Determination of boron and hydrogen in materials for multicrystalline solar cell production with prompt gamma activation analysis

Journal of Radioanalytical and Nuclear Chemistry - For the optimization of the manufacturing process of multicrystalline silicon (mc-Si) for solar cells in order to reduce energy consumption and...     

MaxSynBio: Avenues Towards Creating Cells from the Bottom Up

A large German research consortium mainly within the Max Planck Society (“MaxSynBio”) was formed to investigate living systems from a fundamental perspective. The research program of MaxSynBio relies solely on the bottom‐up approach to synthetic biology. MaxSynBio focuses on the detailed analysis and understanding of essential processes of life through modular reconstitution in minimal synthetic systems. The ultimate goal is to construct a basic living unit entirely from non‐living components. The fundamental insights gained from the activities in MaxSynBio could eventually be utilized for establishing a new generation of biotechnological processes, which would be based on synthetic cell constructs that replace the natural cells currently used in conventional biotechnology.     

Influence of calcium-induced aggregation on the sensitivity of aminobis(methylenephosphonate)-containing potential MRI contrast agents

A novel class of 1,4,7,10-tetraazacyclododecane-1,4,7-tris(methylenecarboxylic) acid (DO3A)-based lanthanide complexes with relaxometric response to Ca(2+) was synthesized, and their physicochemical properties were investigated. Four macrocyclic ligands containing an alkyl-aminobis(methylenephosphonate) side chain for Ca(2+)-chelation have been studied (alkyl is propyl, butyl, pentyl, and hexyl for L(1), L(2), L(3), and L(4), respectively). Upon addition of Ca(2+), the r(1) relaxivity of their Gd(3+) complexes decreased up to 61% of the initial value for the best compounds GdL(3) and GdL(4). The relaxivity of the complexes was concentration dependent (it decreases with increasing concentration). Diffusion NMR studies on the Y(3+) analogues evidenced the formation of agglomerates at higher concentrations; the aggregation becomes even more important in the presence of Ca(2+). (31)P NMR experiments on EuL(1) and EuL(4) indicated the coordination of a phosphonate to the Ln(3+) for the ligand with a propyl chain, while phosphonate coordination was not observed for the analogue bearing a hexyl linker. Potentiometric titrations yielded protonation constants of the Gd(3+) complexes. log K(H1) values for all complexes lie between 6.12 and 7.11 whereas log K(H2) values are between 4.61 and 5.87. Luminescence emission spectra recorded on the Eu(3+) complexes confirmed the coordination of a phosphonate group to the Ln(3+) center in EuL(1). Luminescence lifetime measurements showed that Ca-induced agglomeration reduces the hydration number which is the main cause for the change in r(1). Variable temperature (17)O NMR experiments evidenced high water exchange rates on GdL(1), GdL(2), and GdL(3) comparable to that of the aqua ion.     

Probing the Hydrogen Bonding Structure in the Rieske Protein

The use of the far‐infrared spectral range presents a novel approach for analysis of the hydrogen bonding in proteins. Here it is presented for the analysis of Fe? S vibrations (500–200 cm^?1) and of the intra‐ and intermolecular hydrogen bonding signature (300–50 cm^?1) in the Rieske protein from Thermus thermophilus as a function of temperature and pH. Three pH values were adequately chosen in order to study all the possible protonation states of the coordinating histidines. The Fe? S vibrations showed pH‐dependent shifts in the FIR spectra in line with the change of protonation state of the histidines coordinating the [2Fe? 2S] cluster. Measurements of the low‐frequency signals between 300 and 30 K demonstrated the presence of a distinct overall hydrogen bonding network and a more rigid structure for a pH higher than 10. To further support the analysis, the redox‐dependent shifts of the secondary structure were investigated by means of an electrochemically induced FTIR difference spectroscopic approach in the mid infrared. The results confirmed a clear pH dependency and an influence of the immediate environment of the cluster on the secondary structure. The results support the hypothesis that structure‐mediated changes in the environment of iron? sulfur centers play a critical role in regulating enzymatic catalysis. The data point towards the role of the overall internal hydrogen bonding organization for the geometry and the electronic properties of the cluster.     

GnRH binding RNA and DNA Spiegelmers: a novel approach toward GnRH antagonism

Mirror-image oligonucleotide ligands (Spiegelmers) that bind to the pharmacologically relevant target gonadotropin-releasing hormone I (GnRH) with high affinity and high specificity have been identified using the Spiegelmer technology. GnRH is a decapeptide that plays an important role in mammalian reproduction and sexual maturation and is associated with several benign and malignant diseases. First, aptamers that bind to D-GnRH with dissociation constants of 50-100 nM were isolated out of RNA and DNA libraries. The respective enantiomers of the DNA and RNA aptamers were synthesized, and their binding to L-GnRH was shown. These Spiegelmers bind to L-GnRH with similar affinity to that of the corresponding aptamers that bind to D-GnRH. We further demonstrated dose-dependent inhibition of GnRH-induced Ca(2+) release in Chinese hamster ovary cells that were stably transfected with the human GnRH receptor.     

Optimization of SPME-Arrow-GC/MS Method for Determination of Free and Bound Volatile Organic Compounds from Grape Skins

(1) Background: Solid phase microextraction (SPME)-Arrow is a new extraction technology recently employed in the analysis of volatiles in food materials. Grape volatile organic compounds (VOC) have a crucial role in the winemaking industry due to their sensory characteristics of wine.; (2) Methods: Box–Behnken experimental design and response surface methodology were used to optimise SPME-Arrow conditions (extraction temperature, incubation time, exposure time, desorption time). Analyzed VOCs were free VOCs directly from grape skins and bound VOCs released from grape skins by acid hydrolysis.; (3) Results: The most significant factors were extraction temperature and exposure time for both free and bound VOCs. For both factors, an increase in their values positively affected the extraction efficiency for almost all classes of VOCs. For free VOCs, the optimum extraction conditions are: extraction temperature 60 °C, incubation time 20 min, exposure time 49 min, and desorption time 7 min, while for the bound VOCs are: extraction temperature 60 °C, incubation time 20 min, exposure time 60 min, desorption time 7 min.; (4) Conclusions: Application of the optimized method provides a powerful tool in the analysis of major classes of volatile organic compounds from grape skins, which can be applied to a large number of samples.     

Functionalized Self-Assembled Monolayers on Gold as Binding Matrices for the Screening of Antibody-Antigen Interactions

Two different types of -substituted alkanethiol/disulfide compounds have been used to prepare monolayer architectures on gold serving as platforms for the immobilization of receptor probe molecules – antibodies. These are: (i) carboxylic acid alkanethiols post-reacted with amino biotin to generate streptavidin surfaces, and (ii) N-hydroxysuccinimide-terminated disulfide surfaces. The properties of the monolayers, with and without attached receptor probe molecules, were analysed using infrared spectroscopy, ellipsometry, fluorescence scanning and atomic force microscopy. Several experimental parameters, such as condensation reagents, additives, probe and target concentrations and immobilization time, were systematically varied to determine the dynamic range and to optimize the sensitivity and signal-to-noise ratio of the biochip platforms. Fluorescence screening using Cy5-labelled antigens finally demonstrated that both surfaces could be successfully employed to immobilize the antibodies. The pros and cons of the two approaches are also discussed.Received November 15, 2002; accepted March 25, 2003 Published online July 28, 2003     

Synthese und thermische Eigenschaften von molekularen Clusterverbindungen zusammengesetzt aus Elementen der Gruppen 11‐13‐16

Syntheses and Thermal Properties of Cluster Molecules, formed from Groups 11‐13‐16 Elements In the presence of PPh₃, CuX (X = Cl, CH₃COO) or AgOC(O)C₆H₅ and GaCl₃ react in THF with S(SiMe₃)₂ or Se(SiMe₃)₂ to yield [Cu₆Ga₈Cl₄S₁₃(PPh₃)₆] ( 1 ), [Cu₆Ga₈Cl₄Se₁₃(PPh₃)₆] ( 2 ), [Ag₆Ga₈Cl₄S₁₃(PPh₃)₆] ( 4 ) and [Ag₆Ga₈Cl₄Se₁₃(PPh₃)₆] ( 5 ). The use of PⁿPr₂Ph instead of PPh₃ and subsequent layering with n‐hexane leads to the formation of the cluster [Cu₆Ga₈Cl₄Se₁₃(PⁿPr₂Ph)₁₂] ( 3a , 3b ). Reaction of CuCl, GaCl₃ and PⁿPr₃ with Se(SiMe₃)₂ in THF results in the crystallisation of the ionic cluster (HPⁿPr₃)₂[Cu₂Ga₄Cl₄Se₆(PⁿPr₃)₄] ( 6 ). The structures of 1 — 6 were determined by X‐ray single crystal structure analysis. Thermogravimetric measurements of the cluster molecules and powder diffraction patterns of the remaining powders reveal the potential use of them as single source precursor compounds for the synthesis of the related ternary solid state materials.     

Interactions of Hydrogen with Pd@MOF Composites

Physisorption and chemisorption of hydrogen on solid-state materials are two fundamentally different interactions, both of which display advantages and drawbacks for hydrogen storage. It has been hypothesised that their combination by merging two classes of materials showing different sorption behaviour towards hydrogen in the same composite may synergistically combine their desirable properties. As representatives of such composites, palladium nanoparticles, nanoclusters, and single atoms have been encapsulated in a metal-organic framework matrix, embedded, or immobilised in its pores, respectively. In this minireview, we review advances on the understanding and potential applications of the combination of Pd with metal-organic framework matrices through the analysis of the nanocomposite materials’ interaction with hydrogen and sorption properties.