Carbon monoxide as an intrinsic ligand to iron in the active site of the iron-sulfur-cluster-free hydrogenase H2-forming methylenetetrahydromethanopterin dehydrogenase as revealed by infrared spectroscopy

The iron-sulfur-cluster-free hydrogenase Hmd (H(2)-forming methylenetetrahydromethanopterin dehydrogenase) from methanogenic archaea has recently been found to contain one iron associated tightly with an extractable cofactor of yet unknown structure. We report here that Hmd contains intrinsic CO bound to the Fe. Chemical analysis of Hmd revealed the presence of 2.4 +/- 0.2 mol of CO/mol of iron. Fourier transform infrared spectra of the native enzyme showed two bands of almost equal intensity at 2011 and 1944 cm(-)(1), interpreted as the stretching frequencies of two CO molecules bound to the same iron in an angle of 90 degrees . We also report on the effect of extrinsic (12)CO, (13)CO, (12)CN(-), and (13)CN(-) on the IR spectrum of Hmd.     

Experimental study of heat flux in mixed convective flow over solid waves

In this experimental study, we address transport processes in a mixed convective flow over a heated wavy surface. Therefore, we combine digital particle image velocimetry (DPIV) and two-color planar laser induced fluorescence (PLIF) to simultaneously measure the velocity and temperature field. For this, we propose to use the dye combination Rhodamine B and Rhodamine 110, both excited with the Nd:YAG laser also used for the PIV measurements. We investigate the influence of mixed convection over a wavy surface on the velocity field, turbulence statistics, the temperature field and the heat flux. By computing these quantities we find a correlation between the maximum in the Reynolds stress profiles and the components of the heat flux vector, thus regions of maximum momentum and scalar transport coincide. In addition, we apply a proper orthogonal decomposition (POD) to extract the most dominant flow structures in a measurement plane above the wavy surface. This first POD mode is identified as streamwise-oriented, counter-rotating vortices whose spanwise scaling is also correlated with the maximum of heat flux.     

2‐Nitro‐1,4‐diaminobenzene‐Functionalized Poly(vinyl amine)s as Water‐Soluble UV‐Vis‐Sensitive pH Sensors

Summary: Nucleophilic aromatic substitution of 2,6‐O‐dimethyl‐β‐cyclodextrin (β‐DMCD)‐complexed 4‐fluoro‐3‐nitroaniline derivatives with poly(vinyl amine) (PVAm) in water results in 2‐nitro‐1,4‐benzenediamine‐functionalized water‐soluble PVAms in one step. The 2‐nitro‐1,4‐benzenediamine moiety linked to the polymer is solvatochromic and undergoes protonation and deprotonation as function of pH as shown by UV‐Vis spectroscopy. The occurrence of an isosbestic point in the UV‐Vis spectrum is suitable to directly determine the pK_a value using the Henderson‐Hasselbalch equation. The influence of the methyl group substitution of the polymer and the 2‐nitro‐1,4‐benzenediamine moiety on the pK_a is discussed.

Structure of the 4‐N,N‐dimethyl‐2‐nitro‐1,4‐benzenediamine‐functionalized PVAm and its solution in water at varying pH.     

Opale: Photonische Kristalle

Opals are self‐assembled fcc‐packed colloidal crystals with sphere diameters in the nanometer and submicrometer region. The periodic dielectric structure leads to the opening of photonic band gaps that suppress the propagation of light with wavelengths at the lattice constant scale. This explains e.g. the opals' brilliant color impression. Synthetic opals can be prepared from polymer or metaloxide spheres in a bottom‐up approach that allows for chemical functionalization and processing. Also, they can be used as templates to fabricate inverted structures. Fields of application reach from optical chips, color displays and effect pigments to biosensors.     

Monodomain Liquid Crystal Main Chain Elastomers by Photocrosslinking

A new synthetic strategy for the preparation of macroscopically oriented smectic main chain liquid crystal elastomers (MC‐LCE) by the photocrosslinking of laterally functionalized polyesters is presented. X‐ray measurements proved the formation of the monodomain and allowed a quantitative determination of the order parameter. The thermo‐actuation of our material at the phase transition from the liquid‐crystalline to the isotropic phase was demonstrated by temperature dependent measurements of the sample length, showing a fully reversible shape change of ≈40%. Mechanical measurements showed that the sample can be stretched by up to 60% along the smectic layer normal without any reorientation of the structure, in contrast to earlier experiments and theoretical predictions. The results are discussed in the context of limited smectic layer correlation in different types of smectic materials.

     

Diffusion-wave phenomena

We announce the forthcoming papers [4] and [5] in which we prove the existence and the uniqueness, find properties, asymptotic and regularity of the solution to diffusion-wave phenomena. We give explicit solutions for 1, 2, …, n -term time fractional diffusion-wave equations. For the distributed order equation and for the equation with n-term time fractional derivatives, we prove that the first fundamental solution is always a probability density for x ∈ R . (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Indium doped zinc oxide nanopowders for transparent conducting coatings on glass substrates

Crystalline indium doped zinc oxide (IZO) nanopowders were synthesized using hydrothermal treatment processing. Increasing the doping ratio of indium in the zinc oxide significantly influences the phase structure and shape of the nanopowders resulting in nanorod to nanoparticulate morphologies. As the doping profile increases, the crystallite size decreases, the band gap energy blue shifts and the specific surface area increases (measured by BET method). Additionally Raman spectroscopy exhibited shifts of several peaks, as well as revealed new peaks, confirming the substitution of indium ions within the zinc oxide lattice sites. An IZO suspension made of IZO nanoparticles (In/Zn = 3 atm.%) with a zeta potential greater than 30 mV at pH = 6 was successfully spin-coated on glass substrates for to make transparent conductive coatings evincing sheet resistances as low as 35 kΩ_□ (ρ = 4.9 × 10^?3 Ω m,) with transmission in the visible range as high as 90 %.     

Metallocarbonyl complexes of bromo‐ and dibromomaleimide: synthesis and biochemical application

Bromomaleimides react with cysteine residues to form thiomaleimides that can be further cleaved with TCEP (tris(2‐carboxyethyl)phosphine) to regenerate the cysteine derivatives. Herein we report the preparation of new organometallic Fe complexes containing monobromo and dibromo maleimide ligands. Both of these complexes were characterised by X‐ray diffraction. Organometallic bromomaleimide derivatives were reacted with the thiol‐containing biomolecules: cysteine ethyl ester hydrochloride, glutathione and papain. These cysteine‐containing molecules underwent a substitution reaction with metallocarbonyl bromo‐ or dibromo maleimide complexes, followed by an addition reaction to the thio‐maleimide double bond if thiol was added in excess. The metallocarbonyl mono‐bromomaleimide complex was shown to inhibit the peptidase activity of the enzyme papain. The resulting papain–maleimide product could be cleaved by addition of TCEP to regenerate the catalytically active enzyme. Copyright © 2012 John Wiley & Sons, Ltd.     

Thin-layer chromatography of green leaves extracts: Zinc migrates into pheophytin on TLC silica plates with fluorescence indicator (F254)

JPC – Journal of Planar Chromatography – Modern TLC -