The molecular and crystal structure of (+)-mianserin hydrobromide

X-ray analysis of crystals of (+)-mianserin hydrobromide (1,2,3,4,10,14b-hexahydro-2-methyl-dibenzol[c,f]pyrazino[1,2-a]azepine) has established the stereochemistry and absolute configuration of this compound (S at 14b).The crystals are orthorhombic with unit-cell dimensions: a = 1299(1)pm, b = 1420(1)pm, c = 1002(1)pm; Z = 4. The space group is P2₁2₁2₁. Intensity data for about 1000 reflections were measured on a single-crystal diflractometer with Cu-K_α radiation. The crystal structure was solved by the heavy-atom method and refined by least-squares procedures. Final R-factor 9·4%. The absolute configuration was determined by Bijvoet's technique.     

Synthese und Kristallstrukturen der Polyselenidokomplexe (PPh4)6[M(Se4)2]2[WSe4] · DMF mit M = Zink und Quecksilber

Syntheses and Crystal Structures of the Polyselenido Complexes (PPh₄)₆[M(Se₄)₂]₂[WSe₄] · DMF with M = Zinc and Mercury The title compounds have been prepared by the reactions of the acetates of zinc and mercury, respectively, with excess (PPh₄)₂ WSe₄ in boiling dimethylformamide, forming black-red single crystals. According to the X-ray structure determinations both compounds crystallize isotypically in the space group 12/a with four formula units per unit cell. (PPh₄)₆[Zn(Se₄)₂]₂[WSe₄] · DMF: a = 2888.1(6), b = 1740.3(2), c = 2893.9(4) pm, β = 90.47(1)°. 3230 observed unique reflections, R = 0.009. (PPh₄)₆[Hg(Se₄)₂]₂[WSe₄] · DMF: a = 2891.8(5), b = 1738.0(4), c = 2920.1(5) pm, β = 90.29(2)°. 2978 observed unique reflections, R = 0.115%. The compounds consist of PPh₄⁺ ions, spirocyclic octaseleno metallates [M(Se₄)₂]^2?, tetrahedral WSe₄²-ions, and disordered DMF Molecules.     

Synthesis and self-assembly of giant porphyrin discs

A giant porphyrin disc (M(w)= 15 kDa) has been synthesized and its self-assembly behaviour at an interface studied by liquid STM which reveals the presence of huge domains (>400 x 400 nm2) of very well ordered and molecularly resolved columnar stacks.     

Application of gas-sensor array technology for detection and monitoring of growth of spoilage bacteria in milk: A model study

The aim of this study was to develop a novel, rapid system for detection and monitoring of growth of undesirable bacteria in food using gas-sensor array technology. Three spoilage bacteria isolated from a cheese-processing hall were identified as Serratia marcescens, Serratia proteamacufans and Pseudomonas putida. The growth of these bacteria in milk was investigated using a commercial solid state based gas-sensor array system. On the basis of the temporal sensor readings of the pure cultures, bacterial growth could be monitored and the individual strains identified and followed throughout the complete growth cycle in both single and mixed culture. The gas-sensor signals could be used as early indicators of the onset of bacterial growth. Start detection of volatile bacterial metabolites coincided with the start of the exponential growth phase taking place around 7 h after inoculation and corresponding to bacterial numbers of 10⁴ (cfu/ml). The results were confirmed by comparing the gas profiles with the cell counts and by headspace gas chromatography mass spectrometry (GC/MS) of volatile microbial metabolites. High correlation (r > 0.90, p < 0.001) was found between the gas-sensor readings and major secondary volatile metabolites. Using the sensor readings, cell numbers of single strain cultures could be predicted with an error of less than 5%. The results show that it is possible to monitor growth of individual strains of spoilage bacteria in a mixed culture in milk on the basis of the type and amount of volatile compounds which they produce, using a gas-sensor array system. The system thus affords possibilities for further development for quick, more accurate and full scale determinations of shelf life, the design of spoilage indicators, rapid identification of undesired microorganisms and rapid measurements of spoilage.     

Purification method for recombinant proteins based on a fusion between the target protein and the C-terminus of calmodulin

Calmodulin (CaM) was used as an affinity tail to facilitate the purification of the green fluorescent protein (GFP), which was used as a model target protein. The protein GFP was fused to the C-terminus of CaM, and a factor Xa cleavage site was introduced between the two proteins. A CaM-GFP fusion protein was expressed in E. coli and purified on a phenothiazine-derivatized silica column. CaM binds to the phenothiazine on the column in a Ca(2+)-dependent fashion and it was, therefore, used as an affinity tail for the purification of GFP. The fusion protein bound to the affinity column was then subjected to a proteolytic digestion with factor Xa. Pure GFP was eluted with a Ca(2+)-containing buffer, while CaM was eluted later with a buffer containing the Ca(2+)-chelating agent EGTA. The purity of the isolated GFP was verified by SDS-PAGE, and the fluorescence properties of the purified GFP were characterized.     

Reversible cooperative dihydrogen binding and transfer with a bis-phosphenium complex of chromium

The reversible reaction of H₂ with a bis-phosphenium complex of chromium provides a rare example of 3d transition metal/phosphenium cooperativity. Photolysis induces the activation of H₂ and yields a spectroscopically detectable phosphenium-stabilized (σ–H₂)-complex, readily showing exchange with gaseous H₂ and D₂. Further reaction of this complex affords a phosphine-functionalized metal hydride, representing a unique example of reversible H₂ cleavage across a 3d M P bond. The same species is also accessible via stepwise H⁺/H⁻ transfer to the bis-phosphenium complex, and releases H₂ upon heating or irradiation. Dihydrogen transfer from the H₂-complex to styrene is exploited to demonstrate the first example of promoting hydrogenation with a phosphenium complex.

Photolysis of a phosphenium complex enables reversible activation of H₂ to yield a dihydrogen complex which stimulates H₂ cleavage or catalytic hydrogenation.     

A microfluidic biosensor based on nucleic acid sequence recognition

The development of a generic semi-disposable microfluidic biosensor for the highly sensitive detection of pathogens via their nucleic acid sequences is presented in this paper. Disposable microchannels with defined areas for capture and detection of target pathogen RNA sequence were created in polydimethylsiloxane (PDMS) and mounted onto a reusable polymethylmethacrylate (PMMA) stand. Two different DNA probes complementary to unique sequences on the target pathogen RNA serve as the biorecognition elements. For signal generation and amplification, one probe is coupled to dye encapsulated liposomes while the second probe is coupled to superparamagnetic beads for target immobilization. The probes hybridize to target RNA and the liposome–target-bead complex is subsequently captured on a magnet. The amount of liposomes captured correlates directly to the concentration of target sequence and is quantified using a fluorescence microscope. Dengue fever virus serotype 3 sequences and probes were used as a model analyte system to test the sensor. Probe binding and target capture conditions were optimized for sensitivity resulting in a detection limit of as little as 10 amol L^–1 (10 pmol L^–1) . Future biosensors will be designed to incorporate a mixer and substitute the fluorescence detection with an electrochemical detection technique to provide a truly portable microbiosensor system.     

Induction of Proinflammatory Cytokines in Human Epidermoid Carcinoma Cells by in vitro Ultraviolet A1 Irradiation

Abstract— Ultraviolet radiation-induced expression of cytokines by keratinocytes is important for the pathogenesis of polymorphous light eruption (PLE). Because UVA1 radiation rather than UVB radiation might be a more important trigger for PLE, cells from the human epidermoid carcinoma cell line KB were exposed in vitro to UVA1 radiation (30 J/cm²) and subsequently analyzed for cytokine expression. Ultraviolet A1 irradiation induced tumor necrosis factor (TNF)-a and interleukin (IL)-8 expression in KB cells at the mRNA and protein level. Upregulation of cytokine mRNA levels followed a Diphasic pattern. This effect was specific for TNFa and IL-8 because UVA1 radiation did not induce expression of IL-la or IL-6 in these cells. Ultraviolet Al radiation-induced expression of intercellular adhesion molecule-1 in KB cells previously was found to depend on the thiol status of these cells. Therefore, KB cells were treated with DL-buthionine-[S, R]-sulfoximine (BSO), a specific inhibitor of de novo glutathione synthesis. Exposure of BSO-pretreated KB cells to UVA1 radiation significantly induced IL-1α and IL-6 mRNA and protein expression. These studies demonstrate the capacity of UVA1 radiation to induce cytokine expression in human epidermoid carcinoma cells. This immunomodulatory effect may be mediated by thiol-status-dependent and -independent mechanisms.     

Crystal structure and vibrational spectra of polyamine-copper(II) complexes

The structures of [Cu(en)(H₂O)₂]SO₄ (I), [Cu(en)₂](NO₃)₂ (II) and [Cu(trien)I]I (III) have been determined by single crystal X-ray diffraction. ComplexI is monoclinic, space group C2/c, with unit cell parametera=7.232(1),b=11.725(2),c=9.768(1), =105.50(1)°, andZ=4. ComplexII is also monoclinic, space group P2₁/a, witha=7.978(2),b=9.982(4),c=8.218(3), =111.11(2)°, andZ=2. ComplexIII is orthorhombic, space group P2₁2₁2₁, witha=8.098(1),b=11.902(1),c=13.682(2), andZ=4. The structures were solved by direct methods and refined by full-matrix least-squares to finalR values of 0.031, 0.043 and 0.036 for complexesI, II, andIII, respectively. ComplexesI andII show an octahedral coordination geometry. ComplexIII shows a square pyramidal coordination geometry. ComplexI forms infinite monodimensional chains where the SO ₄ ^2– ions acts as a bridge between two neighboringen molecules. The vibrational spectra of these complexes agree well with their crystal structures. Structure and stability of seven other related Cu(II) complexes of (trien), (dien)₂, (en)₂ and (en) are inferred in this study.     

Comparison of different flow-through adsorptive stripping voltammetric methods for the determination of molybdenum(VI)

Four different complexing reagents namely chloranilic acid, oxine, tropolone, and cupferron were applied for AdSV determinations of molybdenum. The parameters for the determination using a flow-through cell with a hanging mercury drop (HMDE) as working electrode were examined systematically for all four systems and evaluated. Cyclic voltammograms were recorded to examine the electrode reaction, alternating current (AC) voltammetry was used to determine adsorption processes. The comparison includes sensitivity, detection limit, linear concentration range, the susceptibility to interference by organic compounds or foreign ions, and the applicability to sea and tap water samples. The interpretation of the electrode reaction mechanism for the reduction of the Mo cupferron complex published from Jiao et al. [10] was improved. Received: 12 February 1999 / Revised: 10 May 1999 / Accepted: 14 May 1999