Functional Binding Surface of a β‐Hairpin VEGF Receptor Targeting Peptide Determined by NMR Spectroscopy in Living Cells

In this study, the functional interaction of HPLW peptide with VEGFR2 (Vascular Endothelial Growth Factor Receptor 2) was determined by using fast ¹⁵N‐edited NMR spectroscopic experiments. To this aim, ¹⁵N uniformly labelled HPLW has been added to Porcine Aortic Endothelial Cells. The acquisition of isotope‐edited NMR spectroscopic experiments, including ¹⁵N relaxation measurements, allowed a precise characterization of the in‐cell HPLW epitope recognized by VEGFR2.     

Convexity of Domains of Riemannian Manifolds

In this paper the problem of the geodesic connectedness and convexity ofincomplete Riemannian manifolds is analyzed. To this aim, a detailedstudy of the notion of convexity for the associated Cauchy boundary iscarried out. In particular, under widely discussed hypotheses,we prove the convexity of open domains (whose boundaries may benondifferentiable) of a complete Riemannian manifold. Variationalmethods are mainly used. Examples and applications are provided,including a result for dynamical systems on the existence oftrajectories with fixed energy.     

A generalization of an example by V. Ya. Ivrii

A well-known example by Ivrii concerning the operatorP=D _t ² −t^2lD _x ² +at^kD_x (a≠0), shows that there exists a delicate relation amongl, k and the Gevrey index of well-posedness of the Cauchy problem. In this paper we give a generalization to a class of pseudo-differential operators includingP.

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Sunto Un famoso esempio di Ivrii riguardante l'operatoreP=D _t ² −t^2lD _x ² +at^kD_x (a≠0), mostra che c'è una relazione sottile tral, k e l'indice di Gevrey di buona positura del problema di Cauchy. In questo articolo viene data una generalizzazione ad una classe di operatori pseudodifferenziali che comprendeP.

     

Conformational mobility of thianthrene-5-oxide

[reaction: see text] Data on the apparent dipole moment of thianthrene-5-oxide (1) and (1)H NMR spectra in different solvents support the conformational mobility of 1, which flaps between two limit boat conformations with the sulfinyl group in pseudoequatorial and pseudoaxial positions, respectively. The conformational equilibrium of 1 occurs too fast for the (1)H NMR (500 MHz) time-scale even at -130 degrees C, and the equilibrium constant has not been determined. The apparent dipole moments of 1 in n-hexane and 1,4-dioxane and the (1)H NMR spectra of 1 and the model compounds cis- and trans-thianthrene-5,10-dioxides (2) and thianthrene (5) in different solvents and at various temperatures confirm that the relative position of the conformational equilibrium of 1 is solvent-dependent, and more polar solvents favor the conformation with the sulfoxide group in the pseudoaxial position (1(')(ax)). Variable-temperature (1)H NMR spectra have established the interconversion barrier of trans-2 and confirmed that the conformational equilibrium of cis-2 is strongly displaced toward the conformation with both sulfinyl groups in the pseudoequatorial position. The (1)H NMR data support the transannular interaction of the functional groups in 1 and trans-2.     

Baeyer-Villiger oxidation with potassium peroxomonosulfate supported on acidic silica gel

[reaction: see text] Potassium peroxomonosulfate deposited onto silica SiO2 x KHSO5 efficiently reacts with ketones in dichloromethane at room temperature to give the corresponding esters or lactones in quantitative yields. This method avoids hydrolysis of the reaction products. The Baeyer-Villiger reaction is catalyzed by potassium hydrogensulfate present in the supported reagent.     

Synthesen von Heterocyclen, 93. Mitt.

Zusammenfassung Malonsäure und monosubstit. Malonsäuren reagieren in Acetanhydrid mit Cyclanon-anilen in guter Ausbeute zu Spiro-1,3-oxazinen (3–6 bzw.9–13). Diese labilen Verbindungen lassen sich mit POCl₃ leicht in 4-Hydroxy-5,6-polymethylen-pyridone-(2) umwandeln. Analog verhält sich Acetophenonanil.

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Malonic acid and monosubstituted malonic acids react in acetic anhydride with cyclanon-aniles yielding the spiro-1.3-oxazines3–6 and9–13. These compounds are readily converted with POCl₃ to 4-hydroxy-5.6-polymethylene-pyrid-2-ones. Acetophenon-anil reacts in the same manner.

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Herrn Prof. Dr.F. Wessely, Universität Wien, mit den besten Wünschen zum 70. Geburtstag gewidmet.     

The atomic-level structure of bandgap engineered double perovskite alloys Cs2AgIn1−xFexCl6

Although lead-free halide double perovskites are considered as promising alternatives to lead halide perovskites for optoelectronic applications, state-of-the-art double perovskites are limited by their large bandgap. The doping/alloying strategy, key to bandgap engineering in traditional semiconductors, has also been employed to tune the bandgap of halide double perovskites. However, this strategy has yet to generate new double perovskites with suitable bandgaps for practical applications, partially due to the lack of fundamental understanding of how the doping/alloying affects the atomic-level structure. Here, we take the benchmark double perovskite Cs₂AgInCl₆ as an example to reveal the atomic-level structure of double perovskite alloys (DPAs) Cs₂AgIn_1−xFe_xCl₆ (x = 0–1) by employing solid-state nuclear magnetic resonance (ssNMR). The presence of paramagnetic alloying ions (e.g. Fe³⁺ in this case) in double perovskites makes it possible to investigate the nuclear relaxation times, providing a straightforward approach to understand the distribution of paramagnetic alloying ions. Our results indicate that paramagnetic Fe³⁺ replaces diamagnetic In³⁺ in the Cs₂AgInCl₆ lattice with the formation of [FeCl₆]³⁻·[AgCl₆]⁵⁻ domains, which show different sizes and distribution modes in different alloying ratios. This work provides new insights into the atomic-level structure of bandgap engineered DPAs, which is of critical significance in developing efficient optoelectronic/spintronic devices.

Through Fe³⁺-alloying, the bandgap of benchmark double perovskite Cs₂AgInCl₆ can be tuned from 2.8 eV to 1.6 eV. The atomic-level structure of Cs₂AgIn_1−xFe_xCl₆ was revealed by solid-state nuclear magnetic resonance (ssNMR).     

Solid-State NMR Study of Phase Separation and Order of Water Molecules and Silanol Groups in Polysiloxane Networks

Homogeneity and structure of organically modified polysiloxane networks prepared by sol-gel co-condensation, as well as location and nature of water molecules and silanol groups were studied by 1D and 2D solid-state NMR. ¹H–²⁹Si and ¹H–¹H interatomic distances were estimated from variable contact-time CP/MAS experiments, ¹H NMR chemical shifts and off-resonance WISE NMR. A structure model of these networks is proposed and discussed. The fraction of proton-inaccessible units Q⁴ in the networks decreases with increasing amounts of dimethylsiloxane (D) and methylsiloxane (T) units. In contrast to systems prepared by co-condensation of tetraethoxysilane (TEOS) with dimethyl(diethoxy)silane (DMDEOS), proton-inaccessible units form essential fraction in networks prepared by co-condensation of TEOS with methyl(triethoxy)silane (MTEOS). The proton-accessible part of the networks with high O/Si ratios is nano-heterogeneous phase, which is composed of water containing Q ⁱ particles separated by copolymer domains. The overall homogeneity and uniformity of binding sites around silanol groups increases by co-condensation TEOS with DMDEOS or MTEOS, while the amount of physisorbed water as well as the hydrogen bond strength decreases, as compared with neat silica gel prepared by polycondensation of TEOS.