13C NMR spectroscopic data for glutinol and derivatives

The ¹³C NMR chemical shifts of the triterpenes glutinol, glutinone and acetylglutinol were measured and analysed.     

Assembling of dimeric entities of Cd(II) with 6-mercaptopurine to afford one-dimensional coordination polymers: synthesis and scanning probe microscopy characterization

The direct reaction between 6-mercaptopurine (6-MP) and Cd(II) under different conditions yields either [Cd2(6-MP)4(NO3)2](NO3)2 (1) or [Cd(6-MP-)2.2H2O]n (4). Compound 1 behaves as the building block of the polymer [Cd(6-MP2-)2]n[Ca(H2O)6]n (3), by deprotonation of 6-MP ligand. In the reaction of 1 to give 3, the dinuclear compound [Cd2(6-MP)4(H2O)2](NO3)4.2H2O (2) can be isolated as an intermediate. Polymers 3 and 4 convert into each other in water via deprotonation-protonation reactions. The structures of compounds 1-3 have been determined by X-ray diffraction. Given the small differences in the arrangement shown in the crystal structures of the polymer 4 and the polyanion of 3, the stabilities and energetics of the two arrangements have been examined by DFT calculations to determine the possibility of identifying new conformations of both polymers. In addition, the two polymers have been characterized on surfaces by means of AFM. The direct reaction between 6-MP and Cd(II) and the deprotonation of the polymer 4 have proven to be useful routes for the isolation of one-dimensional systems on surfaces. The development of new strategies to characterize these types of polymers on surfaces opens the possibility to perform nanoscale studies on their properties and their potential use as nanomaterials.     

The role of aromaticity on the building of nanohybrid materials functionalized with metalated (Au(III), Ag(III), Cu(III)) extended porphyrins and single‐walled carbon nanohorns: A theoretical study

An ab initio, systematic study on the aromaticity involving the group of metalated extended porphyrins, termed meso‐hexakis(pentafluorophenyl)‐substituted[26]hexaphyrin(1.1.1.1.1.1) (HP), was performed for the first time. The aromatic behavior of the system shifted to antiaromatic in the [28]HP analogue, due to the presence of hydrogen atoms that break the orbital symmetry. The absorption bands observed in the experiment were assigned to an intraligand charge transfer, where the intrametallic character is also important. The excited states reveal the absorption of visible light and the possibility of electronic transfer to different systems. We propose a system such as single‐walled carbon nanohorns (SWCNHs), due to their special electronic properties, and predict a novel nanohybrid material. The evidence of electronic communication between both species is presented in this work. The HP aromaticity and the spatial configuration of the interaction with SWCNHs are also related to the strength of electronic transfer among the systems, making the HP metalated antiaromatic species and their corresponding nanohybrids potential candidates to be used as building blocks in photovoltaic cell materials. © 2012 Wiley Periodicals, Inc.     

Model studies of colloidal silica precipitation using biosilica extracts from<Emphasis Type="Italic"> Equisetum telmateia</Emphasis>

Structural materials containing silicon are produced in single celled organisms through to higher plants and animals. Hydrated amorphous silica is a colloidal mineral of infinite functionality that is formed into structures with microscopic and macroscopic form. Proteins and proteoglycans are suggested to play a critical role in the catalysis of silica polycondensation and in structure direction during the formation of these magnificent structures. This article extends knowledge on the effect of protein containing biosilica extracts from Equisetum telmateia on the kinetics of silica formation and structure regulation. Utilising potassium silicon catecholate as the source of soluble silicon, bioextracts obtained from plant silica by dissolution of the siliceous phase with aqueous HF following extensive acid digestion of the plant cell wall were found to modify the kinetic rate constants for the formation of small silicic acid oligomers under circumneutral pH conditions and to modify the solubility of silicic acid in solution. Addition of the bioextracts at ca. 1 wt% to the reaction medium reduced the sizes and range of sizes of the fundamental silica particles formed and led to the formation of crystalline polymorphs of silica under conditions of ca. neutral pH, room temperature and in the absence of multiply charged cations, conditions assumed to be relevant to the biological mineralization environment. The ability of biological organisms to regulate the formation of silica structures with prevention of crystallinity is discussed as are the implications of this study in terms of the generation of new materials with specific form and function for industrial application.     

Oriented immobilization of a membrane-bound hydrogenase onto an electrode for direct electron transfer

The interaction of redox enzymes with electrodes is of great interest for studying the catalytic mechanisms of redox enzymes and for bioelectronic applications. Efficient electron transport between the biocatalysts and the electrodes has achieved more success with soluble enzymes than with membrane enzymes because of the higher structural complexity and instability of the latter proteins. In this work, we report a strategy for immobilizing a membrane-bound enzyme onto gold electrodes with a controlled orientation in its fully active conformation. The immobilized redox enzyme is the Ni-Fe-Se hydrogenase from Desulfovibrio vulgaris Hildenborough, which catalyzes H(2)-oxidation reversibly and is associated with the cytoplasmic membrane by a lipidic tail. Gold surfaces modified with this enzyme and phospholipids have been studied by atomic force microscopy (AFM) and electrochemical methods. The combined study indicates that by a two-step immobilization procedure the hydrogenase can be inserted via its lipidic tail onto a phospholipidic bilayer formed over the gold surface, allowing only mediated electron transfer between the enzyme and electrode. However, a one-step immobilization procedure favors the formation of a hydrogenase monolayer over the gold surface with its lipidic tail inserted into a phospholipid bilayer formed on top of the hydrogenase molecules. This latter method has allowed for the first time efficient electron transfer between a membrane-bound enzyme in its native conformation and an electrode.     

Theoretical study of electronic spectra of [Pt3(μ‐CO)3(CO)3] (n = 3–5) complexes

The platinum‐platinum attraction and the spectroscopic properties of [Pt₃(μ‐CO)₃(CO)₃] (n = 3–5) were studied at the PBE level. Theoretical calculations are in agreement with experimental geometries. The absorption spectra of these platinum complexes were calculated by the single excitation time‐dependent (TD) density functional method. All complexes showed MLCT transitions interrelated with the intertriangular complexes. The values obtained at the PBE level are in agreement with the experimental color range. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2009     

Determination of organochlorine compounds in human biological samples by GC-MS/MS

A study was undertaken to determine the extent of organochlorine pesticide (OP) and polychlorinated biphenyl (PCB) contamination in infant formula milk and in the human milk, fat and serum of women from an agricultural area in Southern Spain. A procedure is proposed that simultaneously detects trace levels of lindane, endosulfan-ether, vinclozolin, aldrin, endosulfan-lactone, endosulfan-alpha, 4,4'DDE, 2,4'DDT, endosulfan-beta, 4,4'DDT, kepone, endosulfate-sulfate, methoxychlor, mirex, 2,3,4 PCB, 2,2',4,5 PCB, 2,3,4,5 PCB and 2,2',3,3',6,6'PCB. After liquid-liquid or solid-liquid extraction, the extract of the sample was cleaned by high performance liquid chromatography (HPLC) and the fi rst eluted fraction was analysed by gas chromatography (GC) with mass spectrometry (MS) detector in tandem mode. To evaluate the validity of the method the following parameters were studied: linearity, detection limits, quantification limits, specificity, percentage recovery and precision. A study of the uncertainty associated with the analytical method was also carried out.