Polysulfates [SnO3n+1]2−: With the [S6O19]2− Anion,has the End been Reached?

The S₆O₁₉^2? ion was obtained both as rubidium and ammonium salt from the reaction of the respective sulfate with SO₃. It is the largest polysulfate ion known to date and exhibits a chain of six vertex‐connected [SO₄] tetrahedra. The unique compound was comprehensively characterized and the bonding within the anion was elucidated by theoretical investigations.     

The First Homoleptic Bis(trifluoromethanesulfonyl)amide Complex of Yttrium: [bmim][Y(Tf2N)4]

1‐Butyl‐3‐methylimidazolium tetrakis‐(bis(trifluoromethanesulfonyl)amide)yttrium(III), [bmim][Y(Tf₂N)₄], was obtained from the ionic liquid 1‐butyl‐3‐methylimidazoliumbis(trifluoromethanesulfonyl)amide, [bmim][Tf₂N] and yttrium(III)bis(trifluoromethanesulfonyl)amide, Y(Tf₂N)₃. The crystal structure [monoclinic, C2/c (no. 15), a = 2096.(1), b = 1451.5(1), c = 1608.55(9) pm, β = 109.669(6)°, V = 4608.1(5)·10⁶ pm³, Z = 4, R₁ for 3874 symmetry independent reflections with I₀>2σ(I₀): 0.0438] contains Y^III coordinated by four Tf₂N‐ligands which all adopt a transoid‐conformation with respect to their –CF₃ groups. The oxygen coordination polyhedron around Y^III can be best described as a trigonal dodecahedron.One 1‐butyl‐3‐methylimidazolium cation compensates for the charge of the complex [Y(Tf₂N)₄]^? anion.     

Delta-amino group hydroxylation of L-ornithine during coelichelin biosynthesis

The nonribosomally produced hydroxamate siderophore coelichelin from Streptomyces coelicolor contains the nonproteinogenic amino acids N(5)-hydroxyornithine and N(5)-hydroxyformylornithine that are important for iron assembly. The hydroxylation of the delta-amino group of L-ornithine is catalyzed by the flavin-dependent monooxygenase CchB. During the redox reaction nicotinamide adenine dinucleotide phosphate (NADPH) and molecular oxygen are consumed and flavin adenine dinucleotide (FAD) is needed as a cofactor. During this work the monooxygenase was biochemically characterized and it could be shown that the hydroxylation of l-ornithine is most likely the first step in the biosynthesis of the siderophore coelichelin.     

Combinatorial materials research applied to the development of new surface coatings X: a high-throughput electrochemical impedance spectroscopy method for screening organic coatings for corrosion inhibition

The objective of the study was to develop a high-throughput electrochemical impedance spectroscopy (HT-EIS) method for rapid and quantitative evaluation of corrosion protective coatings. A 12-element, spatially addressable electrochemical platform was designed, fabricated, and validated. This platform was interfaced to a commercial EIS instrument through an automated electronic switching unit. The HT-EIS system enables four parallel EIS measurements to be run simultaneously, which significantly reduces characterization time compared to that of serial EIS measurements using a multiplexer. The performance of the HT-EIS system was validated using a series of model systems, including a Randles equivalent circuit, an electrochemical reaction (Ti/K4FeCN6, K3FeCN6), a highly uniform polymer film, and several polymer coatings. The results of the validation studies showed that the HT-EIS system enables a major reduction in characterization time and provides high quality data comparable to data obtained with conventional, single-cell EIS measurement systems.     

A polarizable force field for computing the infrared spectra of the polypeptide backbone

The shapes of the amide bands in the infrared (IR) spectra of proteins and peptides are caused by electrostatically coupled vibrations within the polypeptide backbone and code the structures of these biopolymers. A structural decoding of the amide bands has to resort to simplified models because the huge size of these macromolecules prevents the application of accurate quantum mechanical methods such as density functional theory (DFT). Previous models employed transition-dipole coupling methods that are of limited accuracy. Here we propose a concept for the computation of protein IR spectra, which describes the molecular mechanics (MM) of polypeptide backbones by a polarizable force field of "type II". By extending the concepts of conventional polarizable MM force fields, such a PMM/II approach employs field-dependent parameters not only for the electrostatic signatures of the molecular components but also for the local potentials modeling the stiffness of chemical bonds with respect to elongations, angle deformations, and torsions. Using a PMM/II force field, the IR spectra of the polypeptide backbone can be efficiently calculated from the time dependence of the backbone's dipole moment during a short (e.g., 100 ps) MD simulation by Fourier transformation. PMM/II parameters are derived for harmonic bonding potentials of amide groups in polypeptides from a series of DFT calculations on the model molecule N-methylacetamide (NMA) exposed to homogeneous external electric fields. The amide force constants are shown to vary by as much as 20% for relevant field strengths. As a proof of principle, it is shown that the large solvatochromic effects observed in the IR spectra of NMA upon transfer from the gas phase into aqueous solution are not only excellently reproduced by DFT/MM simulations but are also nicely modeled by the PMM/II approach. The tasks remaining for a proof of practice are specified.     

Solution,Crystal and in Silico Structures of the Organometallic Vitamin B12-Derivative Acetylcobalamin and of its Novel Rhodium-Analogue Acetylrhodibalamin

The natural vitamin B₁₂-derivatives are intriguing complexes of cobalt that entrap the metal within the strikingly skewed and ring-contracted corrin ligand. Here, we describe the synthesis of the Rh(III)-corrin acetylrhodibalamin ( AcRhbl ) from biotechnologically produced metal-free hydrogenobyric acid and analyze the effect of the replacement of the cobalt-center of the organometallic vitamin B₁₂-derivative acetylcobalamin ( AcCbl ) with its group-IX homologue rhodium, to give AcRhbl . The structures of AcCbl and AcRhbl were thoroughly analyzed in aqueous solution, in crystals and by in silico methods, in order to gain detailed insights into the structural adaptations to the two homologous metals. Indeed, the common, nucleotide-appended corrin-ligand in these two metal corrins features extensive structural similarity. Thus, the rhodium-corrin AcRhbl joins the small group of B₁₂-mimics classified as ‘antivitamins B₁₂’, isostructural metal analogues of the natural cobalt-corrins that hold significant potential in biological and biomedical applications as selective inhibitors of key cellular processes.     

Polarization-Dependent Sum-Frequency-Generation Spectroscopy for In Situ Tracking of Nanoparticle Morphology

The surface structure of oxide-supported metal nanoparticles can be determined via characteristic vibrations of adsorbed probe molecules such as CO. Usually, spectroscopic studies focus on peak position and intensity, which are related to binding geometries and number of adsorption sites, respectively. Employing two differently prepared model catalysts, it is demonstrated that polarization-dependent sum-frequency-generation (SFG) spectroscopy reveals the average surface structure and shape of the nanoparticles. SFG results for different particle sizes and morphologies are compared to direct real-space structure analysis by TEM and STM. The described feature of SFG could be used to monitor particle restructuring in situ and may be a valuable tool for operando catalysis.     

Amphiphilic Copolymers Shuttle Drugs Across the Blood–Brain Barrier

Medical treatment of diseases of the central nervous system requires transport of drugs across the blood–brain barrier (BBB). Here, it is extended previously in vitro experiments with a model compound to show that the non‐water‐soluble and brain‐impermeable drug domperidone (DOM) itself can be enriched in the brain by use of an amphiphilic copolymer as a carrier. This carrier consists of poly(N‐(2‐hydroxypropyl)‐methacrylamide), statistically copolymerized with 10 mol% hydrophobic lauryl methacrylate, into whose micellar aggregates DOM is noncovalently absorbed. As tested in a BBB model efficient transport of DOM across, the BBB is achievable over a wide range of formulations, containing 0.8 to 35.5 wt% domperidone per copolymer. In neither case, the polymer itself is translocated across the BBB model. In vivo experiments in mice show that already 10 min after intraperitoneal injection of the polymer/domperidone (PolyDOM) formulation, domperidone can be detected in blood and in the brain. Highest serum and brain levels of domperidone are detected 40 min after injection. At that time point serum domperidone is increased 48‐fold. Most importantly, domperidone is exclusively detectable in high amounts in the brain of PolyDOM injected mice and not in mice injected with bare domperidone.

     

Straightforward stereoselective synthesis of spiro-epoxyoxindoles

[reaction: see text] The in situ preparation of a sulfonium ylide reagent achieved the highly diastereoselective epoxidation of isatins, so that a new and straightforward access to biologically significant spiro-epoxyoxindoles is provided. The first investigations of an asymmetric version are reported with enantiopure sulfides.     

Proteome profiling of keratinocytes transforming to malignancy

To shed light on the multistep process of squamous cell carcinoma development and the underlying pathologic mechanisms, we performed comparative proteome analysis of keratinocytes, keratinocytes stimulated with Il‐1beta, and A431 epidermoid carcinoma cells. Fractionation of the cells into supernatant, nucleus, and cytoplasm was followed by protein separation, proteolytic digest, and nano‐LC separation, and fragmentation using an ion trap mass spectrometer. Specific bioinformatics tools were used to generate a list of keratinocyte‐specific proteins. Ninety percent of these proteins were found to be upregulated in keratinocytes versus the A431 cells. Classification of the identified proteins by biologic function and gene set enrichment analysis revealed that keratinocytes produced more proteins involved in cell differentiation, cell adhesion, cell junction, calcium ion, calmodulin binding, cytoskeleton organization, and cytokinesis, whereas A431 produced more proteins involved in cell cycle checkpoint, cell cycle process, RNA processing and transport, DNA damage and repair, RNA and DNA binding, and chromatin remodeling. The protein signatures of A431 and normal keratinocytes treated with IL‐1beta showed marked similarity, confirming that inflammation is an important step in malignant transformation in nonmelanoma skin cancer. Thus, proteome profiling and bioinformatic processing may support the understanding of the underlying mechanisms, with the potential to facilitate development of early biomarkers and patient‐tailored therapy.