Reversibility in Biological Oxidations

I. The molal electrode potential for the succinate-enzyme- fumarate equilibrium was determined for a series of variations of all the constituents, at 25°. The free energy and the heat of the reaction, determined electrometrically, are compared to the values calculated from known physico-chemical properties of succinic and fumaric acids. The values agree within the limits of experimental error. This, together with the lack of dependence of the free energy on the source of the enzyme, is taken to indicate that the enzyme behaves as a perfect catalyst. II. From the equilibrium constant for the reaction of fumarate and water to form 1-malate in the presence of the enzyme fumarase, the free energy of the reaction was calculated. From this value and the known physico-chemical properties of fumaric acid, the free energy of the formation of 1-malic acid was estimated. III. It was demonstrated that in the presence of toluene-treated B. coli, lactate is oxidized to pyruvate, and that furthermore, pyruvate may also be reduced to lactate. IV. It was shown that in the presence of toluene-treated B. coli electron or hydrogen transfer from one metabolite to another occurs only thru the mediation of a reversible oxidizing agent. V. The implications of these findings for the theory of biological oxidations are discussed.</p

Sucrose- and H+-dependent charge movements associated with the gating of sucrose transporter ZmSUT1

Background: In contrast to man the majority of higher plants use sucrose as mobile carbohydrate. Accordingly proton-driven sucrose transporters are crucial for cell-to-cell and long-distance distribution within the plant body. Generally very negative plant membrane potentials and the ability to accumulate sucrose quantities of more than 1 M document that plants must have evolved transporters with unique structural and functional features. Methodology/Principal Findings: To unravel the functional properties of one specific high capacity plasma membrane sucrose transporter in detail, we expressed the sucrose/H+ co-transporter from maize ZmSUT1 in Xenopus oocytes. Application of sucrose in an acidic pH environment elicited inward proton currents. Interestingly the sucrose-dependent H+ transport was associated with a decrease in membrane capacitance (Cm). In addition to sucrose Cm was modulated by the membrane potential and external protons. In order to explore the molecular mechanism underlying these Cm changes, presteady-state currents (Ipre) of ZmSUT1 transport were analyzed. Decay of Ipre could be best fitted by double exponentials. When plotted against the voltage the charge Q, associated to Ipre, was dependent on sucrose and protons. The mathematical derivative of the charge Q versus voltage was well in line with the observed Cm changes. Based on these parameters a turnover rate of 500 molecules sucrose/s was calculated. In contrast to gating currents of voltage dependent-potassium channels the analysis of ZmSUT1-derived presteady-state currents in the absence of sucrose (I = Q/τ) was sufficient to predict ZmSUT1 transport-associated currents. Conclusions: Taken together our results indicate that in the absence of sucrose, ‘trapped’ protons move back and forth between an outer and an inner site within the transmembrane domains of ZmSUT1. This movement of protons in the electric field of the membrane gives rise to the presteady-state currents and in turn to Cm changes. Upon application of external sucrose, protons can pass the membrane turning presteady-state into transport currents

Flowcytometric assessment of fetomaternal hemorrhage during external cephalic version at term

External cephalic version (ECV) at term is a safe procedure and reduces the incidence of cesarean sections for breech presentation. One of the known complications, however, is an ECV-related disruption of the placental barrier and a subsequent transfusion of fetal blood into maternal circulation. While the incidence of ECV-related fetomaternal hemorrhage (FMH) has been determined recently in a large trial using a manual Kleihauer-Betke test (KBT), questions remain on the amount of ECV-related FMH. KBT, which detects fetal red blood cells (RBC) on the basis of acidic resistance of fetal hemoglobin (HbF), is known to be a sensitive test, yet prone to procedural errors limiting its accuracy in quantifying FMH. In this study we investigated 50 patients for FMH before and after ECV, using a dual-color flow cytometric test kit with a lower limit of quantification of 0.05% fetal RBC in maternal peripheral blood. Three patients had a quantifiable increase of fetal RBC detected after ECV (0.06%; 0.08%; 0.1%). None of these subtle increments was predictable by ECV-related clinical parameters or translated into fetal compromise. Using a sensitive and accurate flow cytometric test method, our data provide further assurance to mothers on the safety of ECV at term

On the theory of quantum measurement

Many so called paradoxes of quantum mechanics are clarified when the measurement equipment is treated as a quantized system. Every measurement involves nonlinear processes. Self consistent formulations of nonlinear quantum optics are relatively simple. Hence optical measurements, such as the quantum nondemolition (QND) measurement of photon number, are particularly well suited for such a treatment. It shows that the so called 'collapse of the wave function' is not needed for the interpretation of the measurement process. Coherence of the density matrix of the signal is progressively reduced with increasing accuracy of the photon number determination. If the QND measurement is incorporated into the double slit experiment, the contrast ratio of the fringes is found to decrease with increasing information on the photon number in one of the two paths

Estudo da fusão e cristalização de nanopartículas de Bi no vidro 72B203-28Na2O

Orientador: Prof. Dr. Guinther KellermannDissertação (mestrado) - Universidade Federal do Paraná, Setor de Ciências Exatas, Programa de Pós-Graduação em Física. Defesa: Curitiba, 26/02/2016Inclui referências : f.95-100Resumo: Nesta dissertação, as técnicas de SAXS e WAXS foram utilizadas no estudo das transições de fase sólido-líquido e líquido-sólido de nanopartículas (NPs) de bismuto imersas em um vidro sódio-borato. O trabalho teve como principal objetivo a determinação da dependência entre o raio de NPs esféricas de Bi e as suas temperaturas de fusão e cristalização. Para esta finalidade foram preparadas amostras contendo NPs de Bi com diferentes valores de raio médio e diferentes dispersões em tamanho. Os resultados obtidos confirmam observações experimentais anteriores e também modelos teóricos que preveem a existência de uma dependência linear entre as temperaturas de fusão e cristalização e o inverso do raio das NPs. A extrapolação das temperaturas de fusão e cristalização obtidas para as NPs; para valores de raio tendendo ao infinito, usando a dependência prevista por modelos teóricos, estão em bom acordo com os dados experimentais para o Bi massivo. Observou-se ainda que para raios menores que 18 Å as temperaturas de fusão e de cristalização do Bi coincidem. Isso sugere que abaixo deste tamanho a existência de uma partícula de Bi com estrutura permanentemente cristalina não é possível, confirmando resultados experimentais anteriores para NPs de Bi no mesmo vidro, e em acordo com estudos teóricos por dinâmica molecular. Os parâmetros da rede da estrutura cristalina do Bi, (a e c para cela hexagonal) determinados a partir dos dados de difração, para as diferentes amostras, são menores que os do Bi cristalino massivo, sendo essa contração maior para o parâmetro de rede c. Essas contrações estão em acordo com modelos teóricos que preveem esse comportamento como consequência da fração relativamente mais alta de átomos na superfície das NPs. A partir da dependência entre os parâmetros de rede e a temperatura foram determinados os coeficientes de expansão térmica dos nanocristais de Bi para as diversas amostras estudadas. Os coeficientes de expansão dos nanocristais de Bi são maiores do que os correspondentes para o Bi massivo. Esse resultado foi confirmado independentemente por SAXS, a partir da dependência do raio de giro dos nanocristais com a temperatura. Além disso, assim como ocorre para o Bi massivo, observa-se que a expansão do parâmetro de rede c é maior do que a do parâmetro de rede a. Por outro lado, contrariamente ao que se observa para o caso dos nanocristais, as nanogotas de Bi apresentam um coeficiente de expansão térmica cerca de 40% menor do que o do Bi líquido massivo.Abstract: SAXS and WAXS techniques were used to study the crystal-to-liquid and liquid-to-crystal transitions of bismuth nanoparticles (NPs) embedded in a sodium-borate glass. The study aimed to determine the dependence of the melting Tf and crystallization Tc temperatures on the radius R of Bi spherical NPs. For that purpose, samples were prepared containing Bi NPs with different average radius and size dispersion. The results confirm previous experimental observations and are also in agreement with theoretical models that predict that there is a linear dependence between melting and crystallization temperatures on the inverse of NPs radius. The values of melting and crystallization temperatures determined from the extrapolation of Tf ? 1/R and Tc ? 1/R curves to 1/R ?0 are in good agreement with the experimental values reported in the literature for the bulk Bi. It was also observed that for Bi NPs having radius smaller than 18 Å the melting and crystallization temperatures coincide. This suggests that for Bi NPs with radius smaller than this value the existence of a permanent crystalline structure is not possible. This behavior confirms previous experimental results for Bi NPs in the same glass, and is in agreement with theoretical studies by molecular dynamics. The lattice parameters of Bi nanocrystals (a and c for hexagonal cell), calculated from the diffraction data for several samples, are smaller than the reported for bulk Bi, this contraction being larger for the lattice parameter c. These contractions are expected by theoretical models that predict this behavior as a result of relatively high fraction of atoms on the surface of NPs. From the dependence between the lattice parameters and the temperature the linear thermal expansion coefficients of Bi nanocrystals was determined. The results show the thermal expansion coefficients of Bi nanocrystals are larger than for bulk Bi. The same behavior was independently obtained from the dependence between the radius of gyration of Bi nanocrystals and the temperature, determined from SAXS. Moreover, as occurs in the case of bulk Bi, it was observed that the expansion of the c lattice parameter is larger than the expansion of the a lattice parameter. On the other hand, differently of nanocrystals the Bi nanodroplets have a thermal expansion coefficient about 40% lower than the value reported for bulk liquid Bi

Schinkel und die Industrialisierung Preußens

Inhalt (ungegliedert): Schinkel und die Industrialisierung Preußens; Inhaltsverzeichnis; Forschungsstand; Abkürzungen; Werdegang Schinkels bis zum Eintritt in die Ober-Bau-Deputation; Ökonomisch-technische Erfordernisse aktivieren die Verwaltung; Vom Agrarland zum Industriestandort; Schinkel und Beuth als ?bürokratische Stützen? des wirtschaftlichen Aufschwungs; Schinkel und die industrielle Erzeugung von Baumaterialien und ihre Verwendung in Preußen; Neue Baukonstruktionen auf tradierten Grundlagen; Zusammenfassung; Anhan

Literaturrundschau

J. van Baal und W.E.A. van Beek: Symbols forcommunication. An introduction to theanthropological study of religion. Assen: vanGorcum 1985, 272 Seiten.Peter G. Horsjield: Religious Television. TheAmerican Experience, New York &amp; London:Langman 1984, 197 Seiten.Erhard Schreiber: Kritik der marxistischenKommunikationstheorie. München: K.G.Saur 1984, 239 Seiten.

Spatiotemporal dynamics of nektonic biodiversity and vegetation shifts during the Smithian–Spathian transition: conodont and palynomorph insights from Svalbard

The Smithian–Spathian transition (~249.2 Ma) is marked by profound environmental changes, carbon cycle perturbations, and the stepwise loss of nektonic biodiversity (ammonoids and conodonts). While biotic and abiotic changes have been intensely studied for the palaeosubtropics and palaeotropics, the global spatio-temporal pattern, including mid- to higher latitudes, remains unresolved. In this study, we present conodont and palynomorph data from the Lower Triassic Vikinghøgda Formation in the Stensiöfjellet section, Svalbard. Conodont samples from this sequence generally yielded relatively few specimens with one exception in the basal Vendomdalen Member, which proved exceptionally abundant and diverse. Most conodont samples of the Lusitaniadalen Member are typically dominated by middle to late Smithian segminiplanate forms, such as Scythogondolella spp. This exceptional horizon in the basal Vendomdalen Member, associated with the cosmopolitan ammonoid Bajarunia, indicates an earliest Spathian age. This sample presents the first-ever recorded conodont fauna from the earliest Spathian in the Boreal realm and associates segminiplanate with numerous segminate forms. The presence of an abundant and diverse segminate conodont fauna in northern mid-latitudes during the Early Triassic suggests that temperature was not the main regulator for their distribution, as opposed to segminiplanate forms, which were apparently more restricted to colder waters. Palynomorphs are poorly preserved but allow the discrimination of three assemblages. Association 1 is lycophyte spore dominated, and associations 2 and 3 are both dominated by bisaccate pollen. The change from lycophyte-dominated to a gymnosperm-dominated vegetation occurs just above the Wasatchites beds. A comparison with the records from the southern palaeosubtropics indicates that the vegetation shift was synchronous and coincided with the onset of a cooling episode, commencing in the latest Smithian. □ Intra-Triassic extinction, palaeoclimate, palaeoenvironment, conodonts, palynomorphs, Svalbard. Marc Leu ✉ [[email protected]], Elke Schneebeli-Hermann [[email protected]] and Hugo Bucher [[email protected]] Department of Palaeontology, University of Zurich, Karl Schmid-Strasse 4, 8006 Zurich, Switzerland; Øyvind Hammer [oyvind. [email protected]] and Franz-Josef Lindemann [[email protected]], Natural History Museum, University of Oslo, Pb. 1172 Blindern, 0318 Oslo, Norway; manuscript received on 04/08/2023; manuscript accepted on 28/02/2024; manuscript published on 20/06/2024 in Lethaia 57(2)