Chemical mimicry: hierarchical 1D TiO2@ZrO2 core-shell structures reminiscent of sponge spicules by the synergistic effect of silicatein-α and silintaphin-1

In nature, mineralization of hard tissues occurs due to the synergistic effect of components present in the organic matrix of these tissues, with templating and catalytic effects. In Suberites domuncula, a well-studied example of the class of demosponges, silica formation is mediated and templated by an axial proteinaceous filament with silicatein-α, one of the main components. But so far, the effect of other organic constituents from the proteinaceous filament on the catalytic effect of silicatein-α has not been studied in detail. Here we describe the synthesis of core-shell TiO(2)@SiO(2) and TiO(2)@ZrO(2) nanofibers via grafting of silicatein-α onto a TiO(2) nanowire backbone followed by a coassembly of silintaphin-1 through its specifically interacting domains. We show for the first time a linker-free, one-step funtionalization of metal oxides with silicatein-α using glutamate tag. In the presence of silintaphin-1 silicatein-α facilitates the formation of a dense layer of SiO(2) or ZrO(2) on the TiO(2)@protein backbone template. The immobilization of silicatein-α onto TiO(2) probes was characterized by atomic force microscopy (AFM), optical light microscopy, and high-resolution transmission electron microscopy (HRTEM). The coassembly of silicatein-α and silintaphin-1 may contribute to biomimetic approaches that pursue a controlled formation of patterned biosilica-based biomaterials.     

Improved valence basis sets for divalent lanthanide 4f-in-core pseudopotentials

Improved energy-optimized (6s5p4d) and (7s6p5d) primitive valence basis sets have been derived for energy-consistent scalar-relativistic 4f-in-core pseudopotentials of the Stuttgart-Cologne variety modeling divalent lanthanides with a $4\hbox{f}^{n+1}$ occupation (n = 0?C13 for La?CYb). Segmented contracted basis sets covering the range of polarized double-, triple-, and quadruple-zeta quality, augmented by 2f1g correlation sets, were created for use in molecular calculations. The basis sets contain smaller (4s4p3d) and (5s5p4d) primitive subsets, which are designed in particular for solid state calculations of crystals containing divalent lanthanide ions. Hartree?CFock, density functional theory and coupled cluster results obtained with the new basis sets for lanthanide atomic ionization potentials as well as of geometry optimizations of various test molecules, i.e. selected lanthanide mono- and dihydrides, mono- and difluorides, and monooxides, show a satisfactory agreement with experimental data as well as with corresponding scalar-relativistic all-electron results. Core-polarization potentials are found to improve the results, especially for the atomic first and second ionization potentials.     

Multiplex digital PCR: breaking the one target per color barrier of quantitative PCR

Quantitative polymerase chain reactions (qPCR) based on real-time PCR constitute a powerful and sensitive method for the analysis of nucleic acids. However, in qPCR, the ability to multiplex targets using differently colored fluorescent probes is typically limited to 4-fold by the spectral overlap of the fluorophores. Furthermore, multiplexing qPCR assays requires expensive instrumentation and most often lengthy assay development cycles. Digital PCR (dPCR), which is based on the amplification of single target DNA molecules in many separate reactions, is an attractive alternative to qPCR. Here we report a novel and easy method for multiplexing dPCR in picolitre droplets within emulsions-generated and read out in microfluidic devices-that takes advantage of both the very high numbers of reactions possible within emulsions (>10(6)) as well as the high likelihood that the amplification of only a single target DNA molecule will initiate within each droplet. By varying the concentration of different fluorogenic probes of the same color, it is possible to identify the different probes on the basis of fluorescence intensity. Adding multiple colors increases the number of possible reactions geometrically, rather than linearly as with qPCR. Accurate and precise copy numbers of up to sixteen per cell were measured using a model system. A 5-plex assay for spinal muscular atrophy was demonstrated with just two fluorophores to simultaneously measure the copy number of two genes (SMN1 and SMN2) and to genotype a single nucleotide polymorphism (c.815A>G, SMN1). Results of a pilot study with SMA patients are presented.     

Quantitative and sensitive detection of rare mutations using droplet-based microfluidics

Somatic mutations within tumoral DNA can be used as highly specific biomarkers to distinguish cancer cells from their normal counterparts. These DNA biomarkers are potentially useful for the diagnosis, prognosis, treatment and follow-up of patients. In order to have the required sensitivity and specificity to detect rare tumoral DNA in stool, blood, lymph and other patient samples, a simple, sensitive and quantitative procedure to measure the ratio of mutant to wild-type genes is required. However, techniques such as dual probe TaqMan(?) assays and pyrosequencing, while quantitative, cannot detect less than ～1% mutant genes in a background of non-mutated DNA from normal cells. Here we describe a procedure allowing the highly sensitive detection of mutated DNA in a quantitative manner within complex mixtures of DNA. The method is based on using a droplet-based microfluidic system to perform digital PCR in millions of picolitre droplets. Genomic DNA (gDNA) is compartmentalized in droplets at a concentration of less than one genome equivalent per droplet together with two TaqMan(?) probes, one specific for the mutant and the other for the wild-type DNA, which generate green and red fluorescent signals, respectively. After thermocycling, the ratio of mutant to wild-type genes is determined by counting the ratio of green to red droplets. We demonstrate the accurate and sensitive quantification of mutated KRAS oncogene in gDNA. The technique enabled the determination of mutant allelic specific imbalance (MASI) in several cancer cell-lines and the precise quantification of a mutated KRAS gene in the presence of a 200,000-fold excess of unmutated KRAS genes. The sensitivity is only limited by the number of droplets analyzed. Furthermore, by one-to-one fusion of drops containing gDNA with any one of seven different types of droplets, each containing a TaqMan(?) probe specific for a different KRAS mutation, or wild-type KRAS, and an optical code, it was possible to screen the six common mutations in KRAS codon 12 in parallel in a single experiment.     

Injection of large volumes of aqueous solutions in capillary supercritical fluid chromatography and sample preconcentration by multiple injections

The possibility of using water or aqueous solutions as the solvent in capillary supercritical fluid chromatography was successfully demonstrated. Large volumes (up to 1 μl) of aqueous sample solutions were injected. Sample preconcentration was performed by means of multiple injections of aqueous sample solutions. The solutes were trapped at the beginning of the column at low density (high temperature and low pressure) and eluted using a density programme. The method can be applied to trace analysis. It proved to be linear in the range examined. Flame ionization detection was used for the studies. As this technique is not sensitive to water, no solvent peak appears, which may be an advantage for certain applications. The influence of water injections on the column performance and the reproducibility of injection was investigated.     

Detection of mycotic pseudoaneurysm of the ascending aorta using MRI

Mycotic pseudoaneurysms of the ascending aorta are rare cardiovascular lesions that carry the risk of potentially disastrous complications such as aortic rupture or widespread sepsis. Regardless of its location in the arterial system, this lesion carries a high mortality rate. Early diagnosis of mycotic pseudoaneurysm is paramount for optimizing the chances of surgical therapy. While imaging strategies of this lesion have included aortography, echocardiography, and computed tomography, the information gained from each of these individual studies may be acquired in a single MR imaging session. MRI offers the fundamental advantages of noninvasiveness, nonionization, and multiplanar imaging capabilities. Additionally, MRI provides excellent soft tissue contrast, a wide field of view, qualitative and quantitative flow analysis, and an independence of operator expertise or patient body habitus.     

Lorentz invariant exact solution of the anomalous chiral Schwinger model

We present an exact solution of the anomalous chiral Schwinger model using Fermionic variables. We implement infrared regularization by considering the model on a spatial circleS ¹. Quantum effects modify the gauge constraints through the appearance of Schwinger terms in the gauge algebra. We perform a careful analysis of the resulting second class gauge constraints by implementing Dirac's method at the quantum level and obtain the spectrum of the theory. We get a consistent unitary Lorentz invariant theory for particular values of the counterterms. We find that when we regulate the fermionic sector of the model without reference to the gauge fields Lorentz invariance requires that we add both Lorentz variant and gauge variant counterterms.     

Organic compounds as contaminants of the Elbe River and its tributaries

GC/MS non target screening has been applied to water samples taken during 1992–1994 from the Elbe river and its tributaries Mulde, Saale, Weiße Elster, Schwarze Elster, and Havel. Based on full scan electron impact mass spectra and supplemented by extensive use of chemical ionisation and high resolution data as well as by synthetic reference compounds, several new classes of compounds, whose possible environmental effects are yet unknown at present, have been identified. Tetrachlorinated bis-(propyl)ethers are new among the most prominent contaminants throughout the Elbe river. The confluence with the Mulde river adds a variety of compounds, related to the chemistry of chloro- and nitroaromatics, azo dyes, benzanilides, carbamates, thiophosphates, and pesticides. The combined load of the Weiße Elster and Saale rivers carries oligoformals, oxathiamacrocycles, and dichloro- and trichloro-bis-(propyl)ethers, whereas chloropropylphosphates are introduced via the Schwarze Elster. The majority of these compounds, originating from sources at the tributaries, are still present at the mouth of the Elbe river. In addition to specific industrial emissions, a variety of more generally observed organic compounds like long chain aliphatics, sterols, phenylalkanes, and plasticizers as well as ubiquitous environmental trace pollutants like polycyclic aromatic hydrocarbons, chlorobenzenes, and hexachlorocyclohexane isomers have been encountered throughout the Elbe river drainage system.Part I: S. Franke, S. Hildebrandt, W. Francke, H. Reincks (1995) Naturwissenschaften 82: 80–83     

Über den geraden Knickstab mit begrenzter Durchbiegung

Zusammenfassung Die Untersuchung des durch ebene, starre Flächen in seiner Durchbiegung begrenzten geraden Knickstabes mit Hilfe der elementaren Biegetheorie führt auf eine interessante Durchschlagerscheinung. Unabhängig von der Art der Lagerung der Stabenden stützt sich nach Überschreitung der zugehörigen Eulerschen Knicklast der Stab an der Stelle seiner größten Durchbiegung gegen eine der Stützflächen ab. Die sich dabei ausbildende Stützkraft wächst mit zunehmender Stablast an, während sich gleichzeitig die Stabkrümmung an der Anlagestelle verringert.Erreicht die Stabkrümmung an der Anlagestelle die Krümmung der Stützfläche, dann bildet sich bei weiterer Steigerung der Stablast ein an der Stützfläche anliegendes, ungekrümmtes und daher momentenfreies Stabstück aus, an dessen Enden Einzelkräfte von der Stützfläche auf den Stab übertragen werden. Die Länge dieses Stabteiles wächst mit der Stablast solange an, bis diese die Größe der Eulerschen Knicklast des als an beiden Enden eingespannt anzusehenden geraden Stabteiles erreicht. Der nun einsetzende Knickvorgang des bis dahin an der Stützfläche anliegenden Stabteiles kann wegen der zunehmenden Knicklänge mit sich verringernder Stablast aufrecht erhalten werden. Bei unveränderter Stablast schlägt daher der mittlere Stabteil durch und kommt an der gegenüberliegenden Stützfläche zur Anlage.Bei weiterer Steigerung der Stablast kann der Stab immer als aus Teilstäben zusammengesetzt aufgefaßt werden, deren Lagerung den hier untersuchten drei Grundfällen entspricht. Es ist daher nicht zu erwarten, daß eine Weiterführung der Untersuchung noch zu grundsätzlich neuen Erkenntnissen führt.