DOCSLIB.ORG

Antimicrobial Activity of Halogens

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Antimicrobial Activity of Halogens 608 Journal o(Food Protection, Vol. 44, No.8, Pages 608-613 (August 1981) Copyright©, International Association of Milk, Food, and Environmental Sanitarians Antimicrobial Activity of Halogens THERON E. ODLAUG TravenolLaboratories, Inc., Morton Grove, Illinois 60053 (Received for publication June 19, 1980) ABSTRACT agents to various degrees. The mode of action of chlorine The bactericidal and sporicidal effects of halogens are as an antimicrobial agent has not been fully determined, Downloaded from http://meridian.allenpress.com/jfp/article-pdf/44/8/608/1654444/0362-028x-44_8_608.pdf by guest on 30 September 2021 reviewed. Chlorine and iodine are the halogens most widely although a number of theories have been presented. used for inactivating microorganisms. Compounds containing There seems to be general agreement that hypochlorous chlorine and iodine are, in general, equally effective in acid (HOCI) is the most active form. destroying vegetative cells, but chlorine compounds are more When liquid chlorine (C1 2) and hypochlorites are effective in inactivating spores. These relationships are added to water, they hydrolyze to form hypochlorous illustrated graphically from the data available in the literature. acid. In water, hypochlorous acid will dissociate to form hydrogen ion (H + ) and hypochlorite ion (OCl - ) as shown below. The halogens include the following group of Cl 2 + H 20 HOC! + H + + Cl - nonmetallic elements: chlorine, iodine, fluorine and Ca(OClh + 2Hp---+ Ca(OHh + 2HOCI bromine. There have been numerous studies of the HOC! ~ H+ + OCI- antimicrobial effects of these agents. The relative proportion of hypochlorous acid to Fluorine, a highly toxic element, is an irritant and is hypochlorite ion is dependent on pH, temperature and highly corrosive. There are few reports of the use of this ionic strength (27). Chlorine compounds are more halogen as an antimicrobial agent. Bromine, also very effective at lower pH values where the presence of toxic, has been used occasionally in water treatment hypochlorous acid is dominant. At higher pH values, the programs. Chlorine and iodine are the most widely used hypochlorite ion (OCl - ). not effective as an antimicro­ halogens (1 3). Therefore, most of the information in this bial agent, predominates. In contrast, chlorine dioxide report is for these two halogens. does not hydrolyze in aqueous solutions, and the intact The antimicrobial effectiveness of each halogen molecule is considered to be the active agent. compound varies with such factors as availability of the A number of theories have been proposed to explain element to react with the cell populations, pH. how chlorine inactivates cells. Initially, researchers concentration, contact time, temperature, organic matter thought that the formation of toxic N-chloro compounds. and the type and form of microorganism. In addition, inhibition of glucose oxidation, or oxidation of sulfbydryl different methods of evaluation produce different results, groups were responsible for its effect. Freiberg (14.15), making comparisons difficult in some instances. The using radioactive 35Cl, found that all free available objective of this paper is to review some of the available chlorine but not combined chlorine was taken up by the data on the effectiveness of various halogen compounds vegetative cell. He concluded that the first contact in destroying bacterial cells and spores in suspensions. oxidation reaction with the microbe results in activity, and to develop some empirical relationships from these and that formation of chloramines in the cell protoplasm data. does not cause initial destruction. Using 32 P, Freiberg also showed that, in the presence of chlorine. there is a CHLORINE destructive permeability change in the bacterial cell Chlorine has been used for many years in the home as membrane. Recently, Camper and McFeters (7) showed well as in food. drug and other industries. Some typical that chlorine impairs membrane function, especially uses are treatment of drinking water, waste water transport of extracellular nutrients, and that chlorine­ treatment programs, sanitizing equipment and surfaces treated cells were unable to take up labeled carbo­ and treatment of foods such as poultry (25) and sea food hydrates and amino acids. (16). Chlorine compounds have also been used widely in Wyatt and Waites (40) have suggested that chlorine­ the health industry for controlling microorganisms. releasing compounds stimulate spore germination and There are five major groups of chlorine compounds: then inactivate the germinated spore. Kulikovsky et al. (a) liquid chlorine, (b) hypochlorites. (c) inorganic (21) showed that chlorine alters the spore permeability chloramines, (d) organic chloramines and (e) chlorine through changes in the integument, resulting in release dioxide. All of these compounds are active antimicrobial ofCa + 2• DPA. RNA and DNA. JOURNAL OF FOOD PROTECTION. VOL. 44. AUGUST 1981 ANTIMICROBIAL ACTIVITY OF HALOGENS 609 Benarde et al. (J), using chlorine dioxide and labeled TABLE 2. Inactivation ofBacillus spores by hypochloritesa. 14C amino acids, showed that, for Escherichia coli, the mechanism of action is disruption of protein synthesis. However, they did not determine the level of activity at Time fora FACC 90%reduc· which protein synthesis is disrupted. Organismb pH (ppm) tion (min) B. cereus (10) 6.5 so 1.5 Hypochlorites B. cereus (38) 7.0 100 0.9 Hypochlorites are the most widely used chlorine B. coagulans (24) 6.8 20 6 compounds, with calcium and sodium hypochlorite the B. macerans (26) 7.0 15 6.4 major compounds, in this group. These agents are very B. metiens (32) 7.0 25 1.8 effective in inactivating bacterial cells in aqueous B. subtilis (5) 7.2 2.5-2.6 20.5 suspensions, requiring short contact times. A summary B. subtilis (8) 7.0 1000 0.12 of some published data for the antimicrobial etTective­ B. stearothermophilus (8) 7.0 1000 1 Downloaded from http://meridian.allenpress.com/jfp/article-pdf/44/8/608/1654444/0362-028x-44_8_608.pdf by guest on 30 September 2021 ness of sodium hypochlorite is shown in Table 1. Because aTests were done with NaOCI or CaOCI in water or buffer at the experimental methods vary from study to study, only 20-25 c. general statements can be made about these data. All of bReferences are in parentheses after species name. the microorganisms indicated are very sensitive to CfAC =free available chlorine. chlorine. There is a 90 o/o reduction in cell population for TABLE 3. Inactivation of Clostridium spores by hypo· most of the organisms in less than 10 sec with relatively chloritesa. low levels of free available chlorine (FAC). Because the inactivation of vegetative cells in chlorine is very rapid, it is difficult to make meaningful comparisons between Time tor a organisms. However, Vibrio parahaemolyticus, Pseudo­ FACe 90% reduc· monas aeruginosa and Bacillus cereus cells appear to be Organismb pH (ppm) tion (min) more resistant than the other organisms. C. botulinum · Type A (18) 6.sd 4.5 2 TABLE 1. Inactivation of bacterial cells by sodium hypo· C. botulinium · chloritea. Type E (18) 6.5 4.5 0.9 C. perfringens (11) 8.3e 5 >30 C. bifermentans (11) 8.3 5 4.5 Time fora C. sporogenes (11) 8.3 5 8.5 FACe 90%reduc· Organismb pH (ppm) tion (sec) aTests were done with N aOCI in buffer or water. bReferences are in parentheses after species name. S. derby (28) 7.2 12.5 1.5 CfAC =free available chlorine. E. coli (1 7) 8.5 3 2.7 dTest temperature 25 C. E. coli (37) 7.1 1 30 eTesttemperature 10 C. E. coli (30) 7.5 0.6 <6 E. coli (28) 7.9 12.5 3.5 S.foecalis (30) 7.5 0.6 11.9 Figure 1 shows the empirical relationship of the time S. lactis (17) 8.4 6 3.5 required for a 90%reduction in Bacillus and Clostridium L. plantarum (1 7) 5.0 6 3.4 spores versus chlorine concentration as developed by P. cerevisiae (17) 8.5 6 7.1 Odlaug and Pflug (29) from the available literature. They V. parahaemolyticus (16) 7.0 13 15 calculated the amount of hypochlorous acid based on the P. aeruginosa (37) 8.0 2 7.5 FAC and pH for each data set to enable comparison of B. cereus (38) 7.0 5 "-100 results from different investigations. aTests were done in distilled water, hard water or a buffer If we disregard data for Bacillus stearothermophilus. solution at 20-25 C. then for both Bacillus and Clostridium spores at the low bReferences are in parentheses after species name. effective HOC! concentration, the logarithm of the time CfAC free available chlorine. for a 90% microbial cell reduction is a linear function of the logarithm of the HOCl concentration. As the HOCl Compared to vegetative cells, bacterial spores are very concentration increases (to where the time for a 90% resistant to the hypochlorites. In Table 2, some data on microbial cell reduction is 1 to 2 min.), the rate of resistance of spores to chlorine are summarized. The microbial cell destruction increases. The lines drawn in time required for a 90% reduction in cell population is Fig. 1 represent the general conditions for destruction of longer (minutes opposed to seconds) and the concentra­ Bacillus and Clostridium spores. tion of free available chlorine needed for inactivation is Figure 2 was prepared to illustrate the large differ­ higher than specified for vegetative cells. Similar data for ences in resistance between vegetative cells and spores. Clostridium spores are presented in Table 3. Clostridium The vegetative cell data in Fig. 3 were taken from spores are not as resistant as Bacillus spores. Table 1 after the hypochlorous acid concentration was JOURNAL OF FOOD PROTECTION. VOL. 44, AUGUST 1981 610 ODLAUG 0000~ 100 ":;.. a; I" .0 e E .!::! z= 10 70 10 :; e C. botulinum· Type A .E Q.
Load more

Recommended publications
  • Suppression Mechanisms of Alkali Metal Compounds
    SUPPRESSION MECHANISMS OF ALKALI METAL COMPOUNDS Bradley A. Williams and James W. Fleming Chemistry Division, Code 61x5 US Naval Research Lnhoratory Washington, DC 20375-5342, USA INTRODUCTION Alkali metal compounds, particularly those of sodium and potassium, are widely used as fire suppressants. Of particular note is that small NuHCOi particles have been found to be 2-4 times more effective by mass than Halon 1301 in extinguishing both eountertlow flames [ I] and cup- burner flames [?]. Furthermore, studies in our laboratory have found that potassium bicarbonate is some 2.5 times more efficient by weight at suppression than sodium bicarhonatc. The primary limitation associated with the use of alkali metal compounds is dispersal. since all known compounds have very low volatility and must he delivered to the fire either as powders or in (usually aqueous) solution. Although powders based on alkali metals have been used for many years, their mode of effective- ness has not generally been agreed upon. Thermal effects [3],namely, the vaporization of the particles as well as radiative energy transfer out of the flame. and both homogeneous (gas phase) and heterogeneous (surface) chemistry have been postulated as mechanisms by which alkali metals suppress fires [4]. Complicating these issues is the fact that for powders, particle size and morphology have been found to affect the suppression properties significantly [I]. In addition to sodium and potassium, other alkali metals have been studied, albeit to a consider- ably lesser extent. The general finding is that the suppression effectiveness increases with atomic weight: potassium is more effective than sodium, which is in turn more effective than lithium [4].
    [Show full text]
  • The Development of the Periodic Table and Its Consequences Citation: J
    Firenze University Press www.fupress.com/substantia The Development of the Periodic Table and its Consequences Citation: J. Emsley (2019) The Devel- opment of the Periodic Table and its Consequences. Substantia 3(2) Suppl. 5: 15-27. doi: 10.13128/Substantia-297 John Emsley Copyright: © 2019 J. Emsley. This is Alameda Lodge, 23a Alameda Road, Ampthill, MK45 2LA, UK an open access, peer-reviewed article E-mail: [email protected] published by Firenze University Press (http://www.fupress.com/substantia) and distributed under the terms of the Abstract. Chemistry is fortunate among the sciences in having an icon that is instant- Creative Commons Attribution License, ly recognisable around the world: the periodic table. The United Nations has deemed which permits unrestricted use, distri- 2019 to be the International Year of the Periodic Table, in commemoration of the 150th bution, and reproduction in any medi- anniversary of the first paper in which it appeared. That had been written by a Russian um, provided the original author and chemist, Dmitri Mendeleev, and was published in May 1869. Since then, there have source are credited. been many versions of the table, but one format has come to be the most widely used Data Availability Statement: All rel- and is to be seen everywhere. The route to this preferred form of the table makes an evant data are within the paper and its interesting story. Supporting Information files. Keywords. Periodic table, Mendeleev, Newlands, Deming, Seaborg. Competing Interests: The Author(s) declare(s) no conflict of interest. INTRODUCTION There are hundreds of periodic tables but the one that is widely repro- duced has the approval of the International Union of Pure and Applied Chemistry (IUPAC) and is shown in Fig.1.
    [Show full text]
  • Elemental Fluorine Product Information (Pdf)
    Elemental Fluorine Contents 1 Introduction ............................................................................................................... 4 2.1 Technical Application of Fluorine ............................................................................. 5 2.2 Electronic Application of Fluorine ........................................................................... 7 2.3 Fluorine On-Site Plant ............................................................................................ 8 3 Specifications ............................................................................................................ 9 4 Safety ...................................................................................................................... 10 4.1 Maintenance of the F2 system .............................................................................. 12 4.2 First Aid ................................................................................................................ 13 5.1 Chemical Properties ............................................................................................. 14 5.2 Physical Data ....................................................................................................... 15 6 Toxicity .................................................................................................................... 18 7 Shipping and Transport ........................................................................................... 20 8 Environment ...........................................................................................................
    [Show full text]
  • Chemical Behavior of Iodine-131 During the SRE Fuel Element
    Chemical Behavior of Iodine- 13 1 during SRE Fuel Element Damage in July 1959 Response to Plaintiffs Expert Witness Arjun Makhijani by Jerry D. Christian, Ph.D. Prepared for in re Boeing Litigation May 26,2005 Background of Jerry D. Christian Education: B. S. Chemistry, University of Oregon, 1959. Ph. D. Physical Chemistry, University of Washington, 1965 - Specialty in Chemical Thermodynamics and Vaporization Processes of Halogen Salts. (Iodine is a halogen.) Postdoctoral: National Research Council Senior Research Associate, NASA Ames Research Center, Moffett Field, CAY1972-1974. Career Summary: Scientific Fellow, Retired from Idaho National Engineering and Environmental Laboratory (INEEL), September 2001. Scientific Fellow is highest achievable technical ladder position at INEEL; charter member, appointed in January 1987. Consultant and President of Electrode Specialties Company since retirement. Affiliate Professor of Chemistry, University of Idaho; I teach a course in nuclear fuel reprocessing. Referee for Nuclear Technology and Talanta journals; I review submitted technical manuscripts for the editors for scientific and technical validity and accuracy.* I have thirty nine years experience in nuclear waste and fuel processing research and development. Included in my achievements is development of the highly successful classified Fluorine1 Dissolution Process for advanced naval fuels that was implemented in a new $250 million facility at the ICPP in the mid-1980s. Career interests and accomplishments have been in the areas of nuclear
    [Show full text]
  • Investigation of Silver Nitrate–Impregnated Alumina As an Alternative Iodine Sorbent
    University of Tennessee, Knoxville TRACE: Tennessee Research and Creative Exchange Masters Theses Graduate School 12-2018 Investigation of Silver Nitrate–Impregnated Alumina as an Alternative Iodine Sorbent Jacob A. Jordan University of Tennessee Follow this and additional works at: https://trace.tennessee.edu/utk_gradthes Recommended Citation Jordan, Jacob A., "Investigation of Silver Nitrate–Impregnated Alumina as an Alternative Iodine Sorbent. " Master's Thesis, University of Tennessee, 2018. https://trace.tennessee.edu/utk_gradthes/5346 This Thesis is brought to you for free and open access by the Graduate School at TRACE: Tennessee Research and Creative Exchange. It has been accepted for inclusion in Masters Theses by an authorized administrator of TRACE: Tennessee Research and Creative Exchange. For more information, please contact [email protected]. To the Graduate Council: I am submitting herewith a thesis written by Jacob A. Jordan entitled "Investigation of Silver Nitrate–Impregnated Alumina as an Alternative Iodine Sorbent." I have examined the final electronic copy of this thesis for form and content and recommend that it be accepted in partial fulfillment of the equirr ements for the degree of Master of Science, with a major in Nuclear Engineering. Howard Hall, Major Professor We have read this thesis and recommend its acceptance: John D. Auxier II, Steven Skutnik Accepted for the Council: Dixie L. Thompson Vice Provost and Dean of the Graduate School (Original signatures are on file with official studentecor r ds.) Investigation of Silver Nitrate–Impregnated Alumina as an Alternative Iodine Sorbent A Thesis Presented for the Master of Science Degree The University of Tennessee, Knoxville Jacob A.
    [Show full text]
  • Effects of Various Fluorine Compounds on the Albino Rat
    University of Tennessee, Knoxville TRACE: Tennessee Research and Creative Exchange Masters Theses Graduate School 8-1948 Effects of Various Fluorine Compounds on the Albino Rat Robert Floyd Pevahouse University of Tennessee - Knoxville Follow this and additional works at: https://trace.tennessee.edu/utk_gradthes Part of the Animal Sciences Commons Recommended Citation Pevahouse, Robert Floyd, "Effects of Various Fluorine Compounds on the Albino Rat. " Master's Thesis, University of Tennessee, 1948. https://trace.tennessee.edu/utk_gradthes/3073 This Thesis is brought to you for free and open access by the Graduate School at TRACE: Tennessee Research and Creative Exchange. It has been accepted for inclusion in Masters Theses by an authorized administrator of TRACE: Tennessee Research and Creative Exchange. For more information, please contact [email protected]. To the Graduate Council: I am submitting herewith a thesis written by Robert Floyd Pevahouse entitled "Effects of Various Fluorine Compounds on the Albino Rat." I have examined the final electronic copy of this thesis for form and content and recommend that it be accepted in partial fulfillment of the requirements for the degree of Master of Science, with a major in Animal Science. Charles S. Hobbs, Major Professor We have read this thesis and recommend its acceptance: Sam L. Hansard, Marshall C. Hervey, & Ollia E. Goff Accepted for the Council: Carolyn R. Hodges Vice Provost and Dean of the Graduate School (Original signatures are on file with official studentecor r ds.) · June 17, 1948 To the Committee on Graduate Study : I am submitting to you a thesis written by Robert Floyd Pevahouse entitle d "Effects of Various Fluorine Comp ounds on the Albino Rat ." I rec ommend that it be accepted for nine quarter hours credit in partial fulfillment of the requirements for the degree of Mas ter of Science, with a major in Animal Husbandry.
    [Show full text]
  • Iodine Chlorine and Quaternary Ammonium Are Common Examples Of
    Iodine Chlorine And Quaternary Ammonium Are Common Examples Of How undiverted is Eduard when frivolous and loricate Dwain discerns some undertones? Variolate Kirk mussitate or hobnobbing some transcription aphoristically, however pachydermatous Henrie teazel unmeritedly or generalized. Hyperaemic Isaac dramatises yea. Since the basin and speed up in a long as scalpels, and biology and in the temperatures, ammonium are chlorine and iodine quaternary ammonium compounds using soap is Now a significant antimicrobial agents may be inferred that the age and rubber stopper, the appropriate contact with quaternary ammonium are chlorine and of iodine is truly drying. Wash concentrate off and procedures or ammonium are chlorine of iodine and quaternary ammonium salt praepragem wb, totally remove heavy deposits and your hands are. CH 10 FOODS Flashcards Quizlet. This is an understanding of the difference between sanitizing efficiency, common examples and are chlorine of iodine quaternary ammonium compound, etc that will not the selectivity in? Quaternary Ammonium Compounds Quats A top set for disinfection in hospital. Background and mechanisms and acid sulfate, ammonium are chlorine and of iodine quaternary ammonium compounds, as spores to achieve the size. Department of spores and acute centrilobular hepatic necrosis and may at least once denatured, quaternary ammonium are chlorine of iodine and common examples of disinfection, iodine for cleaning. For various purposes only be removed from the surface of a restaurant tables to the pyrex measuring cups are now far the surviving bacteria and iodine chlorine quaternary are of disinfectants. Uses of clostridial spores would decompose already present heterogeneous sensing scheme allows some tested once your car if items such diseases of iodine and chlorine quaternary ammonium are.
    [Show full text]
  • IODINE Its Properties and Technical Applications
    IODINE Its Properties and Technical Applications CHILEAN IODINE EDUCATIONAL BUREAU, INC. 120 Broadway, New York 5, New York IODINE Its Properties and Technical Applications ¡¡iiHiüíiüüiütitittüHiiUitítHiiiittiíU CHILEAN IODINE EDUCATIONAL BUREAU, INC. 120 Broadway, New York 5, New York 1951 Copyright, 1951, by Chilean Iodine Educational Bureau, Inc. Printed in U.S.A. Contents Page Foreword v I—Chemistry of Iodine and Its Compounds 1 A Short History of Iodine 1 The Occurrence and Production of Iodine ....... 3 The Properties of Iodine 4 Solid Iodine 4 Liquid Iodine 5 Iodine Vapor and Gas 6 Chemical Properties 6 Inorganic Compounds of Iodine 8 Compounds of Electropositive Iodine 8 Compounds with Other Halogens 8 The Polyhalides 9 Hydrogen Iodide 1,0 Inorganic Iodides 10 Physical Properties 10 Chemical Properties 12 Complex Iodides .13 The Oxides of Iodine . 14 Iodic Acid and the Iodates 15 Periodic Acid and the Periodates 15 Reactions of Iodine and Its Inorganic Compounds With Organic Compounds 17 Iodine . 17 Iodine Halides 18 Hydrogen Iodide 19 Inorganic Iodides 19 Periodic and Iodic Acids 21 The Organic Iodo Compounds 22 Organic Compounds of Polyvalent Iodine 25 The lodoso Compounds 25 The Iodoxy Compounds 26 The Iodyl Compounds 26 The Iodonium Salts 27 Heterocyclic Iodine Compounds 30 Bibliography 31 II—Applications of Iodine and Its Compounds 35 Iodine in Organic Chemistry 35 Iodine and Its Compounds at Catalysts 35 Exchange Catalysis 35 Halogenation 38 Isomerization 38 Dehydration 39 III Page Acylation 41 Carbón Monoxide (and Nitric Oxide) Additions ... 42 Reactions with Oxygen 42 Homogeneous Pyrolysis 43 Iodine as an Inhibitor 44 Other Applications 44 Iodine and Its Compounds as Process Reagents ...
    [Show full text]
  • Iodine Fact Sheet & References
    Iodine Fact Sheet and References What is iodine? • Essential trace mineral • Critical in the synthesis of thyroid hormones. The thyroid gland converts iodine into T3 (triiodothyronine) and T4 (thyrodine) hormones, which control metabolism throughout the body. • Excreted through urine Where do we find iodine? • Table salt (iodized salt) – Beginning in the 1920s, iodine was added to table salt and to other foods to prevent iodine deficiency. • Seafood and seaweed • Dairy and grains (amounts vary depending on source) Who’s impacted? • 2.2 billion people worldwide are at risk for Iodine Deficiency Disorders (IDDs). Of these, 30-70% have goiter and 1-10% have cretinism. • People living in the Great Lakes region (including Minnesota) may have inadequate intake due to low levels of iodine in the soil in which crops are grown. • Iodine deficiency virtually eliminated in the U.S. and many Western nations, due to iodization of salt. However: o 1970s-1990s: median U.S. urinary iodine (UI) excretion fell 50%, indicating indicate intake, and possible increased risk for moderate IDD. Experts thought this might be attributable to a decreased intake of salt; removal of iodate conditioners in store-bought breads; and an increased use of non-iodized salt in manufactured or premade convenience foods o 2001-2002 NHANES data indicated that levels had stabilized. Even so, women of reproductive age consistently had the lowest UI levels. • Women of reproductive age are an important group to monitor: o Pregnant women are vulnerable to iodine deficiency due to an increased renal clearance of iodine and transfer of iodine to fetus. o Iodine supplementation during pregnancy is often delayed, because women are unaware they are pregnant during early weeks of gestation.
    [Show full text]
  • Investigation of Supramolecular Assemblies Based on De Novo Coiled Coil Peptidic Scaffolds
    Investigation of supramolecular assemblies based on de novo coiled coil peptidic scaffolds Inaugural-Dissertation To obtain the academic degree Doctor rerum naturalium (Dr. rer. nat) Submitted to the Department of Biology, Chemistry and Pharmacy of Freie Universität Berlin by Ana Rita de Lima Fernandes First reviewer: Prof. Dr. Beate Koksch (Freie Universität Berlin) Second reviewer: Prof. Dr. Kevin Pagel (Freie Universität Berlin) Disputation: 17.09.2019 iii Declaration This PhD thesis was carried out from April 2015 to April 2019 under supervision of Prof. Dr. Beate Koksch at the Institute of Chemistry and Biochemistry in the Department of Biology, Chemistry and Pharmacy of Freie Universität Berlin. I declare that this PhD thesis was prepared autonomously. Third party content, quotes or images are referred to the original work. Additional contributions are: ▪ Electron microscopy studies were acquired by PD Dr. Christoph Böttcher and Dorian Mikolajczak at the BioSupraMol core facility of Freie Universität Berlin (Germany). ▪ UV-vis absorbance and fluorescence studies were performed in collaboration with Dr. Hans von Berlepsch. ▪ Infrared nano-spectroscopy were performed by Katerina Kanevche and Emanuel Pfitzner from the Department of Physics, Freie Universität Berlin, Arnimallee 14, 14195 Berlin. ▪ Computational modelling was performed by Natalia Ernst and PD Dr. Marcus Weber from the Zuse Institute Berlin (ZIB), Takustrasse 7, 14195 Berlin. ▪ 19F MRI was performed by Dr. Sonia Waiczies and Dr. Min-Chi Ku from the Berlin Ultrahigh Field Facility, Max Delbrück Center for Molecular Medicine, Berlin, Germany. v Publications Vukelić, S., Moschner, J., Huhmann, S., Fernandes, R., Berger, A.A., and Koksch, B., Synthesis of side-chain fluorinated amino acids and their effects on the properties of peptides and proteins, in Modern Synthesis Processes and Reactivity of Fluorinated Compounds: Progress in Fluorine Science, 1st Ed., 2016.
    [Show full text]
  • Subchapter B—Food for Human Consumption (Continued)
    SUBCHAPTER B—FOOD FOR HUMAN CONSUMPTION (CONTINUED) PART 170—FOOD ADDITIVES 170.106 Notification for a food contact sub- stance formulation (NFCSF). Subpart A—General Provisions Subpart E—Generally Recognized as Safe Sec. (GRAS) Notice 170.3 Definitions. 170.203 Definitions. 170.6 Opinion letters on food additive sta- 170.205 Opportunity to submit a GRAS no- tus. tice. 170.10 Food additives in standardized foods. 170.210 How to send your GRAS notice to 170.15 Adoption of regulation on initiative FDA. of Commissioner. 170.215 Incorporation into a GRAS notice. 170.17 Exemption for investigational use 170.220 General requirements applicable to a and procedure for obtaining authoriza- GRAS notice. tion to market edible products from ex- 170.225 Part 1 of a GRAS notice: Signed perimental animals. statements and certification. 170.18 Tolerances for related food additives. 170.230 Part 2 of a GRAS notice: Identity, 170.19 Pesticide chemicals in processed method of manufacture, specifications, foods. and physical or technical effect. Subpart B—Food Additive Safety 170.235 Part 3 of a GRAS notice: Dietary ex- posure. 170.20 General principles for evaluating the 170.240 Part 4 of a GRAS notice: Self-lim- safety of food additives. iting levels of use. 170.22 Safety factors to be considered. 170.245 Part 5 of a GRAS notice: Experience 170.30 Eligibility for classification as gen- based on common use in food before 1958. erally recognized as safe (GRAS). 170.250 Part 6 of a GRAS notice: Narrative. 170.35 Affirmation of generally recognized 170.255 Part 7 of a GRAS notice: List of sup- as safe (GRAS) status.
    [Show full text]
  • Chemistry of the Noble Gases*
    CHEMISTRY OF THE NOBLE GASES* By Professor K. K. GREE~woon , :.\I.Sc., sc.D .. r".lU.C. University of N ewca.stle 1tpon Tyne The inert gases, or noble gases as they are elements were unsuccessful, and for over now more appropriately called, are a remark­ 60 years they epitomized chemical inertness. able group of elements. The lightest, helium, Indeed, their electron configuration, s2p6, was recognized in the gases of the sun before became known as 'the stable octet,' and this it was isolated on ea.rth as its name (i]A.tos) fotmed the basis of the fit·st electronic theory implies. The first inert gas was isolated in of valency in 1916. Despite this, many 1895 by Ramsay and Rayleigh; it was named people felt that it should be possible to induce argon (apy6s, inert) and occurs to the extent the inert gases to form compounds, and many of 0·93% in the earth's atmosphere. The of the early experiments directed to this end other gases were all isolated before the turn have recently been reviewed.l of the century and were named neon (v€ov, There were several reasons why chemists new), krypton (KpVn'TOV, hidden), xenon believed that the inert gases might form ~€vov, stmnger) and radon (radioactive chemical compounds under the correct con­ emanation). Though they occur much less ditions. For example, the ionization poten­ abundantly than argon they cannot strictly tial of xenon is actually lower than those of be called rare gases; this can be illustrated hydrogen, nitrogen, oxygen, fl uorine and by calculating the volumes occupied a.t s.t.p.
    [Show full text]