A compact olfactometer for IMS measurements and testing human perception

Production of easily controllable and measurable odor stimuli is needed when studying human olfaction, olfaction-related physiology and psychological reactions to odors. Controlled odor producing instruments are called olfactometers. For testing and calibrating new olfactometers or sensor arrays, a reliable input signal has to be produced to verify their accurate functionality. A common input signal in various olfactometers has been the use of volatile organic compounds (VOCs) in gaseous form. We present a compact olfactometer able to produce controlled continuous odor stimuli from three individual channels. For measuring the output gas flow, we used a ChemPro 100i (Environics, Finland) device that is based on aspiration ion mobility spectrometry (aIMS). IMS is a robust and sensitive method for measuring VOCs and is used especially in detecting toxic industrial chemicals and chemical warfare agents, but the technology is also suitable for other olfactory-related applications. The olfactometer was used to produce synthetic jasmine scent using three main odor components from jasmine oil and all the components were diluted using propylene glycol. The dilutions were supplied to the system using programmable syringe pumps, which guided the dilutions to individual evaporation units. We conducted experiments to verify the functionality of our olfactometer. Analysis of the ChemPro100i data showed that olfactometer can use different odor components to produce continuous, stable output flows with controlled concentrations.     

Chiral Bifunctional Phosphine‐Carboxylate Ligands for Palladium(0)‐Catalyzed Enantioselective C−H Arylation

Previous enantioselective Pd⁰‐catalyzed C?H activation reactions proceeding via the concerted metalation‐deprotonation mechanism employed either a chiral ancillary ligand, a chiral base, or a bimolecular mixture thereof. This study describes the development of new chiral bifunctional ligands based on a binaphthyl scaffold which incorporates both a phosphine and a carboxylic acid moiety. The optimal ligand provided high yields and enantioselectivities for a desymmetrizing C(sp²)?H arylation leading to 5,6‐dihydrophenanthridines, whereas the corresponding monofunctional ligands showed low enantioselectivities. The bifunctional system proved applicable to a range of substituted dihydrophenanthridines, and allowed the parallel kinetic resolution of racemic substrates.     

Kinetic Analysis and Structural Interpretation of Competitive Ligand Binding for NO Dioxygenation in Truncated Hemoglobin N

The conversion of nitric oxide (NO) into nitrate (NO₃^?) by dioxygenation protects cells from lethal NO. Starting from NO‐bound heme, the first step in converting NO into benign NO₃^? is the ligand exchange reaction FeNO+O₂→FeO₂+NO, which is still poorly understood at a molecular level. For wild‐type (WT) truncated hemoglobin N (trHbN) and its Y33A mutant, the calculated barriers for the exchange reaction differ by 1.5 kcal mol^?1, compared with 1.7 kcal mol^?1 from experiment. It is directly confirmed that the ligand exchange reaction is rate‐limiting in trHbN and that entropic contributions account for 75 % of the difference between the WT and the mutant. Residues Tyr 33, Phe 46, Val 80, His 81, and Gln 82 surrounding the active site are expected to control the reaction path. By comparison with electronic structure calculations, the transition state separating the two ligand‐bound states was assigned to a ²A state.     

Zur Mikrochemie der seltenen Erden

Zusammenfassung Scandium gibt mit Alizarin-3-sulfonat ein in verdünnter Essigsäure schwer lösliches Scandiumalizarin-3-sulfonat, während die übrigen seltenen Erden in nicht zu konzentrierten Lösungen nicht ausfallen. Scandium kann auf diese Weise zusammen mit Thorium, das ebenfalls eine schwer lösliche Verbindung gibt, ineiner Operation von den übrigen seltenen Erden abgetrennt werden, auch wenn nur geringe Mengen Scandium vorhanden sind.Mit Cochenilletinktur geben die seltenen Erden und die Zirkonverbindungen violette, Thoriumsalze dagegen blaue Lösungen. Die violetten Lösungen der Ceriterden von Lanthan bis Samarium werden durch verdünnte Essigsäure orangerot gefärbt, indem die ursprüngliche Farbe der Cochenilletinktur wieder hergestellt wird. Bei den Terbin- und Erbinerden und Zirkon ruft erst konzentriertere Essigsäure einen Farbumschlag nach rot hervor und erst ganz konzentrierte Essigsäure bewirkt Farbumschlag nach orangerot.

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Summary Scandium gives with alizarine-3-sulphonate a precipitate of the scandium salt, difficultly soluble in dilute acetic acid, whilst the remaining rare earths are not precipitated, provided the solutions are not unduly concentrated. Scandium, together with thorium, which also forms a sparingly soluble compound, may be separated in this way by a single operation from the other rare earths, even if only small quantities of scandium are present.The rare earths and zirconium compounds yield violet solutions with tincture of cochineal, whereas thorium salts give blue solutions. The violet solutions of the cerite earths from lanthanum to samarium become reddish-orange on the addition of dilute acetic acid, the original colour of the cochineal tincture being restored. In the case of the terbium and erbium earths and zirconium strong acetic acid is necessary in order to bring about a change of colour to red, and a change to the original reddish-orange only results when quite concentrated acetic acid is used.

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Résumé Le scandium donne avec l'alizarine-3-sulfonate un sel difficilement soluble dans l'acide acétique dilué, tandis que les autres terres rares ne sont pas précipitées dans des solutions diluées. On peut, de cette manière, en une seule opération, séparer le scandium et le thorium (qui, lui aussi, donne un composé peu soluble) des autres terres rares, même en présence de très petites quantités de scandium.Les terres rares et les combinaisons de zirconium donnent des solutions violettes avec la teinture de cochenille, les sels de thorium, par contre, donnent des solutions bleues. Les solutions violettes des terres cérites du lanthane au samarium deviennent rouge-orangé par adjonction d'acide acétique dilué; parallèlement, la couleur originelle de la teinture de cochenille réapparait.Quand on a affaire à des terres de terbium et d'erbium et au zirconium, seul l'emploi d'acide acétique plus concentré amène le virage au rouge, tandis qu'il faut de l'acide acétique absolument concentré pour faire virer au rouge.

     

The effect of alumina on the Sn/Sn redox equilibrium and the incorporation of tin in Na2O/Al2O3/SiO2 melts

Glasses with the basic compositions 10Na₂O · 10CaO · xAl₂O₃ · (80 − x)SiO₂ (x=0, 5, 15, 25) and 16Na₂O · 10CaO · xAl₂O₃ · (74 − x)SiO₂ (x=0, 5, 10, 15, 20) doped with 0.25-0.5 mol% SnO₂ were studied using square-wave-voltammetry at temperatures in the range from 1000 to 1600 °C. The voltammograms exhibit a maximum which increases linearly with increasing temperature. With increasing alumina concentration and decreasing Na₂O concentration the peak potentials get more negative. Mössbauer spectra showed two signals attributed to Sn²⁺ and Sn⁴⁺. Increasing alumina concentrations did not affect the isomer shift of Sn²⁺; however, they led to increasing quadrupole splitting, while in the case of Sn⁴⁺ both isomer shift and quadrupole splitting increased. A structural model is proposed which explains the effect of the composition on both the peak potentials and the Mössbauer parameters.     

Synthesis of the C10-C32 core structure of spirangien A

The synthesis of the C10-C32 core structure of spirangien A is reported. The pivotal aldol coupling between both key intermediates provides a synthetic challenge in the synthesis of this complex natural product.     

Intermolecular vibrational coherence in the bacteriochlorophyll proteins B777 and B820 from Rhodospirillum rubrum

The low-frequency vibrational coherence in the bacteriochlorophyll (BChl)-containing subunit proteins B777 and B820 from the LH1 light-harvesting complex isolated from Rhodospirillum rubrum G9 exhibits rapidly damped modulation components arising from intermolecular, formally nonbonding interactions between the BChl macrocycle and polar groups in the surrounding detergent or protein. The vibrational coherence observed in the monomeric B777 system resembles that observed previously with BChl in acetone because it contains a pair of broad overlapping line shapes with a mean frequency of 191 cm(-1), but the 10:1 intensity ratio of the librational and translational components is distinctive of the motions of the polar head groups in the nonionic detergent micelle that solvates the BChl macrocycle. In contrast, the vibrational coherence observed with the dimeric B820 complex is almost 20 times weaker in intensity and exhibits narrower line shapes and lower average frequencies than observed in B777. The structure of the B820 complex sterically protects the pair of BChl macrocycles from the surrounding solvent, so modulation components assigned to intrinsic interactions between the BChl and the protein and between the pair of BChl's are revealed. A relatively well-ordered interaction between the BChl macrocycle and a tryptophan residue in each alpha-helical polypeptide accounts for a 28 cm(-1) component with a narrow line shape, but most of the intensity arises from a broader 46 cm(-1) component that is assigned to the interaction between the paired BChl macrocycles. The breadth of the line shape for this component is a measure of the disorder in the ensemble of B820 subunits. The results support the hypothesis that the excited-state vibrational dynamics and the optical and/or Marcus charge-transfer reorganization energies of BChl in photosynthetic light-harvesting proteins and reaction centers are strongly controlled by van der Waals modes with neighboring molecules, with dominant contributions to the intermolecular potential arising from the London dispersion and dipole-dipole interactions.     

Determination of gentisin, isogentisin, and amarogentin in Gentiana lutea L. by capillary electrophoresis

A novel, fast, and simple capillary electrophoresis method has been developed for the analysis of gentisin, isogentisin, and amarogentin in roots of Gentiana lutea (yellow gentian), an herb traditionally used as gastric stimulant. Gentisin and isogentisin are xanthones showing potent inhibition of monoamine oxidase type A and B, amarogentin represents one of the bitter principles of Gentiana, responsible for its gastric-roborant effects. Optimal CE-separation conditions comprise a 100 mM sodium tetraborate buffer of pH 9.3, containing 10 mM beta-cyclodextrin as additive; optimum temperature and applied voltage were found to be 30 degrees C and 25 kV, respectively. Direct diode array detection at 260 nm (gentisin, isogentisin) and 242 nm (amarogentin) was performed, and the required analysis time was only 11 min. The developed method was validated for linearity, sensitivity, precision, and accuracy, and utilized to assay several commercially available G. lutea samples. Quantitative data obtained with the developed CE method are compared with HPLC results, and the advantages of each approach are discussed.