Patterns of surface immobilized block copolymer vesicle nanoreactors

The immobilization and positioning of ultra small reaction vessels on solid supports open new pathways in applications such as lab-on-a-chip, sensors, microanalyses and microreactors. In our work block copolymer vesicles made from polystyrene-block-polyacrylic acid (PS-b-PAA) were immobilized from aqueous medium onto 3-amino propyl trimethoxysilane functionalized silicon surfaces exploiting electrostatic interactions. The immobilization of the vesicles was investigated by Fourier transform infrared (FTIR) spectroscopy, as well as fluorescence optical and atomic force microscopy (AFM). In addition, the influence of pH and ionic strength on the surface coverage of vesicles bound to the surface was elucidated. Finally micro-molding in capillaries (MIMIC) was utilized to create line patterns of the vesicles containing the enzyme trypsin and the fluorogenic substrate rhodamine 110 bisamide. The selective positioning of vesicle nanoreactors in conjunction with electrostatic immobilization serves as a proof of principle for potential applications in real-time observation of confined chemical reaction inside vesicles as nanocontainers and for the fabrication of integrated microarray systems.     

Alkaline-earth metal hydrides as novel host lattices for Eu(II) luminescence

Luminescence of divalent europium has been investigated for the first time in metal hydrides. A complete solid-solution series was found for the pseudobinary system Eu(x)Sr(1-x)H(2) [a = 637.6(1) pm -12.1(3)x pm, b = 387.0(1)-6.5(2)x pm, c = 732.2(2)-10.1(4)x pm]. Europium-doped alkaline-earth hydrides Eu(x)M(1-x)H(2) (M = Ca, Sr, Ba) with a small europium concentration (x = 0.005) exhibit luminescence with maximum emission wavelengths of 764 nm (M = Ca), 728 nm (M = Sr), and 750 nm (M = Ba); i.e., the emission energy of divalent europium shows an extremely large red shift compared to the emission energies of fluorides or oxides. Theoretical calculations (LDA+U) confirm decreasing band gaps with increasing europium content of the solid solutions.     

NHC-stabilized 1-hydro-1H-borole and its nondegenerate sigmatropic isomers

Electrophilic quenching of a carbene-stabilized π-boryl anion with the Br?nsted acid Et(3)NHCl provides a convenient synthetic route to the parent NHC-stabilized 1-hydroborole, which isomerizes to the corresponding 3-hydroborole via two successive nondegenerate [1,5]-sigmatropic hydrogen migrations. Molecular structures of both isomers have been determined by X-ray crystallography.     

High temperature shock-tube study of the reaction of gallium with ammonia

The gas-phase reaction of Ga atoms with NH(3) was studied behind reflected shock waves in the temperature range of 1380 to 1870 K at pressures of 1.4 to 4.0 bar. Atomic-resonance-absorption spectroscopy (ARAS) at 403.299 nm was applied for the time-resolved determination of the Ga-atom concentration. Trimethylgallium (Ga(CH(3))(3)) was used as a precursor of Ga atoms. After the initial increase in Ga concentration due to Ga(CH(3))(3) decomposition, the Ga concentration decreases rapidly in the presence of NH(3). For the simulation of the measured Ga-atom concentration profiles from the studied reaction, additional knowledge about the thermal decomposition of Ga(CH(3))(3) is required. The rate coefficient k(4) of the reaction Ga + NH(3) → products (R4) was determined from the Ga-atom concentration profiles under pseudo-first-order assumption and found to be k(4)(T) = 10(14.1±0.4) exp(-11?900 ± 700 K/T) cm(3) mol(-1) s(-1) (error limits at the one standard deviation level). No significant pressure dependence was noticeable within the scatter of the data at the investigated pressure range.     

Interpretation of nuclear resonant vibrational spectra of rubredoxin using a combined quantum mechanics and molecular mechanics approach

Nuclear resonant vibrational spectra of the reduced and oxidized form of a mutant of rubredoxin from Pyrococcus abyssii were measured and are compared with simulated spectra that were calculated by a combined quantum mechanics (QM) and molecular mechanics (MM) method. Density functional theory was used for the QM level. Calculations were performed for different models of rubredoxin. Realistic spectra were simulated with reduced models that include at least the iron center, the four cysteins coordinating it, and the residues connected to the cysteins together with a QM layer that comprises the first two coordination shells of the iron center. Larger QM layers did not lead to significant changes of the simulated spectra.     

Tailorable integrated optofluidic filters for biomolecular detection

Spectral filtering is an essential component of biophotonic methods such as fluorescence and Raman spectroscopy. Predominantly utilized in bulk microscopy, filters require efficient and selective transmission or removal of signals at one or more wavelength bands. However, towards highly sensitive and fully self-contained lab-on-chip systems, the integration of spectral filters is an essential step. In this work, a novel optofluidic solution is presented in which a liquid-core optical waveguide both transports sample analytes and acts as an efficient filter for advanced spectroscopy. To this end, the wavelength dependent nature of interference-based antiresonant reflecting optical waveguide technology is exploited. An extinction of 37 dB, a narrow rejection band of only 2.5 nm and a free spectral range of 76 nm using three specifically designed dielectric layers are demonstrated. These parameters result in an 18.4-fold increase in the signal-to-noise ratio for on-chip fluorescence detection. In addition, liquid-core waveguide filters with three operating wavelengths were designed for F?rster resonance energy transfer detection and demonstrated using doubly labeled oligonucleotides. Incorporation of high-performance spectral processing illustrates the power of the optofluidic concept where fluidic channels also perform optical functions to create innovative and highly integrated lab-on-chip devices.     

Coenzyme Q biosynthesis: Coq6 is required for the C5-hydroxylation reaction and substrate analogs rescue Coq6 deficiency

Coenzyme Q (Q), an essential component of eukaryotic cells, is synthesized by several enzymes from the?precursor 4-hydroxybenzoic acid. Mutations in six of the Q biosynthesis genes cause diseases that can sometimes be ameliorated by oral Q supplementation. We establish here that Coq6, a predicted flavin-dependent monooxygenase, is involved exclusively in the C5-hydroxylation reaction. In an unusual way, the ferredoxin Yah1 and the ferredoxin reductase Arh1 may be the in?vivo source of electrons for?Coq6. We also show that hydroxylated analogs of 4-hydroxybenzoic acid, such as vanillic acid or 3,4-dihydroxybenzoic acid, restore Q biosynthesis and respiration in a Saccharomyces cerevisiae coq6 mutant. Our results demonstrate that appropriate analogs of 4-hydroxybenzoic acid can bypass a deficient Q biosynthetic enzyme and might be considered for the treatment of some primary Q deficiencies.     

Recent developments in the chemistry of antiaromatic boroles

First isolated in 1969, most progress in the chemistry of the antiaromatic 4π electron borole system has been made during the 1980s. However, besides the fundamental aspects of the electronic structure and reactivity, boroles have not encountered serious research efforts for a rather long timeframe. This is somewhat surprising given the fact that boroles feature a unique combination of antiaromaticity, strong electrophilicity and unusual electronic properties. It was not until 2008 that interest was resparked. Since then, tremendous progress has been achieved in this area, particularly with respect to synthetic access, structural characterization and reactivity. Various differently substituted borole derivatives have been successfully isolated and characterized both in solution and in the solid state, which provided a more thorough understanding of the structure/reactivity relationship. This feature article is intended to provide a general overview on the electronic structure and the consequences of antiaromaticity on the inherent properties of these highly reactive species. The different synthetic methodologies to generate boroles and their divergent reactivity patterns will be described in great detail, which will emphasize their high potential and relevance in modern chemistry.     

Sterically demanding hetero-substituted [2]borametallocenophanes of group IV metals: synthesis, structure and reactivity

We report the synthesis and characterisation of unprecedented unstrained [2]diborametallocenophanes of zirconium and hafnium that bear the bulky octamethylfluorenyl (η(5)-C(29)H(36)) system, the proligands of which were pre-constructed by a two-step synthesis. The compounds were fully characterised by NMR spectroscopy, MALDI-TOF mass spectrometry and X-ray diffraction analysis. Typical reactivities relevant to olefin polymerisation such as methylation and chloride abstraction were also investigated. Finally, a sterically demanding bis(octamethylfluorenyl) metallocene was prepared.