Optical activity measurements on solids. 6. Solid state optical activity and circular dichroism measurements of sodium thioantimonate nonahydrate

Summary We have demonstrated that optical circular dichroism (CD) measurements can be carried out on powders suspended in a liquid medium. The refractive indices of the powder and the suspending liquid must be matched, the suspending liquid must not interact significantly with the solid to be measured and must not absorb in the region where the measurements are carried out. Sodium thioantimonate nonahydrate (Na₃SbS₄·9H₂O) powders obtained by grinding oflevo- ordextro-rotatory crystals were found to be excellent examples for the demonstration of this technique. Measurements of the optical rotation forlevo- anddextro-rotatory crystals and powders of Na₃SbS₄·9H₂O were also carried out and provided additional characterization of this salt. In the course of developing the CD measurement technique, CD of NaClO₃ and NaBrO₃ crystals was also measured.Dedicated to Prof. Dr. Karl Schlögl on the occasion of his 70^th birthday with our warmest wishes     

Kinetic ordering of atoms in sodium chlorate-bromate solid solutions

Kinetic ordering of anions in Na((ClO₃)_1−x(BrO₃)_x) solid solutions with anomalous birefringence was studied by means of single crystal X-ray diffraction. The crystal structures of the two samples (x=0.10 and 0.255) cut out from the {100} growth sectors were refined in the ideal space group P2₁3 and in two of its subgroups—monoclinic P2₁ and triclinic P1 with R=0.030-0.038. The final choice of monoclinic symmetry was confirmed by the analysis of the diffraction pattern and Cl/Br distribution over the halogen crystallographic sites. The Cl/Br ordering reflects the geometrical difference of these sites with respect to the growth front orientation. The observed optical indicatrix was successfully reproduced in the point-dipole approximation. According to our data and the data of Crundwell et al. (Acta Crystallogr. Sect. B 53 (1997) 189), the degree of ordering increases in the middle of the isomorphous series along with the birefringence. The obtained results confirm the hypothesis of growth dissymmetrization.     

The n→π* optical activity of chiral carbonyl compounds predicted to be optically inactive by the octant rule

The one-electron model of n* optical activity in chiral carbonyl compounds is carried to second-order in perturbation theory and the results are applied to systems which are predicted by the octant rule to yield zero n* optical activity. It is shown that second-order contributions to the n* rotatory strength lead to sector rules which are qualitatively different from those obtained from first-order contributions. Inclusion of three-way interactions involving the carbonyl chromophore and two different extrachromophoric perturbing groups (or atoms) lead to second-order contributions to the rotatory strength which can account for the n* optical activity in chiral carbonyl systems predicted to be optically inactive by the conventional quadrant and octant rules. These results are shown to be in agreement with the conclusions derived by Ruch and Schönhofer from a purely algebraic theory of molecular chirality.     

Helical polyurethane@attapulgite nanocomposite: Preparation, characterization and study of optical activity

Helical polyurethane@attapulgite (BM-ATT) based on R-1,1′-binaphthyl-2′,2-diol (R-BINOL) composite was prepared after the surface modification of attapulgite (ATT). BM-ATT was characterized by Fourier-transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HTEM) and vibrational circular dichroism (VCD) spectroscopy. FT-IR and XRD analyses indicate that the helical polyurethane has been successfully grafted onto the surfaces of the modified ATT without destroying the original crystalline structure of ATT. BM-ATT exhibits the rod-like structure by SEM, TEM, and HTEM photographs. BM-ATT displays obvious Cotton effect for some absorbance in VCD spectrum, and its optical activity results from the singlehanded conformation of helical polyurethane.     

Calorimetric and optical study of micellar aggregates of sodium taurodeoxycholate

Calorimetric measurements, carried out on aqueous solutions of sodium taurodeoxycholate at different NaCl concentrations, show that the molar heat of dilution decreases with the bile salt concentration and, to a lesser extent, with the NaCl concentration. Circular dichroism spectra, recorded from aqueous solutions of bile salt as a function of concentration, change the sign of the molar ellipticity under 230 nm.¹H NMR spectra show an increase of the half-height line width of the C₁₈ methyl group with the concentration of both bile salt and NaCl. These results, together with those inferred from viscosity measurements, favour the assumption of a model, observed from the crystal structure of sodium taurodeoxycholate and based on an equilibrium between two types of helices.     

Neurotropic activity of organogermanium compounds

Neurotropic activity of several classes of organogermanium compounds (namely germatranes, germanols, germsesquioxanes, germyladamantanes, germylamides, germylimides and germylsubstituted amines, imines and hydroxamic acids) and their synthesis are reviewed.     

Modeling the analytical response of optical fiber sensors for aromatic compounds determination

In recent years, there has been an increasing interest in the application of optical fiber sensors for in situ monitoring of chemical pollutants, including volatile organic compounds, regarding air quality assurance. In order to enhance the usefulness and applicability of this methodology to environmental analysis, a proper study of the analytical signal and an adequate calibration model are required. This contribution is focused on the model for optical fiber sensors calibration, discussing some problems associated with the estimates of the figures of merit of these analytical systems. We also suggest and discuss a calibration model based on a cumulative symmetric double sigmoidal (SDS) function, as a suitable and general alternative to the more limited and classical linear calibration model.     

Measurement of pH at elevated temperatures using the optical indicator acridine

A new method of measuring the pH of high-temperature aqueous solutions using optical indicators was developed. The absorbance spectrum of acridine changes as a function of pH, allowing its use as an optical indicator for pH. The pK_a of acridine were experimentally determined in KOH-AcOH pH-buffer solutions at temperatures from 5 to 250°C at vaporsaturated pressures:

Lipoxygenase inhibitory activity of Cuspidaria pulchra and isolated compounds

This work evaluated the in vitro inhibitory activity of the crude ethanolic extract from the aerial parts of Cuspidaria pulchra (Cham.) L.G. Lohmann against 15-lipoxygenase (15-LOX). The bioassay-guided fractionation of the n-butanol fraction, which displayed the highest activity, led to the isolation of three compounds: caffeoylcalleryanin (1), verbascoside (2) and 6-hydroxyluteolin-7-O-β-glucoside (3). Assessment of the ability of the isolated compounds to inhibit 15-LOX revealed that compounds 1, 2 and 3 exerted strong 15-LOX inhibitory activity; IC₅₀ values were 1.59, 1.76 and 2.35 μM respectively. The XTT assay showed that none of the isolated compounds seemed to be significantly toxic.     

Synthesis and nonlinear optical absorption properties of two new conjugated ferrocene-bridge-pyridinium compounds

Two electron donor-π-acceptor (D-π-A) chromospheres, with ferrocene as the electron donor and pyridinium as the electron acceptor, were synthesized. The nonlinear optical absorption (NOA) properties in the solution state were investigated by the Z-scan technique. Both compounds exhibited reverse saturable absorption (RSA) and optical limiting effect under nanosecond pulse irradiation.     

具有实验抗癌活性的二烃基锡衍生物的研究进展

自从Crown报道了一些二烃基锡衍生物具有抗癌活性以来, 这一领域的研究引起了人们极大的兴越。许多二烃基锡衍生物被制备得到, 并且测定了它们在离体及活性情况下的抗癌活性。本文综述了二烃基锡衍生物抗癌活性的研究进展,包括化合物的结构类型, 抗癌作用机制以及利用QSAR方法对有机锡化合物的抗癌活性进行计算预测等。     

Optical manipulation of charged microparticles in polar fluids

In this study, we report a systematic study of the response of a charged microparticle confined in an optical trap and driven by electric fields. The particle is embedded in a polar fluid, hence, the role of ions and counterions forming a double layer around the electrodes and the particle surface itself has been taken into account. We analyze two different cases: (i) electrodes energized by a step‐wise voltage (DC mode) and (ii) electrodes driven by a sinusoidal voltage (AC mode). The experimental outcomes are analyzed in terms of a model that combines the electric response of the electrolytic cell and the motion of the trapped particle. In particular, for the DC mode we analyze the transient particle motion and correlate it with the electric current flowing in the cell. For the AC mode, the stochastic and deterministic motion of the trapped particle is analyzed either in the frequency domain (power spectral density, PSD) or in the time domain (autocorrelation function). Moreover, we will show how these different approaches (DC and AC modes) allow us, assuming predictable the applied electric field (here generated by plane parallel electrodes), to provide accurate estimation (3%) of the net charge carried by the microparticle. Vice versa, we also demonstrate how, once predetermined the charge, the trapped particle acts as a sensitive probe to reveal locally electric fields generated by arbitrary electrode geometries (in this work, wire‐tip geometry).     

Vibrational studies on the selective solvation of Na+ and ClO3- ions in dimethylformamide-formamide mixture

Raman and infrared spectra of sodium chlorate in binary mixture of N,N-dimethylformamide (DMF) and formamide (FA) were obtained. The addition of FA to the NaClO3-DMF system allow us to observe a new band at 1709 cm-1. This has been possible since the large dissociation of Na+ and ClO3- ions produced by the addition of FA helps to observe the coordination effect of DMF on the Na+ ions, in full agreement with the Gutmann donor number of this later. Quantitative measurements performed in the CO stretching region in the binary mixture give a solvation number value for the sodium cation equal at 3 in full agreement with others authors. In the NH stretching region of FA, the arising of the 3580 cm-1 band is assigned to FA-ClO3- interactions via hydrogen bonding. In addition, our results show that the solvation number of the sodium cation remain constant in all concentration range studied. Such fact suggests that mixture of solvents with considerable differences in the donor-acceptor characters can be used to prepare electrolyte solutions where the ion pairs formation seems uncertain.     

含硫氰基邻甲酰氨基苯甲酰胺类化合物的合成与杀虫活性研究

本文合成了8个未见文献报道的类似于氯虫苯甲酰胺的化合物——含硫氰基邻甲酰氨基苯甲酰胺类化合物,并用核磁共振氢谱、碳谱以及高分辨质谱予以表征。并且对这8个化合物针对小菜蛾和斜纹夜蛾的毒力进行测试并与氯虫苯甲酰胺进行对比,发现这8个化合物均对小菜蛾和斜纹夜蛾都具有较好的杀灭活性,尽管其活性比氯虫苯甲酰胺稍弱,但也非常接近,可以作为候选农药进行进一步考察。     

樟脑基苯基硫脲类化合物的合成及生物活性研究

以D-(+)-樟脑为原料,经肟化、还原得到樟脑胺,再与取代苯基异硫氰酸酯反应,合成得到10个未见文献报道的樟脑基苯基硫脲化合物(5a~5j),其结构通过FT IR、1H NMR、13C NMR和ESI-MS表征确认。初步生物活性测试表明,目标化合物在浓度50mg/L下对5种供试植物病原菌显示不同程度的抑菌活性,其中化合物5f(R=m-OCH3)和5d(R=p-CH3)对苹果轮纹病菌(Physalospora piricola)和番茄早疫病菌(Cercospora arachidicola)的抑制率分别达83.9%和82.2%;在浓度100mg/L下,化合物5i(R=p-Br)对油菜(Brassica campestris)胚根生长的抑制率为60.2%。     

Synthesis of crosslinked resin based on methacrylamide, styrene and divinylbenzene obtained from polymerization in aqueous suspension

A series of porous copolymer beads based on methacrylamide (MA), styrene and divinylbenzene (DVB) was prepared by aqueous suspension polymerization in the presence of diluents to act as precipitants. As MA is totally soluble into aqueous phase, the use of two types of phase transfer agent was investigated, namely: TritonX-100^TM [polyoxyethylene-(10)-isooctylphenyl-ether] and tetrabutylammonium perchlorate. The effect of the diluents on the surface appearance and the porous structure of copolymer beads was studied. Suitable particle stabilisation was achieved by using a combination of two suspension agents, namely: gelatin and 2-hydroxy-ethyl-cellulose. The network resins were characterized by optical and scanning electron microscopy, IR spectroscopy, elemental analysis (CHN), apparent density, swelling in different solvents and specific area by BET method. It was observed that the MA incorporation was more effective when Triton^TM was employed as phase transfer agent.     

Antifungal,anti-inflamatory and neuritogenic activity of newly-isolated compounds from Disporopsis aspersa

Abstract

A new ester (1) and a terpenoid (2) were isolated from the dried whole plant of Disporopsis aspersa (H_UA) E_NGL. ex D_IELS for the first time and their structures were elucidated, as well as their biological activities are described. The two compounds all showed good antifungal activities, especially furanone (2) exhibited better antifungal activity against Pseudoperonospora cubensis and Phytophthora infestans with EC₅₀ value of 22.82, 18.90?μg/mL, respectively. Compound 1 exhibited a significant promotion on the neurite outgrowth in NGF-induced PC-12 cells, and moderate inhibition on the NO production induced by lipopolysaccharide (LPS) in BV-2 microglial cells.     

Construction of optical active metallo-supramolecular polymers from enantiopure bis-pybox ligands

Two types of optical active metallo-supramolecular polymers were successfully constructed from the complexation of two enantiopure bis-pyridine-dioxazole (bis-pybox) ligands and 3d transition metal ions such as Zn²⁺ and Fe²⁺ in organic solution. The self-assembly process was investigated via UV–vis and fluorescent titration. The chiral characteristic of polymers was detected by circular dichroism. It was revealed that the phenyl-substituted polymers showed higher stability than the benzyl-substituted ones. Temperature-dependent circular dichroism spectra demonstrated the dynamic structure of this type polymer under the variation of temperature. This work highlights the opportunity in designing and constructing of the optical active metallo-supramolecular polymers from the organic privilege ligands in the field of asymmetric catalysis.     

Breath analysis by optical fiber sensor for the determination of exhaled organic compounds with a view to diagnostics

Breath analysis constitutes a promising tool in clinical and analytical fields due to its high potential for non-invasive diagnostics of metabolic disorders and monitoring of disease status. An optical fiber (OF) sensor has been developed for determination of volatile organic compounds (ethane, pentane, heptane, octane, decane, benzene, toluene and styrene) in human breath for clinical diagnosis.The analytical system developed showed a high performance for breath analysis, inferred for the analytical signal intensity and stability, linear range, and detection limits ranging from 0.8 pmol L⁻¹, for heptane, and to 9.5 pmol L⁻¹, for decane. The OF sensor also showed advantageous features of near real-time response and low instrumentation costs, besides showing an analytical performance equivalent to the breath analysis by gas chromatography-mass spectrometry (GC-MS), used as the reference method.     

Measurement uncertainty in testing for antimicrobial activity on textile materials

Measurement uncertainty is widely recognized among physicists and chemists, but is a relatively new concept to many microbiologists. Generally, available documents about measurement uncertainty in microbiological testing are applicable to food and water microbiology. Two quantitative methods for evaluation of antimicrobial activity of textile materials are used commonly in textile laboratories. Methodology and expression of results for the two methods are similar; thus, calculation and expression of measurement uncertainty for results obtained by these test methods are also similar. This contribution describes the way in which measurement uncetainty for these methods can be evaluated and reported.