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Indole zum Vergleich mit Amanita-Giften. 6. Hydroxylierung von Tryptophan und Tryptophylpeptiden
(1968)
Im System Fe2⊕, Äthylendiamintetraacetat, Ascorbat und Luftsauerstoff gelingt die Hydroxylierung von Tryptophan, Tryptophyl-glycin, Tryptophyl-glycyl-isoleucyl-glycin und Phalloidin, wobei verschiedene Stellen des Indolrings verschieden stark betroffen werden. Produkte einer 2-, 5-, 6- und 2.6-Hydroxylierung konnten spektroskopisch und papierchromatographisch nachgewiesen werden. Bei den Peptiden gewann die Hydroxylierung des Benzolteils des Tryptophans die Überhand. Vom Phalloidin wurde nur die Bildung eines phenolartigen Produkts, vergleichbar mit Amanitin, festgestellt, wobei über die Stellung der neu eingeführten Hydroxylgruppe keine Aussage gemacht werden kann.
The behaviour of molecules and particles of 2 - 400 nm radius in gel chromatography was investigated using sephadex, agarose, and pearl shaped cellulose gel of different porosity. Correlations between elution volumes and particle sizes are given in Fig. 1. We found that particles from ca. 400 nm diameter upwards were more or less irreversibly adsorbed depending on the particle size. So only 15% of rat liver mitochondria and 5% of E. coli bacteria could be eluted from the loose cellulose Cu3. It is assumed that this adsorption is due to the absence of Brownian motion of large particles, which therefore are more or less subject to the gravity and to adsorption forces of the gel.
Gel layers of crosslinked polyacrylamide with different porosities were synthesized and their properties compared. At high concentrations of bifunctional monomers macroporous gels were formed, one of which (total monomer concentration 14%, methylene-bis-acrylamide 40%) permitted even high molecular weight proteins (e. g. γ-globulins) to diffuse more readily than in 2 per cent agar or agarose gels. Different immunological techniques were modified for application with this polymer. It offers advantages especially with respect to porosity, storability and sample application for quantitative diffusion techniques.
7-Dehydrocholesterol and ergosterol are oxidised by iodine and FeCl3 under "physiologically similar" conditions to highly reactive alkylating species. These can be trapped by nucleophiles, such as 1-methylimidazole.
The oxidation of the sterols to those alkylating species is discussed as a model-reaction for the first step in chemical carcinogenesis by endogene substrates.
Kristallisierte Lactat-Dehydrogenasen aus Schweineherz, Kaninchenskelettmuskel, Rattenherz und Rattenskelettmuskel wurden mit Trypsin abgebaut und die durch Hochspannungs-Elektrophorese der Verdauungsansätze erhaltenen Peptidmuster nach Anfärbung mit Ninhydrin und diazotierter Sulfanilsäure miteinander verglichen. Es ergaben sich die in den Abb. 1-4 dargestellten Unterschiede.
In der vorliegenden Arbeit wurden selbstanordnende Monolagen (SAMs) entwickelt, welche als gassensitive Schichten auf Goldoberflächen mit kanzerogenem Benzol reversibel wechselwirken. Der Fokus lag dabei auf elektronenarmen Systemen und insbesondere auf hochfluorierten Aromaten. Insgesamt wurden 18 neuartige SAM-Präkursoren mit Substituenten, die starke Dipolmomente induzieren, hergestellt, die mit Hilfe von Thiolat- bzw. Selenolat-Ankergruppen an Goldoberflächen angebunden wurden. Die Charakterisierung dieser Schichten erfolgte mit diversen oberflächenanalytischen Methoden, wie Ellipsometrie und Infrarot-Reflexions-Absorptions-Spektroskopie (IRRAS). Für die Erforschung der Selektivität und Sensitivität der präparierten Monolagen wurden Austrittsarbeitsänderungen mit Hilfe einer KELVIN-Sonde gemessen und aus diesen Erkenntnissen systematische Veränderungen an den sensoraktiven Molekülen vorgenommen. So wurden der Fluorierungsgrad des aromatischen Systems, die Kettenlänge des Spacers sowie weitere vielversprechende Strukturmotive untersucht. Insbesondere hochfluoriere Derivate mit CF3-Substituenten zeigten die höchsten Sensitivitäten gegenüber Benzol. Weiterhin wurde ein neues Infrarot-Messprinzip entwickelt und etabliert, welches in situ Messungen während eines Überleitens gasförmiger Analyten ermöglichte. Diese Ergebnisse belegen eine Interaktion zwischen Analyten und Monolage.
Ein weiteres Projekt befasste sich mit elektronenarmen aromatischen Monolagen, die über Cystamin-Einheiten an Goldoberflächen angebunden wurden, sich aber in den dipolaren Kopfgruppen unterschieden. Dieses Vorgehen ermöglicht die Herstellung von SAMs gleicher Packungsdichten, sodass lediglich die unterschiedlichen Substituenten die elektronischen Eigenschaften beeinflussen. Die resultierenden Monolagen wurden mittels mit Rastertunnelmikroskopie, Ellipsometrie, IRRAS sowie Wasserkontaktwinkel-Goniometrie untersucht. Durch eine relativ einfache Veränderung der Kopfgruppe, wobei F3C , F3CS, H3C- sowie NC-Reste eingeführt wurden, war es möglich, die Austrittsarbeit einer Goldoberfläche in einem Bereich von 4.9 bis 5.6 eV einzustellen. Zusätzlich konnte ein gemischtes Disulfid synthetisiert werden, welches eine echte gemischte SAM auf der Goldoberfläche bildete. Dieses Konzept könnte in Zukunft eine noch präzisere Modifizierung der Austrittsarbeit zulassen, was die Entwicklung von effizienteren elektronischen Bauelementen auf Basis von organischen n Typ-Halbleitern ermöglicht.
Abschließend wurden teilfluorierte Benzonitril-Derivate mit Thiolat- bzw. Selenolat-Ankergruppen erforscht, welche als SAMs Informationen über den dynamischen Ladungstransport lieferten. Die Präkursoren unterscheiden sich lediglich im Fluorierungsmuster, welches das Dipolmoment der Gesamtstruktur beeinflusst. Die hergestellten Monolagen wurden mit einer Vielzahl oberflächenanalytischer Methoden (IRRAS, Ellipsometrie, Röntgenphotoelektronen- sowie Röntgen-Nahkanten-Absorptions-Spektroskopie) charakterisiert, die alle die Bildung geordneter SAMs belegten und auf eine eher aufrechte Orientierung der Moleküle auf der Oberfläche hindeuteten. Die Bestimmung der Elektronentransfer-Zeiten mit Hilfe der sogenannten core-hole-clock-Methode zeigte überraschenderweise, dass durch eine Änderung des Substitutionsmusters der Fluoratome der Elektronenübergang nicht beeinflusst werden. Dementsprechend hat das Dipolmoment innerhalb des molekularen Gerüsts keinen signifikanten Einfluss auf die Elektronentransfer-Dynamik.
Modularity is an aspect of a decomposable system with a coordinating authority that acts as a glue which holds the loosely held components. These multi-component entities (“modules”) facilitate rewiring into different designs allowing for change. Such modular character is a fundamental property of many biological entities, especially the family of megasynthases such as polyketide synthases (PKSs). The ability of these PKSs to produce diverse product spectra is strongly coupled to their broad architectural modularity. Decoding the molecular basis of modularity, i.e. identifying the folds and domains that comprise the modules as well as understanding constrains of the assembly of modules, is of utmost importance for harnessing megasynthases for the synthesis of designer compounds. In this study, we exploit the close semblance between PKSs and animal FAS to re-engineer animal FAS to probe the modularity of the FAS/PKS family. Guided by structural and sequence information, we truncate and dissect animal FAS into its components, and reassemble them to generate new PKS-like modules as well as bimodular constructs. The novel engineered modules resemble all four common module types of PKSs and demonstrate that this approach can be a powerful tool to create higher catalytic efficiency. Our data exemplify the inherent plasticity and robustness of the overall FAS/PKS fold, and open new avenues to explore FAS-based biosynthetic pathways for custom compound design.
Single-particle electron cryo-microscopy (cryoEM) has undergone a “resolution revolution” that makes it possible to characterize megadalton (MDa) complexes at atomic resolution without crystals. To fully exploit the new opportunities in molecular microscopy, new procedures for the cloning, expression and purification of macromolecular complexes need to be explored. Macromolecular assemblies are often unstable, and invasive construct design or inadequate purification conditions or sample preparation methods can result in disassembly or denaturation. The structure of the 2.6 MDa yeast fatty acid synthase (FAS) has been studied by electron microscopy since the 1960s. We report a new, streamlined protocol for the rapid production of purified yeast FAS for structure determination by high-resolution cryoEM. Together with a companion protocol for preparing cryoEM specimens on a hydrophilized graphene layer, our new protocol has yielded a 3.1 Å map of yeast FAS from 15,000 automatically picked particles within a day. The high map quality enabled us to build a complete atomic model of an intact fungal FAS.
Engineering of assembly line polyketide synthases (PKSs) to produce novel bioactive compounds has been a goal for over twenty years. The apparent modularity of PKSs has inspired many engineering attempts in which entire modules or single domains were exchanged. In recent years, it has become evident that certain domain-domain interactions are evolutionarily optimized, and if disrupted, cause a decrease of the overall turnover rate of the chimeric PKS. In this study, we compared different types of chimeric PKSs in order to define the least invasive interface and to expand the toolbox for PKS engineering. We generated bimodular chimeric PKSs in which entire modules were exchanged, while either retaining a covalent linker between heterologous modules or introducing a non-covalent docking domain- or SYNZIP domain-mediated interface. These chimeric systems exhibited non-native domain-domain interactions during intermodular polyketide chain translocation. They were compared to otherwise equivalent bimodular PKSs in which a non-covalent interface was introduced between the condensing and processing parts of a module, resulting in non-native domain interactions during the extender unit acylation and polyketide chain elongation steps of their catalytic cycles. We show that the natural PKS docking domains can be efficiently substituted with SYNZIP domains and that the newly introduced non-covalent interface between the condensing and processing parts of a module can be harnessed for PKS engineering. Additionally, we established SYNZIP domains as a new tool for engineering PKSs by efficiently bridging non-native interfaces without perturbing PKS activity.
Die im Trockenweißkraut vorkommende Kropfnoxe wird durch haushaltsübliches Kochen zerstört. Durch Wasserdampfdestillation verliert das Kraut rund 50% seines Gesamtschwefelgehaltes sowie seine strumigene Aktivität. Eine Isolierung der wahrscheinlich S-haltigen Noxe ist bisher nicht gelungen.
Die Noxe des getrockneten Weißkrautes ist im Gegensatz zu der des weißen Senfsamens in heißem Alkohol unlöslich.
Das Senfölglykosid Sinalbin scheint bei Anwesenheit von Myrosinase die Schilddrüse im Sinne einer Struma diffusa parenchymatosa zu beeinflussen.
Die Reizschwelle des in kürzester Zeit basedowifizierend wirkenden Allylthioharnstoffs liegt bei gewöhnlichen Kaninchen zwischen 30 und 40 mg pro 1 kg Körpergewicht, für Angorakaninchen darunter. Allylthioharnstoff verändert die Schilddrüse zunächst im Sinne einer Struma diffusa parenchymatosa, die aber sehr schnell in eine Struma basedowificata übergeht. Tyronorman beeinflußt die Allylthioharnstoffwirkung, wenn es gleichzeitig mit der chemischen Noxe verabfolgt wird; die Drüse verharrt dabei in einem Präbasedowzustand.
Dijodtyrosin ruft unter den gleichen Bedingungen eine ähnliche, aber stärkere Wirkung hervor. Bei kurzfristiger Behandlung einer bereits längere Zeit durch Allylthioharnstoff geschädigten SD kommt es zur Ausbildung einer SD, die histologisch der Jodbasedow-Struma gleicht. Benzylthioharnstoff verändert die SD vorwiegend im Sinne einer Struma diffusa parenchymatosa und steht somit in seiner Wirkung der im Weißkraut vorhandenen Kropfnoxe nahe. Auch für Benzylthioharnstoff scheint die Reizschwelle im gleichen Größenbereich wie beim Allylthioharnstoff zu liegen.
Bei langdauernder Injektion von Benzylthioharnstoff, der schwer resorbiert wird, entsteht beim Kaninchen keine Struma baśedowificata, sondern nur ein Präbasedow-Zustand. Eine Aktivierung der Schilddrüsen(SD)-Follikel tritt bei kurzfristiger Verfütterung von Benzylthioharnstoff auf.
Der symm. Dibenzylthioharnstoff erzeugt bei täglicher Injektion ein Vorstadium der Struma diffusa parenchymatosa. Seine Resorption ist schlecht.
Die Isothioharnstoffe sind für den Tierversuch wahrscheinlich zu giftig.
Thiouracil, subcutan gespritzt, ruft SD-Vergrößerung hervor und ist bei weitem nicht so toxisch wie Allylthioharnstoff. Die Größen der entarteten Drüsen sind den zugeführten Thiouracilmengen nicht proportional und meines Erachtens von der Konstitution der Versuchstiere weitgehend abhängig.
2-Thio-barbitursäure wirkt bei einer Injektion über drei Monate schwach schilddrüsenaktiv.
Die Natriumsalze des S-Kupfer-N-Allyl-N'-[m-carboxyphenyl]-iso-thioharnstoffes (Cuprion) und des S-Gold-N-Allyl-N'-[m-carboxyphenyl]-iso-thioharnstoffes (Lopion), parenteral gegeben, üben einen nachteiligen Einfluß auf die Schilddrüse aus. Lopion wird besser als Cuprion vertragen. Der N-Allyl-N'-[m-carboxyphenyl]-iso-thioharnstoff wird offenbar schnell vom Körper ausgeschieden, weshalb große Mengen des Grundkörpers erforderlich sind, um eine stärkere SD-Aktivität hervorzurufen.
Sulfanilylthioharnstoff verändert ein wenig die Kaninchen-SD, wenn er über zwei Monate verabfolgt wird.
Mengt man Sulfanilylguanidin dem Futter bei, dann wird die SD in geringem Grade aktiviert. Eine leichte Hypertrophie der Drüse wurde bei subcutaner Behandlung eines Tieres festgestellt.
Möglicherweise führen unter gewissen Bedingungen Benzylthioharnstoff, Sulfanilylguanidin, Cupro-N-Allyl-N'- [m-carboxyphenyl]-iso-thioharnstoff und Thiouracil, in dieser Reihe zunehmend wirksam, zu einer SD-Hypertrophie.
Die Art und Weise, wie die Kaninchen auf die schilddrüsenwirksamen Substanzen reagierten, weist auf die Entwicklung eines anormalen Zustandes der Thyreoidea hin. Unsere Befunde stehen mit der Erklärung der thyreostatischen Wirksamkeit chemischer Verbindungen durch amerikanische Autoren in Einklang.
Zur Biochemie der Schilddrüsenfunktion VII : Anzeichen der tierexperimentellen E-Hypervitaminose
(1947)
Vitamin-E-reiche Fütterung von männlichen jungen Kaninchen führt nach mehreren Wochen zu krankhaften Erscheinungen an der Schilddrüse (SD). Die drei Symptome der entstandenen E-Hypervitaminose in dem innersekretorischen Organ sind: 1. Abnorme Volumen- und Gewichtszunahme, 2. Jodfreiheit bzw. -mangel und 3. histologische Veränderung (gesteigertes Epithelwachstum). Vitamin-E-Gaben neutralisieren nicht die schilddrüsenschädigende Wirkung von Kohlkropfnahrung. Ein täglicher α-Toko-pherol-Zusatz zum Normalfutter verhindert nicht den kropferzeugenden Thiouracil-Effekt an Kaninchen, sondern wirkt im gleichen Sinne.
The thermal and the photochemical reactions of the endoperoxide of Tetrabenzo(bc,fg.lm,pq)- pentacene have been investigated with respect to its photochromic properties. The thermal yield of irreversible rearrangement reactions was determined to be Adec = 0.045. From the activation parameters of the thermal cycloreversion. forming the parent hydrocarbon and oxygen, a half life time of 114 years at 20 °C has been extrapolated. For the quantum yield of the irreversible photochemical rearrangement a value of Qdec = 0.03 was obtained. As can be seen from the wavelength dependence of the photocycloreversion quantum yield Q1, cycloreversion occurs not only from the thermalized S2(πccπ*cc) but from higher excited states too. The maximum quantum yield was found at 302 nm to be (Q1 = 0.15. From our results it follows that this endoperoxide is of high quality in respect to the colour change colourless/blue and to thermal stability, whereas the reversibility is only moderate.
The photochemical cleavage of the endoperoxides of anthradichromene and benzodixanthene into the parent hydrocarbon and oxygen is shown to be an adiabatic photoreaction originating from an upper excited singlet state. This photochemical behaviour is described by a theory for the photochemistry of endoperoxides developed by Kearns and Khan.
The order-disorder phase transition which occurs at Tc = 296.9 K in anilinium bromide, C6H5NH3Br, is studied by inelastic neutron time-of-flight measurements. Data are taken from hydrogenated and partially deuterated samples (C6D5NH3Br and C6H5ND3Br) below and above the transition temperature. From the inelastic scattering data the phonon frequency distribution in the range of the intermolecular vibrations is calculated. The assignment of bands is given and changes in the spectra with temperature are discussed. The analysis of the quasielastic line revealed substantial broadening due to rotational diffusion of the -NH3⊕ group. These jump diffusion processes were observed in the orthorhombic high temperature and - with markedly diminished rate - in the monoclinic phase below Tc. From the correlation times at different temperatures the activation energies are estimated for both phases. Comparison with calculated elastic incoherent structure factors suggests jumps of 60° for hindered rotation.
The crystal structure of the high temperature phase of anilinium bromide, C6H5NH3⊕Br⊖ , was studied by X-ray and neutron diffraction at T = 343 K. The refinement supports disordered positions of the -NH3⊕ group. A split-atom model is proposed which includes disorder of the benzene ring. The thermal parameters, hydrogen bond distances, and other experimental data (NMR, NQR, inelastic neutron scattering) are in accordance with this model.
The crystal structure of the low temperature phase of anilinium bromide, C6H5NH3⊕Br⊖, was studied by neutron diffraction at T = 100 K. The refinement supports an ordered structure. The structures of the low and high temperature phases are compared and the mechanism of the phase transformation is discussed.
Potential energy, dipole moment, and electronic transition moment functions for the A 3Πand X3Σ- states of PH have been calculated from highly correlated electronic wavefunctions. The electric dipole moments in the vibrational ground state of PH are calculated to be 0.637 Debye (A 3Π) and 0.403 Debye (X3Σ-). The predicted rates of spontaneous emission between low lying vibrational states of the X state lie in the range of 46 to 109 sec-1 (PH) and 12 to 30 sec-1 (PD). The calculated radiative lifetime of the v' = 0 level in the A 3Π state of 400 ns is lower by about 10 percent than the most recent experimental value. The classical intersection of the 5Σ- and the A 3Πstate has been calculated to lie between v' = 2 and 3 with an expected uncertainty of about 500 cm−1, whereas the onset of the rotationally dependent predissociation lies at v' = 0, J' = 11.
This paper contains further applications on symmetrical liquid mixtures of the molecular thermodynamic theory which has been developped in part I of this series. The essential feature of this theory is the superposition of "chemical" and “random” exchange equilibria between “complexes” formed by a given molecule and its z nearest neighbours, thus allowing a unified treatment of the thermodynamic phenomena in binary liquid mixtures using the equilibrium constant K of the ideal law of mass action and the energy w of pair interactions as parameters.
The temperature and pressure dependences of K and the evaluation of experimental excess enthalpy and excess volume data are treated. Formulas and examples for the calculation of K and w from isothermal and non-isothermal vapour-liquid equilibrium data are given. The conditions for azeotropy with minimum or maximum vapour pressure, resp., are derived. Melting curves for a symmetric eutectic system with superposed miscibility gap are discussed. Further models for partially miscible liquids with competing self-association and complex-formation are treated showing the phenomenon of two separated miscibility gaps.
Influence of rotational relaxation on tropospheric OH laser induced fluorescence measurements
(1982)
Rotational relaxation of OH molecules in the 2II electronic ground state has been observed to occur in collisions with water molecules with gas kinetic probability. It causes an additional contribution to the already well known sources of interference when LIF is used to monitor tropospheric OH. As the laser generated OH is originally produced mostly in high rotational states, the fast relaxation phenomenon leads to a further population of OH in low rotational states. These states are used to monitor tropospheric OH by spectroscopic methods. The observed effect therefore increases the interference. A mathematical analysis is presented, revealing the effect of all relevant parameters.
The application of laser induced fluorescence (LIF) in the uv to monitor tropospheric OH concentrations is limited for several reasons. In general the sensitivity of this method increases with the laser intensity. But at the low OH concentrations present in the atmosphere the beginning nonlinearity of the absorption (saturation effect) severely restricts the use of higher laser intensities. The high sensitivity of the LIF technique can be further compromised by the presence of an OH interference signal. This signal is generated by the monitoring laser light itself from laser photolysis of ambient ozone and the succeeding reaction of the photolysis product O (1D) with water to produce hydroxyl radicals. The results of the calculations are presented in a diagram from which the range of laser parameters can be deduced, which can be applied with confidence to monitor OH by the LIF method. The maximum number of signal counts for these working conditions is in the range of 10-3 per laser pulse.
Stimulated emission from chemically formed excited iodine molecules has been observed. The emission originates from the vibrational state ν′ = 55 of I2(B 3 II). The excited molecules are produced by a three body recombination reaction.
Nuclear magnetic resonance measurements were carried out on neutron activated 20F(T1/2=11s) nuclei in a single crystal of KZnF3. The quadrupolar splitted NMR spectrum, detected via the 20F β-radiation asymmetry, could be observed using a radio frequency modulation technique. The quadrupole coupling constant was determined to e2 q Q/h= + (12.0 ± 1.5) MHz at room temperature. The sign of e2 q Q was obtained from a simultaneous γ-ray anisotropy measurement on the succeeding 20Ne transition. Utilising a calculated field gradient of the fluorine atom, an fQ = 4.6% is determined. This value is compared with literature data of similar compounds.
The ion-molecule reactions of thiothionylfluoride have been studied by ion cyclotron resonance spectrometry. The major secondary ions are S2F3+ , S3F+ , and S3F2+. In a consecutive reaction of S3F2+ the tertiary ion S4F2+ is formed. The rate constant of the IMR with the greatest yield S2F2+ + SSF2 → S3F2+ + SF was estimated to k = 2 · 10-9 cm 3 molecule -1 sec -1 . The results were compared with the mass spectrum of thiothionylfluoride. They permit conclusions on chemical reactions of lower sulphurfluorides.
The low temperature IR stretching vibrations of difluorodisulfane (FSSF) and thiothionylfluoride (SSF2), in the solid phase and in a cyclohexane matrix, of the mixtures FSSF -SSF2, FSSF-OSF2 and SSF, -OSF2, and of solid difluorotrisulfane (FS3F) have been investigated. While SSF, forms no distinct oligomers, a dimer with absorption bands at 635 and 682 cm-1 has been detected in the case of FSSF. These differences between FSSF and SSF, are rationalized by the different S-F bond lengths. A structure of the FSSF dimer similar to that of the sulfur tetrafluoride dimer is proposed. The low temperature spectrum of FS3F shows 3 bands in the frequency range between 460 and 1000 cm-1: 590, 605 and 680 cm-1, due to associated molecules. FS3F decomposes on warming. The main decomposition products containing fluorine are FSSF and SSF2. Mechanisms for the rearrangement and decomposition of the three compounds studied are discussed.
The theoretical IR-frequencies of sulphurdifluoride are computed from force constants, which are evaluated by means of molecules with S-F-bonds: ν1 = 795 ± 10cm-1, ν2 = 430± 5cm-1, ν3= 830 ± 10cm-1.
The radiative lifetimes of the C3Il-X3II transition of the CSi radical have been calculated from highly correlated electronic wavefunctions and compared with available experimental data. For this transition, the Franck-Condon approximation fails due to the strong R-dependency of the transition moment function.
Potential energy and dipole moment functions have been calculated for the ground states of the NeH+ (1.0 ≦ R ≦ 15 a. u.) and the KrH+ (1.6 ≦ R ≦ 20 a. u.) ion from highly correlated SCEP/VAR and SCEP/CEPA electronic wave functions. The following spectroscopic constants have been derived: Ne20H+ re = 0.996 ± 0.003 Å, ωe = 2896 ± 20cm-1 , D0(Ne + H+) = 2.10 ± 0.05 eV; Kr84H+ re = 1.419 ± 0.003 Å, ωe = 2561 ±20 cm-1 , D0(Kr + H+) = 4.65 ±0.05 eV. The Einstein transition probability coefficients of spontaneous emission have been calculated for all transitions v ≦ 5 of Ne20H+, Ne20D+, Kr84H+ and Kr84D+, respectively.
Near equilibrium potential energy and dipole moment functions have been calculated for the electronic ground state of the XeH+ ion from highly correlated SCEP/CEPA electronic wavefunctions. The following spectroscopic constants for 132XeH+ are obtained: Re= 1.611 ± 0.005 Å, ωe = 2313 ± 50cm-1, ωexe = 41 ± 5cm-1 and D0(Xe+ + H) = 3.90 ± 0.1 eV.
Infrared transition dipole matrix elements and probability coefficients for 132XeH+ and 132XeD+ are given. The electric dipole moment functions of the protonated rare gas atoms HeH+ to XeH+ are discussed.
In this paper equilibrium models for the calculation of the excess Gibbs free energy of binary liquid mixtures are developed, the component A of which undergoes chain-forming self-association whilst the component B acts as an 'inert' solvent. It is shown that the extension of the well-known chain-association model of Mecke and Kempter, in which the probability of chain prolongation is assumed to be independent of chain length, is unable to establish satisfactory results because it does not exhibit sufficient unsymmetry. Reduction of the probability of chain growth with in-creasing chain length leads to an improved model with the geometric series replaced by the exponential series. This model, in which only two parameters are used, i. e. the equilibrium constants K for mutual solvation of A and B, and ρ for self-association of A, allows fitting of isothermal experimental GE /R T literature data on cycloalkanol-cycloalkane, alkanol-alkane, and NMF -CCl4 systems within the limits of experimental error. Compared with the two-parameter Wilson equation which gives equally small standard deviations, our equilibrium model has the advantage of allowing passage from GE to HE data and of being applicable to liquid-liquid equilibria.
The enthalpies of mixing at 25° of diethyl ether, di-n-propyl ether, di-n-butyl ether, di-isopropyl ether, propylene oxide, tetrahydrofuran, and tetrahydropyran with chloroform are determined by an isothermal titration method. As a result, the functions HM-f(N CHCl3) are obtained with a step width of 0.025 of the mole fraction and a relative accuracy of 1 per cent or better. Evaluation of the heat of mixing data by means of equilibrium models ("ideal associated mixture") shows that the systems of aliphatic ethers with chloroform behave rather precisely as one-step equilibria of the type A + B = AB (A = ether; B = chloroform). In the systems of cyclic ethers with chloroform, a second equilibrium step, AB + B = AB2 , must be considered, the importance of which decreases with increasing ring size of the ether. The equilibrium data calculated for the seven ether-diloroform systems are discussed.
Phasentrennung als Folge der Konkurrenz zwischen "statistischer" und "chemischer" Vermischung
(1977)
The fact that common thermodynamic conditions are valid for all known types of critical phases (liquid-liquid, liquid-gas, and "gas-gas") suggests that a common principle for the interpretation of material phase instability from a molecular point of view must exist. In this paper we show that the principle of competition between "statistical mixing" (i. e. random mixing) and "chemical mixing" (i. e. mixing effected under the influence of chemical interactions) can give this common inter pretation. If the equilibrium states resulting from both types of mixing are sufficiently different, phase separation occurs. We refer to our earlier papers (since 1972) in which we have applied this principle to describe liquid-liquid phase equilibria by "chemical" models, using the equilibrium constants of exchange equilibria between nearest-neighbour complexes as a measure of "chemical" mixing. In this paper we show that the well-known reduced gas-liquid coexistence curve, T/Tc =f(q/qc), can accurately be fitted by a very simple "mixture" model of molecules A with "vacan cies", provided that the contributions of both statistical and chemical mixing are incorporated into the formula for GE. From a discussion of the application to "gas-gas" phase equilibria in the hyper critical region it results that the weight factor r, by which the contribution of statistical mixing enters into GE, must depend on the density of the gas mixture. Phase separation can only occur if, by increasing pressure, the contributions to GE of statistical and chemical mixing have reached the same order of magnitude. From an attempt to apply the same principle to solid-liquid equilibria it is shown under which external conditions a critical point for this type of phase transition can be expected.
A thermodynamic theory of liquid mixtures based on a simple molecular model is developed which describes the equilibrium state as the result of a coupling between a "chemical" and a "statistical" equilibrium. The intermolecular interactions are taken into account by considering "complexes" formed between a given molecule and its z nearest neighbours. The equilibrium mole fractions of these complexes are calculated by application of the ideal law of mass action to an appropriate set of "exchange equilibria". Formulae for the excess functions GE and HE and for the activities of the components are derived for the cases z=1 and z=4. GE depends on an equilibrium constant K describing the deviation from random distribution of the equilibrium mole fractions of the complexes. HE depends on K and on an energy parameter w which is related to differences of pair interactions. K and w are independent parameters, and there is no limitation in respect to amount and sign of the excess functions. The conditions for the existence of a critical solution point are formulated; at this point GE has a value of about 0.56 R T. If a model with two equilibrium constants is used allowing for instance competition between "self-association" and "complex-formation", the existence of closed miscibility gaps becomes possible. Closed miscibility curves are calculated and the conditions for their appearance are discussed. The relations between this theory and Guggenheim's statistical lattice theory of symmetrical mixtures are pointed out.
As we have shown in a recent paper, the principle of competition between "statistical" and "chemical" mixing represents a molecular thermodynamic approach to all known types of phase separation. This principle is effective if the contributions of two independent spontaneous processes enter into the thermodynamic potential by which the resulting equilibrium state of the system is determined. This is equivalent with the statement that two different forms of entropy exist which are not interchangeable, and for which the law of increasing entropy independently must be valid. As "cooperativity" is introduced by this principle, critical phenomena may be described by simple equilibrium models in which only nearest-neighbour interactions are considered.
Starting from the molar Gibbs free energy GM of the most simple binary equilibrium model z = 1 with nearest-neighbour pairs, nonclassical critical-point exponents α = 0.33 of the molar heat capacity, β = 0.33 of the coexistence curve, γ = 1.33 of the isothermal compressibility, and δ = 4.33 of the critical isotherm, are derived, which are consistent with the well-known exponent in equalities. These non-classical critical-point exponents are independent of the chemical nature of the particles because they are obtained by applying thermodynamic arguments on the coupling constant τ, by which the contribution of "statistical mixing" to GM is weighted.
LANGEVIN equations of the type dn× (t)/dtn+...+c × (t)=K (t) constitute the starting point of a phenomenological fluctuation theory of irreversible processes. These equations are not constructed from transport equations (as in the older theory), but via a generalized MASTER equation from phase space mechanics. The MARKOFF processes of first and higher order defined by the various LANGEVIN equations are studied by the prediction theory of stationary stochastic processes. Instead of the variation principle of the ONSAGEB–MACHLUP theory one has the minimization of the prediction error. The mean relaxation path and the entropy of the considered processes are calculated. It is shown that the entropy consists of one part which is given by the relaxation path and another which is determined by the prediction error.
The relations of the theory of real gases which have first been derived by Mayer and his co-workers can be obtained in a simple way by the functional method. In this case the assumption of the pairwise additivity of the intermolecular potential can be dropped. Apart from some new relations for distributions functions the expansion of the direct correlation functions is obtained as a power series in density with coefficients consisting of integrals over Husimi functions.
Es werden allgemeine Gleichungen zur Berechnung der Verteilung der Nullstellen von der großen kanonischen Verteilungsfunktion Ξ (y) eines Gittergases in der komplexen Ebene der Fugazität y in Bethescher Näherung angegeben, die nach einem graphischen Verfahren gelöst werden können. Für das zweidimensionale, quadratische Gitter und das dreidimensionale, kubische Gitter werden die Bestimmungsgleichungen für die Nullstellenverteilung mit Hilfe des graphischen Verfahrens explizit gelöst. Die Nullstellenverteilung von Ξ (y) des eindimensionalen Gittergases wird in geschlossener Form angegeben.
The cooperative problem for a lattice gas on a plane, square lattice and on a simple cubic lattice is solved by a system of two coupled, transcendental equations, derived by a combinatorial method, which describes a homogeneous or periodical particle density on the lattice as a function of the temperature and the chemical potential of the lattice-gas.
For the particle interaction a Hard-Core potential (nearest neighbour exclusion) with a soft long-range tail is assumed. The zero-component of the Fourier-transform of this long-range interaction part can be positive or negative.
The system of transcendental equations is solved by a graphic method. As a result, the complete pressure-density state diagram and the pressure-temperature phase diagram can be drawn.
The lattice-gas exists in three stable phases: gas, liquid and solid. Three phase changes are possible: condensation, crystallization and sublimation.
Critical points of condensation and freezing are examined. The number of possible phases and phase changes at a fixed temperature depends on the geometric structure of the particle interaction.
Die „Selbstenergien“ Gn in 1 wurden durch näherungsweise Auswertung einer größeren Klasse von Selbstenergiediagrammen approximativ berechnet. Das Gleichungssystem (3.3) in 1 für die renormierten Semiinvarianten wurde umgeformt und durch zusätzliche Näherungsannahmen vereinfacht. Durch Näherungsansätze für die Semiinvarianten M2, M3,... konnten einfache Gleichungen für die Magnetisierung M1 hergeleitet werden. Diese Gleichungen wurden numerisch gelöst. Auf der Grundlage der Beziehungen (3.5) und (4.8) in 1 wurden ferner die innere Energie, die freie Energie und die Atomwärme des zweidimensionalen Ising-Ferromagneten sowie die Druck-Dichte-Isothermen des zweidimensionalen Gittergases numerisch ausgerechnet.
Die FOURIER-Nullkomponente der Bindungsmatrix Gij G(0) in 1 Beziehung (5.16) wurde durch Summation spezieller Diagramme in der sogen. „Kettenapproximation“ und der „Wassermelonenapproximation“ näherungsweise berechnet. Auf der Basis von (5.16) in 1 wurde in der Kettenapproximation und der Wassermelonenapproximation die magnetische Suszeptibilität und die Magnetisierung des dreidimensionalen ISING-Modells bestimmt. In der Kettenapproximation wurden ferner die freie Energie, die innere Energie und die Atomwärme des dreidimensionalen ISING-Ferromagneten sowie die Druck-Dichte-Isothermen des dreidimensionalen Gittergases ausgerechnet.
A theory of the luminescence lifetime of a radiation-damped classical electrical point dipole near a plane interface to a medium with different optical constants is given. The influence of the interface on the lifetime of the dipole is calculated in first approximation with the methods of molecular optics. Theoretical and experimental results for a purely dielectric interface are compared.
Excitation of CO molecules into the lowest vibrational level of the B1Σ+ electronic state by absorption of the (B 1Σ+υ′=0 →X 1Σ+ ,υ′′=0) resonance band at 1150 Å has been studied under various experimental conditions by observing the steady state fluorescence of the (B 1Σ+→A1Π) Angstrom bands. Stern-Volmer plots of the fluorescence intensities at the addition of various foreign gases yielded straight lines whose slopes k̃qм = kqм · τeff were strongly dependent on the CO sample pressure. This effect was found to be due to changes of the effective radiative lifetime of the B 1Σ+υ′=0 because of resonance trapping of the (0,0) band of the (B → X) fluorescence. The CO(B 1Σ+υ′=0) molecules are found to be quenched by He, Ne, Ar, H2 and D2 with effective collision cross sections of 0.23, 0.48, 22.4, 10.7, and 11.4 Å2, respectively, at 298 °K. In addition, an approximate value for the ratio ABA/ (ABA+ABX)of the radiative transition probabilities of the (B → A) and (B → X) transitions could be derived from the measurements.
The mass spectra and the ion molecule reactions of methylphosphine, dimethylphosphine and dimethyldeuterophosphine have been studied by ion cyclotron resonance spectrometry. About 50 ion molecule reaction are observed for each compound. The product ions can be classified as ions with two phosphorus atoms: P2R5+, P2R3+, P2R2+ and P2R+ (R = CH3 or H), as phosphonium and phosphinium ions and ions resulting from collision dissociations and charge exchange reactions. Tertiary ions with three phosphorus atoms like CH3P3H2+ (from CH3PH2) and (CH3)4P3H2 (from (CH3)2PH) have also been detected. The mechanisms of the ion molecule reactions, rearrangements, P -H- and C-H-reactivities and product ion structures are discussed, using in the case of dimethylphosphine the results obtained with the deuterated compound. Rate constants of formation of the more abundant product ions from the molecular ion and the CH3P+ ion, both odd electron particles, have been determined. The reactions with dimethylphosphine have much smaller rate constants than the reactions with methylphosphine.