Showing papers on "Chemical binding published in 2009"

Rhodamine spiroamides for multicolor single-molecule switching fluorescent nanoscopy

Abstract: The design, synthesis, and evaluation of new rhodamine spiro- A are described. These molecules have applications in optical nanoscopy based on random switching of the fluo- rescent single molecules. The new markers may be used in (co)localiza- tion studies of various objects and their (mutual) positions and shape can be determined with a precision of a few tens of nanometers. Multicolor stain- ing, good photoactivation, a large number of emitted photons, and selec- tive chemical binding with amino or thiol groups were achieved due to the presence of various functional groups on the rhodamine spiroamides. Rigi- dized sulfonated xanthene fragment fused with six-membered rings, N,N'- bis(2,2,2-trifluoroethyl) groups, and a combination of additional double bonds and sulfonic acid groups with simple aliphatic spiroamide residue provide multicolor properties and im- prove performance of the rhodamine spiroamides in photoactivation and bioconjugation reactions. Having both essential parts of the photoswitchable assembly—the switching and the fluo- rescent (reporter) groups—combined in one chemical entity make this ap- proach attractive for further develop- ment. A series of rhodamine spiro- A is presented along with charac- terizations of their most relevant prop- erties for application as fluorescent probes in single-molecule switching and localization microscopy. Optical images with resolutions on the nano- meter scale illustrate the potential of the labels in the colocalization of bio- logical objects and the two-photon acti- vation technique with optical sectioning.

Polymer-Functionalized Single-Walled Carbon Nanotubes as a Novel Sol−Gel Solid-Phase Micro-extraction Coated Fiber for Determination of Poly-brominated Diphenyl Ethers in Water Samples with Gas Chromatography−Electron Capture Detection

Abstract: Single-walled carbon nanotubes (SWNTs) were functionalized with a hydroxyl-terminated silicone oil (TSO-OH). It is synthesized by the reactions of carbonyl chloride groups on the surface of SWNTs and hydroxyl groups of silicone oil (TSO-OH). The functionalized product SWNTs-TSO-OH was first used as precursor and selective stationary phase to prepare the sol-gel derived poly(SWNTs-TSO-OH) solid-phase microextraction (SPME) fiber for determination of polybrominated diphenyl ethers (PBDEs) in water samples. The possible major reaction of the sol-gel coating process was discussed and confirmed by IR spectra, Raman spectroscopy, and scanning electron microscopy. Some parameters of SPME fiber for the determination of PBDEs were investigated by headspace SPME/gas chromatography with electron-capture detection (HS-SPME/GC-ECD). Compared with the commercial SPME fiber, the new coated fiber showed higher extraction efficiency to PBDEs, better thermal stability (over 340 degrees C), and longer life span (over 200 times). All of these advantages are mainly due to the incorporation of SWNTs, which enhanced the pi-pi interaction with PBDEs and increased the surface area of extraction in contact with the sample. Moreover, the sol-gel coating technology additionally provided the porous structure of the 3-D silica network and the strong chemical binding provided which also will improve the extraction efficiency. Under optimized conditions, the method detection limits for seven PBDEs were 0.08-0.8 ng/L (S/N = 3) and the precision (RSD, n = 5) was 2.2-7.5% at the 50 ng/L level. The linearity of the developed method is in the range of 5-500 ng/L with coefficients of correlation greater than 0.995. The developed method was successfully applied for the analysis of trace PBDEs in reservoir water and wastewater samples. The recoveries obtained at spiking 50 ng/L were between 74% and 109% (n = 5) for PBDEs in water samples.

Characterization of Granulations of Calcium and Apatite in Serum as Pleomorphic Mineralo-Protein Complexes and as Precursors of Putative Nanobacteria

Abstract: Calcium and apatite granulations are demonstrated here to form in both human and fetal bovine serum in response to the simple addition of either calcium or phosphate, or a combination of both. These granulations are shown to represent precipitating complexes of protein and hydroxyapatite (HAP) that display marked pleomorphism, appearing as round, laminated particles, spindles, and films. These same complexes can be found in normal untreated serum, albeit at much lower amounts, and appear to result from the progressive binding of serum proteins with apatite until reaching saturation, upon which the mineralo-protein complexes precipitate. Chemically and morphologically, these complexes are virtually identical to the so-called nanobacteria (NB) implicated in numerous diseases and considered unusual for their small size, pleomorphism, and the presence of HAP. Like NB, serum granulations can seed particles upon transfer to serum-free medium, and their main protein constituents include albumin, complement components 3 and 4A, fetuin-A, and apolipoproteins A1 and B100, as well as other calcium and apatite binding proteins found in the serum. However, these serum mineralo-protein complexes are formed from the direct chemical binding of inorganic and organic phases, bypassing the need for any biological processes, including the long cultivation in cell culture conditions deemed necessary for the demonstration of NB. Thus, these serum granulations may result from physiologically inherent processes that become amplified with calcium phosphate loading or when subjected to culturing in medium. They may be viewed as simple mineralo-protein complexes formed from the deployment of calcification-inhibitory pathways used by the body to cope with excess calcium phosphate so as to prevent unwarranted calcification. Rather than representing novel pathophysiological mechanisms or exotic lifeforms, these results indicate that the entities described earlier as NB most likely originate from calcium and apatite binding factors in the serum, presumably calcification inhibitors, that upon saturation, form seeds for HAP deposition and growth. These calcium granulations are similar to those found in organisms throughout nature and may represent the products of more general calcium regulation pathways involved in the control of calcium storage, retrieval, tissue deposition, and disposal.

Effect of silver doping on optical property of diamond like carbon films

Abstract: Optical properties of silver doped diamond like carbon films (Ag:DLC) deposited by the RF reactive sputtering technique were studied in detail. The chemical binding energy and the composition of the films were investigated by using an X-ray photoelectron spectroscopy. Optical transparency and optical band gap decreased with the silver incorporation to the DLC film. Optical band gap calculated from transmittance spectra decreased from 2.55 to 1.95 eV with a variation of Ag concentration from 0 to 12.5 at.%. Urbach parameter determined from the band tail of the transmittance spectra showed to increase with the doping concentration.

Liquid expanded monolayers of lipids as model systems to understand the anionic hofmeister series: 1. A tale of models.

Abstract: In this work, we use Langmuir monolayers of dipalmitoyl phosphatidylcholine (DPPC) as model systems to enhance the understanding of specific anion effects in physicochemical and biological systems. The 298 K isotherms (equation of state, EOS) of DPPC over solutions of a range of sodium salts depend strongly on the type and concentration of the salt in the subphase. We focus in particular on the liquid expanded phase region of the DPPC EOS and assume that the deviation of the isotherms over electrolyte solutions from that over pure water is due entirely to the charging of the lipid monolayer by the ions. We then examine the ability of a range of phenomenological continuum models to explain the pressure increase in the presence of electrolytes. The important finding is that insoluble lipid monolayers allow the discrimination between possible modes of ion−lipid interaction. Chemical binding models, simple or modified, cannot fit the range of data presented in this work. Both dispersion interaction and partit...

Sensory irritation and pulmonary irritation by airborne allyl acetate, allyl alcohol, and allyl ether compared to acrolein

Abstract: The propene derivatives, allyl acetate, allyl alcohol, allyl ether, and acrolein were investigated for their property as sensory irritant in Ssc:CF-1 mice. The concentration of the chemicals necessary to depress the respiratory rate by 50% ( RD50 ) due to sensory irritation of the upper respiratory tract were 2.9, 3.9, 5.0 and 2.9 p.p.m., respectively. The potency of these propene derivatives varied very little for their concentration in air, in p.p.m., to depress the respiratory rate by 50%. However, when the potency is expressed in terms of thermodynamic activity acrolein was found to be 10 times more potent than the other propene derivates. This may be explained either by a higher reactivity of the carbon-carbon double bond or the involvement of the aldehyde group in a secondary chemical binding. No secondary chemical binding can be invoked for allyl acetate, allyl alcohol or allyl ether. In general, the chemical structure CH2 = CH-CH-O may be suspected to allow a molecule to act as a strong sensory irritant. The TLV's were predicted from the relation: TLV approximately equal to 0.03 X RD50 and were found to be 0.1, 0.1, 0.15, and 0.1 for allyl acetate, allyl alcohol, allyl ether, and acrolein, respectively. No pulmonary irritation was found at the concentration causing a 50% decrease in respiratory rate.

Sorption of Pb(II) on Mg‐Fe Layered Double Hydroxide

Abstract: Mg-Fe layered double hydroxide (LDH) with a Mg/Fe molar ratio of 3:1 was synthesized by using a coprecipitation method and the sorption removal of Pb(II) by the LDH sample from Pb(NO3)2 solution was investigated. It was found that Mg-Fe LDH showed a good sorption ability for Pb(II) from Pb(NO3)2 solution, indicating that the use of LDH as a promising inorganic sorbent for the removal of heavy metal ions is possible. The sorption kinetics and the sorption isotherm of Pb(II) on the LDH sample obeyed the pseudo-second order kinetic model and Aranovich-Donohue equation, respectively. The sorption mechanism of Pb(II) on the LDH may be attributed to the surface-induced precipitation and the chemical binding adsorption, and the removal ability arising from the surface-induced precipitation is much higher than that from the chemical binding adsorption.

Electrostatic correlations at the Stern layer: physics or chemistry?

Abstract: We introduce a minimal free energy describing the interaction of charged groups and counterions including both classical electrostatic and specific interactions. The predictions of the model are compared against the standard model for describing ions next to charged interfaces, consisting of Poisson–Boltzmann theory with additional constants describing ion binding, which are specific to the counterion and the interfacial charge (“chemical binding”). It is shown that the “chemical” model can be appropriately described by an underlying “physical” model over several decades in concentration, but the extracted binding constants are not uniquely defined, as they differ depending on the particular observable quantity being studied. It is also shown that electrostatic correlations for divalent (or higher valence) ions enhance the surface charge by increasing deprotonation, an effect not properly accounted within chemical models. The charged phospholipid phosphatidylserine is analyzed as a concrete example with good agreement with experimental results. We conclude with a detailed discussion on the limitations of chemical or physical models for describing the rich phenomenology of charged interfaces in aqueous media and its relevance to different systems with a particular emphasis on phospholipids.

Atomic layer deposition of hafnium silicate film for high mobility pentacene thin film transistor applications

Abstract: The performance of pentacene thin film transistors (TFTs) was improved using a hafnium silicate (HfxSi1−xO2) thin film as a high-k dielectric layer. For growth of the HfxSi1−xO2 thin films, an atomic layer chemical vapor deposition (ALCVD) process was optimized using silicon alkoxide and hafnium amido as precursors. The self-limiting surface reactions of each precursor were observed, indicating the ALCVD growth characteristics. The film thickness linearly increased depending on the number of process cycles, with a remarkably high growth rate of 2.3 A per cycle. The chemical binding states, thermal stability and electrical characteristics of the films grown were investigated using XPS, XRD and capacitance–voltage and leakage current–voltage analysis. The pentacene TFTs fabricated with the ALCVD-grown Hf0.67Si0.33O2 dielectric layer were characterized and the results were compared to the pentacene TFTs using Al2O3 and SiO2 film as dielectric layers. The pentacene/Hf0.67Si0.33O2 TFT showed a three-fold and five-fold higher mobility than a pentacene/Al2O3 TFT and a pentacene/SiO2 TFT, respectively. With additional treatments to enhance the characteristics of the OTFT, pentacene/HfxSi1−xO2 TFTs have great potential as high mobility devices with low operational voltage.

Comparison of chemical binding to recombinant fathead minnow and human estrogen receptors alpha in whole cell and cell‐free binding assays

Abstract: Mammalian receptors and assay systems are generally used for in vitro screening of endocrine-disrupting chemicals with the assumption that minor differences in amino acid sequences among species do not translate into significant differences in receptor function. Objectives of the present study were to evaluate the performance of two different in vitro assay systems (a whole cell and a cell-free competitive binding assay) in assessing whether binding of chemicals differs significantly between full-length recombinant estrogen receptors from fathead minnows (fhERalpha) and those from humans (hERalpha). It was confirmed that 17beta-estradiol displays a reduction in binding to fhERalpha at an elevated temperature (37 degrees C), as has been reported with other piscine estrogen receptors. Several of the chemicals (17beta-estradiol, ethinylestradiol, alpha-zearalanol, fulvestrant, dibutyl phthalate, benzyl butyl phthalate, and cadmium chloride) displayed higher affinity for fhERalpha than for hERalpha in the whole cell assay, while only dibutyl phthalate had a higher affinity for fhERalpha than for hERalpha in the cell-free assay. Both assays were effective in identifying strong binders, weak binders, and nonbinders to the two receptors. However, the cell-free assay provided a less complicated and more efficient binding platform and is, therefore, recommended over the whole cell binding assay. In conclusion, no strong evidence showed species-specific binding among the chemicals tested.

Contrasting influence of NADPH and a NADPH-regenerating system on the metabolism of carbonyl-containing compounds in hepatic microsomes.

Abstract: Carbonyl containing xenobiotics may be susceptible to NADPH-dependent cytochrome P450 (P450) and carbonyl-reduction reactions. In vitro hepatic microsome assays are routinely supplied NADPH either by direct addition of NADPH or via an NADPH-regenerating system (NRS). In contrast to oxidative P450 transformations, which occur on the periphery of a microsome vesicle, intraluminal carbonyl reduction depends on transport of cofactors across the endoplasmic reticulum (ER) membrane into the lumen. Glucose 6-phosphate, a natural cofactor and component of the NRS matrix, is readily transported across the ER membrane and facilitates intraluminal NADPH production, whereas direct addition of NADPH has limited access to the lumen. In this study, we compared the effects of direct addition of NADPH and use of an NRS on the P450-mediated transformation of propiconazole and 11β-hydroxysteroid dehydrogenase type 1 (HSD1) carbonyl reduction of cortisone and the xenobiotic triadimefon in hepatic microsomes. Our results demonstrate that the use of NADPH rather than NRS can underestimate the kinetic rates of intraluminal carbonyl reduction, whereas P450-mediated transformations were unaffected. Therefore, in vitro depletion rates measured for a carbonyl-containing xenobiotic susceptible to both intraluminal carbonyl reduction and P450 processes may not be properly assessed with direct addition of NADPH. In addition, we used in silico predictions as follows: 1) to show that 11β-HSD1 carbonyl reduction was energetically more favorable than oxidative P450 transformation; and 2) to calculate chemical binding score and the distance between the carbonyl group and the hydride to be transferred by NADPH to identify other 11β-HSD1 substrates for which reaction kinetics may be underestimated by direct addition of NADPH.

The study on the effect of erbium on diamond-like carbon deposited by pulsed laser deposition technique

Abstract: Diamond-like carbon (DLC) films doped with a small fraction of erbium (0.5–2.0 at. %, at 0.5 at. % interval) were prepared by using a 248 nm KrF pulsed laser deposition technique. The effects of erbium on the surface morphology, microstructure, chemical binding states, tribological property, and the adhesion strength of DLC films were investigated. Atomic force microscopy showed that the surface roughness of the films increased with the increasing of erbium fraction, but generally the nanocomposite films were smooth with rms below 1 nm. Raman analysis showed broad peaks centered at 1550 cm−1 on all the samples. The deconvoluted Raman spectra on DLC doped with different fractions of erbium showed that the ID/IG ratio increased with increasing erbium content, and the comparative percent of sp3 is between 50% and 58% for erbium fraction between 0.5 and 2.0 at. %. High resolution x-ray photoelectron spectroscopy confirmed that the C 1s peaks had slightly shifted away from 285.2 (diamond) to 284.5 eV (graphite...

Superhydrophobic treatment for textiles via engineering nanotextured silica/polysiloxane hybrid material onto fibres

Abstract: A rapid, cost effective and easy to implement method for treating wool and wool blend textiles to superhydrophobic with controllable interference on other properties such as handle is demonstrated. The process is based on in situ chemical binding of inexpensive silica and polysiloxane hybrid material onto fibres. Superhydrophobicity is achieved upon architecting nanoroughness on textile surfaces using silica nanoparticles. Modified textiles exhibit extremely high water repellency with contact angle reaching 166° and sliding angle ≤6°. Superhydrophobicity was maintained after three times of accelerated washing (equally 15 times of standard laundry wash). Topographical studies using AFM indicate that nanoscale roughness has been engineered on fibres with original size ~22 μm. The rough structure at two length scales plays a key role in enhancing surface hydrophobicity. Simplicity of processing such coatings onto textiles makes it possible for potentially large scale production.

Photoemission spectroscopy and atomic force microscopy investigation of vapor-phase codeposited silver/poly(3-hexylthiophene) composites.

Abstract: Nanocomposite matrices of silver/poly(3-hexylthiophene) (P3HT) were prepared in ultrahigh vacuum through vapor-phase codeposition. Change in microstructure, chemical nature, and electronic properties with increasing filler (Ag) content were investigated using in situ XPS and UPS, and ambient AFM. At least two chemical binding states occur between Ag nanoparticles and sulfur in P3HT at the immediate contact layer, but no evidence of interaction between Ag and carbon (in P3HT) was found. AFM images reveal a change in Ag nanoparticles size with concentration which modifies the microstructure and the average roughness of the surface. Under codeposition, P3HT largely retains its conjugated structures, which is evidenced by the similar XPS and UPS spectra to those of P3HT films deposited on other substrates. We demonstrate here that the magnitude of the barrier height for hole injection (evF) and the position of the highest occupied band edge (HOB) with respect to the Fermi level of Ag may be controlled and cha...

Substrate bias voltage influenced structural, electrical and optical properties of dc magnetron sputtered Ta2O5 films

Abstract: Tantalum oxide (Ta2O5) films were formed on silicon (111) and quartz substrates by dc reactive magnetron sputtering of tantalum target in the presence of oxygen and argon gases mixture. The influence of substrate bias voltage on the chemical binding configuration, structural, electrical and optical properties was investigated. The unbiased films were amorphous in nature. As the substrate bias voltage increased to -50 V the films were transformed into polycrystalline. Further increase of substrate bias voltage to -200 V the crystallinity of the films increased. Electrical characteristics of Al/Ta2O5/Si structured films deposited at different substrate bias voltages in the range from 0 to -200 V were studied. The substrate bias voltage reduced the leakage current density and increased the dielectric constant. The optical transmittance of the films increased with the increase of substrate bias voltage. The unbiased films showed an optical band gap of 4.44 eV and the refractive index of 1.89. When the substrate bias voltage increased to -200 V the optical band gap and refractive index increased to 4.50 eV and 2.14, respectively due to the improvement in the crystallinity and packing density of the films. The crystallization due to the applied voltage was attributed to the interaction of the positive ions in plasma with the growing film.

Chemical Binding of Unsaturated Fluorenes to Poly(2-chloroxylylene) Thin Films

Abstract: A series of substituted fluorenes with vinyl groups as reactive sites were synthesized and characterized. Fluorene-based polymers with vinyl groups as end chains and side chains functionalities were also prepared. In both cases, successful preparation of functionalized Parylene C films (modylayers) was achieved. The set of spectral methods used has allowed us to conclude that such functionalization is based on the chemical reaction of double bonds with xylylene radicals during deposition process. Parylene C films chemically modified with specially synthesized polyfluorenes showed PL quantum efficiency comparable with neat polyfluorenes.

Binding entropy and its application to solids.

Abstract: The concept of binding entropy is introduced and information theoretical approach is combined with orbitalfree density functional theory. It is shown that binding entropy expresses the deviation of the molecular electron density from the promolecular density and the deviation of the molecular kinetic energy density from the promolecular kinetic energy density. The change of the kinetic energy density during the chemical bond formation explicitly appears in the binding entropy expression. The binding entropy and binding entropy density are analyzed using experimental electron density for solid germanium, gallium arsenide and dinitrogen tetroxide. It is demonstrated that the binding entropy joined with deformation electron density and “deformation” kinetic energy density, carries information about both the bonding and binding details and provides a deeper insight into the nature of chemical bond. Atomic and global binding entropies also appeared to be useful descriptors giving a compact description of chemical binding.

Multilayered printed circuit board

Abstract: PROBLEM TO BE SOLVED: To a multilayered printed circuit board with magnetic material and mounting form most effective for reducing a radiation noise caused by operating a circuit. SOLUTION: In a multilayered printed circuit board having a ground layer 321 and a power supply layer 322 as internal conductive layers, on surfaces of the ground layer 321 and the power supply layer 322 opposite signal layers 351, 352, magnetic substance layers 331, 332 that do not contain a non-magnetic component such as a binder, namely, the magnetic substance layers 331, 332 constituted of only a magnetic component, are tightly formed without gap by chemical binding or Van der Vaals forces operating thereon. COPYRIGHT: (C)2009,JPO&INPIT

Chemical binding in small molecules by the spin‐density‐functional formalism

Abstract: A brief review is given of some results within the spin-density- functional (SDF) formalism. The local-spin-density (LSD) approximation, that is, the approximation which is formally exact in the limit of slow and weak spatial variations, gives results of a useful accuracy for valence electrons in atoms and solids, and the accuracy for molecules may be illustrated by the hydrogen- molecule energy curves in the lowest $sup 1$$Sigma$$sup +$ sub g/ and $sup 3$$Sigma$$sup +$ /sub u/ states being about 0.3 eV from the exact result. Good results are obtained for H$sub 3$$sup +$, H$sub 3$, and H$sub 3$$sup -$, too. Applications to He$sub 2$$sup +$ and He$sub 2$$sup 2+$ inform about the range of applicability of the approximation. Further, the new numerical method developed for these molecular applications allows an evaluation of the multiple-scattering X$alpha$ method, showing shortcomings of both the potential and the multiple- scattering approach used in this method. It is argued that the SDF formalism within the LSD approximation is physically superior to the X$alpha$ method and provides a simple and useful method for applications within a broad range, such as calculations on molecules and chemisorption systems. (auth)