Chemical Modifications on Polystyrene Latex: Preparation and Characterization for Use in Immunological Applications

Polystyrene latex microspheres are efficient supports for immunological reactions. In the presence of suitable functional groups these microspheres may react by covalent binding with antigens or antibodies and have been extensively used in immunoassay technique. By using the emulsion polymerization and diazotization methods, a kind of functionalized latex was prepared. The preparation of this latex consisted of six syntheses of polystyrene followed by nitration, amination and diazotization. A narrow distribution of particle size was obtained in all the cases. The synthesis that presented 98% of monomer conversion and the largest particle size diameter 0.2 ± 0.05 μm was chosen for the subsequent chemical treatments. The chemical characterizations of every step were performed by Fourier transform infrared and Raman spectroscopies. The particle size was determined by a submicrometer particle analyzer and scanning electron microscopy. The polydiazostyrene latex obtained was sensitized using bovine serum albumin (BSA) and when it was submitted to agglutination assay in the presence of a rabbit serum containing specific antibodies to BSA demonstrated efficient results. © 1997 John Wiley & Sons, Ltd.     

Ultrathin Covalently Bound Organic Layers on Mica: Formation of Atomically Flat Biofunctionalizable Surfaces

Mica is the substrate of choice for microscopic visualization of a wide variety of intricate nanostructures. Unfortunately, the lack of a facile strategy for its modification has prevented the on‐mica assembly of nanostructures. Herein, we disclose a convenient catechol‐based linker that enables various surface‐bound metal‐free click reactions, and an easy modification of mica with DNA nanostructures and a horseradish peroxidase mimicking hemin/G‐quadruplex DNAzyme.     

Preparation of Polystyrene Beads with Dendritically Embedded TADDOL and Use in Enantioselective Lewis Acid Catalysis

A full account is given of the preparation and use of TADDOLates, which are dendritically incorporated in polystyrene beads (Scheme 1). A series of styryl‐substituted TADDOLs with flexible, rigid, or dendritically branching spacers between the TADDOL core and the styryl groups (2–16 in number) has been prepared ( 5 – 7, 20, 21, 26 in Schemes 2–4 and Fig. 1–3). These were used as cross‐linkers in styrene‐suspension polymerization, leading to beads of ca. 400‐μm diameter (Schemes 5 and 6, b). These, in turn, were loaded with titanate and used for the Lewis acid catalyzed addition of Et₂Zn to PhCHO as a test reaction (Scheme 6). A comparison of the enantioselectivities and degrees of conversion (both up to 99%), obtained under standard conditions, shows that these polymer‐incorporated Ti‐TADDOLates are highly efficient catalysts for this process (Table 1). In view of the effort necessary to prepare the novel, immobilized catalysts, emphasis was laid upon their multiple use. The performance over 20 cycles of the test reaction was best with the polymer obtained from the TADDOL bearing four first‐generation Fréchet branches with eight peripheral styryl groups ( 6 , p‐ 6 , p‐ 6 ⋅Ti(OⁱPr)₂): the enantioselectivity (Fig. 4), the rate of reaction (Fig. 5), and the swelling factor (Fig. 6) were essentially unchanged after numerous operations carried out with the corresponding beads of 400‐μm diameter and a degree of loading of 0.1 mmol TADDOLate/g polymer, with or without stirring (Fig. 7). The rate with the dendritically polymer‐embedded Ti‐TADDOLate (p‐ 6 ⋅Ti(OⁱPr)₂) was greater than that measured with the corresponding monomer, i.e., 6 ⋅Ti(OⁱPr)₂ (Fig. 8). Possible interpretations of this phenomenon are proposed. A polymer‐bound TADDOL, generated on a solid support (by Grignard addition to an immobilized tartrate ester ketal) did not perform well (Scheme 4 and Table 2). Also, when we prepared polystyrene beads by copolymerization of styrene, a zero‐, first‐, or second‐generation dendritic cross‐linker, and a mono‐styryl‐substituted TADDOL derivative, the performance in the test reaction did not rival that of the dendritically incorporated Ti‐TADDOLate ((p‐ 6 ⋅Ti(OⁱPr)₂) (Scheme 7 and Fig. 10). Finally, we have applied the dendritically immobilized Cl₂ and (TsO)₂Ti‐TADDOLate as chiral Lewis acid to preferentially prepare one enantiomer of the exo and the endo (3+2) cycloadduct, respectively, of diphenyl nitrone to 3‐crotonoyl‐1,3‐oxazolidinone; in one of these reaction modes, we have observed an interesting conditioning of the catalyst: with an increasing number of application cycles, the amount of polymer‐incorporated Lewis acid required to induce the same degree of enantioselectivity, decreased; the degrees of diastereo‐ and enantioselectivity were, again, comparable to those reported for homogeneous conditions (Fig. 9).     

Effects of Cosolvents and pH on Protein Adsorption on Polystyrene Latex: A Dynamic Light Scattering Study

Dynamic light scattering was used to study the adsorption of two proteins with different surface properties (IgG and HSA) on negatively charged polystyrene latex. The proteins were adsorbed from water and from water/methanol and water/glycerol mixtures at various pH. Some striking differences between the adsorption behaviors of the proteins were observed. Whereas the thickness of the adsorbed layer of HSA was extremely sensitive to pH and solvent composition, that of IgG was not. IgG mainly showed an end-on orientation on polystyrene whereas several different surface orientations are suggested for HSA under different conditions. The addition of methanol inhibited the adsorption of HSA on the latex, but it did not affect the adsorption of IgG. In contrast, the addition of glycerol increased the thickness of the adsorbed layers of both proteins. So, the orientation of IgG on the latex is insensitive to pH but is a function of the kind of solvent whereas both pH and solvent strongly affect the adsorption of HSA. This is a puzzling result since both cosolvents should equally affect the adsorption of both proteins if the dominant forces for adsorption are the same. Therefore, we concluded that, whereas hydrophobic interactions are the dominant force in the adsorption behavior of HSA, van der Waals forces are the main forces involved in the attachment of IgG to the lattices. Copyright 2000 Academic Press.     

Electrostatic Interactions and Stability of Poly-l-lysine Covered Polystyrene Latex Particles Investigated by Dynamic Light Scattering

Adsorption isotherms of the pH dependent positively charged polyelectrolyte poly-l-lysine (PLL) on negatively and positively charged polystyrene latices are determined. With photon correlation spectrometry (PCS) the influence of the fluctuating PLL domaines in solution on the diffusion coefficient is observed at low salt concentrationsc_NaBr< 10⁻³M with λ =c_PE/c_NaBr< 0.1 (c_PE= concentration of the polyelectrolyte units). Screening of the charged layer by increasing electrolyte concentration results in large adsorbed amounts and layer thicknesses. At low molar mass of PLL the suspensions become unstable and the state and kinetic of flocculation is followed by the decreasing diffusion coefficient. PLL of higher molar mass (M_w≥ 100 000) stabilizes the particles sterically and the adsorbed layer thicknesses can be determined. The conclusions drawn from PCS features are confirmed directly by raster electron micrographs of the filtered particles.     

Bitumen-in-Water Emulsions: An Overview on Formation,Stability, and Rheological Properties

This paper describes the most relevant issues associated with the development of a technology; the formation of highly concentrated bitumen-in-water emulsions. Viscosity values for bitumen-in-water emulsions, containing between 70 and 85% (v/v) of bitumen, have been found to be several order of magnitude lower than the viscosity of the hydrocarbon itself. Thus, these emulsions, have potential applications in the processes of production, transportation, handling and commercialization of these extremely highly viscous hydrocarbons. The emulsions, the properties of which are discussed in this paper, were stabilized with mixtures of nonionic and natural surfactants (1,2) and formed using the HIPR (high internal phase ratio) technique (3). Information on the conditions required to produce emulsions with very narrow droplet diameter distributions is given. Results indicate that the mean droplet diameter, the droplet diameter distribution, and the bitumen volume fraction, significantly modify the rheological behavior. Emulsion stability was measured by following changes in the mean droplet diameter and in the rheological parameters with storage time.     

The Phosphorus Bond,or the Phosphorus-Centered Pnictogen Bond: The Covalently Bound Phosphorus Atom in Molecular Entities and Crystals as a Pnictogen Bond Donor

The phosphorus bond in chemical systems, which is an inter- or intramolecular noncovalent interaction, occurs when there is evidence of a net attractive interaction between an electrophilic region associated with a covalently or coordinately bonded phosphorus atom in a molecular entity and a nucleophile in another, or the same, molecular entity. It is the second member of the family of pnictogen bonds, formed by the second member of the pnictogen family of the periodic table. In this overview, we provide the reader with a snapshot of the nature, and possible occurrences, of phosphorus-centered pnictogen bonding in illustrative chemical crystal systems drawn from the ICSD (Inorganic Crystal Structure Database) and CSD (Cambridge Structural Database) databases, some of which date back to the latter part of the last century. The illustrative systems discussed are expected to assist as a guide to researchers in rationalizing phosphorus-centered pnictogen bonding in the rational design of molecular complexes, crystals, and materials and their subsequent characterization.     

Changes in the Structural Dimensionality of Selenidostannates in Ionic Liquids: Formation,Structures, Stability,and Photoconductivity

In situ transformations of selenidostannate frameworks in ionic liquids (ILs) were initiated by treatment of the starting phase K₂[Sn₂Se₅] and the consecutive reaction products by means of temperature increase and/or amine addition. Along the reaction pathway, the framework dimensionalities of the five involved selenidostannate anions develop from 3D to 1D and back, both in top‐down and bottom‐up style. Addition of ethane‐1,2‐diamine (en) led to the reversion of the 2D→1D step from 2D‐{[Sn₂₄Se₅₆]^16?} to 1D‐{[Sn₆Se₁₄]^4?}. As rationalized by DFT investigations, the 2D anion is thermodynamically favored. Photoconductivity measurements reveal that all samples show Schottky contact behavior with absolute thresholds below 10 V. One of the samples exhibits conductive states within the energy range of visible photons.     

白砂糖酸性絮凝物的主要成分及其形成的影响因素

分析了白砂糖中酸性絮凝物的主要成分,结果表明,白砂糖中酸性絮凝物含淀粉等多糖类38.7%～47.4%(质量分数),蛋白质等含氮物质21.5%～33.7%,灰分等无机物21.56%～25.17%,蔗脂蔗腊等类脂物7.0%～11.3%。白砂糖中酸性絮凝物的形成速度受pH值和温度的影响,在pH值1.0～4.0和10.0～12.0范围内,絮凝物形成速度较快,温度在5～50℃范围内,絮凝物形成速度随着温度的升高而提高。     

Carotenoid Contents of Lycium barbarum: A Novel QAMS Analyses,Geographical Origins Discriminant Evaluation,and Storage Stability Assessment

Given the standard substances of zeaxanthin and its homologues obtained from Lycium barbarum L. (LB) are extremely scarce and unstable, a novel quantitative analysis of carotenoids by single marker method, named QAMS, was established. Four carotenoids including lutein, zeaxanthin, β-carotene, and zeaxanthin dipalmitate were determined simultaneously by employing trans-β-apo-8′-carotenal, a carotenoid component which did not exist in LB, as standard reference. Meanwhile, β-carotene, another carotenoid constituent which existed in LB, was determined as contrast. The QAMS methods were fully verified and exhibited low standard method difference with the external standard method (ESM), evidenced by the contents of four carotenoids in 34 batches of LB samples determined using ESM and QAMS methods, respectively. HCA, PCA, and OPLS-DA analysis disclosed that LB samples could be clearly differentiated into two groups: one contained LB samples collected from Ningxia and Gansu; the other was from Qinghai, which was directly related to the different geographical location. Once exposed under high humidity (RH 75 ± 5%) at a high temperature (45 ± 5 °C) as compared with ambient temperature (25 ± 5 °C), from day 0 to day 28, zeaxanthin dipalmitate content was significantly decreased, and ultimately, all the decrease rates reached about 80%, regardless of the storage condition. Our results provide a good basis for improving the quality control of LB.     

Hapten Syntheses,Antibody Generation,and Ultrasensitive Enzyme-Linked Immunosorbent Assay for the Determination of Tonalid in Human Blood

Two novel and high-throughput enzyme-linked immunosorbent assays (ELISA) were developed for determining tonalide in human blood samples. For establishing the proposed methods, the tonalide hapten and immunogen primarily were prepared. After the immunization, the polyclonal antibody and biotinylated polyclonal antibody were obtained. The biotin-streptavidin system and polyamidoamine-gold nanoparticle conjugation were applied respectively to establish thebiotin-streptavidin-ELISA and Au-polyamidoamine-ELISA. For reducing the background interference, some factors and procedures were also discussed and optimized. Under the optimal conditions, the IC₁₀ of biotin-streptavidin-ELISA was 0.046?µg/L and the IC₁₀ of Au-polyamidoamine-ELISA was 0.016?µg/L. The Au-polyamidoamine-ELISA was used to determine tonalide in human blood and the recovery values and coefficients of variation were acceptable. In this study, tonalide was detected in 92.2% of the samples; the median and the maximum values were 0.62 and 1.76?µg/L, respectively. In general, due to the specificity of the antibody and novel nanoprobe design, this Au-polyamidoamine-ELISA simplified the sample preparation and provided a useful and potential way for trace determination of tonalide. The results also suggested that tonalide concentrations were not significantly relative to gender, but the high concentrations of tonalide in human blood should encourage further toxicological studies.     

ChemInform Abstract: A New Bond from an Old Molecule: Formation,Stability, and Structure of P4H+.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.     

Formation Mechanism,Geometric Stability and Catalytic Activity of a Single Iron Atom Supported on N-Doped Graphene

Based on density functional theory (DFT) calculations, the formation geometries, stability and catalytic properties of single-atom iron anchored on xN-doped graphene (xN-graphene-Fe, x=1, 2, 3) sheet are systemically investigated. It is found that the different kinds and numbers of gas reactants can effectively regulate the electronic structure and magnetic properties of the 3 N-graphene-Fe system. For NO and CO oxidation reactions, the coadsorption configurations of NO/O₂ and CO/O₂ molecules on a reactive substrate as the initial state are comparably analyzed. The NO oxidation reactions through the Langmuir–Hinshelwood (LH) and Eley-Rideal (ER) mechanisms have relatively smaller energy barriers than those of the CO oxidation processes. In comparison, the preadsorbed 2NO reacting with 2CO molecules (2NO+2CO→2CO₂+N₂) through ER reactions (<0.4 eV) are energetically more favorable processes. These results can provide beneficial references for theoretical studies on NO and CO oxidation and designing graphene-based catalyst for toxic gas removal.     

Effect of Oil Type,Aliphatic Alcohol,and Ionic Surfactants on the Formation and Stability of Ceramide-2 Enriched Nanoemulsions

Oil-in-water nanoemulsions are finding increasing use as delivery systems to encapsulate lipophilic bioactive components in personal care and pharmaceutical. The aim of this study was to optimize the composition and stability of ceramide-2 nanoemulsions. The nanoemulsions were prepared by high pressure homogenizer emulsification method using sodium dilauramidoglutamide lysine (DLGL) as surfactant. Results showed that the oil type and concentration had an appreciable impact on the particle size and stability of the ceramide-2 enriched nanoemulsions. The presence of the aliphatic alcohol altered the curvature of the surfactant molecular and increased the stability of nanoemulsions. The zeta potential of nanoemulsions decreased with the addition of cetyl trimethyl ammonium chloride (1631), which weakens the electrostatic interactions between droplets and lowers the stability of the nanoemulsions. The particle size decreased with increasing concentrations of both sodium dodecyl sulfate (SDS) and cocoamidopropyl betaine (CAB). The variation of zeta potential with SDS and CAB was insignificant, which was attributed to the high zeta potential value resulted from anionic gemini surfactant DLGL. The instability mechanism of nanoemulsions was the Ostwald ripening. This study demonstrated that the addition of aliphatic alcohol, SDS, or CAB was beneficial to the stability of ceramide-2 nanoemulsions and decreased the Ostwald ripening rate.     

Photochemistry of Bacteriochlorophylls in Human Blood Plasma: 1. Pigment Stability and Light-induced Modifications of Lipoproteins

Transmetalated derivatives of bacteriochlorophyll are promising sensitizers in photodynamic therapy. Protocols using short delay times between injection and irradiation cause interest in the photochemistry of these pigments in the blood. Using near-infrared irradiation where these pigments absorb strongly, we have studied the photochemistry of Zn- and Pd-bacteriopheophorbide (WST09), and of the highly polar taurinated Pd-derivative, WST11, in isolated fractions of human blood plasma. The stability of all pigments is increased in blood plasma, compared with monomeric solutions. Pd-bacteriopheophorbide is much more stable than the other two derivatives. It also has a higher capacity for inducing reactive oxygen species, yet the consumption of oxygen is comparable. There is furthermore evidence for photobleaching under anoxic conditions. The generation of hydroperoxides (ROOH) is faster with Pd- than with Zn-complexes; the formation of endoperoxides (ROOR′), measured as thiobarbituric acid reactive substances, is comparable with the two central metals. Formation of both ROOH and ROOR′ is increased in low-density lipoproteins (LDL) compared with high-density lipoproteins (HDL), which is probably related to the higher concentration of target molecules in the former. In HDL, extensive cross-linking is induced among the apolipoproteins; judged from the electrophoretic mobility of LDL and HDL particles, there is also a gross structural change. Photosensitized cross-linking is much less pronounced with high-density proteins.     

Dual Functionalization of White Phosphorus: Formation,Characterization, and Reactivity of Rare‐Earth‐Metal Cyclo‐P3 Complexes

The [3+1] fragmentation reaction of rare‐earth metallacyclopentadienes 1 a – c with 0.5 equivalents of P₄ affords a series of rare‐earth metal cyclo‐P₃ complexes 2 a – c and a phospholyl anion 3. 2 a – c demonstrate an unusual η³ coordination mode with one P−P bond featuring partial π‐bonding character. 2 a – c are the first cyclo‐P₃ complexes of rare‐earth metals, and also the first organo‐substituted polyphosphides in the category of Group 3 and f‐block elements. Rare‐earth metallacyclopentadienes play a dual role in the combination of aromatization and Diels–Alder reaction. Compounds 2 a – c can coordinate to one or two [W(CO)₅] units, yielding 4 a – c or 5 c , respectively. Furthermore, oxidation of 2 a with p ‐benzoquinone produces its corresponding phospholyllithium and regenerated P₄.     

Dual Functionalization of White Phosphorus: Formation,Characterization, and Reactivity of Rare‐Earth‐Metal Cyclo‐P3 Complexes

The [3+1] fragmentation reaction of rare‐earth metallacyclopentadienes 1 a – c with 0.5 equivalents of P₄ affords a series of rare‐earth metal cyclo‐P₃ complexes 2 a – c and a phospholyl anion 3. 2 a – c demonstrate an unusual η³ coordination mode with one P−P bond featuring partial π‐bonding character. 2 a – c are the first cyclo‐P₃ complexes of rare‐earth metals, and also the first organo‐substituted polyphosphides in the category of Group 3 and f‐block elements. Rare‐earth metallacyclopentadienes play a dual role in the combination of aromatization and Diels–Alder reaction. Compounds 2 a – c can coordinate to one or two [W(CO)₅] units, yielding 4 a – c or 5 c , respectively. Furthermore, oxidation of 2 a with p ‐benzoquinone produces its corresponding phospholyllithium and regenerated P₄.