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.     

Studies on the track formation mechanism of the heavy ions in CR-39

The bulk etch rate for two types of CR-39 detector was measured as a function of temperature and the activation energies of bulk etching was determined. Experimental values of track etch rate were derived directly from the function of the succesive measured track length vrs. etching time for ²⁰⁹Bi, ¹²⁹Xe and ²⁰Ne ions.

The maximum etchable length of 13 MeV/u ²⁰⁹Bi and 13.04 MeV/u ¹²⁹Xe ions have been measured at and below these energies. A comparison of the measured and calculated track length data is presented.     

Effect of iron restriction on outer membrane protein composition of Pseudomonas strains studied by conventional and microchip electrophoresis

In this study the outer membrane protein (OMP) composition of six Pseudomonas aeruginosa strains had been analyzed by conventional CE and microchip electrophoresis. Bacterial OMPs are important virulence factors and play a significant role in the pathogenesis of infectious diseases. Changes in their composition might refer to the altered pathogenic properties and antibiotic sensitivity of a certain strain. Pathogenic bacteria invading the human host have to multiplicate under iron-restricted conditions that induce changes in the OMP composition. High-molecular-weight OMPs have to be expressed, which serve as receptors for the iron-siderophore complexes. OMP patterns of bacteria obtained by the two different methods in this study were similar, all major proteins could be detected by both techniques, and the molecular weights showed good correlations, although direct comparison of the peak areas is not straightforward due to the different detection methods (UV and LIF). Changes in OMP composition under iron restriction could be detected, and appearance of a 92 kDa protein in all six P. aeruginosa strains and a 94 kDa protein in the KT 2 strain could be demonstrated. Besides that up- and downregulation of certain proteins could be also detected. The increased separation speed, picoliters of sample consumption, baseline separation achieved more frequently by this method--especially in the high-molecular-weight region--showed the advantages of microchip electrophoresis in the analysis of clinical samples.     

In vitro study of antibiotic effect on bacterial adherence to acrylic intraocular lenses

Implantation of artificial intraocular lenses into the eye during ophthalmic surgical procedures ensures an unliving surface on which bacterial pathogens may attach and form biofilms. Despite antibiotic treatment bacteria growing in biofilms might cause inflammation and serious complications. In this study the adhesive ability of 7 Staphylococcus aureus and 11 coagulase-negative Staphylococcus (CNS) strains to the surface of acrylic intraocular lenses had been examined by the ultrasonic method. In untreated cases adhesion of the S. aureus and CNS strains did not differ significantly. We could not demonstrate significant differences between the adhesive ability of the standard strains and the clinical isolates. In this study a single – 60 min long – antibiotic (ciprofloxacin and tobramycin) treatment had been applied, that correlate well with the single or intermittant antibiotic prophylaxis of patients. Ciprofloxacin administration was able to reduce significantly the number of attached cells on the surface of acrylic lenses both in the case of S. aureus and CNS strains. Dependence of the effect from concentration could also be demonstrated. Tobramycin treatment was able to inhibit significantly the attachment of S. aureus cells. Despite the debate on antibiotic prophylaxis we presented in our experiments that a single antibiotic administration can decrease the attachment of bacterial cells to the surface of acrylic intraocular lenses, and might be effective in the prevention of postoperative endophthalmitis, that is a rare but serious complication of ophthalmic surgery.     

Debye screening of dislocations

Debye-like screening by edge dislocations of some externally given stress is studied by means of a variational approach to coarse grained field theory. Explicitly given are the force field and the induced geometrically necessary dislocation (GND) distribution, in the special case of a single glide axis in 2D, for (i) a single edge dislocation and (ii) a dislocation wall. Numerical simulation demonstrates that the correlation in relaxed dislocation configurations is in good agreement with the induced GND in case (i). Furthermore, the result (ii) well predicts the experimentally observed decay length for the GND developing close to grain boundaries.     

Brightening of an accretion disk due to viscous dissipation of gravitational waves during the coalescence of supermassive black holes

Mergers of supermassive black hole binaries release peak power of up to approximately 10(57) erg s(-1) in gravitational waves (GWs). As the GWs propagate through ambient gas, they induce shear and a small fraction of their power is dissipated through viscosity. The dissipated heat appears as electromagnetic (EM) radiation, providing a prompt EM counterpart to the GW signal. For thin accretion disks, the GW heating rate exceeds the accretion power at distances farther than approximately 10(3) Schwarzschild radii, independently of the accretion rate and viscosity coefficient.     

Examination of typical bacterial strains in septic arthritis by isoperibol calorimeter

The accurate diagnosis of different types of arthritis is a great clinical challenge. It has a special importance to reach the right diagnosis in case of septic joint infections. The clarification of aetiology is crucial to minimize the complications and mortality of these cases. Therefore, novel methods like synovial sample analyses by differential scanning calorimetry (DSC) could have the potential to provide further information in the diagnostic process (Dandé et al. in J Therm Anal Calorim. doi: https://doi.org/10.1007/s10973-017-6179-6, 2017). A retrospective analysis of patients treated with septic joint infections over the last 5 years at the Department of Traumatology and Hand Surgery has been conducted. Human synovial samples were inoculated with six different, frequently occurring human pathogenic bacterial strains. The proliferation of inoculated synovial fluid samples was monitored by SETARAM Micro DSC-II calorimeter in isotherm mode (isoperibol calorimeter). Based on our results, 47.45% of the cases involved small joint (SG) infections and 52.55% of them occurred in large joints (LG). Synovial aspirates collected from infected joints indicated the presence of the following bacteria and incidences: Staphylococcus aureus 43 (22.16%), Staphylococcus epidermidis 3 (1.54%), Methicillin-resistant Staphylococcus aureus, MRSA 4 (2.06%), Streptococcus pyogenes 9 (4.63%), Escherichia coli 1 (0.51%) and Pseudomonas aeruginosa 4 (2.06%). The isoperibolic curves of human synovial samples inoculated with different bacterial strains clearly demonstrated specific/representative results in case of each bacterium. The control of human synovial fluid samples by isotherm calorimetry could be a useful tool in the differential diagnosis of human septic arthritis.     

Conservative spatial chaos of buckled elastic linkages

Buckling of an elastic linkage under general loading is investigated. We show that buckling is related to an initial value problem, which is always a conservative, area-preserving mapping, even if the original static problem is nonconservative. In some special cases, we construct the global bifurcation diagrams, and argue that their complicated structure is a consequence of spatial chaos. We characterize spatial chaos by the associated initial value problem's topological entropy, which turns out to be related to the number of buckled configurations.     

Synthesis and Photophysical Properties of a Series of Cyclopenta[b]naphthalene Solvatochromic Fluorophores

The synthesis and photophysical properties of a series of naphthalene-containing solvatochromic fluorophores are described within. These novel fluorophores are prepared using a microwave-assisted dehydrogenative Diels-Alder reaction of styrene, followed by a palladium-catalyzed cross coupling reaction to install an electron donating amine group. The new fluorophores are structurally related to Prodan. Photophysical properties of the new fluorophores were studied and intriguing solvatochromic behavior was observed. For most of these fluorophores, high quantum yields (60-99%) were observed in methylene chloride in addition to large Stokes shifts (95-226 nm) in this same solvent. As the solvent polarity increased, so did the observed Stokes shift with one derivative displaying a Stokes shift of ～300 nm in ethanol. All fluorophore emission maxima, and nearly all absorption maxima were significantly red-shifted when compared to Prodan. Shifting the absorption and emission maxima of a fluorophore into the visible region increases its utility in biological applications. Moreover, the cyclopentane portion of the fluorophore structure provides an attachment point for biomolecules that will minimize disruptions of the photophysical properties.     

On the Linear Dependence of a Finite Set of Additive Functions

In this note we prove the following: Let n?≥ 2 be a fixed integer. A system of additive functions ${A_{1},A_{2},\ldots,A_{n}:\mathbb{R} \to\mathbb{R}}$ is linearly dependent (as elements of the ${\mathbb{R}}$ vector space ${\mathbb{R}^{\mathbb{R}}}$ ), if and only if, there exists an indefinite quadratic form ${Q:\mathbb{R}^{n}\to\mathbb{R} }$ such that ${Q(A_{1}(x),A_{2}(x),\ldots,A_{n}(x))\geq 0}$ or ${Q(A_{1}(x),A_{2}(x),\ldots,A_{n}(x))\leq 0}$ holds for all ${x\in\mathbb{R}}$ .