Shear induced relaxation of polymer micelles at the solid-liquid interface

A 20% aqueous solution of (ethylene oxide) 99-(propylene oxide) 65-(ethylene oxide) 99, F127, was investigated by combining rheology in a cone/plate-geometry and surface-sensitive grazing incident neutron scattering. The crystalline structure formed by the polymer micelles becomes less pronounced for low shear rates, but correlations increase for higher shear rates. After stopping shear a slow relaxation of the micelles is found in the vicinity (50 mum thick layer) of a hydrophilic silicon wall (strong micelle-wall interaction), while a fast relaxation is observed in the boundary layer against the hydrophobic silicon wall (weak micelle-wall interaction). The results show that in the vicinity of the interface wall-particle interactions compete heavily with the shear force acting on the liquid.     

Mössbauer spectroscopy and DFT calculations on all protonation states of the 2Fe-2S cluster of the Rieske protein

The Thermus thermophilus Rieske protein (TtRP) contains a 2Fe-2S cluster with one iron (Fe-Cys) coordinated by four sulfur atoms (2xS^2? and 2xCys) and one iron (Fe-His) by two sulfur and two nitrogen atoms (2xS^2?, His134 and His154). Here, the protein is investigated at three pH values (6.0, 8.5 and 10.5) in order to elucidate the protonation states of the His-ligands. Examination of the effect of protonation on the electronic structure of the cluster via Mössbauer spectroscopy gives a deeper understanding of the coupling of electron transfer to the protonation state of the His-ligands. Two components (1 referring to Fe-Cys and 2 to Fe-His) with parameters typical for a diamagnetic [2Fe-2S]²⁺ cluster are detected. The Mössbauer parameters and the protonation state clearly correlate: while δ remains almost pH-independent with δ ₁ (pH6.0) =?0.23 (±?0.01) mms^??1 and δ ₁ (pH10.5) =?0.24 (±?0.01) mms^??1 for Fe-Cys, it decreases for Fe-His from δ ₂ (pH6.0) =?0.34 (±?0.01) mms^??1 to δ ₂ (pH10.5) =?0.28 (±?0.01) mms^??1. ΔE _Q changes from ΔE _Q1 (pH6.0) =?0.57 (±?0.01) mms^??1 to ΔE _Q1 (pH10.5) =?0.45 (±?0.01) mms^??1 and from ΔE _Q2 (pH6.0) =?1.05 (±?0.01) mms^??1 to ΔE _Q2 (pH10.5) =?0.71 (±?0.01) mms^??1. Density functional theory (DFT)-calculations based on the crystal structure (pdb 1NYK) (Hunsicker-Wang et al. Biochemistry 42, 7303, 2003) have been performed for the Rieske-cluster with different His-ligand protonation states, reproducing the experimentally observed trend.     

Über die Synthese von 4-Amino-2H-imidazolen aus Imidazolin-Δ3-thionen-(5)

Zusammenfassung 2,4,5-substituierte 4-Alkylamino-2H-imidazole entstehen mit guten Ausbeuten aus 2-Methyl-2,4-diaryl-imidazolin-³-thionen-(5) durch Umsetzung mit prim. bzw. sek. aliphatischen oder heterocyclischen Aminen in Benzol bei Rückflußtemperatur.

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2.4.5-substituted 4-alkylamino-2H-imidazoles are formed in good yields by the reaction of 2-methyl-2.4-diaryl-³-imidazoline-5-thiones with prim. or sec. aliphatic or heterocyclic amines in boiling benzene.

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55. Mitt.:F. Asinger, E.-Chr. Witte undW. Schäfer, Ann. Chem., im Druck.

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Teil der DissertationG. Kriebel, Techn. Hochschule Aachen, 1965.     

Steroide—XL: 16,17-azido- und 16,17-aminoalkohole des östra-1,3,5(10)-trien-3-methyläthers

The four epimeric azido alcohols of estra-1,3,5(10)-trien-3-methyl ether with nitrogen at C-16 and oxygen at C-17 were prepared by the following reactions: cleavage of the 16α,17α-epoxide 1 with sodium azide affords the 16β,17α-azido alcohol 2a. The analogous reaction of the 16β,17β-epoxide 4 gives the 17α,16β-azido alcohol 5a and the desired 16α,17β-azido alcohol 6a in low yield. 6a is obtained in a smooth reaction by substitution of the 16β,17β-bromohydrine 8 with sodium azide. Sodium borohydride reduction of the 16β-azido-17-ketone 9 yields the 16β,17β-azido alcohol 10a, reduction of 16α-azido-17-ketone 13 with lithium borohydride gives the 16α,17α-azido alcohol 14a. From the azido alcohols the corresponding amino alcohols 3a, 7a, 11a and 15a are prepared with hydrazine hydrate/Raney nickel. The amino alcohols give the acetic anhydride the corresponding acetylamino alcohols. The cis-amino alcohols 11a and 15a react with acetone to the corresponding oxazolidines 12 and 16.     

Ab initio studies of structural features not easily amenable to experiment: Part 20. Structural aspects of ethyl groups

The molecular structures of a number of stable conformations of ethanol, ethylamine, methylethyl ether, methylethylamine and of the ethyl anion have been determined by ab initio geometry optimizations using Pulay's Force method on the 4–21G level. The calculated geometries characterize the extent to which structural groups in a molecule are sensitive to asymmetries in their environment. Characteristic structural trends are consistently found for the CH bond distances and CCH angles in the C₂H₅ groups of trans-ethanol, trans-methylethyl ether and in the ethyl anion. They differ from those previously found for C₂H₅ groups in hydrocarbons. There is qualitative disagreement between the trends calculated for CH bond distances in trans-ethanol and trans-methylethyl ether and those found in the microwave substitution structures of these compounds. Since the substitution parameters are unresolved because of relatively large experimental or model uncertainties, it is presently impossible to decide whether this discrepancy is the result of computational or experimental deficiency. The methyl groups in methylethyl ether and methylethylamine exhibit the characteristic structural distortions which are usually found for CH₃ groups adjacent to electron lone pairs. The CC bond distances in C₂H₅ in the systems studied here are sensitive to the conformational arrangement of ethyl relative to the rest of a system in a way which can be rationalized by orbital interactions involving antibonding orbitals on sp³-hybridized carbon atoms. The calculated conformational stabilities agree qualitatively with experimental trends, except in the case of ethanol where the trans — gauche energy difference is small (about 0.1 kcal mol^?1) and within the uncertainties of the calculations. Our conformational energies for CH₃CH₂NH₂ are in disagreement with a previous ab initio investigation based on a comparison of unoptimized standard geometries. In general, the agreement between calculated structural parameters and corresponding reliable experimental values is very good in all comparable cases.     

Nitrogen‐Doped Ordered Mesoporous Carbon Supported Bimetallic PtCo Nanoparticles for Upgrading of Biophenolics

Hydrodeoxygenation (HDO) is an attractive route for the upgrading of bio‐oils produced from lignocellulose. Current catalysts require harsh conditions to effect HDO, decreasing the process efficiency in terms of energy and carbon balance. Herein we report a novel and facile method for synthesizing bimetallic PtCo nanoparticle catalysts (ca. 1.5 nm) highly dispersed in the framework of nitrogen‐doped ordered mesoporous carbon (NOMC) for this reaction. We demonstrate that NOMC with either 2D hexagonal (p6m) or 3D cubic (Im m) structure can be easily synthesized by simply adjusting the polymerization temperature. We also demonstrate that PtCo/NOMC (metal loading: Pt 9.90 wt %; Co 3.31 wt %) is a highly effective catalyst for HDO of phenolic compounds and “real‐world” biomass‐derived phenolic streams. In the presence of PtCo/NOMC, full deoxygenation of phenolic compounds and a biomass‐derived phenolic stream is achieved under conditions of low severity.