Inclusion of molybdenocene dichloride (Cp2MoCl2) in 2-hydroxypropyl- and trimethyl-β-cyclodextrin: Structural and biological properties

Organometallic-cyclodextrin inclusion compounds were obtained by the treatment of molybdenocene dichloride (Cp₂MoCl₂) with the modified cyclodextrins (CDs) heptakis-2,3,6-tri-O-methyl-β-CD (TRIMEB) and 2-hydroxypropyl-β-CD (HPβCD) in aqueous solution. The products were isolated by liophilisation and characterised in the solid-state by powder XRD, thermogravimetric analysis, Raman and FTIR spectroscopy, and ¹³C CP MAS NMR spectroscopy. The results are consistent with inclusion of Cp₂MoCl₂, rather than hydrolysis products such as [Cp₂Mo(H₂O)X]⁺ (X = Cl, OH) or [Cp₂Mo(H₂O)₂]²⁺. The pure non-included metallocene Cp₂MoCl₂ and its inclusion compounds with unmodified β-CD, TRIMEB and HPβCD were screened for their potential antiproliferative and cytotoxic activity, in both human cancer and healthy cell lines. Inclusion in CD was found to enhance the cytotoxic effect of Cp₂MoCl₂, with the TRIMEB adduct displaying the highest anti-tumour activity, along with the lowest toxicity towards non-neoplastic cells.     

Indene and pseudoazulene discotic liquid crystals: a synthetic and structural study

Several new liquid-crystalline indene and pseudoazulene systems are reported. These molecules give rise to either columnar hexagonal mesophases and/or columnar plastic phases. The unique nature of these compounds stems from their non-classical discotic structure. Although the molecules have rigid aromatic cores, they lack terminal tails and instead the polarizable atoms (S, halogens) or polar groups (CN, CO) act as unusual soft parts. On the basis of many structurally related materials, we conclude that for this type of compound molecular stacking in the solid state is a prerequisite for the appearance of a columnar mesophase, although other intermolecular interactions within the layers are also important in establishing liquid-crystalline order. The behavior reported for these mesomorphic molecules opens up new possibilities in the search for related molecular interactions that might be useful for the construction of supramolecular architectures with particular properties.     

Application of molecular absorption properties of horseradish peroxidase for self-indicating enzymatic interactions and analytical methods

In this paper an in depth study is presented of the use of the horseradish peroxidase (HRP) enzyme as a self-indicating biorecognition reagent in UV-vis molecular absorption spectrometry. The HRP/H2O2 reaction mechanism in the absence of an external substrate has been clarified, and the interaction between HRP and glucose oxidase (GOx) has been studied. It has been demonstrated that GOx can act as a substrate of HRP; in both cases the kinetic constants have been obtained and mathematical models have been developed. Second, the HRP/H2O2 reaction is used to follow a H2O2-producing enzymatic reaction, the glucose reaction with GOx being used as a model. As an application of this, two methodologies have been proposed for glucose determination: with or without previous incubation of glucose with GOx. In both cases mathematical models relating HRP absorbance changes to glucose concentration have been developed and tested; both methods have been optimized, analytically characterized, and tested for glucose determination in samples. The methodology described could be applied to other heme-proteins and to other H2O2-producing enzymatic reactions. The models permit the reaction constants to be calculated. From the analytical chemistry point of view the models allow the prediction of the method sensitivity for other analytes involved in this type of reaction if the kinetic constants are known and can be used in the design of optical sensors.     

Evaluation of different quantitative approaches for the determination of noneasily ionizable molecules by different atmospheric pressure interfaces used in liquid chromatography tandem mass spectrometry: Abamectin as case of study

The liquid chromatography tandem mass spectroscopy residue determination of compounds without any acidic or basic centers such as abamectin has been investigated. Several approaches regarding the interface used and adduct formation have been compared. The low acidity of the hydroxyl groups only made deprotonation feasible using the atmospheric pressure chemical ionization (APCI) interface. To obtain sufficient sensitivity for residue analysis, the Ion Sabre APCI interface was necessary. However, the sensitivity attained was lower than for monitoring adducts in positive ion mode. Using electrospray ionization, different adducts with Na+, NH4+, and Li+ were tested and compared. The best results were obtained for the ammoniated adduct in electrospray ionization (ESI) because of its high sensitivity and the presence of several product ions with similar abundance. The highest sensitivity was reached using an in-source fragment as precursor ion, leading to a limit of detection (LOD) of 2 microg/L with low relative standard deviation. The relatively high abundance of other transitions allowed abamectin confirmation at concentrations close to the LOD (6 microg/L). Alkali ions were found to be a suitable alternative to determine and confirm abamectin at residue levels. The [M + Na]+ also presented various product ions with similar abundance, which allowed confirmation at LOD levels. However, this LOD was found to be almost four times higher than with [M + NH4]+ because of the poor sensitivity of the transitions obtained. Although the use of Li+ facilitated the fragmentation of the adduct [M + Li]+, with similar sensitivity to [M + NH4]+, this fragmentation preferentially generated only one product ion, which did not allow confirmation at concentration levels lower than 15 microg/L. The use of APCI for monitoring adducts was also feasible, but with less sensitivity. The sensitivity increased with the Ion Sabre APCI, although it was still five times lower than with ESI. Other adduct formers such as Co2+ and Ni2+ also were tested with unsatisfactory results.     

Excited state enantiodifferentiating interactions between a chiral benzophenone derivative and nucleosides

Time-resolved measurements using nanosecond laser flash photolysis have revealed significant enantiodifferentiation in the interaction between ketoprofen (a chiral benzophenone derivative) and two relevant nucleosides, namely, thymidine and 2'-deoxyguanosine. In both cases, the highest quenching rate constants have been observed for (R)-ketoprofen, the enantiomer with lower pharmacological activity. Photoproduct studies performed in the case of thymidine suggest that the enantiodifferentiating process corresponds to a Paterno-Büchi reaction, leading to the formation of oxetanes. With 2'-deoxyguanosine, the quenching is associated with an electron-transfer process monitored through the generation of a ketyl radical.     

A new concept in lightning parameters measurement

Nowadays the electrical activity measured in tall objects has been widely characterized, but the collected data of lightning rods installed in buildings do not amount to enough to obtain reliable statistics. The measures stored at relatively few points are not representative of the different types of installations. Furthermore, the protection model applied for lightning air terminal installations is based on theoretical models. This paper describes the design of a micro-station to measure some lightning parameters in real lightning air terminal installations correlated to the nature of emplacement instead of triggering lightning or choosing points with a high number of lightning impacts.     

Efficient and reliable mixture critical points calculation by global optimization

Multicomponent systems may exhibit several critical points or no critical point at all. Local methods can find only one critical point for a given initial guess. Recently, several global methods have been proposed for finding all the solutions of the problem. In the present work, we propose a gradient-based calculation method using global optimization, with temperature and molar volume as primary variables, and with analytical partial derivatives calculated from a two-parameter cubic equation of state. The Tunneling global optimization method is used for finding all the global minima. The implementation is based on a unique feature of the Tunneling method, which is able to find efficiently and reliably multiple minima at the same level. Several mixtures from binaries to petroleum reservoir fluids are used to test the proposed method. Numerical experiments proved the efficiency and reliability of the Tunneling method for finding all mixture critical points.     

Determination of trace chromium(VI) in drinking water using X-ray fluorescence spectrometry after solid-phase extraction

A new, simple, and selective method for preconcentration and determination of Cr(VI) in aqueous samples. After adsorption in “batch mode” on Aliquat 336-AC, determinations were made directly on the solid by X-ray fluorescence spectrometry, which had the advantage of not requiring the step of elution of the chromium retained. The enrichment factor was calculated considering that the tablets obtained from 10 mL solution of Cr(VI) (1000 μg L^-1) had a final thickness of 0.64 mm and a diameter of 16.7 mm; the volume deposited on the pellet was 0.14 cm³. The preconcentration factor obtained was 71-fold, which was highly satisfactory for chromium trace analysis by XRF. Finally, the method was successfully applied to the determination of Cr(VI) in drinking water samples.     

Classification of wines from five Spanish origin denominations by aromatic compound analysis

Wine is a complex matrix in which aroma compounds play an important role in the characterization of the flavor pattern of a given wine. Twelve volatile compounds were determined in 244 samples of Spanish red wines from different denominations of origin: Rioja, Navarra, Valdepe?as, La Mancha, and Cari?ena. The samples were analyzed by GC using headspace solid-phase microextraction. The concentration (mg/mL) intervals obtained were 3-methyl-butyl acetate (3.9 to 116), 3-methyl-1-butanol (93 to 724), ethyl hexanoate (0.8 to 39), 1-hexanol (0.3 to 6.7), ethyl octanoate (1.4 to 41), diethyl succinate (0.2 to 13), 2-phenyl ethyl acetate (0 to 5.3), hexanoic acid (0 to 8.3), geraniol (0 to 3.0), 2-phenylethanol (1.5 to 56), octanoic acid (0 to 20), and decanoic acid (0 to 3.3). Wines were classified by multivariate statistical methods: principal component analysis, and lineal discriminant analysis. A correct differentiation among wines according to their origin was obtained by lineal discriminant analysis.