Structural variability of endotoxins from R-type isogenic mutants of Shigella sonnei

The structural variations in the rough-type endotoxins [lipopolysaccharides (LPSs)] of Shigella sonnei mutant strains (S. sonnei phase II-4303, R41, 562H and 4350) were investigated by Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) and tandem MS. A series of S. sonnei mutants had previously been the subject of analytical studies on the biosynthesis of heptose components in the core oligosaccharide region of LPSs. This study gives a complete overview on the structures of the full core and lipid A of S. sonnei mutant strains by MS. We found that the LPSs of the isogenic rough mutants were formed in a step-like manner containing 0:1:2:3 heptose in the deep core region of 4350, 562H, R41 and 4303, respectively, and the longest LPS from the mutant S. sonnei 4303 contained also five hexoses. The structural variations in the lipid A moiety and in the oligosaccharide part of the intact LPS were followed by MALDI-TOF-MS/MS. For the dissolution and the ionization of the samples, 2,5-dihydroxybenzoic acid in citric acid solution was applied as matrix. The detailed evaluation of the mass spectra indicates heterogeneity in the lipid part due to the differences in the phosphate and fatty acid composition.     

Suzuki-Miyaura cross-coupling reactions of halo derivatives of 4H-pyrido[1,2-a]pyrimidin-4-ones

The palladium-catalyzed Suzuki-Miyaura cross-coupling reactions of halo derivatives of 4H-pyrido[1,2-a]pyrimidin-4-one with (het)arylboronic acids allow easy access to (het)aryl and vinyl derivatives of this bicycle in good to excellent yields, even from chloro derivatives. The sequence of reactivity of the halogen in the different positions of the ring system was also investigated. 6-Phenyl-4H-pyrido[1,2-a]pyrimidin-4-one could be prepared by thermal cyclization of isopropylidene (6-phenylpyrid-2-ylamino)methylenemalonate, together with a small amount of 7-phenyl-1,4-dihydro-1,8-naphthyridin-4-one.     

On the molecular structure of (CH3)2NSO2N(CH3)2 as studied by gas electron diffraction

The following bond lengths and bond angles have been deduced from a vapour phase electron diffraction study of (CH₃)₂NSO₂N(CH₃)₂: r(C-H) 1.114 ± 0.005 Å, r(S-O) 1.432 ± 0.010 Å, r(N-C) 1.475 ± 0.013 Å, r(S-N) 1.651 ± 0.003 Å, ∠N-C-H 109.3 ± 2.0°, ∠C-N-C 118.0 ± 302°, ∠S-N-C 115.2 ± 1.1°, ∠N-S-N 110.5±1.3° and ∠O-S-O 114.7±2.5°. The sulphur bond configuration and the prevailing conformation, which was identical to that in the crystal, are discussed in relation to analogous sulphide and sulphoxide derivatives.     

Thermal decomposition and antimicrobial activity of zinc(II) 2-bromobenzoates with organic ligands

New zinc(II) 2-bromobenzoate complex compounds with general formula Zn(2-BrC₆H₄COO)₂·nL·xH₂O (where L = urea, nicotinamide, N-methylnicotinamide, N,N-diethylnicotinamide, isonicotinamide, phenazone n = 0–2, x = 0–2) were prepared and characterized by elemental analysis, IR spectroscopy and thermal analysis. The thermal decomposition of hydrated compounds started with dehydration process. During the thermal decomposition organic ligand, carbon dioxide and bis(2-bromophenyl)ketone were evolved. The solid intermediates and volatile products of thermal decomposition were proved by IR spectroscopy and mass spectrometry. The final solid product of the thermal decomposition heated up to 1073 K was zinc oxide. Antimicrobial activity of the prepared compounds was tested against various strains of bacteria, yeasts and filamentous fungi (E. coli, S. aureus, C. albicans, R. oryzae, A. alternate and M. gypseum). It was found that the selected bacteria were more sensitive to the studied zinc(II) complex compounds than the yeast and the filamentous fungi.     

Probing dynamic protein ensembles with atomic proximity measures

The emerging role of internal dynamics in protein fold and function requires new avenues of structure analysis. We analyzed the dynamically restrained conformational ensemble of ubiquitin generated from residual dipolar coupling data, in terms of protruding and buried atoms as well as interatomic distances, using four proximity-based algorithms, CX, DPX, PRIDE and PRIDE-NMR (http://hydra.icgeb.trieste.it/protein/). We found that Ubiquitin, this relatively rigid molecule has a highly diverse dynamic ensemble. The environment of protruding atoms is highly variable across conformers, on the other hand, only a part of buried atoms tends to fluctuate. The variability of the ensemble cautions against the use of single conformers when explaining functional phenomena. We also give a detailed evaluation of PRIDE-NMR on a wide dataset and discuss its usage in the light of the features of available NMR distance restraint sets in public databases.     

Thermoanalytical, spectral and biological study of 4-bromobenzoatozinc(II) complexes containing bioactive organic ligands

New zinc(II) 4-bromobenzoate complex compounds with general formula [Zn(4-BrC₆H₄COO)₂L₂]·xH₂O (where L?=?urea, nicotinamide, phenazone or thiourea, x?=?0?C2) were prepared and characterized by elemental analysis, IR spectroscopy and thermal analysis. The thermal decomposition of hydrated compounds started with dehydration process. During the thermal decomposition, the neutral organic ligand, bis(4-bromophenyl)methanone and carbon dioxide were evolved. The solid intermediates and volatile products of thermal decomposition were proved by IR spectroscopy and mass spectrometry. The final solid product of the thermal decomposition heated up to 800?°C was zinc oxide, which was confirmed by X-ray powder diffractometry. Antimicrobial activity of the prepared compounds was tested against various strains of bacteria, yeasts and filamentous fungi (E. coli, S. aureus, C. albicans, R. oryzae, A. alternata and M. gypseum). It was found that bacterium S. aureus and fungi A. alternata are the most sensitive to the studied compounds.     

Mössbauer and XRD study of pulse plated Fe–P and Fe–Ni thin layers

⁵⁷Fe conversion electron Mössbauer spectroscopy, X-ray diffraction, electrochemical and magnetic measurements were used to study pulse electroplated Fe–P and Ni–Fe coatings. XRD and ⁵⁷Fe CEMS measurements revealed the amorphous character of the novel pulse plated Fe–P alloys. CEM spectra indicated significant differences in the short range order and in the magnetic anisotropy between the Fe–P deposits pulse plated at medium long deposition time (t _on?=?2 ms), with short relaxation time (t _off?=?9 ms) and low current density (I _p?=?0.05 Acm^?2) or at short deposition time (t _on?=?1 ms) with long relaxation time (t _off?=?250 ms) and high current density (I _p?=?1.0 Acm^?2). The broad peaks centred around the fcc reflections in XRD of the pulse plated Ni-22 wt.% Fe deposit reflected a microcrystalline Ni–Fe alloy with a very fine, 5–8 nm, grain size. The CEM spectrum of the pulse plated Ni-22 wt.% Fe coating corresponded to a highly disordered solid solution alloy containing a minute amount of ferrihydrite. Extreme favourable soft magnetic properties were observed with these Ni–Fe and Fe–P pulse plated thin layers.     

Biological variability in the ratios of protochlorophyllide forms in leaves and epicotyls of dark-grown pea (Pisum sativum L.) seedlings (a statistical method to resolve complex spectra)

Low-temperature (77K) fluorescence emission spectra of 100 dark-grown pea (Pisum sativum L.) seedlings of various ages were measured. The spectra of the 100 leaf samples were collected into a separate data group and those of epicotyls formed another one. This group was divided into three sub-groups as spectra of uppermost, middle and lowermost 3 cm sections. Further sub-groups were formed on the basis of the ages of the plants. The spectra were normalized to their total integral values (within the 580-780 nm region) then the AVERAGE (arithmetic mean function) and AVEDEV (average of the absolute deviations of data points of their mean function) spectra were calculated. Very sharp bands were found in the AVEDEV spectra. Even the strongly overlapped 629 and 636 nm emission bands appeared as separate peaks, due to the decrease of their half-bandwidth values in the AVEDEV function. Both types of spectra were resolved into Gaussian components. The results showed that the variabilities of the 633 and 655 nm protochlorophyllide forms were similar in the leaves. In epicotyls, the protochlorophyllide forms had different variabilities, especially in the middle sections. The most variable was the amplitude of the 636 nm band and the variabilities of the 629 and 655 nm bands were smaller but still remarkable. The calculation of AVEDEV spectra is an effective method to study the biological variability and spectral resolution of biological samples containing chromophores with multiple spectral properties.     

Examination of Factors Influencing the Sensitivity and Accuracy of Boron Determination by Carminic Acid

Summary Detailed experiments have been carried out to find the factors which influence the sensitivity and accuracy of boron determination by carminic acid. It has been found that the water and hydrochloric acid content of the sample solution can be characterized by an optimum curve concerning the developing colour-intensity. The optimum water content is about 5%, and the optimum hydrochloric acid content is 1–3% (taken 38% HCl).The colour intensity of the complex is considerably influenced by the keeping time of the sample solution. 2 hours keeping time is necessary to get duly sensitive and suitably accurate results. The different water-content of the sulphuric acid of different origin has also an effect on the colour-intensity of the complex.Warming during the keeping time is pronouncedly harmful, because the sensitivity is considerably decreased by it. The most convenient concentration of carminic acid (0.025%) and the optimum wavelength (628 nm) for the analytical measurement were pointed out.The absorption-spectrum of boron-carminic acid complex between 330–800 nm is demonstrated.

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Empfindlichkeit und Genauigkeit der Borbestimmung mit Karminsäure

Zusammenfassung Faktoren, die die Genauigkeit und Empfindlichkeit der Borbestimmung mit Karminsäure beeinflussen, wurden untersucht. Der optimale Wasserund Salzsäuregehalt der schwefelsauren Meßlösung läßt sich an der maximalen Farbintensität erkennen. Er beträgt etwa 5% Wasser und 1–3% Salzsäure (38%ig). Die Reaktionszeit der Meßlösung beeinflußt die Farbintensität des Komplexes stark. Empfindliche und genaue Resultate ergeben sich nach 2 Stunden Reaktionszeit. Schwefelsäuren verschiedener Herkunft können infolge ihres verschiedenen Wassergehaltes die Farbintensität des Bor-Karminsäure-Komplexes stark beeinflussen. Die Meßlösung während der Standzeit zu erwärmen, setzt die Empfindlichkeit der Reaktion bedeutend herab. Die für analytische Zwecke optimale Konzentration der Karminsäurelösung ist 0,025%, die optimale Wellenlänge für die Farbmessung 628 nm. Das Absorptionsspektrum des Bor-Karminsäure-Komplexes zwischen 330 und 800 nm wurde angegeben.

     

Ring transformation of unsaturated N-bridgehead fused pyrimidin-4(3H)-ones: role of repulsive electrostatic nonbonded interaction

Thermal ring transformation ability of unsaturated N-bridgehead fused pyrimidin-4(3H)-ones A is governed by both the steric and the electrostatic interactions between the oxygen of the carbonyl group and the substituent in the peri position.