Effect of a physical phase plate on contrast transfer in an aberration-corrected transmission electron microscope.

In this theoretical study we analyze contrast transfer of weak-phase objects in a transmission electron microscope, which is equipped with an aberration corrector (C(s)-corrector) in the imaging lens system and a physical phase plate in the back focal plane of the objective lens. For a phase shift of pi/2 between scattered and unscattered electrons induced by a physical phase plate, the sine-type phase contrast transfer function is converted into a cosine-type function. Optimal imaging conditions could theoretically be achieved if the phase shifts caused by the objective lens defocus and lens aberrations would be equal to zero.

Isothiocyanate-functionalized RGD peptides for tailoring cell-adhesive surface patterns.

With the advances made in surface patterning by micro- and nanotechnology, alternative methods to immobilize biomolecules for different purposes are highly desired. RGD peptides are commonly used to create cell-attractive surfaces for cell-biological and also medical applications. We have developed a fast, one-step method to bind RGD peptides covalently to surfaces by thiourea formation, which can be applied to structured and unstructured materials.

Functional consequences of leucine and tyrosine mutations in the dual pore motifs of the yeast K(+) channel, Tok1p.

Tandem pore-loop potassium channels differ from the majority of K(+) channels in that a single polypeptide chain carries two K(+)-specific segments (P) each sandwiched between two transmembrane helices (M) to form an MP(1)M-MP(2)M series. Two of these peptide molecules assemble to form one functional potassium channel, which is expected to have biaxial symmetry (commonly described as asymmetric) due to independent mutation in the two MPM units. The resulting intrinsic asymmetry is exaggerated in fungal 2P channels, especially in Tok1p of Saccharomyces, by the N-terminal presence of four more transmembrane helices.

AtRECQ2, a RecQ helicase homologue from Arabidopsis thaliana, is able to disrupt various recombinogenic DNA structures in vitro.

RecQ helicases play an important role in the maintenance of genomic stability in pro- and eukaryotes. This is highlighted by the human genetic diseases Werner, Bloom's and Rothmund-Thomson syndrome, caused by respective mutations in three of the five human RECQ genes. The highest numbers of RECQ homologous genes are found in plants, e.

1,2-Addition of trialkylaluminium reagents to N-diphenylphosphinoylketimines in the absence of any additional reagents.

Using reactive trialkylaluminium reagents for the 1,2-addition on acetophenone- and benzophenone-derived ketimines, alpha-trisubstituted amines were obtained in excellent yields up to 99%.

Augmented reality assistance for realization of incision planning and model-based analysis of the modified surface model.

In this paper an application for incision planning, AR-visualization of plan data and model-based analysis of the modified anatomical structure due to realization of the planned incision is presented. The developed algorithm detects modifications of the acquired surface model and generates a parameterized description of the wound.

Nucleophilic additions to alkylidene bis(sulfoxides): stereoelectronic effects in vinyl sulfoxides.

Conjugate additions of nucleophiles (e.g. enolates, amines and malonate anions) to bis(p-tolylsulfinyl)alkenes, alkylidene-1,3-dithiane-1,3-dioxides and alkylidene-1,3-dithiolane-1,3-dioxides have recently been published.

Theoretical investigation of clusters of phosphorus and arsenic: fascination and temptation of high symmetries.

We present a theoretical study of the energetic and thermodynamic stability of selected phosphorus and arsenic clusters containing 18 to 168 atoms. For this purpose we employ MP2 as well as DFT functionals BP86 and B3LYP with extended basis sets. All procedures predict the family of one-dimensional polymers X18+12n, each with 2n-1 isomers of virtually identical energy, to be more stable than other structures investigated so far.

Molecular evolution and expression of zebrafish St8SiaIII, an alpha-2,8-sialyltransferase involved in myotome development.

Enzymes of the St8Sia family, a subgroup of the glycosyltransferases, mediate the transfer of sialic acid to glycoproteins or glycolipids. Here, we describe the cloning of the zebrafish St8SiaIII gene and study its developmental activity. A conserved synteny relationship among vertebrate chromosome regions containing St8SiaIII loci underscores an ancient duplication of this gene in the teleost fish lineage and a specific secondary loss of one paralog in the zebrafish.

On the thermal unimolecular decomposition of the cyclohexoxy radical--an experimental and theoretical study.

The kinetics of the thermal unimolecular decomposition of the cyclohexoxy radical (c-C(6)H(11)O) was experimentally studied, and the results were analyzed in terms of statistical rate theory with molecular and transition state data from quantum chemical calculations. Laser flash photolysis of cyclohexylnitrite at 351 nm was used to produce c-C(6)H(11)O radicals, and their concentration was monitored by laser-induced fluorescence after excitation at 356.2 or 365.

Shape-persistent macrocycles with intraannular alkyl groups: some structural limits of discotic liquid crystals with an inverted structure.

The synthesis and thermal properties of new shape-persistent macrocycles of different sizes decorated with intraannular alkyl chains are described. The alkyl chain length is in all cases sufficient to cross the rings and to fill their interior completely. The investigation of the thermal behavior has shown that the smaller cycles do not exhibit thermotropic mesophases.

Towards a systematic evaluation of protein mutation extraction systems.

The development of text analysis systems targeting the extraction of information about mutations from research publications is an emergent topic in biomedical research. Current systems differ in both scope and approach, thus preventing a meaningful comparison of their performance and therefore possible synergies. To overcome this evaluation bottleneck, we developed a comprehensive framework for the systematic analysis of mutation extraction systems, precisely defining tasks and corresponding evaluation metrics, that will allow a comparison of existing and future applications.

Enhanced semantic access to the protein engineering literature using ontologies populated by text mining.

The biomedical literature is growing at an ever-increasing rate, which pronounces the need to support scientists with advanced, automated means of accessing knowledge. We investigate a novel approach employing description logics (DL)-based queries made to formal ontologies that have been created using the results of text mining full-text research papers. In this paradigm, an OWL-DL ontology becomes populated with instances detected through natural language processing (NLP).

Formation of brominated products in irradiated titanium dioxide suspensions containing bromide and dissolved organic carbon.

We report the irradiation of TiO(2) suspensions containing Br(-) and dissolved organic carbon (DOC). In the absence of DOC, we found no evidence for the formation of BrO(3)(-) upon irradiation of 1gL(-1) P25 suspensions with UV light for initial Br(-) concentrations up to 10mgL(-1). In the presence of DOC (Lake Hohloh, Germany and salicylic acid), we found no evidence for the formation of either BrO(3)(-) or trihalomethanes (THMs).

Ge4Br4[Mn(CO)5]4 and Ge6Br2[Mn(CO)5]6: first germanium cluster compounds containing Mn(CO)5 ligands.

Cluster compounds of germanium exhibiting germanium-germanium bonds, where the germanium atoms are additionally bound to transition metal ligands, are rare. Here a synthetic pathway to such cluster compounds is described, starting from metastable Ge I halide solutions leading to the two cluster compounds Ge4Br4[Mn(CO)5]4 and Ge6Br2[Mn(CO)5]6, being the first examples of germanium cluster compounds bearing Mn(CO)5 ligands. The Ge6 compound exhibits a novel arrangement of germanium atoms that has not been previously observed in ligand stabilized cluster compounds of germanium, neither with organic nor with transition metal ligands.

Time-resolved polaron dynamics in molten solutions of cesium-doped cesium iodide.

Temperature-dependent investigations of excess electrons in molten solutions of cesium-doped cesium iodide (Cs-CsI) (mole fraction of Cs approximately 0.003) were performed applying femtosecond pump-probe absorption spectroscopy. The pulse-limited induced bleach observed at probe wavelengths from 600 to 1240 nm was attributed to the excitation of equilibrated excess electrons which were initially formed by melting a Cs-CsI mixture.

Computer based optimization of biventricular pacing according to the left ventricular 17 myocardial segments.

Cardiac resynchronization therapy (CRT) has shown to improve hemodynamics and clinical symptoms of congestive heart failure. The present article investigates an automated non-invasive strategy based on a computer model of the heart to optimize biventricular pacing as a CRT with respect to electrode positioning and timing delays. Accurate simulations of the electrical activities of the heart require suitable anatomical and electrophysiological models.

Computer based modeling of the congenital long-QT 2 syndrome in the Visible Man torso: from genes to ECG.

The congenital long-QT syndrome is commonly associated with a high risk for polymorphic ventricular tachy-cardia and sudden cardiac death. This is probably due to an intensification of the intrinsic heterogeneities present in ventricular myocardium. Increasing the electrophysiological heterogeneities amplifies the dispersion of repolarization which directly affects the morphology of the T wave in the ECG.

Isostable DNA.

The high fidelity detection of multiple DNA sequences in multiplex assays calls for duplexes whose stability is independent of sequence (isostable DNA), forming under universally stringent conditions. Nature did not evolve DNA to form isostable duplexes. Here we report how probe strands can be modified so that an all-A/T target strand is bound with the same or slightly higher affinity than the corresponding all-G/C strand with the same sequence of purines and pyrimidines.

The weak orthogonality functional in explicitly correlated pair theories.

Recent advances have seen the convergence of the R12 and Gaussian geminal explicitly correlated methods, such that the principal remaining distinction is the way in which the many-electron integrals are handled. Here we examine the weak orthogonality functional and the resolution of the identity and find that the first, although exact in the limit of infinite basis, introduces a conflict between the physical description of the electronic cusp and the satisfaction of the strong orthogonality constraint. This leads us to propose an improved weak orthogonality functional where the explicitly correlated pair functions are almost orthogonal to the occupied orbitals by construction.

Semi-automated XML markup of biosystematic legacy literature with the GoldenGATE editor.

Today, digitization of legacy literature is a big issue. This also applies to the domain of biosystematics, where this process has just started. Digitized biosystematics literature requires a very precise and fine grained markup in order to be useful for detailed search, data linkage and mining.

Physicochemical influences on electrohydrodynamic transport in compressible packed beds of colloidal boehmite particles.

Production and processing of colloidal particles require a deeper understanding of the surface charge of particles and the interaction of mass and charge transport in packed beds. The assessment of fundamental parameters is rather complex due to the additional influence of the particle charge on the structure of a packed bed. The combination of different measurement techniques (streaming potential and electroosmosis) allows for separating the effects, based on the postulation of a new method to quantify the ratio of surface conductance to liquid conductance.

Stable organic azides based on rigid tetrahedral methane and adamantane structures as high energetic materials.

A four-folded azidation of tetrakis(4-iodophenyl)methane and -adamantane leads to stable organic azides, but yet energetic materials, measured by differential scanning calorimetry (DSC). The rigid and symmetrical structures can be useful for new polymer and nanomaterial developments in material sciences as well as bioconjugations, after 1,3-dipolar cycloaddition reactions with terminal alkynes to 1,2,3-triazoles.

Hartwig-Buchwald amination on solid supports: a novel access to a diverse set of 1H-benzotriazoles.

Hartwig-Buchwald amination reactions of bromo- and chloroarenes were performed on solid supports with triazene-linked arenes. Immobilized 2-haloarenes were treated with diverse primary amines and anilines at 100 degrees C under palladium catalysis to yield N-substituted 2-aminoarenes. The latter were alternatively formed through reaction of bromo- and chloroarenes with immobilized primary 2-aminobenzenes.

Search for basic relationships between "molecular size" and "chemical structure" of aquatic natural organic matter--answers from 13C and 15N CPMAS NMR spectroscopy.

To investigate the structural composition of natural organic matter (NOM), a 3-step micro- and ultrafiltration procedure was applied to 3 surface waters from southern Germany, and fractions from all filtration steps were collected. The NOM was characterized using solid-state 13C and 15N nuclear magnetic resonance (NMR) techniques. Routine integration of the 13C NMR spectra and extended data analysis procedures were carried out for a quantitative comparison of the structural components as well as for the elucidation of structural fractionation patterns.