins are taken animals (0.49%). In the cases where up by hepatocytes via the sodium-dependent transport system and inhibit nuclear the animal survived, the type of mush- RNA polymerase II, which results in decreased protein synthesis and secondary room was unknown at the time of the 5 cell death.
    [Show full text]
  • Poisonous Mushrooms; a Review of the Most Common Intoxications A
    Nutr Hosp. 2012;27(2):402-408 ISSN 0212-1611 • CODEN NUHOEQ S.V.R. 318 Revisión Poisonous mushrooms; a review of the most common intoxications A. D. L. Lima1, R. Costa Fortes2, M. R.C. Garbi Novaes3 and S. Percário4 1Laboratory of Experimental Surgery. University of Brasilia-DF. Brazil/Paulista University-DF. Brazil. 2Science and Education School Sena Aires-GO/University of Brasilia-DF/Paulista University-DF. Brazil. 3School of Medicine. Institute of Health Science (ESCS/FEPECS/SESDF)/University of Brasilia-DF. Brazil. 4Institute of Biological Sciences. Federal University of Pará. Brazil. Abstract HONGOS VENENOSOS; UNA REVISIÓN DE LAS INTOXICACIONES MÁS COMUNES Mushrooms have been used as components of human diet and many ancient documents written in oriental coun- Resumen tries have already described the medicinal properties of fungal species. Some mushrooms are known because of Las setas se han utilizado como componentes de la their nutritional and therapeutical properties and all over dieta humana y muchos documentos antiguos escritos en the world some species are known because of their toxicity los países orientales se han descrito ya las propiedades that causes fatal accidents every year mainly due to medicinales de las especies de hongos. Algunos hongos misidentification. Many different substances belonging to son conocidos por sus propiedades nutricionales y tera- poisonous mushrooms were already identified and are péuticas y de todo el mundo, algunas especies son conoci- related with different symptoms and signs. Carcino- das debido a su toxicidad que causa accidentes mortales genicity, alterations in respiratory and cardiac rates, cada año, principalmente debido a errores de identifica- renal failure, rhabidomyolisis and other effects were ción.
    [Show full text]
  • Amanita Phalloides Poisoning: Mechanisms of Toxicity and Treatment
    Food and Chemical Toxicology 86 (2015) 41–55 Contents lists available at ScienceDirect Food and Chemical Toxicology journal homepage: www.elsevier.com/locate/foodchemtox Review Amanita phalloides poisoning: Mechanisms of toxicity and treatment Juliana Garcia a,∗, Vera M. Costa a, Alexandra Carvalho b, Paula Baptista c,PaulaGuedesde Pinho a, Maria de Lourdes Bastos a, Félix Carvalho a,∗∗ a UCIBIO-REQUIMTE, Laboratory of Toxicology, Department of Biological Sciences, Faculty of Pharmacy, University of Porto, Rua José Viterbo Ferreiran° 228, 4050-313 Porto, Portugal b Department of Cell and Molecular Biology, Computational and Systems Biology, Uppsala University, Biomedical Center, Box 596, 751 24 Uppsala, Sweden c CIMO/School of Agriculture, Polytechnique Institute of Bragança, Campus de Santa Apolónia, Apartado 1172, 5301-854 Bragança, Portugal article info abstract Article history: Amanita phalloides, also known as ‘death cap’, is one of the most poisonous mushrooms, being involved Received 10 April 2015 in the majority of human fatal cases of mushroom poisoning worldwide. This species contains three main Received in revised form 8 September 2015 groups of toxins: amatoxins, phallotoxins, and virotoxins. From these, amatoxins, especially α-amanitin, Accepted 10 September 2015 are the main responsible for the toxic effects in humans. It is recognized that α-amanitin inhibits RNA Available online 12 September 2015 polymerase II, causing protein deficit and ultimately cell death, although other mechanisms are thought Keywords: to be involved. The liver is the main target organ of toxicity, but other organs are also affected, especially Amanita phalloides the kidneys. Intoxication symptoms usually appear after a latent period and may include gastrointestinal Amatoxins disorders followed by jaundice, seizures, and coma, culminating in death.
    [Show full text]
  • A. Phalloides Intoxication
    Combination therapy of benzylpenicillin IV and silybin IV vs. monotherapy of benzylpenicillin IV or silybin IV in the treatment of A. phalloides intoxication University of Groningen Mentor: S. Notenboom Student: Anne Kamphuis, S2995727 Abstract Amanita phalloides mushroom poisoning is a rare but serious occurrence, which seems to have the highest frequency in Europe. The phalloides syndrome is hard to recognize and institution of an effective treatment as soon as possible is important in order to avoid fatal complications. Since the occurrence of the poisoning is rare, there is not many known about effective treatments. The aim of this thesis is to decide whether combination therapy of benzylpenicillin IV and silybin IV is more effective against Amanita phalloides poisoning than intravenous monotherapy of these drugs. Comparing clinical studies and in vitro studies from European countries, it seems that silybin IV is the most effective therapy. Contents Abstract ................................................................................................................................................................... 2 1. Introduction ............................................................................................................................................... 4 1.1. Amanita phalloides: biology and appearance in Europe ................................................................... 4 1.1.1. Phallotoxins: characteristics and toxicology ....................................................................................
    [Show full text]
  • Interactions Between Drugs and Chemicals in Industrial Societies. G.L
    © 1987 Elsevier Science Publishers B.V. (Biomedical Division) Interactions between drugs and chemicals in industrial societies. G.L. Plaa, P. du Souich, S. Erill, editors. 255 NEW TRENDS IN MUSHROOM POISONING THEODOR WIELAND Max-Planck-Institut fur medizinische Forschung, Jahnstr. 29 D-6900 Heidelberg (FRG) Among the naturally growing products, mushrooms are suspected to be the most poisonous ones. Some people would not eat any mushrooms; the majority is cautious, and consume only a few species confirmed as absolutely innocuous, although the number of edible mushrooms is much greater than it is commonly assumed. The term "poisonous" is a matter of definition. If one defines a substance as poisonous that after ingestión causes transcient irritation of the stomach abdominal pain, nausea and diarrhea then a considreable number of mushrooms are toxic. If one, however, defines a poison as a substance that, in relatively small amounts, can lead to death, only a few species exist that must be designated poisonous fungi. 95% of all lethal intoxications by ingestión are caused by specimens of the genus Amanita. Before treating the important chapter of mushroom poisoning, I would like to mention those species that in rare cases have been reported to have caused death of patients. A. most recent, amply illustrated treatise on poisonous mushrooms has been compiled by Besl and Bresinzki (1). Traditionally, fatal toxicity has been attributed to the red fly-agaric, Amanita muscaria, the mushroom of fairy tales. The reason for this is perhaps the observation that houseflies that suckled enough of the sweetened sap of the mushroom lost their mobility and eventually died.
    [Show full text]
  • Coherent Two Dimensional Infrared Spectroscopy of a Cyclic Decapeptide Antamanide
    J. Phys. Chem. B 2008, 112, 12479–12490 12479 Coherent Two Dimensional Infrared Spectroscopy of a Cyclic Decapeptide Antamanide. A Simulation Study of the Amide-I and A Bands Cyril Falvo, Tomoyuki Hayashi, Wei Zhuang, and Shaul Mukamel* Department of Chemistry, UniVersity of CaliforniasIrVine, IrVine, California ReceiVed: February 19, 2008; ReVised Manuscript ReceiVed: June 19, 2008 The two-dimensional infrared photon echo spectrum of Antamanide (-1Val-2Pro-3Pro-4Ala-5Phe-6Phe-7Pro- 8Pro-9Phe-10Pro-) in chloroform is calculated using an explicit solvent molecular dynamics (MD) simulation combined with a density functional theory (DFT) map for the effective vibrational Hamiltonian. Evidence for a strong intramolecular hydrogen bonding network is found. Comparison with experimental absorption allows the identification of the dominant conformation. Multidimensional spectroscopy reveals intramolecular couplings and gives information on its dynamics. A two-color amide-I and amide-A crosspeak is predicted and analyzed in terms of local structure. 1. Introduction Understanding the structure and folding dynamics of peptides in solution is an important challenge. 2D-NMR techniques introduced in the 1970s are an important structure determination tool with a microsecond time resolution.1,2 A large number of experimental and theoretical studies have been devoted to the development of femtosecond multidimensional techniques in the infrared, visible, and ultraviolet regions.3-11 In a 2D-IR photon echo experiment, three femtosecond pulses with wavevectors k1, k2, and k3 interact with the molecule to generate a coherent signal which is heterodyne detected in the direction kI )-k1 + k2 + k3 (see Figure 1). The signal is recorded as a function of the three time delays between pulses.11 2D-IR spectroscopy probes high frequency vibrations.
    [Show full text]