Temporal Development of a Laser-Induced Helium Nanoplasma Measured through Auger Emission and Above-Threshold Ionization.

Femtosecond pump-probe electron and ion spectroscopy is applied to study the development of a helium nanoplasma up to the nanosecond timescale. Electrons, bound by the deep confining mean-field potential, are elevated toward the vacuum level in the nanoplasma expansion. Subsequent electron recombination gives rise to transitions between He^{+} states, resulting in autoionization. The time-resolved analysis of the energy transfer to quasifree electrons reveals a transient depletion of the Auger emission, which allows for a temporal gate to map the distribution of delocalized electrons in the developing mean field. Furthermore, we trace the recombination of delocalized electrons near the vacuum level into highly excited Rydberg states. Transient above-threshold ionization is introduced as a diagnostic tool to resolve the dynamics. Thus, the development of the electron distribution in the nanoplasma mean-field potential can be monitored via the features observed in the emission spectra.

Auger emission from the Coulomb explosion of helium nanoplasmas.

The long-time correlated decay dynamics of strong-field exposed helium nanodroplets is studied by means of photoelectron spectroscopy. As a result of the adiabatic expansion of the laser-produced, fully inner-ionized nanoplasma, delocalized electrons in the deep confining mean field potential are shifted towards the vacuum level. Meanwhile, part of the electrons localize in bound levels of the helium ions. The simple hydrogenlike electronic structure of He+ results in clear signatures in the experimentally observed photoelectron spectra, which can be traced back to bound-free and bound-bound transitions. Auger electron emission takes place as a result of the transfer of transition energy to weakly bound electrons in the quasifree electron band. Hence, the spatial and temporal development of the nanoplasma cloud is encoded in the experimental spectra, whereas the electronic properties of He+ help resolve the different contributions.

Structure-function relationships of purple acid phosphatase from red kidney beans based on heterologously expressed mutants.

Purple acid phosphatases are binuclear metalloenzymes, which catalyze the conversion of orthophosphoric monoesters to alcohol and orthophosphate. The enzyme from red kidney beans is characterized with a Fe(III)-Zn(II) active center. So far, the reaction mechanisms postulated for PAPs assume the essentiality of two amino acids, residing near the bimetallic active site. Based on the amino acid sequence of kidney bean PAP (kbPAP), residues H296 and H202 are believed to be essential for catalytic function of the enzyme. In the present study, the role of residue H202 has been elucidated. Mutants H202A and H202R were prepared by site-directed mutagenesis and expressed in baculovirus-infected insect cells. Based on kinetic studies, residue H202 is assumed to play a role in stabilizing the transition state, particularly in charge compensation, steric positioning of the substrate, and facilitating the release of the product by protonating the substrate leaving groups. The study confirmed the essentiality and elucidates the functional role of H202 in the catalytic mechanism of kbPAP.

Signs of rapidly progressive dementia in a case of intravascular lymphomatosis.

Intravascular lymphomatosis (IVL), a rare type of non-Hodgkin's lymphoma, is an uncommon cause of progressive dementia, usually followed by death within a few months of onset of clinical disease. Often this aggressive tumor is only diagnosed at autopsy, because of misleading clinical features mimicking a broad spectrum of syndromes and the absence of circulating lympoma cells in the blood, bone marrow or cerebrospinal fluid in many cases. Here we present IVL in a 78-year-old woman with findings leading to the clinical diagnosis of vascular dementia with sudden beginning and positive 14-3-3 protein in the CSF, commonly reported in Creutzfeldt-Jakob disease (CJD).

Self-assembling of proteins and enzymes at nanoscale for biodevice applications.

Different nanotechnological strategies have been selected to implement biomolecular devices following a bottom-up or top-down approach depending on the biomolecule and on its functionality. Biomolecules have particular functionality and self-assembling capabilities that can be exploited for the implementation of both bioelectronic devices and multipurpose engineered biosurfaces. Surface preparation with supramolecular methods and microcontact printing have been developed and optimised to realise suitable functionalised surfaces. These surfaces can be used to link metalloproteins and enzymes for the implementation of nanobioelectronic devices and planar biosensors or to bind cells in order to promote their growth along predefined tracks and grooves. Some possible applications of these biosurfaces are shown and discussed. Results are presented for the realisation of a biomolecular nanodevice working in air based on the metalloprotein azurin immobilised in the solid state, the formation and characterisation of functional glutamate Dehydrogenase monolayers for nanobiosensing applications, the results of soft lithography processes on azurin for biosensor implementation, and the development of physiological self-assembled patterns of laminin-1 for cell culture applications and hybrid devices.

[One catches not only mice with bacon. An atraumatic treatment for cutaneous myiasis]. / Mit Speck fängt man nicht nur Mäuse - Eine atraumatische Behandlungsmethode der kutanen Myiasis -

HISTORY AND ADMISSION FINDINGS: A 37 year old patient was admitted because of four prurigous furunculoid swellings on his right upper knee. The patient had a history of traveling in Brasil for 6 weeks, returning 2 weeks before admission. The nodular skin lesions, 2.5 cm in diameter, had a central opening, from where under little pressure a seropurulent fluid discharged. In the central opening moving, whitish structures were visible. TREATMENT AND COURSE: A piece of raw bacon, serving as occlusion-material, was fixated on the affected skin for two hours. The larvae emerged due to oxygen deficiency. After retraction of the bacon it was possible to grasp the emerged end of the larvae with tweezers and pull them out completely. The larvae were identified as third instar of dermatobia hominis. CONCLUSION: Cutaneous myiasis is a worthy differential diagnosis in patients presenting with furunculoid skin lesions after traveling to endemic areas. The treatment with bacon as an occlusion-material offers an atraumatic alternative to surgical excision.

Diagnostic significance of blood eosinophilia in returning travelers.

This study was conducted to investigate the predictive value of blood eosinophilia (total white blood cell count with > or =8% eosinophils) for the diagnosis of travel-related infections in 14,298 patients who returned from developing countries. The data show that blood eosinophilia in travelers returning from developing countries has only limited predictive value for the presence of travel-related infections. However, the likelihood of the presence of helminth infections increases considerably with the extent of eosinophilia.

The X-ray absorption spectroscopy Debye-Waller factors of an iron compound and of met-myoglobin as a function of temperature.

Protein dynamics can be characterized by the mean square displacements of the individual atoms of a molecule. This concept is extended to X-ray absorption spectroscopy (XAS) of proteins where the physical information in the Debye-Waller factor is in general neglected. In a first step, a procedure for the investigation of the temperature dependence of XAS spectra has been developed for a small iron compound. Subsequently, experiments have been performed on met-myoglobin. It is shown that the mean square displacements of XAS are smaller than those obtained by Mössbauer spectroscopy and far smaller than crystallographic mean square displacements. This behavior is explained by the different sensitivity of the methods. XAS measures a relative mean square displacement between the absorbing and backscattering atoms only. A comparison with mean square displacements calculated from normal modes shows that static displacements contribute significantly. It becomes obvious that the atoms of the active center show a high correlation of their motions.

Tetrameric fluorophosphazene, (NPF(2))(4), planar or puckered?

The results obtained in a comprehensive experimental study on the redetermination of the structure of N(4)P(4)F(8) with single-crystal X-ray diffraction, gas electron diffraction (GED), and differential scanning calorimetry (DSC) establish clearly that, in contrast to the previous report, the eight-membered heterocycle is not planar. Above the phase transition temperature of -74 degrees C, the ring appears pseudoplanar. However, the N(4)P(4) ring is disordered and is puckered above the phase transition when the disorder is modeled correctly. Below the phase transition the ring clearly resembles that of the saddle (K form) of N(4)P(4)Cl(8). The unit cell of the low-temperature phase is derived from that of the higher temperature phase by doubling the c-axis and removing one-half of the symmetry elements. Full structure optimizations were performed at the HF/6-31G and B3LYP/6-31G levels and fully support the experimental diffraction data.

Cellular accumulation determines the activity of three novel tricyclic platinum agents.

BACKGROUND: Cisplatin (CDDP) is a very useful chemotherapeutic agent, but cellular resistance limits its efficacy in malignant glioma. In order to analyze and overcome this resistance, we synthesized three novel platinum compounds; aminoplatin, methylplatin and oxiplatin, using tricyclic DNA intercalating molecules as models. MATERIALS AND METHODS: The novel compounds differ only in one chemical group, which is positioned opposite to the DNA binding site. DNA binding, cellular penetration, and cytotoxicity were compared in three human glioma cell lines (T98G, U87-MG, and U25 IN) and a human fibroblast cell strain (HS 68). 2 RESULT: Binding to isolated DNA was most effective in aminoplatin, followed by methylplatin and oxiplatin. It differed by factors I. I, 0.35, 0.23, from the DNA binding of CDDP (factor I) for the three compounds, respectively. The cellular penetration, however, was fastest with oxiplatin (factor 10.1) followed by CDDP (1), aminoplatin (0.55), and methylplatin (0.27). The cytotoxicity of the three novel compounds followed the pattern of their cellular penetration with oxiplatin being the most active. U87-MG cells were resistant to CDDP, and in this cell line oxiplatin was more effective than CDDP in overcoming the resistance. CONCLUSION: This indicates cellular penetration to be an important feature and the ketogroup of oxiplatin to be beneficial in tricyclic platinum compounds.

Isozymes of Ipomoea batatas catechol oxidase differ in catalase-like activity.

The amino acid sequences of two isozymes of catechol oxidase from sweet potatoes (Ipomoea batatas) were determined by Edman degradation of BrCN cleavage fragments of the native protein and by sequencing of amplified cDNA fragments. Sequence alignment and phylogenetic analysis of plant catechol oxidases revealed about 80% equidistance between the two I. batatas catechol oxidases and approximately 40--60% to catechol oxidases of other plants. When H(2)O(2) was applied as substrate the 39 kDa isozyme, but not the 40 kDa isozyme, showed catalase-like activity. The structure of the 40 kDa isozyme was modeled on the basis of the published crystal structure of the 39 kDa isozyme [T. Klabunde et al., Nat. Struct. Biol. 5 (1998) 1084]. The active site model closely resembled that of the 39 kDa isozyme determined by crystallography, except for a mutation of Thr243 (40 kDa isozyme) to Ile241 (39 kDa isozyme) close to the dimetal center. This residue difference affects the orientation of the Glu238/236 residue, which is thought to be responsible for the catalase-like activity of the 39 kDa isozyme for which a catalytic mechanism is proposed.

Enantiomerically pure cyclopropyl hemiacetals: lipase-catalyzed synthesis of chiral, nonracemic ester homoenolate equivalents.

[figure: see text] Enantiomerically pure cyclopropyl hemiacetals can be obtained by lipase-catalyzed kinetic resolution of their acylated congeners. It is demonstrated that lipases from Candida antarctica and Pseudomonas cepacia show enantiodivergent behavior toward these substrates. Subsequent ring opening of these building blocks can be achieved with ZnCl2 leading to chiral, nonracemic alpha-substituted homoenolate anions.

High-throughput generation and engineering of recombinant human antibodies.

The first version of the Human Combinatorial Antibody Library (HuCAL) is a single-chain Fv-based phage display library (HuCAL-scFv) with 2x10(9) members optimised for high-throughput generation and targeted engineering of human antibodies. 61% of the library genes code for functional scFv as judged by sequencing. We show here that since HuCAL-scFv antibodies are expressed in high levels in Escherichia coli, automated panning and screening in miniaturised settings (96- and 384-well format) have now become feasible. Additionally, the unique modular design of HuCAL-genes and -vectors allows the distinctly facilitated conversion of scFv into Fab, miniantibody and immunoglobulin formats, and the fusion with a variety of effector functions and tags not only convenient for therapeutic applications but also for high-throughput purification and detection. Thus, the HuCAL principle enables the rapid and high-throughput development of human antibodies by optimisation strategies proven useful in classical low molecular weight drug development. We demonstrate in this report that HuCAL is a very convenient source of human antibodies for various applications.

Syntheses and structural characterization of dinuclear and tetranuclear iron(III) complexes with dinucleating ligands and their reactions with hydrogen peroxide.

The iron(III) complexes [Fe(2)(HPTB)(mu-OH)(NO(3))(2)](NO(3))(2).CH(3)OH.2H(2)O (1), [Fe(2)(HPTB)(mu-OCH(3))(NO(3))(2)](NO(3))(2).4.5CH(3)OH (2), [Fe(2)(HPTB)(mu-OH)(OBz)(2)](ClO(4))(2).4.5H(2)O (3), [Fe(2)(N-EtOH-HPTB)(mu-OH)(NO(3))(2)](ClO(4))(NO(3)).3CH(3)OH.1.5H(2)O (4), [Fe(2)(5,6-Me(2)-HPTB)(mu-OH)(NO(3))(2)](ClO(4))(NO(3)).3.5CH(3)OH.C(2)H(5)OC(2)H(5).0.5H(2)O (5), and [Fe(4)(HPTB)(2)(mu-F)(2)(OH)(4)](ClO(4))(4).CH(3)CN.C(2)H(5)OC(2)H(5).H(2)O (6) were synthesized (HPTB = N,N,N',N'-tetrakis(2-benzimidazolylmethyl)-2-hydroxo-1,3-diaminopropane, N-EtOH-HPTB = N,N,N',N'-tetrakis(N' '-(2-hydroxoethyl)-2-benzimidazolylmethyl)-2-hydroxo-1,3-diaminopropane, 5,6-Me(2)-HPTB = N,N,N',N'-tetrakis(5,6-dimethyl-2-benzimidazolylmethyl)-2-hydroxo-1,3-diaminopropane). The molecular structures of 2-6 were established by single-crystal X-ray crystallography. Iron(II) complexes with ligands similar to the dinucleating ligands described herein have been used previously as model compounds for the dioxygen uptake at the active sites of non-heme iron enzymes. The same metastable (mu-peroxo)diiron(III) adducts were observed during these studies. They can be prepared by adding hydrogen peroxide to the iron(III) compounds 1-6. Using stopped-flow techniques these reactions were kinetically investigated in different solvents and a mechanism was postulated.

Release measurements for materials out of controlled areas

Large amounts of dismantled materials from nuclear power plants show such a weak level of radioactivity that they could be released after decision measurements. Till some years ago, the decision measurements taken for the release were based only on determining the mass-specific activity of samples by means of gamma spectrometry and/or manual sequential measurements of the surface activity with large area gas flow counters. The choice of an appropriate measuring method, the layout of the release measurement facility (RMF), the way of preparing the material and the development of smart release procedures are very important for a large throughput and an economic performance of the release process. NIS and RADOS have developed RMF based on gross gamma activity. The NIS-RMFs have been applied for the last 10 years for decision measurements in different operated but also in dismantled nuclear power plants. Together with RMFs from RADOS, more than 12,000 Mg of various types of materials have been measured up to now with this method in Germany.

An inward rectifier and a voltage-dependent K+ current in single, cultured pericytes from bovine heart.

OBJECTIVE: The purpose of this study was to describe passive electrical properties and major membrane currents in coronary pericytes. METHODS: 78 single, cultured bovine pericytes were studied with the patch-clamp technique in the whole-cell mode. RESULTS: The membrane potential of the cells was -48.9+/-9.6 mV (mean+/-S.D.) with 5 mM and -23.2+/-2.2 mV with 60 mM extracellular K+. The membrane capacitance was 150.2+/-123.2 pF. The current-voltage relation of the pericytes was dominated by an inward current at hyperpolarized potentials and an outward current at depolarized potentials. Increasing extracellular K+ from 5 to 60 mM led to an increase of the inward current and to a shift of this current to more depolarized potentials. The inward current was very sensitive to extracellular barium (50 microM). The maximum slope conductance of the cells at hyperpolarized potentials was 2.9+/-2.8 nS. Inward rectification of whole-cell currents was steep (slope factor = 6.8 mV). With elevated external K+ the outward current reversed near the potassium equilibrium potential. Onset of the outward current was sigmoid and inactivation of this current was monoexponential, slow (time constant = 12.8 s) and incomplete. Voltage-dependence of outward current steady-state activation was steep (slope factor = 4.6 mV). The outward current was very sensitive to 4-aminopyridine (dissociation constant = 0.1 mM). The maximum slope conductance at depolarized potentials was 16.6+/-15.6 nS. CONCLUSION: We report for the first time, patch-clamp recordings from coronary pericytes. An inward rectifier and a voltage-dependent K+ current were identified and characterized. Regulation of these currents may influence coronary blood flow.

Overcoming cisplatin resistance: design of novel hydrophobic platinum compounds.

BACKGROUND: The anticancer activity of cisplatin derives from its ability to crosslink DNA. Cisplatin-resistance is partially caused by enhanced nucleotide excision repair (NER). Major 1,2-intrastrand crosslinks can create a hydrophobic notch at the damage site, which can be specifically bound by damage-recognition proteins, thus shielded from NER-activity. We aimed at preventing resistance by enhancing this mechanism using more hydrophobic platinum compounds. METHODS: We synthesized three platinum analogs with increased hydrophobic characteristics. Performing MTT-assays, the efficacy of cisplatin and the novel agents was compared in a fibroblast and eight brain tumour cell lines. RESULTS: Among the novel compounds, the most hydrophobic molecule, methylpyridineplatinum, was most cytotoxic (LC50 = 5.84 x 10(-5) M), followed by methylpyrazineplatinum, the second most hydrophobic (LC50 = 1.79 x 10(-4) M), and pyridineplatinum (LC50 = 2.76 x 10(-4) M). Overall, cisplatin revealed highest cytotoxicity (LC50 = 8.77 x 10(-6) M). CONCLUSIONS: Comparison of the novel compounds supports the hypothesis that increased hydrophobicity contributes to higher antitumour-activity. Other advantageous characteristics of cisplatin might relate to its remaining highest efficacy.

Methane monooxygenase and its related biomimetic models.

The past year has seen significant advances in the understanding of the dioxygen-activating chemistry of non-heme diiron enzymes, such as methane monooxygenase. Recent spectroscopic and structural studies on various biomimetic model compounds have provided new and valuable insights into this enzyme's mechanism of action and the important dioxygen-activation process.

Trimethylsilyl- and trimethylstannyldimethylphosphane--convenient and versatile reagents for the synthesis of polyfluoroaryldimethylphosphanes.

Trimethylsilyldimethylphosphane (Me3SiPMe2) and the corresponding tin compound (Me3SnPMe2) were used as reagents for the substitution of fluorine by the Me2P group in polyfluoroarenes C6F5X (X = F, H, Cl, CF3) and C5NF5. The reactions occur even under mild conditions (T = 0-20 C), either in benzene or without solvent, to give as a rule 4-X-1-(dimethylphosphano)tetrafluorobenzenes (XC6F4PMe2, 1-4) and 4-(dimethylphosphano)tetrafluoropyridine (C5NF4PMe2, 5), respectively, in yields between 75 and 95%. In the case of C6F6, double substitution is also observed, which affords 1,4-bis(dimethylphosphano)tetrafluorobenzene (6). A very efficient route to the compounds XC6F4PMe2 (X = F, H, Cl, CF3) and C5NF4PMe2 was developed as a one-pot reaction of the corresponding fluoroarenes with tetramethyldiphosphane (P2Me4) and trimethyltin hydride (Me3SnH) at moderate temperatures. This process was tested for C6F6 and perfluorobiphenyl which gave C6F5PMe2 (1) and 4,4'-bis(dimethylphosphano)octafluorobiphenyl (7), respectively. The results, which included kinetic measurements that used the intensities of the 31P signals, revealed the influence of the substrate type on the rate of reaction in the sequence: C5NF5>C6F5CF3> C6F5Cl, C6F5PMe2>C6F5H>C6F6>> C6H5F. Ab initio calculations were carried out on the model reactions of pentafluoropyridine with silylphosphane, phosphane or phosphide to discriminate between possible reaction mechanisms. The novel phosphanes were characterised by spectroscopic investigations (NMR, MS), by preparation of the related thiophosphanes ArFP(=S)Me2 (8-14), their spectroscopic and analytic data and single crystal X-ray diffraction studies on five of these derivatives.