Radical Cation States of 2,3,5,6,7,8-Hexamethylidenebicyclo [2.2.2]octane

The photoelectron spectrum of the title compound is reported and assigned by correlation with the photoelectron spectra of related molecules.     

Fluorescent behavior of B-phycoerythrin in microemulsions of aerosol OT/water/isooctane

Taking advantage of its unusual fluorescent properties, the incorporation of B-phycoerythrin (B-PE) in aerosol OT (AOT, sodium bis-(2-ethylhexyl) sulphosuccinate)/water/isooctane microemulsions was investigated by following their steady-state and time-resolved fluorescence as a function of the water-to-surfactant molar ratio, w(0). The fluorescent intensity at 575 nm increased continuously with increasing water content, saturating at a w(0) around 35 and staying practically constant at w(0)> or =40. The steady-state anisotropy showed an initial increase with increasing water content until w(0)=23 and then decreased strongly, staying practically constant when w(0)> or =40. The values of the fluorescent parameters, anisotropy and fluorescent intensity, were unchanged when the water content of the system increased in the range between w(0)=40 to 50. This implies the effective incorporation of B-PE in the microemulsion droplets with w(0)> or =40, as well as the equilibrium of the dispersion at these water/surfactant ratios, since higher water content does not affect the main surrounding microenvironment of the protein. The overall incorporation in the microemulsion droplets caused minor spectroscopic changes with respect to biliprotein in aqueous solution of 20 mM sodium phosphate buffer, pH 7.0, such as a blue absorption shift of 3 nm and an emission shift of 1.5 nm, as well as a slight increase in excitation anisotropy spectrum mainly caused by a decrease in protein mobility. Therefore, there are no important interactions between the chromophores and the AOT sulfonate head groups. Emission intensity decays followed complex kinetics in both aqueous and dispersion media. The stability with time and temperature of the biliprotein in the microemulsion was higher than in the aqueous solution. All the results can be explained in terms of B-PE inclusion in the water droplets of AOT microemulsions where the protein has similar configuration and conformation to that in aqueous solution but with the chromophores more protected.     

Preferential solubilization of dodecanol from dodecanol-limonene binary oil mixture in sodium dihexyl sulfosuccinate microemulsions: effect on optimum salinity and oil solubilization capacity

Solubilization of dodecanol-limonene binary oil mixtures has been studied in saturated Winsor type I and III sodium dihexyl sulfosuccinate microemulsions. The systems showed different oil solubilization behavior below and above dodecanol volume fraction 0.2. Below 0.2 dodecanol volume fraction regular Winsor type microemulsions formed. The oil solubilization was characterized in this concentration range by the optimum salinity and the maximum characteristic length. Dodecanol showed Langmuirian-type surface excess adsorption at the vicinity of the surfactant layer. Variation of the optimum salinity and middle phase characteristic length with increasing dodecanol concentration could be linked to changes in the dodecanol surface excess. These relationships were used to develop new mathematical models for the optimum salinity and characteristic length as a function of oil phase composition. Both models yield excellent agreement with the data. Above dodecanol volume fraction 0.2 regular Winsor type III microemulsions are not formed. Therefore our new models are not applicable in this concentration range.     

A genetic algorithm for structure-based de novo design

Genetic algorithms have properties which make them attractive in de novo drug design. Like other de novo design programs, genetic algorithms require a method to reduce the enormous search space of possible compounds. Most often this is done using information from known ligands. We have developed the ADAPT program, a genetic algorithm which uses molecular interactions evaluated with docking calculations as a fitness function to reduce the search space. ADAPT does not require information about known ligands. The program takes an initial set of compounds and iteratively builds new compounds based on the fitness scores of the previous set of compounds. We describe the particulars of the ADAPT algorithm and its application to three well-studied target systems. We also show that the strategies of enhanced local sampling and re-introducing diversity to the compound population during the design cycle provide better results than conventional genetic algorithm protocols.     

Interpretation der Absorptionsspektren der Komplexionen [Mo(CN)8]4−, [Mo(CN)8]3−, [W(CN)8]4− und [W(CN)8]3−

Zusammenfassung Die Absorptions- und Reflexionsspektren der Oktocyanokomplexe desMo(IV) undW(IV) sowie die Absorptionsspektren der Oktocyanotomplexe desMo(V) undW(V) werden mitgeteilt. Die Spektren werden unter Zugrundelegung der durch Raman- und IR-spektroskopische Untersuchungen gefordertenD _4d-Symmetrie dieser Verbindungen interpretiert. Die beobachteten Banden niedriger Intensität (log<3) werden Übergängen in einem Termsystem zugeordnet, das für die Konfigurationend ² undd ₁ und die SymmetrieD _4d berechnet worden ist. Banden hoher Intensität (log>3) werden auf Übergänge in antibindende Zustände zurückgeführt, an denen höherep-Zustände des Zentralions sowie Ligandenzustände beteiligt sind. Die erhaltenen Werte des Feldparameters stimmen mit ligandenfeldtheoretischen Erwartungen überein.

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Absorption and reflection spectra of the octacyanides ofMo(IV) andW(IV) and the absorption spectra of the octacyanides ofMo(V) andW(V) are presented. The spectra are interpreted in terms of theD _4d symmetry of the compounds supported by investigations of Raman and infrared spectra. Bands of low intensity (log<3) correspond to transitions between levels obtained in the case of the configurationsd ² andd ¹ respectively, in a field ofD _4d symmetry. Bands of high intensity (log>3) are attributed to transitions into antibonding levels in which p-orbitals of the central ion and ligand orbitals participate. The values of the field parameter obtained are in accord with ligand field theory.

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Résumé Les spectres d'absorption et de réflexion des complexes octocyanurés duMo(IV) et duW(IV) ainsi que les spectres d'absorption des mêmes complexes deMo(V) et de W(V) sont présentés. Les spectres sont interprétés en supposant la symétrieD _4d des molécules indiquée par des analyses des spectres Raman et infrarouges. Les bandes de faible intensité (log<3) sont attribuées à des transitions dans un système de niveaux, calculé pour les configurationsd ² etd ¹, respectivement, en symétrieD _4d. Des bandes de forte intensité (log>3) sont attribuées à des transitions vers des niveaux antiliants auxquels participent des fonctions élevéesp de l'ion central et des fonctions des groupes liés. Les valeurs obtenues pour le paramètre de champ sont en accord avec les prévisions de la théorie.

     

Excess thermodynamic properties of the 2-propanol + dichloromethane system at 25°C

Densities, viscosities, enthalpies, vapor-liquid equilibria, and surface tensions were determined at 25°C for the 2-propanol+dichloromethane system. From the experimental results excess volumes, viscosities, enthalpies, Gibbs energies, and excess surface tensions were calculated. An attempt has been made to explain the observed deviations from ideal behavior on the basis of intermolecular interactions.     

Solid-phase synthesis of the cyclic lipononadepsipeptide [N-Mst(Ser1), d-Ser4, L-Thr6, L-Asp8, L-Thr9]syringotoxin

An optimized solid-phase strategy for the preparation of the cyclic lipononadepsipeptide [N-Mst(L-Ser1), D-Ser4, L-Thr6, L-Asp8, L-Thr9]syringotoxin is reported. The strategy is based on the use of a mild orthogonal protection scheme and the incorporation of the nonproteinogenic amino acid (Z)-Dhb into the peptide chain as the dipeptide Fmoc-Thr(tBu)-(Z)-Dhb-OH. The didehydrodipeptide was synthesized by a water-soluble carbodiimide-induced beta-elimination of a protected dipeptide containing a residue of Thr with its free hydroxy side chain unprotected.     

Uranium analysis in urine by inductively coupled plasma dynamic reaction cell mass spectrometry

Urine uranium concentrations are the best biological indicator for identifying exposure to depleted uranium (DU). Internal exposure to DU causes an increased amount of urine uranium and a decreased ratio of ²³⁵U/²³⁸U in urine samples, resulting in measurements that vary between 0.00725 and 0.002 (i.e., natural and depleted uraniums ²³⁵U/²³⁸U ratios, respectively). A method based on inductively coupled plasma dynamic reaction cell mass spectrometry (ICP-DRC-MS) was utilized to identify DU in urine by measuring the quantity of total U and the ²³⁵U/²³⁸U ratio. The quantitative analysis was achieved using ²³³U as an internal standard. The analysis was performed both with and without the reaction gas oxygen. The reaction gas converted ionized ²³⁵U⁺ and ²³⁸U⁺ into ²³⁵UO₂⁺ (m/z=267) and ²³⁸UO₂⁺ (m/z=270). This conversion was determined to be over 90% efficient. A polyatomic interference at m/z 234.8 was successfully removed from the ²³⁵U signal under either DRC operating conditions (with or without oxygen as a reaction gas). The method was validated with 15 urine samples of known uranium compositions. The method detection limit for quantification was determined to be 0.1 pg U mL^–1 urine and an average coefficient of variation (CV) of 1–2% within the sample measurements. The method detection limit for determining ²³⁵U/²³⁸U ratio was 3.0 pg U mL^–1 urine. An additional 21 patient samples were analyzed with no information about medical history. The measured ²³⁵U/²³⁸U ratio within the urine samples correctly identified the presence or absence of internal DU exposure in all 21 patients.The opinions and assertions expressed herein are those of the authors and are not to be construed as official or as representing the views of the Armed Forces Institute of Pathology, the Department of the Army, or the Department of Defense     

Correction: Click activated protodrugs against cancer increase the therapeutic potential of chemotherapy through local capture and activation

Correction for ‘Click activated protodrugs against cancer increase the therapeutic potential of chemotherapy through local capture and activation’ by Kui Wu et al., Chem. Sci., 2021, 12, 1259–1271, DOI: 10.1039/D0SC06099B.

The authors regret that the reference to the bond-breaking bioorthogonal chemistry, termed ‘click-to-release’ was omitted from the original article. In addition, we would like to include a reference describing the synthesis of compound 1, which is an intermediate to the protodrugs described in the original article. These references are listed below as ref. 1 and 2.The Royal Society of Chemistry apologizes for these errors and any consequent inconvenience to authors and readers.     

Differential conductance switching of planar tunnel junctions mediated by oxidation/reduction of functionally protected ferrocene

Planar tunnel junctions were fabricated by self-assembling 1,1'- ferrocenedicarboxylic acid (FDCA) onto native oxides of thermally deposited aluminum films and subsequently depositing a second aluminum film. Junctions were characterized using Reflection-Absorption Fourier Transform Infrared Spectroscopy (RAIRS) and current-voltage (I-V) spectroscopy. Before deposition of the second aluminum film, RAIRS of FDCA and ferrocenecarboxylic acid (FCA) films revealed COO(-), C=O, and Fc ring stretching modes, indicating that both types of molecules can interact strongly with the oxide and remain intact. After deposition, systems exhibited prominent COO(-) modes and weakened C=O modes, indicating further reaction with aluminum/aluminum oxide. Fc ring modes persisted in FDCA systems but disappeared in FCA systems, suggesting that the second COOH group in the FDCA molecule can act as a protecting group for the ferrocene moiety. Cyclic I-V measurements of FDCA tunnel junction systems revealed very strong ( approximately 10-fold) hysteretic differential conductance switching that was both reversible and stable. Control measurements using as prepared junctions, as well as junctions containing 1,6-hexanedioic acid, 1,9-nonanedioic acid, 1,4-dibenzoic acid, or FCA revealed only very weak ( approximately 10%) differential conductance changes. We attribute FDCA junction switching to barrier profile modifications induced by oxidation/reduction of the functionally protected ferrocene moieties.