Rotaxanes capable of recognising chloride in aqueous media

A new, versatile chloride-anion-templating synthetic pathway is exploited for the preparation of a series of eight new [2]rotaxane host molecules, including the first sulfonamide interlocked system. (1)H NMR spectroscopic titration investigations demonstrate the rotaxanes' capability to selectively recognise the chloride anion in competitive aqueous solvent media. The interlocked host's halide binding affinity can be further enhanced and tuned through the attachment of electron-withdrawing substituents and by increasing its positive charge. A dicationic rotaxane selectively binds chloride in 35% water, wherein no evidence of oxoanion binding is observed. NMR spectroscopy, X-ray structural analysis and computational molecular dynamics simulations are used to account for rotaxane formation yields, anion binding strengths and selectivity trends.     

How does dielectric solvation affect the size of an ion?

The effect of solvation by a continuum dielectric on the size of an ion is examined using electronic structure calculations. Various measures correlated with size are considered, including the root-mean-square radius of the electronic charge density, the amount of solute charge penetrating outside the cavity, the electronic radial distribution function, the nucleus-electron potential energy, and the electron-electron potential energy. Calculations are made on several representative ionic solutes, and it is found that every measure indicates that the application of a dielectric makes the cations larger and the anions smaller. These counterintuitive trends are examined, and a plausible explanation is offered for the observed behavior.     

Preparation, characterization and in vitro cytotoxicity of BSA-based nanospheres containing nanosized magnetic particles and/or photosensitizer

This study reports on the preparation, characterization and in vitro toxicity test of a new nano-drug delivery system (NDDS) based on bovine serum albumin (BSA) nanospheres which incorporates surface-functionalized magnetic nanoparticles (MNP) and/or the silicon(IV) phthalocyanine (NzPc). The new NDDS was engineered for use in photodynamic therapy (PDT) combined with hyperthermia (HPT) to address cancer treatment. The BSA-based nanospheres, hosting NzPc, MNP or both (NzPc and MNP), present spherical shape with hydrodynamic average diameter values ranging from 170 to 450 nm and zeta potential of around −23 mV. No difference on the fluorescence spectrum of the encapsulated NzPc was found regardless of the presence of MNP. Time-dependent fluorescence measurements of the encapsulated NzPc revealed a bi-exponential decay for samples incorporating only NzPc and NzPc plus MNP, in the time window ranging from 1.70 to 5.20 ns. The in vitro assay, using human fibroblasts, revealed no cytotoxic effect in all samples investigated, demonstrating the potential of the tested system as a synergistic NDDS.     

A simple branching model that reproduces language family and language population distributions

Human history leaves fingerprints in human languages. Little is known about language evolution and its study is of great importance. Here we construct a simple stochastic model and compare its results to statistical data of real languages. The model is based on the recent finding that language changes occur independently of the population size. We find agreement with the data additionally assuming that languages may be distinguished by having at least one among a finite, small number of different features. This finite set is also used in order to define the distance between two languages, similarly to linguistics tradition since Swadesh.     

Gravitational wave generation in power-law inflationary models

We investigate the generation of gravitational waves in power-law inflationary models. The energy spectrum of the gravitational waves is calculated using the method of continuous Bogoliubov coefficients. We show that, by looking at the interval of frequencies between 10⁻⁵ and 10⁵ Hz and also at the GHz range, important information can be obtained, both about the inflationary period itself and about the thermalization regime between the end of inflation and the beginning of the radiation-dominated era. We thus deem the development of gravitational wave detectors, covering the MHz/GHz range of frequencies, to be an important task for the future.     

Histological and histochemical effects after occlusion alteration in suprahyoid muscles

This study verified the effect of unilateral teeth extraction on the suprahyoid muscles in gerbils (Meriones unguiculatus). Ten adult male gerbils weighing about 50g had induced occlusal alterations by upper molar teeth extraction on the left side while the other ten animals were only subjected to surgical stress, control group. After 60 days, animals of both groups, experimental and control had the suprahyoid muscles removed and processed for histological and histochemical (adenosine triphosphatase (ATPase), nicotine adenine dinucleotide tetrazolium reductase (NADH-TR) and succinate dehydrogenase (SDH)) purposes. The fiber type area was estimated in % according to Weibel method (point-counting method) using a test-system. The myosinic ATPase pH 4.7 activity in the control group of the digastric, milohyoid and geniohyoid muscles presented a small area of type I fiber and a larger area of type IIa fibers; in the experimental group, significant contractile capacity alteration was not observed. Samples of the digastric, milohyoid and geniohyoid muscles, after SDH activity, showed a small area with high metabolic activity fibers, and a large area with intermediary and low metabolic activity fibers in the control group. The milohyoid muscle of the experimental group presented low metabolic fibers in a reduced area, in both sides, however without significant difference. In the experimental group, high metabolic fibers were observed on the left side in a reduced area in the geniohyoid muscle, but without statistical significance. Thus, the geniohyoid muscle did not change the metabolic activity after occlusal alteration. In conclusion, 60 days of unilateral malocclusion induced was able to alter the fibers oxidative activity of the suprahyoid muscles, however, it does not affect the contractile property of the fibers. The digastric muscle has adequate fibers to produce fast contraction and able to resist to fatigue in intermediate degrees, but became more fatigable after unilateral exodontia.     

Collagen fibers evaluation after rhBMP-2 insertion in critical-sized defects

The objective of this investigation was to assess the quantity of collagen fibers with different dosages of recombinant human bone morphogenetic protein, type 2 (rhBMP-2) associated with two different carriers, monoolein and poloxamer gels, in critical bone defects created in the calvaria of Wistar rats. Forty male adult Wistar rats were divided into eight groups of 5 animals each—group I: critical bone defect with application of 1 μg of rhBMP-2 combined with monoolein gel; group II: 3 μg of rhBMP-2 combined with monoolein gel; group III: 7 μg of rhBMP-2 combined with monoolein gel; group IV: 1 μg of rhBMP-2 combined with poloxamer gel; group V: 3 μg of rhBMP-2 combined with poloxamer gel; group VI: 7 μg of rhBMP-2 combined with poloxamer gel; group VII: monoolein gel only and group VIII: poloxamer gel only. A critical-sized defect of 6 mm diameter was produced in the left parietal bone using a surgical round bur and a high-speed micromotor. The bone defects were filled according to the group that animals belonged and after two weeks the rats were perfused and their calvarial bones were removed for histological processing, and collagen fibers quantification. Differences among the eight groups were statistically analyzed by Anova and Bonferroni test (p < 0.05). The results did not show statistical difference between the groups, in exception, between the comparisons II and III. According to the experimental methodology used in this research, it was observed, in a general way, a qualitative inverse relationship between collagen fibers presence and rhBMP-2 quantity inserted in the critical bone defect, associated or not to a material carrier.     

Determination of l-ascorbic acid in wines by direct injection liquid chromatography using a polymeric column

A rapid method for the identification and quantification of l-ascorbic acid in wines by direct injection liquid chromatography equipped with a UV detection was developed. The levels of ascorbic acid were determined using a polymeric PLRP-S 100 A (5 μm) column (150 mm × 4.6 mm) with a mobile water/trifluoroacetic acid (99/1, v/v) phase. The method is rapid (less than 5 min) and sensitive (LOQ of 5 mg L⁻¹). The calibration curve of ascorbic acid was linear (r = 0.999) over a concentration range between 1 and 200 mg L⁻¹. Repeatability was less than 2.5% and the recovery over 95%.     

Synthesis, structural characterization, and theoretical studies of gold(I) and gold(I)-gold(III) thiolate complexes: quenching of gold(I) thiolate luminescence

The gold(I) thiolate complexes [Au(2-SC6H4NH2)(PPh3)] (1), [PPN][Au(2-SC6H4NH2)2] (2) (PPN = PPh3=N=PPh3), and [{Au(2-SC6H4NH2)}2(mu-dppm)] (3) (dppm = PPh2CH2PPh2) have been prepared by reaction of acetylacetonato gold(I) precursors with 2-aminobenzenethiol in the appropriate molar ratio. All products are intensely photoluminescent at 77 K. The molecular structure of the dinuclear derivative 3 displays a gold-gold intramolecular contact of 3.1346(4) A. Further reaction with the organometallic gold(III) complex [Au(C6F5)3(tht)] affords dinuclear or tetranuclear mixed gold(I)-gold(III) derivatives with a thiolate bridge, namely, [(AuPPh3){Au(C6F5)3}(mu2-2-SC6H4NH2)] (4) and [(C6F5)3Au(mu2-2-SC6H4NH2)(AudppmAu)(mu2-2-SC(6)H4NH2)Au(C6F5)3] (5). X-ray diffraction studies of the latter show a shortening of the intramolecular gold(I)-gold(I) contact [2.9353(7) or 2.9332(7) A for a second independent molecule], and short gold(I)-gold(III) distances of 3.2812(7) and 3.3822(7) A [or 3.2923(7) and 3.4052(7) A] are also displayed. Despite the gold-gold interactions, the mixed derivatives are nonemissive compounds. Therefore, the complexes were studied by DFT methods. The HOMOs and LUMOs for gold(I) derivatives 1 and 3 are mainly centered on the thiolate and phosphine (or the second thiolate for complex 2), respectively, with some gold contributions, whereas the LUMO for derivative 4 is more centered on the gold(III) fragment. TD-DFT results show a good agreement with the experimental UV-vis absorption and excitation spectra. The excitations can be assigned as a S --> Au-P charge transfer with some mixture of LLCT for derivative 1, an LLCT mixed with ILCT for derivative 2, and a S --> Au...Au-P charge transfer with LLCT and MC for derivative 3. An LMCT (thiolate --> Au(III) mixed with thiolate --> Au-P) excitation was found for derivative 4. The differing nature of the excited states [participation of the gold(III) fragment and the small contribution of sulfur] is proposed to be responsible for quenching the luminescence.     

Sorting variables by using informative vectors as a strategy for feature selection in multivariate regression

A new procedure with high ability to enhance prediction of multivariate calibration models with a small number of interpretable variables is presented. The core of this methodology is to sort the variables from an informative vector, followed by a systematic investigation of PLS regression models with the aim of finding the most relevant set of variables by comparing the cross‐validation parameters of the models obtained. In this work, seven main informative vectors i.e. regression vector, correlation vector, residual vector, variable influence on projection (VIP), net analyte signal (NAS), covariance procedures vector (CovProc), signal‐to‐noise ratios vector (StN) and their combinations were automated and tested with the main purpose of feature selection. Six data sets from different sources were employed to validate this methodology. They originated from: near‐Infrared (NIR) spectroscopy, Raman spectroscopy, gas chromatography (GC), fluorescence spectroscopy, quantitative structure‐activity relationships (QSAR) and computer simulation. The results indicate that all vectors and their combinations were able to enhance prediction capability with respect to the full data sets. However, regression and NAS informative vectors from partial least squares (PLS) regression, both built using more latent variables than when building the model presented in most of tested data sets, were the best informative vectors for variable selection. In all the applications, the selected variables were quite effective and useful for interpretation. Copyright © 2008 John Wiley & Sons, Ltd.