Synthesis and spectroscopic studies of CoII, NiII, FeIII and ThIV complexes derived from 2,2'-dihydroxy-3,3'-di(carboxymethyl)-1,1'-binaphthyl

The synthesis of 2,2'-dihydroxy-3,3'-di(carboxymethyl)-1,1'-binaphthyl (H2L) and its novel metal complexes with Co(II), Ni(II), Fe(III) and Th(IV) salts are reported. The ligand and its metal complexes have been characterized on the basis of analytical, conductance, spectral (IR, UV-vis, 1H NMR, mass) and magnetic susceptibility measurements. The M?ssbauer spectrum of the Fe(III) complex indicates a low-spin octahedral geometry around the Fe(III) ion. The IR and 1H NMR spectral data show that the ligand behaves in a dibasic bidentate fashion coordinating to two metal atoms through the two deprotonated naphthyl OH groups and acts in a dibasic tetradentate manner using both carbonyl oxygen's and the deprotonated naphthyl OH groups coordinating to two metal ions. Thermal studies (TGA, DTA) confirm the presence of solvents either inside or outside the coordination sphere and support the mechanism of the decomposition process. The value of [alpha]D20 for the ligand has been determined in DMSO.     

Surface structure and interface dynamics of alkanethiol self-assembled monolayers on Au(111)

Scanning tunneling microscopy (STM) and high-resolution electron energy loss spectroscopy (HREELS) were used to examine the structural transitions and interface dynamics of octanethiol (OT) self-assembled monolayers (SAMs) caused by long-term storage or annealing at an elevated temperature. We found that the structural transitions of OT SAMs from the c(4 x 2) superlattice to the (6 x square root 3) superlattice resulting from long-term storage were caused by both the dynamic movement of the adsorbed sulfur atoms on several adsorption sites of the Au(111) surface and the change of molecular orientation in the ordered layer. Moreover, it was found that the chemical structure of the sulfur headgroups does not change from monomer to dimer by the temporal change of SAMs at room temperature. Contrary to the results of the long-term-stored SAMs, it was found that the annealing process did not modify either the interfacial or chemical structures of the sulfur headgroups or the two-dimensional c(4 x 2) domain structure. Our results will be very useful for a better understanding of the interface dynamics and stability of sulfur atoms in alkanethiol SAMs on Au(111) surfaces.     

Chemoselective transfer hydrodechlorination of aryl chlorides catalyzed by Cp*Rh complexes

An effective Cp*Rh catalyzed transfer hydrodechlorination of aryl chlorides was achieved with high tolerance towards a variety of functional groups using 2-butanol as a hydrogen source.     

Rigid-rod polymers with polysiloxane side chains. I. Synthesis and characterization of rigid-rod polyimides with polysiloxane side chains and their compatibility with linear polysiloxanes

Rigid-rod aromatic polyimdies having polydimethylsiloxane side chains were prepared for the purpose of dispersing rigid-rod molecules in silicone matrices for molecular reinforcement. The polyimides were obtained by imidizing the polyamide-acids bearing the side chains either thermally or chemically, which were synthesized by reacting 4,4′-diaminobiphenyl-terminated polysiloxane macromonomers with pyromellitic dianhydride in THF. The polyamide-acid films obtained by removing the solvent were soluble in THF, but the polyimides were insoluble in any common solvent. The polyimides showed no melting transition below 350°C on DSC analysis, at which temperature the side chain started decomposing. Although all the polyimides were anisotropic as observed by a polarizing microscope, x-ray diffraction analysis suggested the presence of only limited chain organization. Blends with linear polydimethylsiloxanes were prepared by casting the THF solution containing the polyamide-acid and the polydimethylsiloxane, followed by solvent evaporation and thermal imidization. With relatively longer side chains, the polyimides were proved to be compatibilized with polydimethylsiloxanes. © 1994 John Wiley & Sons, Inc.     

Using multidimensional projection techniques for reaching a high distinguishing ability in biosensing

Recent advances in the control of molecular engineering architectures have allowed unprecedented ability of molecular recognition in biosensing, with a promising impact for clinical diagnosis and environment control. The availability of large amounts of data from electrical, optical, or electrochemical measurements requires, however, sophisticated data treatment in order to optimize sensing performance. In this study, we show how an information visualization system based on projections, referred to as Projection Explorer (PEx), can be used to achieve high performance for biosensors made with nanostructured films containing immobilized antigens. As a proof of concept, various visualizations were obtained with impedance spectroscopy data from an array of sensors whose electrical response could be specific toward a given antibody (analyte) owing to molecular recognition processes. In addition to discussing the distinct methods for projection and normalization of the data, we demonstrate that an excellent distinction can be made between real samples tested positive for Chagas disease and Leishmaniasis, which could not be achieved with conventional statistical methods. Such high performance probably arose from the possibility of treating the data in the whole frequency range. Through a systematic analysis, it was inferred that Sammon's mapping with standardization to normalize the data gives the best results, where distinction could be made of blood serum samples containing 10(-7) mg/mL of the antibody. The method inherent in PEx and the procedures for analyzing the impedance data are entirely generic and can be extended to optimize any type of sensor or biosensor.     

Information visualization techniques for sensing and biosensing

The development of new methods and concepts to visualize massive amounts of data holds the promise to revolutionize the way scientific results are analyzed, especially when tasks such as classification and clustering are involved, as in the case of sensing and biosensing. In this paper we employ a suite of software tools, referred to as PEx-Sensors, through which projection techniques are used to analyze electrical impedance spectroscopy data in electronic tongues and related sensors. The possibility of treating high dimension datasets with PEx-Sensors is advantageous because the whole impedance vs. frequency curves obtained with various sensing units and for a variety of samples can be analyzed at once. It will be shown that non-linear projection techniques such as Sammon's Mapping or IDMAP provide higher distinction ability than linear methods for sensor arrays containing units capable of molecular recognition, apparently because these techniques are able to capture the cooperative response owing to specific interactions between the sensing unit material and the analyte. In addition to allowing for a higher sensitivity and selectivity, the use of PEx-Sensors permits the identification of the major contributors for the distinguishing ability of sensing units and of the optimized frequency range. The latter will be illustrated with sensing units made with layer-by-layer (LbL) films to detect phytic acid, whose capacitance data were visualized with Parallel Coordinates. Significantly, the implementation of PEx-Sensors was conceived so as to handle any type of sensor based on any type of principle of detection, representing therefore a generic platform for treating large amounts of data for sensors and biosensors.     

Rapid determination of fumagillin residues in honey by liquid chromatography-tandem mass spectrometry using the QuEChERS method

A new, rapid, and efficient method for determining the fumagillin residues in honey was developed. The samples extracted were analyzed using LC/MS/MS. Chromatographic separation of fumagillin was performed in gradient mode on a C8 column (100 x 2.0 mm, 5 microm) at 40 degrees C. The mobile phase consisted of a mixture of 2 mM ammonium formate-0.01% formic acid solution and methanol; the flow rate was set to 0.2 mL/min. Under these conditions, it was possible to measure fumagillin and its isomers as a single peak. The sample preparation procedure used is based on the QuEChERS (quick, easy, cheap, effective, rugged, and safe) method, which is fast (approximately 30 min) and uses less organic solvent. The fumagillin was extracted with acetonitrile containing 0.1% formic acid, then purified using a solid-phase extraction method with an Oasis mixed-mode weak anion-exchange cartridge. The overall recovery of fumagillin ranged from 88.1 to 99.4%; the intra- and interassay CVs were <4.5% and <4.9%, respectively. The LOQ was 0.1 microg/kg. LC/MS/MS coupled with the QuEChERS method showed strong potential as a method for determining fumagillin residues in honey.     

Preparation and characterization of poly(l-phenylalanine) chiral stationary phases with varying peptide length

Three new chiral stationary phases with different lengths of l-phenylalanine peptide were prepared by solid-phase synthesis with tert-butoxycarbonyl (Boc)-l-phenylalanine on silica. The effect of phenylalanine peptide length on enantioselectivity was studied. The best separation of R/S-warfarin was achieved by the chiral stationary phase with intermediate peptide length. These stationary phases were found to exist mainly in alpha-helical conformation by using FT-IR spectra. The end-capping reagents for the N-terminus of the peptide were also evaluated.     

Rational development of caged-biotin protein-labeling agents and some applications in live cells

Biotin-(strept)avidin complex is widely used in biotechnology because of its extremely high binding constant, but there is no report describing spatiotemporally controlled formation of the complex in live cells. Here, based on X-ray crystal structure analysis and calorimetric data, we designed and synthesized photoreleasable biotins, which show greatly reduced affinity for (strept)avidin, but recover native affinity after UV irradiation. For application at the cell surface, we introduced an amine-reactive moiety into these "caged" biotin molecules. Specific fluorescence imaging of live cells that had been labeled with these agents and then UV-irradiated, was accomplished by addition of streptavidin conjugated with a fluorophore. We also demonstrated the applicability of these compounds for UV-irradiated-cell-specific drug delivery by using caged-biotin-labeled cells, a prodrug, and streptavidin conjugated with a prodrug-activating enzyme.     

Novel synthesis of zerumbone-pendant derivatives and their biological activity

Zerumbone 1, having powerful latent reactivity and containing two conjugated double bonds and a double conjugated carbonyl group is the major component of the essential oil of wild ginger, Zingiber zerumbet Smith. The conjugation system plays an important role in the expression of biological activity. N-Bromosuccinimide (NBS) reaction of 1 gave high reactive intermediate 2 with an exo-methylene group, which was obtained from 1 quantitatively. Treatment of 2 with nucleophiles gave various zerumbone-pendant derivatives, including C–H, C–O, C–N, and C–C bond formation, maintaining the conjugation system through S_N2′-type reaction. Almost all zerumbone-pendant derivatives showed a good value of IC₅₀ against the suppressive effect of NO generation. Among them, amine derivative 5, binding with 2 mol of zerumbone, showed the strongest activity (IC₅₀: 0.24 μM).