Diffusion Coefficient Analysis by Dynamic Light Scattering Enables Determination of Critical Micelle Concentration.

The critical micelle concentration is an important property of supramolecular detergents. Two dynamic light scattering approaches have been developed for critical micelle concentration analysis, i. e.

Molar Mass Determination for Small and Large Molecules Using Diffusion-Ordered Spectroscopy.

The development of the most comprehensive universal calibration of molar mass dependences will be presented. For the first time, diffusion-ordered spectroscopy (DOSY) can now provide structure-, solvent-, and temperature-independent molar mass determinations for both small and large molecules. This fundamental theoretical approach provides only one single function which could perfectly describe all molar mass dependences.

Online coupling of liquid chromatography and two-dimensional diffusion ordered spectroscopy for the analysis of oligostyrenes.

The aim of this study was to introduce a powerful coupling of Liquid Adsorption Chromatography (LAC) and Diffusion-Ordered Spectroscopy (DOSY) for comprehensive structure analysis. This new hyphenation approach facilitated the simultaneous separation of a polymer mixture and the determination of molar masses within a single 3D experiment. The online coupling of High-Performance Liquid Chromatography (HPLC) and two-dimensional DOSY-NMR will be called 3D-LAC-NMR-DOSY experiment.

The accuracy limit of chemical shift predictions for species in aqueous solution.

Interpreting NMR experiments benefits from first-principles predictions of chemical shifts. Reaching the accuracy limit of theory is relevant for unambiguous structural analysis and dissecting theoretical approximations. Since accurate chemical shift measurements are based on using internal reference compounds such as trimethylsilylpropanesulfonate (DSS), a detailed comparison of experimental with theoretical data requires simultaneous consideration of both target and reference species ensembles in the same solvent environment.

The Universal Calibration for Structure- and Solvent-Independent Molar Mass Determinations of Polymers Using Diffusion-Ordered Spectroscopy.

It will be shown how diffusion-ordered spectroscopy (DOSY) can produce a universal calibration of molar mass dependences of polymers compared to size exclusion chromatography (SEC) or recently published DOSY methods. Whereas SEC can deliver only structure-independent universal calibrations for a particular solvent, DOSY was used for creating solvent-independent calibrations for a certain polymer. Now, we can demonstrate a universal calibration method that generates both a structure- and solvent-independent molar mass calibration.

Gauging the Strength of the Molecular Halogen Bond via Experimental Electron Density and Spectroscopy.

Strong and weak halogen bonds (XBs) in discrete aggregates involving the same acceptor are addressed by experiments in solution and in the solid state. Unsubstituted and perfluorinated iodobenzenes act as halogen donors of tunable strength; in all cases, quinuclidine represents the acceptor. NMR titrations reliably identify the strong intermolecular interactions in solution, with experimental binding energies of approx.

Medical Encounters and Treatment Outcomes in Ironman-Distance Triathlon.

Purpose: This study aimed to examine the injury and illness characteristics, treatments, and outcomes at elite ultraendurance triathlon events.

Methods: We quantified participant demographics, injury types, treatments, and disposition for medical encounters at 27 Ironman-distance triathlon championships from 1989 to 2019. We then calculated the likelihood of concurrent medical complaints in each encounter.

Extending Chirality in Group XIV Metallatranes.

The syntheses of the racemic amino alcohol -N(CHCMeOH)(CMeCHOH)(CHCHMeOH) (H, ) and its representative N(CHCMeOH)(CMeCHOH)(CHC()HMeOH) (H, ) with the stereogenic carbon center being -configured are reported. Also reported are the stannatranes SnO-Bu () SnO-Bu () and germatranes GeOEt () and GeOEt () as well as the trinuclear tin oxocluster [(μ-O)(μ-O--Bu){Sn}] (). NMR and IR spectroscopy, electrospray ionization mass spectrometry (ESI MS), and single crystal X-ray diffraction analysis characterize these compounds.

Fragtory: Pharmacophore-Focused Design, Synthesis, and Evaluation of an sp-Enriched Fragment Library.

Fragment-based drug discovery has played an important role in medicinal chemistry and pharmaceutical research. Despite numerous demonstrated successes, the limited diversity and overrepresentation of planar, sp-rich structures in commercial libraries often hamper the full potential of this approach. Hence, the thorough design of screening libraries inevitably determines the probability for meaningful hits and subsequent structural elaboration.

Comprehensive Study of the Enhanced Reactivity of Turbo-Grignard Reagents.

Since its introduction in 2004, Knochel's so called Turbo-Grignard reagents revolutionized the usage of Grignard reagents. Through the simple addition of LiCl to a magnesium alkyl an outstanding increase in reactivity can be achieved. Though the exact composition of the reactive species remained mysterious, the reactive mixture itself is readily used not only in synthesis but also found its way into more distant fields like material science.

Maximized axial helicity in a PdL cage: inverse guest size-dependent compression and mesocate isomerism.

Helicity is an archetypal structural motif of many biological systems and provides a basis for molecular recognition in DNA. Whilst artificial supramolecular hosts are often helical, the relationship between helicity and guest encapsulation is not well understood. We report a detailed study on a significantly coiled-up PdL metallohelicate with an unusually wide azimuthal angle (∼176°).

Generation of Aurachin Derivatives by Whole-Cell Biotransformation and Evaluation of Their Antiprotozoal Properties.

The natural product aurachin D is a farnesylated quinolone alkaloid, which is known to possess activity against the causative agent of malaria, spp. In this study, we show that aurachin D inhibits other parasitic protozoa as well. While aurachin D had only a modest effect on , two other trypanosomatids, and , were killed at low micromolar and nanomolar concentrations, respectively, in an in vitro assay.

Myxococcus xanthus as Host for the Production of Benzoxazoles.

Benzoxazoles are important structural motifs in pharmaceutical drugs. Here, we present the heterologous production of 3-hydroxyanthranilate-derived benzoxazoles in the host bacterium Myxococcus xanthus following the expression of two genes from the nataxazole biosynthetic gene cluster of Streptomyces sp. Tü 6176.

Amamistatins isolated from .

Four new phenolic siderophores were isolated from the actinomycete along with the known natural product amamistatin B and a putative biosynthetic shunt product. The structures of all compounds were elucidated through 1D and 2D NMR analyses as well as mass spectrometry. The iron-chelating properties of the retrieved metabolites were evaluated in a chrome azurol S assay.

Discovery, Biosynthetic Origin, and Heterologous Production of Massinidine, an Antiplasmodial Alkaloid.

Bacteria of the genus represent an underexplored source of bioactive natural products. Here, we report the discovery of massinidine (), a guanidine alkaloid with antiplasmodial activity, from these microbes. The unusual scaffold of massinidine is shown to originate from l-phenylalanine, acetate, and l-arginine.

Polyurea Thickened Lubricating Grease-The Effect of Degree of Polymerization on Rheological and Tribological Properties.

Lubricating greases based on urea thickeners are frequently used in high-performance applications since their invention in 1954. One property that has so far been neglected in the further development of these systems due to their low solubility and the resulting difficulty of analysis, is to better understand how the degree of polymerization affect such polyurea lubricating systems. In this work, we prepared three different oligo- or polyurea systemswith different degrees of polymerization (DP) and investigated the influence of DP on rheological and tribological properties.

Hidden intermediates in Mango III RNA aptamer folding revealed by pressure perturbation.

Fluorescent RNA aptamers have the potential to enable routine quantitation and localization of RNA molecules and serve as models for understanding biologically active aptamers. In recent years, several fluorescent aptamers have been selected and modified to improve their properties, revealing that small changes to the RNA or the ligands can modify significantly their fluorescent properties. Although structural biology approaches have revealed the bound, ground state of several fluorescent aptamers, characterization of low-abundance, excited states in these systems is crucial to understanding their folding pathways.

Mutasynthesis of Physostigmines in .

The alkaloid physostigmine is an approved anticholinergic drug and an important lead structure for the development of novel therapeutics. Using a complementary approach that merged chemical synthesis with pathway refactoring, we produced a series of physostigmine analogues with altered specificity and toxicity profiles in the heterologous host . The compounds that were generated by applying a simple feeding strategy include the promising drug candidate phenserine, which was previously accessible only by total synthesis.

Molecular Cage Assembly by Sn-O-Sn Bridging of Di-, Tri- and Tetranuclear Organotin Tectons: Extending the Spacing in Double Ladder Structures.

Hydrolysis reactions of di- and trinuclear organotin halides yielded large novel cage compounds containing Sn-O-Sn bridges. The molecular structures of two octanuclear tetraorganodistannoxanes showing double-ladder motifs, viz., [{Me SiCH (Cl)SnCH YCH Sn(OH)CH SiMe } (μ-O) ] [1, Y=p-(Me) SiC H -C H Si(Me) ] and [{Me SiCH (I)SnCH YCH Sn(OH)CH SiMe } (μ-O) ] ⋅0.

Weak yet Decisive: Molecular Halogen Bond and Competing Weak Interactions of Iodobenzene and Quinuclidine.

The halogen bonded adduct between the commonly used constituents quinuclidine and iodobenzene is based on a single weak nitrogen-iodine contact, and the isolation of this adduct was initially unexpected. Iodobenzene does not contain any electron-withdrawing group and therefore represents an unconventional halogen bond donor. Based on excellent diffraction data of high resolution, an electron density study was successfully accomplished and confirmed one of the longest N···I molecular halogen bonds with a distance of 2.

On the Heterogeneous Nature of Cisplatin-1-Methyluracil Complexes: Coexistence of Different Aggregation Modes and Partial Loss of NH Ligands as Likely Explanation.

The conversion of the 1 : 1-complex of Cisplatin with 1-methyluracil (1MeUH), cis-[Pt(NH ) (1MeU-N3)Cl] (1 a) to the aqua species cis-[Pt(NH ) (1MeU-N3)(OH )] (1 b), achieved by reaction of 1 a with AgNO in water, affords a mixture of compounds, the composition of which strongly depends on sample history. The complexity stems from variations in condensation patterns and partial loss of NH ligands. In dilute aqueous solution, 1 a, and dinuclear compounds cis-[(NH ) (1MeU-N3)Pt(μ-OH)Pt(1MeU-N3)(NH ) ] (3) as well as head-tail cis-[Pt (NH ) (μ-1MeU-N3,O4) ] (4) represent the major components.

[Uncommon tumor of the gastric wall].

We report on a 72-year-old male patient suffering from weight loss, diarrhea, and epigastric pain. By means of endosonographic ultrasound, a well-circumscribed tumor mass was found in the gastric wall, suggesting a gastrointestinal stromal tumor (GIST). Biopsies were taken and processed for standard histopathological analysis.

MeSi(CH SnRO) (R=Ph, Me SiCH ): Building Blocks for Triangular-Shaped Diorganotin Oxide Macrocycles.

The syntheses of the novel silicon-bridged tris(tetraorganotin) compounds MeSi(CH SnPh R) (2, R=Ph; 5, R=Me SiCH ) and their halogen-substituted derivatives MeSi(CH SnPh I ) (3, n=1; 4, n=2) and MeSi(CH SnI R) (6, R=Me SiCH ) are reported. The reaction of compound 4 with di-t-butyltin oxide (t-Bu SnO) gives the oktokaideka-nuclear (18-nuclear) molecular diorganotin oxide [MeSi(CH SnPhO) ] (7) while the reaction of 6 with sodium hydroxide, NaOH, provides the trikonta-nuclear (30-nuclear) molecular diorganotin oxide [MeSi(CH SnRO) ] (8, R=Me SiCH ). Both 7 and 8 show belt-like ladder-type macrocyclic structures and are by far the biggest molecular diorganotin oxides reported to date.