bluuebunny/crossref_metadata_2025 huggingface dataset:
Synthesis and properties for interpenetrating polymer network of modified epoxy resins
Authors: Ho T. H. , Leu T. S. , Cheng S. S.
Published: May 2006

The control epoxy resin, CE (i.e., without modified), containing naphthalene group was synthesized directly from 1,6‐dihydroxynaphthalene with epichlorohydrin and a stoichiometric of NaOH. The MDI (4,4′‐diphenylmethane diisocyanate)‐modified epoxy resins, ME, were prepared from the direct process, MDI with CE. Subsequently, they were cured from various composition of ME/CE with 4,4′‐diaminodiphenylsulfone (DDS) and tetramethyl bisphenol F dicyanate (TBFD) in equal equivalent, respectively. In addition, the cure reaction was studied through a cross‐reference between in situ Fourier transform infrared and DSC (differential scanning calorimeter) dynamic scanning. The kinetic model gives a good description of curing paths. The modified epoxy systems had higher activation energy than that of control epoxy resin. The epoxy resins with 10 wt % ME‐modified was found to obtain appropriate result in combination with optimum properties and content (e.g., thermal stability, glass‐transition temperature, coefficient of thermal expansion, moisture absorption, dielectric constant, and modulus etc.), which may be attributed to the naphthalene, oxazolidinone structure, and crosslink density contributed to optimal state in polymer matrices. Furthermore, the intermolecular interaction hydrogen bonding of interpenetrating polymer networks. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1872–1879, 2006
Polybenzyl methacrylate brush used in the top‐down/bottom‐up approach for nanopatterning technology
Authors: Tsai Yuhsin , Wang Wei‐Ching
Published: May 2006

Atom‐transfer radical polymerization (ATRP) of benzyl methacrylate (BzMA) at ambient temperature was applied to step and flash imprint lithography. This process involved the formation of patterned polymeric networks (top‐down) and the grafting polymerization of BzMA from these networks (bottom‐up) via ATRP. Confocal laser scanning microscope and scanning electron microscope were used to determine the change in line‐to‐line separation (width) resulting from poly BzMA brush. The increase in line width at 400 nm could be maximized given a reaction time of 2 h. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1953–1957, 2006
Hydrophobic polymers as barrier dispersion coatings
Authors: Vähä‐Nissi Mika , Kervinen Kirsi , Savolainen Antti , Egolf Scott , Lau Willie
Published: May 2006

The aim of this study was to evaluate the properties of polymer dispersions prepared from hydrophobic monomers as barrier coatings. These dispersions were produced using a new emulsion polymerization process involving cyclodextrin as a phase‐transport catalyst. Conventional emulsion polymerization techniques are not applicable due to the low water solubility of the monomers, such as lauryl and stearyl (meth)‐acrylates. The experimental polymers showed improvements in water and water vapor barriers, as a result of the incorporation of hydrophobic monomers. The barrier properties could be further improved with functional groups, crosslinking, and chain‐regulating agents, as well as fillers. Grease and water barriers were strongly affected by pinholes, and functional monomers appeared to be effective in enhancing the grease barrier property. Particle morphology, glass transition temperature, and drying affected the performance of these dispersions. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1958–1962, 2006
Synthesis and in vitro degradation of novel copolymers of cyclic carbonate and D,L‐lactide
Authors: Xu Jian , Liu Zhi‐Lan , Zhuo Ren‐Xi
Published: May 2006

Cyclic carbonate 9‐phenyl‐2,4,8,10‐tetraoxaspiro‐[5,5]undcane‐3‐one is a six‐membered carbonate monomer with a rigid side group. Novel biodegradable poly(carbonate‐ester), poly(9‐phenyl‐2,4,8,10‐tetraoxaspiro‐[5,5]undecan‐3‐one‐co‐D,L‐lactide) P(CC‐co‐DLLA), was synthesized by ring‐opening polymerization in bulk, using stannous octanoate catalyst. Effects of polymerization conditions such as catalyst concentration, reaction time, and reaction temperature on the polymerization were investigated. The structure of the copolymers was characterized by FTIR, 1H NMR, and 13C NMR. Their molecular weights and polydispersity index were determined by gel permeation chromatography. The protecting benzyl ketal group was removed subsequently by catalytic hydrogenation to give a poly(carbonate‐ester) containing pendant hydroxyl groups. The in vitro degradation of the copolymers was performed at (37 ± 0.5)°C in two media: phosphate buffer solution (pH 7.4) or Tris‐HCl buffer solution (pH 8.6) in the presence of proteinase K. The degradation rate can be regulated by adjusting the composition of two monomers. The pendant hydroxyl groups in the copolymers resulted in a prominent enhancement of the degradation rate in PBS. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1988–1994, 2006
Salt and pH responsive property of a starch‐based amphoteric superabsorbent hydrogel with quaternary ammonium and carboxyl groups (II)
Authors: Xu Shimei , Cao Liqin , Wu Ronglan , Wang Jide
Published: May 2006

Swelling behaviors of a starch‐based amphoteric superabsorbent hydrogel cationic starch/sodium acrylate (CAS/AA) with quaternary ammonium and carboxyl groups were studied by immersion of the gels in various salt and pH solutions. It was found that swelling behaviors are heavily dependent of feed composition. Besides, it is also sensitive to pH, the concentration, and the ionic charge of the saline solution, but not to temperature. A kinetic study disclosed that the water transport mechanism in the CAS/AA was controlled by polymer relaxation. CAS/AA gels showed a good reversibility in the 0.9% NaCl solution after repeating the absorb‐dry process for more than 20 times. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1995–1999, 2006
Depolymerization of poly(ethylene terephthalate) wastes using ethanol and ethanol/water in supercritical conditions
Authors: De Castro Rubens E. N. , Vidotti Gentil J. , Rubira Adley F. , Muniz Edvani C.
Published: May 2006

Chemical recycling of poly(ethylene terephthalate) (PET) in supercritical ethanol has been investigated. In the presence of water, under supercritical conditions (temperature and pressure above 516 K and 6,384 kPa, respectively) excess ethanol reacts with PET to form diethyl terephthalate (DET) as the main product. A laboratory‐made 0.1L‐batch reactor was used at 528 K under pressures from 7,600 and 11,600 kPa. After the required reaction times, the reaction products were analyzed by reverse phase high pressure liquid chromatography and nuclear magnetic resonance. It was found that PET is completely depolymerized into monomers in about 5 h. The influences of water, pressure, ethanol/PET weight ratio, PET sources, as well as depolymerization time were investigated. Maximum DET recovery yield was 98.5%. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 2009–2016, 2006
Preparation and anisotropic mechanical behavior of highly‐oriented electrospun poly(butylene terephthalate) fibers
Authors: Mathew G. , Hong J. P. , Rhee J. M. , Leo D. J. , Nah C.
Published: May 2006

This work describes the effect of the speed of drum‐type rotating collector in an electrospinning process on the orientation of electrospun poly(butylene terephthalate) fiber mats, and its effect on the tensile properties. The degree of orientation increased with the increase in the drum speed (surface velocity) up to a critical level, and thereafter, wavy fibers were observed. The average diameter reduced and its distribution became narrower with increase in the velocity. The mechanical properties in a parallel direction improved about three times with increase in the surface velocity. The anisotropic mechanical behavior could be predicted with a simple classical equation. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 2017–2021, 2006
Property of ethylene vinyl acetate copolymer in melting processing
Authors: Chen Zhe , Fang Pengfei , Wang Hongmei , Zhang Shaoping , Wang Shaojie
Published: May 2006

The study is focused on the processing behavior of poly(ethylene‐co vinyl acetate) (EVA) in high temperature, such as 200°C. The specimens are characterized using HAAKE minilab, dynamic mechanical analysis (DMA), and positron annihilation lifetime spectroscopy (PALS) to understand the rheological behavior and microstructure of EVA. It was concluded that in high processing temperature, the viscosity declined first and then increased. The PALS results showed that the free volume of EVA became large at the beginning, and became small afterwards. The glass transition temperature measured with DMA got lower at first and then nearly unchanged with increasing handling time. The results can be explained that the degradation of EVA prevailed, and then degradation was not dominant. A good correlation has been found between the processing time and temperature of the transition point in the viscosity curve. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 2022–2026, 2006
Viscoplastic deformation of an epoxy resin at elevated temperatures
Authors: Kontou E.
Published: May 2006

The tensile behavior under monotonic loading and stress‐relaxation testing of an epoxy resin has been studied. Experimental data at various strain rates and three temperatures from ambient up to just below Tg were performed, to study the transition from the brittle behavior to a ductile and therefore viscoplastic one. Dynamic mechanical analysis was applied to study the glass transition region of the material. Furthermore, a three‐dimensional viscoplastic model was used to simulate the experimental results. This model incorporates all features of yield, strain softening, strain hardening, and rate/temperature dependence. The multiplicative decomposition of the deformation tensor into an elastic and viscoplastic part has also been applied, following the element arrangement in the mechanical model. A stress‐dependent viscosity was controlling the stress–strain material behavior, involving model parameters, calculated from the Eyring plots. A new equation for the evolution of the activation volume with deformation was proposed, based on a probability density function. The model capability was further verified by applying the same set of parameters to predict with a good accuracy the stress‐relaxation data as well. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 2027–2033, 2006
Shrink‐induced striped pattern on a thin gold film and switching of its orientation
Authors: Watanabe Masashi
Published: May 2006

A well‐ordered striped pattern was formed on a thin gold film, which had been deposited using an ion sputtering technique onto an elastic silicone substrate prestretched by 20%. We also prepared a two‐layer (silicone/conducting rubber) substrate onto which a thin gold film with a striped pattern was produced using a similar method. By applying a voltage (24 V) between both ends of the conducting rubber to heat the substrate, I succeeded in reversibly changing the orientation of the striped pattern. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 2040–2044, 2006
Water absorption behavior of acrylonitrile‐butadiene (NBR) latex impregnated jute nonwoven fabric composites
Authors: Kumar M. N. Satheesh , Siddaramaiah
Published: May 2006

Composites were fabricated by impregnating the jute nonwoven fabric in acrylonitrile–butadiene (NBR) latex. The effect of different pickup ratio (dry, wt/wt) of NBR latex to jute nonwoven fabric, viz., 0.5 : 1, 1 : 1.5, 1.5 : 1, 2 : 1, and 2.5 : 1 on the water absorption behavior of the composites were evaluated. Water absorption studies were carried out at different temperatures, viz. 30, 50, and 70°C, based on immersion weight gain method. From the sorption result, the diffusion (D) and permeation (P) coefficients of water penetrant have been calculated. Significant increase in the diffusion and permeation coefficients was observed with increase in the temperature of sorption experiments. Drastic reductions in diffusion and permeation coefficients were noticed with increase in the pickup ratio of NBR on to jute nonwoven fabric. Attempts were made to estimate the empirical parameters like n, which suggests the mode of transport, and K is a constant that depends on the structural characteristics of the composite in addition to its interaction with water. The temperature dependence of the transport coefficients has been used to estimate the activation energy parameter for diffusion (ED) and permeation processes (Ep) from Arrhenius plots. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 2045–2050, 2006
Properties of organic–inorganic composite materials prepared from acrylic resin emulsions and colloidal silicas
Authors: Wada Tamaki , Inui Kuniaki , Uragami Tadashi
Published: May 2006

To design an organic–inorganic composite material with colloidal silica as the inorganic component, an acrylic resin emulsion and an organic silane hybridized acrylic resin emulsion were prepared by emulsion polymerization. The organic–inorganic composite films were prepared by blending the emulsion and the colloidal silica. The contact angles for water, gloss at 60°, and the transparencies of those films were measured. The dispersion state of colloidal silica in films was observed with a scanning electron microscope (SEM) and a transmission electron microscope (TEM). From these results, the contact angle for water of the organic–inorganic composite film obtained from the silane hybridized acrylic resin emulsion was lower than that of the organic–inorganic composite film obtained from an acrylic resin emulsion. The contact angles for water in organic–inorganic composite films with colloidal silicas were lower than those of the films without the colloidal silicas. The films prepared from silane hybridized acrylic resin emulsion composites with colloidal silicas of less than 100 nm were more hydrophilic. SEM and TEM observations demonstrated that some aggregations of the small colloidal particle silica were densely dispersed on the film surface. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 2051–2056, 2006
Poly(ethylene‐alt‐maleic acid) as complexing reagent to separate metal ions using membrane filtration
Authors: Rivas Bernabé L. , Pooley S. Amalia , Pereira Eduardo , Montoya Erika , Cid Rocío
Published: May 2006

Commercial, water‐soluble poly(ethylene‐alt‐maleic anhydride), P(E‐alt‐MAn), was quantitatively hydrolyzed by 0.2M NaOH to yield poly(ethylene‐alt‐maleic acid), P(E‐alt‐MAc). The polymer structure is confirmed by FT‐IR spectroscopy. As the pH increases, metal ion affinity increases because the majority of the functional groups are present as carboxylate anions, which can form more stable complexes at a higher pH. By increasing the filtration factor, Z, metal ion affinity does not significantly decrease, which means that the ligand–metal interaction is strong and cannot be destroyed by washing with water at the filtration cell's pH. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 2057–2061, 2006
Kinetic study of radical polymerization. IV. Determination of reactivity ratio in copolymerization of styrene and itaconic acid by 1H‐NMR
Authors: Mahdavian Ali Reza , Abdollahi Mahdi , Mokhtabad Leila , Reza Bijanzadeh Hamid , Ziaee Farshid
Published: May 2006

Here, online 1H‐NMR spectroscopy has been successfully applied to investigate the kinetic parameters of radical copolymerization of styrene (St) and itaconic acid (IA). This technique was used because it allowed us to individually map out the monomer conversions of St and IA during the course of the polymerization at various conversions. This was possible because the individual contributions to the overall monomer conversion from St and IA could be measured through their nonoverlapping vinylic proton signals. The results of monomer conversion during the time in the corresponding 1H‐NMR spectra was the basis of our analysis to determine the reactivity ratios of St and IA in the solution and radical copolymerization reaction by several methods. In addition to linear least‐squares methods, such as Finemann–Ross, inverted Finemann–Ross, Mayo–Lewis, Kelen–Tudos, extended Kelen–Tudos, and Mao–Huglin, a nonlinear least‐square method (Tidwell–Mortimer) was used for this purpose, at low conversions. Extended Kelen–Tudos and Mao–Huglin were applied to determine the reactivity ratio values at high conversions too. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 2062–2069, 2006
Preparation and characterization of genistein containing poly(ethylene glycol) microparticles
Authors: Motlekar Nusrat , Khan Mansoor A. , Youan Bi‐Botti C.
Published: May 2006

The purpose of this study was to prepare, characterize, and evaluate genistein‐containing microparticles with enhanced dissolution profile using poly(ethylene glycol) (PEG) as polymer matrix. Genistein loaded microparticles were prepared by a solvent evaporation process and their surface, thermal, chemical, and dissolution properties were analyzed by microscopy, differential scanning calorimetry, ATR‐FTIR spectroscopy, and USP dissolution apparatus II, respectively. The wettability index was also determined. Genistein exhibited an elongated crystal habit. However, the drug containing PEG microparticles were discrete and quasispherical. The ATR‐FTIR studies performed on the formulation suggested hydrogen bonding between the drug and the polymer matrix. Thermal analysis indicated a conversion of the crystalline form of the drug to an amorphous form. Genistein, exhibiting low solubility and high permeability, is a Class II drug of the Biopharmaceutical Classification Scheme. However, there was a ∼9‐fold increase in the rate of dissolution of genistein in the case of all formulations as compared to native genistein. This study showed that genistein could be effectively encapsulated into PEG microparticles using an emulsion‐solvent evaporation technique, therefore avoiding the potential disadvantages of other solid dispersion techniques. This approach provided a significant enhancement in the drug dissolution profile. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 2070–2078, 2006
Structure and properties of UHMWPE fiber/carbon fiber hybrid composites
Authors: Lu Sheng‐Hua , Liang Guo‐Zheng , Zhou Zhi‐Wei , Li Fang
Published: May 2006

Ultrahigh molecular weight polyethylene (UHMWPE) fiber/carbon fiber hybrid composites were prepared by inner‐laminar and interlaminar hybrid way. The mechanical properties, dynamic mechanical analysis (DMA), and morphologies of the composites were investigated and compared with each other. The results show that the hybrid way was the major factor to affect mechanical and thermal properties of hybrid composites. The resultant properties of inner‐laminar hybrid composite were better than that of interlaminar hybrid composite. The bending strength, compressive strength, and interlaminar shear strength of hybrid composites increased with an increase in carbon fiber content. The impact strength of inner‐laminar hybrid composite was the largest (423.3 kJ/m2) for the UHMWPE fiber content at 43 wt % to carbon fiber. The results show that the storage modulus (E′), dissipation factor (tan δ), and loss modulus (E″) of the inner‐laminar hybrid composite shift toward high temperature remarkably. The results also indicate that the high‐performance composite with high strength and heat resistance may be prepared by fibers' hybrid. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1880–1884, 2006
Synthesis and characterization of xanthan gum‐g‐N‐vinyl formamide with a potassium monopersulfate/Ag(I) system
Authors: Banerjee Jaya , Srivastava Arti , Srivastava Abhishek , Behari Kunj
Published: May 2006

A xanthan gum‐g‐N‐vinyl formamide graft copolymer was synthesized through the graft copolymerization of N‐vinyl formamide (NVF) onto xanthan gum with an efficient system, that is, potassium monopersulfate (PMS)/Ag(I) in an aqueous medium. The effects of the concentrations of Ag(I), PMS (KHSO5), hydrogen ion, xanthan gum, and NVF along with the time and temperature on the graft copolymerization were studied by the determination of the grafting parameters (grafting ratio, add‐on, conversion, grafting efficiency, and homopolymer) and the rate of grafting. The maximum grafting ratio was obtained at a 0.6 g/dm3 concentration of xanthan gum. All the parameters showed an increasing trend with an increasing concentration of peroxymonosulfate, except the homopolymer percentage, which showed a decreasing trend. The grafting ratio, add‐on conversion, grafting efficiency, and rate of grafting increased with the concentration of Ag(I) increasing from 0.8 × 10−2 to 1.2 × 10−2 mol/dm3. The optimum time and temperature for the maximum degree of grafting were 90 min and 35°C, respectively. The graft copolymer was characterized with IR spectral analysis, thermogravimetric analysis, and differential calorimetry analysis. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1637–1645, 2006
Energy of chemical bonds and spatial energy principles of the hybridization of atom orbitals
Authors: Korablev G. A. , Zaikov G. E.
Published: May 2006

Methods for the evaluation of energy directedness of atom orbital hybridization and the calculation of the energy of chemical bonds in simple and complex structures are proposed on the basis of the application of the spatial energy parameter concept. Appropriate calculations and comparisons for 68 compounds were made. The calculation results agreed with the experimental data. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 2101–2107, 2006
Time course and development of light adaptation processes in the outer zebrafish retina
Authors: Hodel Corinne , Neuhauss Stephan C.F. , Biehlmaier Oliver
Published: May 2006

Retinomotor movements are morphological changes in the outer retina in response to changing light conditions. They can be separated into two components: Migration of pigment granules within the microvilli of the retinal pigment epithelium (RPE) and positional changes in photoreceptor cells. These positional changes optimize exposure of the cone and rod photoreceptors to light. The aim of this study was to analyze both the time course of retinomotor movements in the adult zebrafish and the maturation of these processes in the developing fish. We show that retinomotor movements are used as a dark/light adaptation mechanism in zebrafish. In adult zebrafish, melanin granules of the RPE migrate with constant speed and reach the fully light adapted (LA) state approximately after 1h. In contrast, about two thirds of double cone outer segment movements are finished in 5min, and are fully completed in 10 to 20min. During development there are three crucial stages leading to mature retinomotor movements in response to light: at 5dpf (days post fertilization) the migration of pigment granules begins, at 20dpf the pigment granules condense in the apical part of the RPE microvilli, and at 28dpf, concomitant with the functional maturation of rods, the double cones contract as in adult retinas. Anat Rec Part A 288A:653–662, 2006. © 2006 Wiley‐Liss, Inc.
On Egghe's version of continuous concentration theory
Authors: Burrell Quentin L.
Published: May 2006

In a recent article, Egghe (2005) discussed what he terms Lorenz concentration theory, covering the Lorenz curve and concentration measures such as the coefficient of variation and the Theil and Gini coefficients. In this note, we point out that neither the curve construction nor the concentration measures conform to the standard statistical/econometric definitions. We here give the standard formulations and apply them to the (truncated) Pareto distributions that are the subject of Egghe's (2005) article. We also interpret Egghe's usage.
On the solution of multislab atmospheric radiation problems with an arbitrary number and type of stationary layers
Authors: de Abreu Marcos Pimenta
Published: May 2006

We report here a computer implementation of a recently developed discrete ordinates methodology for efficiently solving a set of multislab atmospheric radiation problems with an arbitrary number and type of stationary layers. Numerical results are presented for a set of typical problems for a multislab model atmosphere in the shortwave. Copyright © 2006 Royal Meteorological Society
Effect of pierced metallic objects on sar distributions at 900 MHz
Authors: Fayos‐Fernandez Jose , Arranz‐Faz Carlos , Martinez‐Gonzalez Antonio M. , Sanchez‐Hernandez David
Published: May 2006

A study of the interaction between mobile phone antennas and a human head in the presence of different types of metallic objects, attached and pierced to the compressed ear, is presented in this article. Computed and measured results have been performed by considering a quasi‐half‐wavelength dipole as the radiating source and measurements with the DASY4 dosimetric assessment system. Two different human head models have been implemented: a homogeneously shaped sphere and a three‐level head model with four different kinds of tissue. Antenna input impedance, reflection coefficient, radiation patterns, SAR distribution, absorbed power, and peak SAR values have been computed and measured for diverse scenarios, electromagnetic simulators, and organs. Despite the measuring accuracy limitations of the study, both simulated and measured results suggest that special attention has to be paid to peak SAR averaged values when wearing metallic objects close to the radiation source, since some increment of peak SAR averaged values is expected. Bioelectromagnetics 27:337–353, 2006. © 2006 Wiley‐Liss, Inc.
Computational verification of anesthesia effect on temperature variations in rabbit eyes exposed to 2.45 GHz microwave energy
Authors: Hirata Akimasa , Watanabe Soichi , Kojima Masami , Hata Ikuho , Wake Kanako , Taki Masao , Sasaki Kazuyuki , Fujiwara Osamu , Shiozawa Toshiyuki
Published: May 2006

This paper computationally verifies the effect of anesthesia on temperature variations in the rabbit eye due to microwave energy. The main reason for this investigation is that our previous paper suggested a reduction in blood flow due to the administration of anesthesia, resulting in an overestimated temperature increase. However, no quantitative investigation has yet been conducted. The finite‐difference time‐domain (FDTD) method is used for calculating power absorption and temperature variation in rabbits. For this purpose, we used a computational rabbit phantom, which is comprised of 12 tissues (including 6 eye tissues) with a resolution of 1 mm. Thermal constants of the rabbit were derived by comparing measured and calculated temperatures. For intense microwave exposure to the rabbit eye, time courses of calculated and measured temperatures were in good agreement for cases both with and without the administration of anesthesia. The point to be stressed is that under anesthesia the thermoregulatory response was inactivated and blood flow and basal metabolism was reduced. Bioelectromagnetics 27:602–612, 2006. © 2006 Wiley‐Liss, Inc.
Time‐resolved rapid‐scan Fourier transform infrared difference spectroscopy on a noncyclic photosystem: Rhodopsin photointermediates from Lumi to Meta II
Authors: Lüdeke Steffen , Fonfría Víctor A. Lórenz , Siebert Friedrich , Vogel Reiner
Published: May 2006

The visual pigment rhodopsin has been extensively studied for the kinetics of its photointermediates by various spectroscopic methods. Unlike such archaeal retinal proteins as bacteriorhodopsin, visual rhodopsin does not thermally recover its dark state after photoexcitation, which precludes repeated excitation of a single sample and thereby complicates time‐resolved experiments. Kinetic data on the late rhodopsin photointermediates have so far been available mainly from time‐resolved ultraviolet (UV)‐visible spectroscopy, but not from Fourier transform infrared (FTIR) spectroscopy. The latter has the advantage of being informative of structural changes of both chromophore and protein, but does not allow the highly reproducible, automated sample exchange procedures available to UV‐visible spectroscopy. Using rapid‐scan FTIR difference spectroscopy, we obtained time‐resolved data sets that were analyzed by a maximum entropy inverse Laplace‐transform. Covering the time range from 8 ms to 15 s at temperatures of 0 and −7°C, the transitions from the Lumi to the Meta I and from the Meta I to the Meta II photoproduct states could be resolved. In the transition from Meta I to Meta II, our data reveal a partial deprotonation of the retinal Schiff base preceding the conformational change of the receptor protein to Meta II. The technique and the results are discussed in regard to its advantages as well as its limitations. © 2006 Wiley Periodicals, Inc. Biopolymers 83: 159–169, 2006

This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com
DNA Containing Side Chains with Terminal Triple Bonds: Base‐Pair Stability and Functionalization of Alkynylated Pyrimidines and 7‐Deazapurines
Authors: Seela Frank , Sirivolu Venkata Ramana
Published: May 2006

The synthesis of a series of oligonucleotides containing 5‐substituted pyrimidines as well as 7‐substituted 7‐deazapurines bearing diyne groups with terminal triple bonds is reported. The modified nucleosides were prepared from the corresponding iodo nucleosides and diynes by the Sonogashira cross‐coupling reaction. They were converted into phosphoramidites and employed in solid‐phase synthesis of oligonucleotides. The effect of the diyne modifications on the duplex stability was investigated. The modified nucleosides were used for further functionalization using the protocol of Huisgen–Sharpless [2+3] cycloaddition (‘click chemistry’).
Studies on Cage‐Type Tetranuclear Metal Clusters with Ferrocenylphosphonate Ligands
Authors: Wu Jie , Song Yinglin , Zhang Erpeng , Hou Hongwei , Fan Yaoting , Zhu Yu
Published: May 2006

Reaction of FcCH2PO3H2 [Fc=(η5‐C5H5)Fe(η5‐C5H4)] (H2FMPA) and 1,10‐phenanthroline (phen) with Cd(OAc)2⋅2 H2O or ZnSO4⋅7 H2O in methanol in the presence of triethylamine resulted in the formation of two new ferrocenylphosphonate metal‐cage complexes [M4(fmpa)4(phen)4]⋅ 7 CH3OH (M=Cd 1, M=Zn 2). Both structures contain two kinds of isomeric tetranuclear metal phosphonate cages, which are linked to one another by π–π interactions between the phen molecules. In 1, the Cd1, Cd3, and Cd4 atoms are all pentacoordinate, while the Cd2 atom is coordinated by four oxygen atoms from three phosphonate ligands and two nitrogen atoms from the chelating phen in a distorted octahedral geometry. Four Cd atoms from each unit are interconnected through bridging phosphonate ligands with different coordination modes, such as 5.221, 4.211, and 2.11 (Harris notation), yielding a {Cd4} cage. In 2, each Zn atom is coordinated by three oxygen atoms from three phosphonate ligands and two nitrogen atoms from phen, leading to a distorted square‐pyramidal geometry. The four Zn atoms of each isomeric unit are also interconnected through four bridging phosphonate ligands to yield a {Zn4} cage. Fluorescent studies indicate that ligand‐to‐ligand charge‐transfer photoluminescence is observed for 1, while the emisson bands of 2 can be assigned to an admixture of ligand‐to‐ligand and metal‐to‐ligand charge transfer. Solution‐state differential pulse voltammetry indicates that the half‐wave potentials of the ferrocenyl moieties in 1 and 2 have different deviations relative to the relevant H2FMPA ligand. This may be because the highest occupied molecular orbital (HOMO) in 1 is located in the FMPA2− groups, while in 2 the HOMO is located in the phen and ZnII groups, so the FeII centers in complex 1 are more easily oxidized to FeIII centers than those of 2. The third‐order nonlinear optical (NLO) measurements show that both 1 and 2 exhibit strong third‐order NLO self‐focusing effects; hence, they are promising candidates for NLO materials. By calculating the component of the lowest unoccupied molecular orbitals of 1 and 2, we confirmed that the co‐planar phen rings control their optical nonlinearity, while the H2FMPA ligands and metal ions have only a weak influence on their NLO properties.
DNA‐Binding Properties and Photocleavage Activity of Cationic Water‐Soluble Chlorophyll Derivatives
Authors: Taima Hidetoshi , Okubo Akihiro , Yoshioka Naoki , Inoue Hidenari
Published: May 2006

Three cationic water‐soluble chlorin e6 derivatives, that is, 6a‐,γb‐,7c‐tris(2‐trimethylammonioethyl)chlorin e6 (1), 6a‐,γb‐,7c‐tris(3‐methylpyridiniummethyl)chlorin e6 (2), and 6a‐,γb‐, 7c‐tris(2‐trimethylammonioethyl)‐2‐(3‐trimethylammonioprop‐1‐enyl)chlorin e6 (3), have been designed and synthesized to allow the study of their DNA‐binding and ‐photocleavage activities. The DNA‐unwinding assay, measurements of melting temperatures of double‐stranded DNA, and the induced CD and visible absorption spectra have revealed that 1 and 3 are intercalated into the base pairs of the double‐helical DNA, while 2 is bound to outside the minor groove of the double‐helical DNA. The cationic water‐soluble chlorin e6 derivatives effectively cleave the double‐helical DNA under photoirradiation and the DNA‐photocleavage activity increases in the order 3>1>2. The DNA‐binding and ‐photocleavage characteristics of the three cationic water‐soluble chlorin e6 derivatives are influenced by aspects of their molecular structure, such as the kind, number, and position of the cationic substituents.
A Second Metalloid Ga18 Cluster and Its Topological Similarity to the High‐Pressure Ga‐II Modification
Authors: Steiner Jochen , Schnöckel Hansgeorg
Published: May 2006

The topology of many modifications of elemental gallium is reflected in the large variety of metalloid Ga clusters that have been isolated as intermediates on the way from the metastable molecular GaX species (X=Cl, Br, I) by means of disproportionation to the bulk metal. Herein, we report the synthesis and characterization of the first metalloid cluster anion [Ga18(PtBu2)10]3− with the singular core topology that resembles the gallium high‐pressure modification Ga‐II. The stabilization of the cluster anion through ion‐pair contacts with a chainlike “Li4Br2 backbone” is discussed. Furthermore, the compound is discussed in context of the other metalloid clusters Ga18R8 and Ga22R8 (R=SitBu3) and their structural relation to the elemental modifications Ga‐III and β‐Ga, respectively.
Remarkable Interplay of Redox States and Conformational Changes in a Sterically Crowded, Cross‐Conjugated Tetrathiafulvalene Vinylog
Authors: Amriou Samia , Perepichka Igor F. , Batsanov Andrei S. , Bryce Martin R. , Rovira Concepció , Vidal‐Gancedo José
Published: May 2006

Derivatives of 9‐[2‐(1,3‐dithiol‐2‐ylidene)ethylidene]thioxanthene have been synthesized using Horner–Wadsworth–Emmons reactions of (1,3‐dithiol‐2‐yl)phosphonate reagents with thioxanthen‐9‐ylidene‐acetaldehyde (5). Further reactions lead to the sterically crowded cross‐conjugated “vinylogous tetrathiafulvalene” derivative 9‐[2,3‐bis‐(4,5‐dimethyl‐1,3‐dithiol‐2‐ylidene)‐propylidene]thioxanthene (10). X‐ray crystallography, solution electrochemistry, optical spectroscopy, spectroelectrochemistry, and simultaneous electrochemistry and electron paramagnetic resonance spectroscopy, combined with theoretical calculations performed at the B3LYP/6‐31G(d) level, elucidate the interplay of the electronic and structural properties in these molecules. For compound 10, multistage redox behavior is observed: the overall electrochemical process can be represented by 10→10.+→102+→104+ with good reversibility for the 10→10.+→102+ transformations. At the tetracation stage there is the maximum gain in aromaticity at the dithiolium and thioxanthenium rings. Theory predicts that for 10, 10.+, and 102+ the trans isomers are more stable than the cis isomers (by ca. 2–18 kJ mol−1), whereas for 104+ the cis isomer becomes more stable than the trans isomer (by ca. 25 kJ mol−1) [trans and cis refer to the arrangement of the two dithiole moieties with respect to the central C(R)C(H) fragment]. These data explain the detection in cyclic voltammograms of both trans and cis isomers of 10 and 10.+ during the reduction of 104+ at fast scan rates (>100 mV s−1) when the cis–trans isomerization is not completed within the timescale of the experiment. The X‐ray structure of the charge‐transfer complex (CTC) of 10 with 2,4,5,7‐tetranitrofluorene‐9‐dicyanomethylenefluorene (DTeF) [stoichiometry: 10.+⋅(DTeF)2.−⋅2 PhCl] reveals a twisted conformation of 10.+ (driven by the bulky thioxanthene moiety) and provides a very rare example of segregated stacking of a fluorene acceptor in a CTC.
Cu4Mo6Se8: Synthesis, Crystal Structure, and Electronic Structure of a New Chevrel Phase Structure Type.
Authors: McGuire Michael A. , Ranjan Chinmoy , DiSalvo Francis J.
Published: May 2006

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.
Isothermal Section of the Y2Se3—Cu2Se—GeSe2 System at 870 K and Crystal Structure of the Y3CuGeSe7 Compound.
Authors: Lychmanyuk O. S. , Gulay L. D. , Olekseyuk I. D.
Published: May 2006

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.
Synthesis and Characterization of f‐Element Iodate Architectures with Variable Dimensionality, α‐ and β‐Am(IO3)3.
Authors: Runde Wolfgang , Bean Amanda C. , Brodnax Lia F. , Scott Brian L.
Published: May 2006

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.
Lewis Base Activation of Lewis Acids. Vinylogous Aldol Addition Reactions of Conjugated N,O‐Silyl Ketene Acetals to Aldehydes.
Authors: Denmark Scott E. , Heemstra John R. Jr.
Published: May 2006

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.
P‐Chiral Tetraphosphine Dirhodium Complex as a Catalyst for Asymmetric Hydrogenation: Synthesis, Structure, Enantioselectivity, and Mechanism. Stereoselective Formation of a Dirhodium Tetrahydride Complex and Its Reaction with Methyl (Z)‐α‐Acetamidocinnamate.
Authors: Imamoto Tsuneo , Yashio Keiji , Crepy Karen V. L. , Katagiri Kosuke , Takahashi Hidetoshi , Kouchi Mitsuhiro , Gridnev Ilya D.
Published: May 2006

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.
Pt‐Catalyzed sp3 C—H Bond Activation of o‐Alkyl Substituted Aromatic Carboxylic Acid Derivatives for the Formation of Aryl Lactones.
Authors: Lee Ji Min , Chang Sukbok
Published: May 2006

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.
1‐Phenylthio‐3‐vinyl‐3‐cyclohexenol, a New Reagent for Bis‐Annelation of Silyl Enol Ethers.
Authors: Konstantinova Olga , Saraber Florence C. E. , Melguizo Enrique , Jansen Ben J. M. , de Groot Aede
Published: May 2006

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.
Bis(allyl)—Ruthenium(IV) Complexes as Highly Efficient Catalysts for the Redox Isomerization of Allylic Alcohols into Carbonyl Compounds in Organic and Aqueous Media: Scope, Limitations, and Theoretical Analysis of the Mechanism.
Authors: Cadierno Victorio , Garcia‐Garrido Sergio E. , Gimeno Jose , Varela‐Alvarez Adrian , Sordo Jose A.
Published: May 2006

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.
Enantioselective Synthesis of 2‐Aryl Cyclopentanones by Asymmetric Epoxidation and Epoxide Rearrangement.
Authors: Shen Yu‐Mei , Wang Bin , Shi Yian
Published: May 2006

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.
Reaction of Primary Amines with Pt/C Catalyst in Water under Microwave Irradiation: A Convenient Synthesis of Secondary Amines from Primary Amines.
Authors: Miyazawa Akira , Saitou Kaori , Tanaka Kan , Gaedda Thomas M. , Tashiro Masashi , Prakash G. K. Surya , Olah George A.
Published: May 2006

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.
Highly Enantioselective Carbonyl Reduction with Borane Catalyzed by Chiral Spiroborate Esters Derived from Chiral 1,2‐Aminoalcohols.
Authors: Stepanenko Viatcheslav , Ortiz‐Marciales Margarita , Correa Wildeliz , De Jesus Melvin , Espinosa Sandraliz , Ortiz Lymaris
Published: May 2006

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.
Nucleophilic Addition of Ethyl 3‐Bromodifluoromethyl‐3‐benzyloxyacrylate to Imines: An Effective Entry to Novel gem‐Difluorinated Amino Esters and Their Derivatives.
Authors: Peng Weimin , Zhao Jingwei , He Ping , Zhu Shizheng
Published: May 2006

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.
Suzuki—Miyaura, α‐Ketone Arylation and Dehalogenation Reactions Catalyzed by a Versatile N‐Heterocyclic Carbene—Palladacycle Complex.
Authors: Navarro Oscar , Marion Nicolas , Oonishi Yoshihiro , Kelly Roy A. III , Nolan Steven P.
Published: May 2006

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.
Highly Enantioselective Synthesis of Glycidic Amides Using Camphor‐Derived Sulfonium Salts. Mechanism and Applications in Synthesis.
Authors: Aggarwal Varinder K. , et al. et al.
Published: May 2006

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.
Facile One‐Pot Three‐Component Synthesis of Functionalized Pyridylfuran‐2‐amines.
Authors: Adib Mehdi , Sayahi Mohammad Hosein , Koloogani Somayeh Aali , Mirzaei Peiman
Published: May 2006

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.
Stereochemistry of Bromomethylation of Methyl cis‐ and trans‐ 2‐Oxo‐octahydrobenzofuran‐3‐carboxylate.
Authors: Bukowska M. , Prejzner J. , Szczecinski P.
Published: May 2006

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.
Zinc Perchlorate Catalyzed One‐Pot Amination—Annulation of α‐Cyanomethyl‐β‐ketoesters in Water. Regioselective Synthesis of 2‐Aminopyrrole‐4‐carboxylates.
Authors: Demir Ayhan S. , Emrullahoglu Mustafa
Published: May 2006

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.
Regioselective Synthesis of 3‐ and 5‐Functional Derivatives of Pyrazolidine. Part 1. Synthesis of Ketones of the Pyrazolidine Series.
Authors: Sviridova L. A. , Tavtorkin A. N. , Terentiev P. B. , Lescheva I. F. , Kolotyrkina N. G. , Kochetkov K. A.
Published: May 2006

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.
A Novel and Highly Efficient Protocol for Markovnikov′s Addition Using Ionic Liquid as Catalytic Green Solvent.
Authors: Xu Jian‐Ming , Wu Wei‐Bo , Qian Chao , Liu Bo‐Kai , Lin Xian‐Fu
Published: May 2006

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.
Microwave‐Assisted Synthesis of N‐Heterocyclic Carbene Precursors.
Authors: Aidouni Adila , Demonceau Albert , Delaude Lionel
Published: May 2006

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.
[3 + 2] Cross‐Coupling Reactions of Aziridines with Isocyanates Catalyzed by Nickel(II) Iodide.
Authors: Munegumi Takeshi , Azumaya Isao , Kato Takako , Masu Hyuma , Saito Shinichi
Published: May 2006

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.
Conversions of Coumarins Accompanied by Intermediate Opening and Recyclization of the Lactone Ring. Part 2. Study of the Interaction of Malonic Acid Hydrazide and Amide Derivatives with 3‐Acyl(3‐cyano, 3‐ethoxycarbonyl)coumarins.
Authors: Nemeryuk M. P. , Dimitrova V. D. , Anisimova O. S. , Sedov A. L. , Solov'eva N. P. , Traven V. F.
Published: May 2006

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.
Natural Phosphate and Potassium Fluoride Doped Natural Phosphates as New Catalysts for the Vilsmeier—Haack Type Reaction.
Authors: Zahouily Mohamed , Bahlaouan Bouchaib , Abrouki Younes , Salah Mohamed , Bahlaouan Ouafa , Rayadh Ahmed , Aadil Mina , Sebti Said
Published: May 2006

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.
Synthesis of Stable Azomethine Ylides by the Rearrangement of 1,3‐Dipolar Cycloadducts of 3,4‐Dihydroisoquinoline‐2‐oxides with DMAD.
Authors: Coskun Necdet , Tuncman Selen
Published: May 2006

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.
A Simple Approach for the Regioselective Synthesis of Imidazo[1,2‐a]pyrimidinones and Pyrimido[1,2‐a]pyrimidinones.
Authors: Font David , Linden Anthony , Heras Montserrat , Villalgordo Jose M.
Published: May 2006

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.
Synthesis of 6‐Thioxo‐1,2,5‐oxadiazinan‐3‐ones and Transformation into 3‐Amino‐2‐thiohydantoins and 3‐Hydroxy‐2‐thiohydantoins.
Authors: Geffken Detlef , Ploetz Alf
Published: May 2006

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.
Diastereoselective Cycloalkylation of Phosphoryl and Thiophosphoryl Acetonitriles by α,ψ‐Dihalogenalkanes under Phase Transfer Catalysis Conditions.
Authors: Odinets I. L. , Vinogradova N. M. , Lyssenko K. A. , Petrovskii P. V. , Mastryukova T. A. , Roeschenthaler G‐V.
Published: May 2006

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.