Compaction of RNA Duplexes in the Cell**

The structure and flexibility of RNA depends sensitively on the microenvironment. Using pulsed electron-electron double-resonance (PELDOR)/double electron-electron resonance (DEER) spectroscopy combined with advanced labeling techniques, we show that the structure of double-stranded RNA (dsRNA) changes upon internalization into Xenopus lævis oocytes. Compared to dilute solution, the dsRNA A-helix is more compact in cells. We recapitulate this compaction in a densely crowded protein solution. Atomic-resolution molecular dynamics simulations of dsRNA semi-quantitatively capture the compaction, and identify non-specific electrostatic interactions between proteins and dsRNA as a possible driver of this effect.     

Conformationally Restricted Isoindoline‐Derived Spin Labels in Duplex DNA: Distances and Rotational Flexibility by Pulsed Electron–Electron Double Resonance Spectroscopy

Three structurally related isoindoline‐derived spin labels that have different mobilities were incorporated into duplex DNA to systematically study the effect of motion on orientation‐dependent pulsed electron–electron double resonance (PELDOR) measurements. To that end, a new nitroxide spin label, ^ExIm U , was synthesized and incorporated into DNA oligonucleotides. ^ExIm U is the first example of a conformationally unambiguous spin label for nucleic acids, in which the nitroxide N?O bond lies on the same axis as the three single bonds used to attach the otherwise rigid isoindoline‐based spin label to a uridine base. Continuous‐wave (CW) EPR measurements of ^ExIm U confirm a very high rotational mobility of the spin label in duplex DNA relative to the structurally related spin label ^Im U , which has restricted mobility due to an intramolecular hydrogen bond. The X‐band CW‐EPR spectra of ^ExIm U can be used to identify mismatches in duplex DNA. PELDOR distance measurements between pairs of the spin labels ^Im U , ^Ox U , and ^ExIm U in duplex DNA showed a strong angular dependence for ^Im U , a medium dependence for ^Ox U , and no orientation effect for ^ExIm U . Thus, precise distances can be extracted from ^ExIm U without having to take orientational effects into account.     

Synthesis and characterization of RNA containing a rigid and nonperturbing cytidine-derived spin label

The nitroxide-containing nucleoside ?m is reported as the first rigid spin label for paramagnetic modification of RNA by solid-phase synthesis. The spin label is well accommodated in several RNA secondary structures as judged by its minor effect on the thermodynamic stability of hairpin and duplex RNA. Electron paramagnetic resonance (EPR) spectroscopic characterization of mono-, bi-, and trimolecular RNA structures shows that ?m will be applicable for advanced EPR studies to elucidate structural and dynamic aspects of folded RNA.     

New chemical constituents from the fruits of Zanthoxylum armatum and its in vitro anti-inflammatory profile

Chemical investigations on the fruits of Zanthoxylum armatum Roxb. (Rutaceae) led to the isolation of two new constituents characterised as 2α-methyl-2β-ethylene-3β-isopropyl-cyclohexan-1β, 3α-diol (1) and phenol-O-β-D-arabinopyranosyl-4′-(3″, 7″, 11″, 15″-tetramethyl)-hexadecan-1″-oate (2) along with known compounds m-methoxy palmityloxy benzene (3), acetyl phenyl acetate (4), linoleiyl-O-α-D-xylopyranoside (5), m-hydroxyphenoxy benzene (6) and palmitic acid (7). The chemical structures were established with the help of physical, chemical and spectroscopic methods. The anti-inflammatory potential of isolated compounds 1 and 2 was evaluated using in vitro target-based anti-inflammatory activity in LPS-stimulated primary peritoneal macrophages isolated from mice. Production of pro-inflammatory cytokines (TNF-α and IL-6) was significantly inhibited by the treatment of isolated compounds 1 and 2 in a dose-dependent manner.     

1,2,3-Triazole tethered acetophenones: Synthesis,bioevaluation and molecular docking study

A small focused library of eighteen new 1,2,3-triazole tethered acetophenones has been efficiently prepared via click chemistry approach and evaluated for their antifungal and antioxidant activity. The antifungal activity was evaluated against five human pathogenic fungal strains: Candida albicans, Fusarium oxysporum, Aspergillus flavus, Aspergillus niger, and Cryptococcus neoformans. Among the synthesized compounds, 9c, 9i, and 9p found to be more potent antifungal agents that the reference standard. These 1,2,3-triazole based derivatives were also evaluated for antioxidant activity, and compound 9h was found to be the most potent antioxidant as compared to the standard drug. Furthermore, molecular docking study of the newly synthesized compounds was performed and results showed good binding mode in the active site of fungal C. albicans enzyme P450 cytochrome lanosterol 14a-demethylase. Moreover, the synthesized compounds were also analyzed for ADME properties and showed potential as good oral drug candidates.     

Polymerizable Solvent-free Organic Liquids: A New Approach for Large Area Flexible and Foldable Luminescent Films

The high demand for light-emitting and display devices made luminescent organic materials as attractive candidates. Solvent-free organic liquids are one of the promising emitters among them due to the salient features. However, the inherent limitations of forming sticky and noncurable surfaces must be addressed to become an alternate emitter for large-area device applications. Herein, we functionalized solvent-free organic liquids having monomeric emission in bulk with polymerizable groups to improve the processability. The polymerizable group on carbazole, naphthalene monoimide, and diketopyrrolopyrrole-based solvent-free liquid emitters enabled on-surface polymerization. These emitters alone and in combinations can be directly coated on a glass substrate without the help of solvents. Subsequent photo or thermal polymerization leads to stable, non-sticky, flexible, foldable, and free-standing large-area films with reasonably high quantum yield. Our demonstration of the tunable and white light-emitting films using polymerizable solvent-free liquids might be a potential candidate in flexible/foldable/stretchable electronics. The new concept of polymerizable liquid can be extended to other functional features suitable for futuristic applications.     

Wärmeübergang bei einphasiger freier Konvektion in der Nähe des kritischen Zustandes

Zusammenfassung Mit den Halogenkältemitteln R12 (CF₂Cl₂), R115 (C₂F₅Cl) und RC318 (C₄F_S) wurden an einem elektrisch beheizten, horizontalen Rohr (d=8 mm) Versuche zur einphasigen freien Konvektion in der Nähe des kritischen Zustandes durchgeführt. Die Messungen erstrecken sich von etwa der halben bis zur doppelten kritischen Dichte und zum 1,8-fachen kritischen Druck; dabei wurden die Fluidzustände außerhalb der beheizten Zone längs der kritischen und einer überkritischen Isotherme variiert.Je nach dem Ausgangszustand des Fluids ist die Abhängigkeit des Wärmeübergangskoeffizienten von der Heizflächenbelastung q ähnlich wie beim Filmsieden oder wie bei freier Konvektion weit unterkritischer Fluide, oder es treten Maxima im (q)-Zusammenhang auf. Die unterschiedlichen Ergebnisse können durch Analyse des Dichte- bzw. Enthalpieverlaufs in der wandnahen, beheizten Fluidzone erklärt werden.

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Free convective heat transfer near the critical state

Experiments were performed on free convective heat transfer from a horizontal, electrically heated tube (d=8 mm) to the halocarbon refrigerants R12 (CF₂Cl₂), R115 (C₂F₅Cl) and RC318 (C₄F₈) near the critical state. Density varied from approx. half to twice the critical value and pressure up to 1.8 times the critical value; the bulk fluid state was varied along the critical and one supercritical isotherm.As is partially known, at different bulk fluid states either peaks are found in the heat transfer coefficients as a function of heat flux or a behaviour similar to film boiling or to free convection at far subcritical states is observed. The different results can be explained by analyzing the density- and enthalpy-variation within the fluid near the heated wall.

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Herrn Prof. Dr.-Ing. H. Glaser, Stuttgart, zum 70. Geburtstag gewidmet.

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Die für die vorliegende Arbeit verwendete versuschanlage wurde mit Mitteln aus dem Schwepunktprogramm Siedevorgänge der Deutschen Forschungsgemeinschaft aufgebaut. Die als Versuchsstoffe benutzten Kältemittel wurden dankenswerterweise von don Farbwerken Hoechst zur Verfügung gestellt.     

Graphene Oxide as Recyclable Catalyst for One-Pot Synthesis of α-Aminophosphonates

We report the synthesis of α-aminophosphonates from aromatic aldehydes, aromatic and aliphatic amines, and trimethylphosphite (Kabachnik–Fields reaction) using a “carbocatalyst,” graphene oxide, at room temperature with excellent yield and recyclability. Enhanced catalytic activity of graphene oxide as compared to other catalysts studied is possibly due to the presence of carboxylic acid and hydroxyl groups.