Cluster chemistry: XXXIX. Gold—ruthenium clusters with sulphur ligands: Synthesis and structure of HRu3Au(μ3-S)(CO)9(PPh3), Ru3Au(μ3-SBut)(CO)9(PPh3) and Ru3Au2(μ3-S)(CO)9(PPh3)2

H₂Ru₃(μ₃-S)(CO)₉ is deprotonated by K[HBBu^s₃] to give cluster anions which react with [O{Au(PPh₃)}₃]⁺ or with AuCl(PPh₃)/T1⁺ to give HRu₃Au(μ₃-S)(CO)₉(PPh₃) (1) and Ru₃Au₂(μ₃-S)(CO)₉(PPh₃)₂ (3). A similar sequence with HRu₃(μ₃-SBu^t)(CO)₉ leads to Ru₃Au(μ₃-SBu^t)(CO)₉(PPh₃) (2) as the main product although some 1 also forms, indicating SC cleavage competes with deprotonation of HRu₃(μ₃-SBu^t)(CO)₉ by [HBBu^s₃]^?. The X-ray crystal structures of 1, 2 and 3 are described; (1) and (2) have “butterfly” AuRu₃ cores with markedly different hinge angles of 119 and 148° respectively, while 3 has a trigonal-bipyramidal Au₂Ru₃ skeleton. All three clusters have the sulphur atom symmetrically bridging the Ru₃ triangular face.     

Nonaqueous capillary electrophoretic separation of basic enantiomers using octakis(2,3-O-dimethyl-6-O-sulfo)-gamma-cyclodextrin, a new, single-isomer chiral resolving agent

The enantiomers of 34 pharmaceutical weak-base analytes were separated by nonaqueous capillary electrophoresis in acidic methanol background electrolytes using the sodium salt of the new, single-isomer chiral resolving agent, octakis(2,3-O-dimethyl-6-O-sulfo)-gamma-cyclodextrin (ODMS). The effective mobilities, separation selectivities and peak resolution values of the weak-base analytes were determined as a function of the ODMS concentration in the 0-40 mM range and were found to follow the theoretical predictions of the charged resolving agent migration model (CHARM model) modified for ionic strength effects. Fast, efficient separations were achieved for both comparatively small and large enantiomers.     

Utility of certain pi-acceptors for the spectrophotometric determination of some penicillins

Two simple and sensitive spectrophotometric methods are described for the determination of six penicillin derivatives. The methods are based on the reaction of these drugs as n-electron donors with either 2,3-dichloro-5,6-dicyano-p-benzoquinone (DDQ) or 7,7,8,8-tetracyanoquinodimethane (TCNQ) as pi-acceptors, to give a highly coloured radical anion. The coloured products are quantified spectrophotometrically at 460 and 842 nm for DDQ and TCNQ, respectively. The optimization of the different experimental conditions is described. The interference from streptomycin sulphate and common degradation products was also studied. The proposed methods were applied successfully to the determination of the different penicillins investigated, either in pure or dosage forms, with good accuracy and precision. The results were compared with those given by the official United States Pharmacopeial XXI method.     

Estudios sobre ácidos hidroxámicos

Résumé On propose un procédé de microdosage des groupements méthoxyles dans les pectines, qui repose sur la libération de ces groupements par saponification de l'hydroxylamine alcoolique dans un appareil, sur leur transformation en formiates de méthyle et sur leur distillation. Le formiate de méthyle forme ainsi l'acide formhydroxamique que l'on dose par colorimétrie à l'état de chélate avec le fer-III.On réalise l'hydrolyse de la pectine à 100° C en tube scellé. On fait réagir avec l'acide formique en excès, une partie aliquote de l'hydrolysat dans le micro-appareil de distillation déjà décrit. Le procédé convient pour 1 à 3 mg de pectine et la durée des opérations est de deux heures et demies. Sa spécificité est satisfaisante bien que le groupe éthoxyle puisse gêner. Son action est d'ailleurs peu vraisemblable, puisqu'il ne fait pas partie de la molécule de pectine. Les résultats du procédé sont en générale un peu plus bas que ceux des méthodes volumétriques servant à ce dosage. On a étudié la reproductibilité pour les esters méthyliques et l'on a mis en évidence une erreur par défaut de 2 à 4%. Les plus petites quantités de groupes méthoxyles que l'on puisse doser sont de 20g. Le procédé recommandé est une application particulière de méthodes applicables de façon générale au dosage des esters méthyliques dans les substances organiques. Ce sera l'objet d'une autre communication de cette série.

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Summary A micromethod is given for determining methoxyl groups in pectins. It is based of the liberation of these groups by saponification, conversion into methyl formate, and distillation of the latter into a receiver containing alcoholic hydroxylamine. The methyl formate reacts to give formhydroxamic acid, which is determined colorimetrically as iron(III) chelate.The hydrolysis of the pectin is conducted at 100° C in a sealed tube. An aliquot part of the hydrolysate is brought into reaction with excess formic acid in a microdistillation apparatus that was described previously. The procedure is suitable for 1 to 3 mg pectin and requires 21/2 hours for all partial operations. The specificity is satisfactory, even though ethoxyl may interfere. However, this latter is not likely to be encountered since ethoxyl has not been shown to be a constituent of the pectin molecule. The results given by the procedure are in general inferior to those of volumetric methods. The reproducibility was tested on methyl esters and showed a minus error of 2 to 4%. The smallest amount of methoxyl which can be determined in this way is 20g. The method proposed here is a special application of a method which can be applied in general to the determination of methyl esters in organic substances, which will be the subject of a later paper in this series.

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Zusammenfassung Es wird ein Mikroverfahren zur Bestimmung der Methoxylgruppen in Pektinen angegeben, das auf der Freisetzung dieser Gruppen durch Verseifung, deren Umwandlung in Methylformiat und dessen Destillation in eine Vorlage von alkoholischem Hydroxylamin beruht. Das Methylformiat bildet damit Formhydroxamsäure, die als Eisen(III)-chelat kolorimetrisch bestimmt wird.Die Hydrolyse des Pektins wird bei 100° C in einem verschlossenen Rohr ausgeführt. Einen aliquoten Teil des Hydrolysates läßt man in einem schon früher beschriebenen Mikrodestillationsapparat mit überschüssiger Ameisensäure reagieren. Das Verfahren eignet sich für 1 bis 3 mg Pektin und erfordert für alle Teiloperationen 2^1/2 Stunden. Seine Spezifität ist befriedigend, obwohl Äthoxyl stören kann. Dessen Einwirkung ist jedoch wenig wahrscheinlich, da es nicht als Bestandteil des Pektinmoleküls nachgewiesen ist. Die Ergebnisse des Verfahrens sind im allgemeinen niedriger als die Resultate volumetrischer Methoden. Die Reproduzierbarkeit wurde an Methylestern überprüftund zeigte einen Minusfehler von 2 bis 4%. Die Mindestmenge bestimmbares Methoxyl beträgt 20g. Das vorgeschlagene Verfahren ist eine spezielle Anwendung einer allgemein für die Bestimmung von Methylestern in organischen Substanzen anwendbaren Methode, die Gegenstand einer weiteren Mitteilung dieser Serie sein wird.

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Resumen Se indica una microtécnica de valoración de metoxilos en pectinas, basada en la liberación del radical metilo éster por saponificación; en su conversion en formiato de metilo y en su simultanea destilación y recepción en hidroxilamina alcalinizada. El formiato de metilo se transforma así en ácido formohidroxámico, cuya determinación fotocolorimétrica se realiza como quelato férrico.Estas operaciones requieren efectuar la hidrólisis de la pectina en tubo cerrado y a 100° C, y en tomar una alícuota del hidrolizado, que se pasa con un exceso de ácido fórmico al aparato de microdestilación, detallado en comunicaciones anteriores. El método permite operar con 1 a 3 mg de pectina y todas las operaciones insumen unas dos y media horas. La técnica presenta condiciones satisfactorias de especificidad, pudiendo interferir los radicales etoxilos, cosa poco probable, pues no son reconocidos como componente de la molécula de pectina. Los resultados obtenidos, comparados con los del método titrimétrico, son por lo general inferiores a éste y su reproducibilidad, verificada con ésteres metílicos, tiene errores por defecto de un 2 a 4%. La cantidad mínima de metoxilo valorado alcanza a 20g. La técnica que se indica, es una aplicacion particular de otra de carácter general, aplicable a la valoración de ésteres metílicos en sustancias orgánicas, que será motivo de otra futura comunicación de esta serie.

     

Affinity adsorption of recombinant human interferon-α on a porous dye-affinity adsorbent

Interferons are potent biologically active proteins synthesized and secreted by somatic cells of all mammalian species. Dye-affinity adsorption is increasingly used for protein separation. Hollow fibers have several advantages as adsorbents in comparison to conventional bead supports because they are not compressible and they eliminate internal diffusion limitations. The aim of this study was to explore in detail the performance of polyamide hollow fibers to which Cibacron Blue F3GA was attached for adsorption of recombinant interferon-α (rHuIFN-α). The hollow fiber was characterized by scanning electron microscopy. These dye-carrying hollow fibers (35.8 μmol/g) were used in the rHuIFN-α adsorption-elution studies. The effects of initial concentration of rHuIFN-α, medium pH, ionic strength and temperature on the adsorption efficiency of dye-attached hollow fibers were studied in a batch system. The non-specific adsorption of rHuIFN-α on the hollow fibers was 1.2 mg/g. Cibacron Blue F3GA attachment significantly increased the rHuIFN-α adsorption up to 99.8 mg/g. Significant amount of the adsorbed rHuIFN-α (up to 94.8%) was eluted in 1 h in the elution medium containing 1.0 M NaCl. In order to determine the effects of adsorption conditions on possible conformational changes of rHuIFN-α structure, fluorescence spectrophotometry was employed. We resulted that dye-affinity hollow fibers can be applied for rHuIFN-α adsorption without causing any significant conformational changes. Repeated adsorption/elution processes showed that these dye-attached hollow fibers are suitable for rHuIFN-α adsorption.     

Ternary and tetrahedral symmetry in hybrid fluorides, fluoride carbonates and carbonates

Tren amine cations and carbonate anions adopt a ternary symmetry while tetra amine cations are tetrahedral. The symmetry of these constitutive ions influences strongly the nature of the solids which crystallise from solutions. Large fluorinated aluminate polyanions with tetrahedral symmetry appear in the presence of tren amine, while infinite chains of AlF₆ octahedra are observed with tetra amine and that noncentrosymmetric structures are frequently encountered in rare earth fluoride carbonates.     

In situ assembled ZIF superstructures via an emulsion-free soft-templating approach

Assembling well-defined MOF superstructures remains challenging as it requires easily removable hard templates or readily available immiscible solutions for an emulsion-based soft-template approach. In this work, a single-step emulsion-free soft templating approach is reported to spontaneously prepare hollow ZIF-8 and ZIF-67 colloidosomes with no further purification. These superstructures can load different enzymes regardless of the size and charge with a high encapsulation efficiency of 99%. We envisage that this work will expand the repertoires of MOF superstructures by the judicious selection of precursors and the reaction medium.

An emulsion-free approach for the preparation of hollow ZIF-8 superstructures in a single step is established based on metal sulfate hydrates in methanol.     

Cyphostemmins A-B, two new antifungal oligostilbenes from Cyphostemma crotalarioides (Vitaceae)

Two new antifungal resveratrol dimers, cyphostemmins A-B (1–2), have isolated from the roots of Cyphostemma crotalarioides planch (Vitaceae) together with resveratrol 3 and previously known reseveratrol dimers (4–7). Structures of these new compounds have been established on the basis of their MS and ¹H and ¹³C NMR spectroscopic data.     

A new approach for the derivation of bounds for the Jensen difference

There are many useful applications of Jensen's inequality in several fields of science, and due to this reason, a lot of results are devoted to this inequality in the literature. The main theme of this article is to present a new method of finding estimates of the Jensen difference for differentiable functions. By applying definition of convex function, and integral Jensen's inequality for concave function in the identity pertaining the Jensen difference, we derive bounds for the Jensen difference. We present integral version of the bounds in Riemann sense as well. The sharpness of the proposed bounds through examples are discussed, and we conclude that the proposed bounds are better than some existing bounds even with weaker conditions. Also, we present some new variants of the Hermite–Hadamard and Hölder inequalities and some new inequalities for geometric, quasi-arithmetic, and power means. Finally, we give some applications in information theory.