bluuebunny/crossref_metadata_2025 huggingface dataset:
Oral administration of docosahexaenoic acid attenuates colitis induced by dextran sulfate sodium in mice
Authors: Cho Jae Young , Chi Sung‐Gil , Chun Hyang Sook
Published: September 2010

Scope: Dietary supplementation of n‐3 PUFAs, containing docosahexaenoic acid (DHA), modulates the symptoms of colitis. Hence, we investigated the effects of oral administration of pure DHA and the therapeutic agent sulfasalazine (SAL) on chemically induced colitis in mice, and analyzed the expression levels of DHA‐responsive genes in colonic tissue using cDNA arrays.

Methods and results: Colitis in BALB/c mice was induced by feeding 5% dextran sulfate sodium (DSS) in drinking water for 7 days. DHA (30 mg/kg/day, DHA) or SAL (100 mg/kg/day, SAL) was administered orally throughout the treatment along with DSS. The DHA‐treated group showed significant reduction of the weight loss and colon shortening compared to the DSS‐treated colitis group. In contrast, SAL treatment was effective in reducing colon shortening, stool consistency and bleeding scores. DHA and SAL treatments also significantly reduced the changes in inflammation of the colon, and reversed the increase in myeloperoxidase activity induced by DSS. Among DSS‐responsive genes, those for inflammatory cytokines (IL‐1β, CD14 antigen and tumor necrosis factor receptor superfamily, member 1b), membrane remodeling genes (matrix metalloproteinase‐3, ‐10 and ‐13) and acute phase proteins (S100 calcium‐binding protein A8), which were increased by DSS, were downregulated by DHA or SAL treatment.

Conclusions: DHA was effective in alleviating DSS‐induced colitis in mice, partly by modulating the expression levels of genes involved in colitis.
The insulin sensitivity response is determined by the interaction between the G972R polymorphism of the insulin receptor substrate 1 gene and dietary fat
Authors: Marín Carmen , Pérez‐Martínez Pablo , Delgado‐Lista Javier , Gómez Purificación , Rodríguez Fernando , Yubero‐Serrano Elena María , García‐Ríos Antonio , Camargo Antonio , Pérez‐Jiménez Francisco , López‐Miranda José
Published: September 2010

Scope: Insulin resistance, a condition associated with type 2 diabetes mellitus, results from the interaction of environmental and genetic factors. The aim of this study was to explore the influence of the G972R polymorphism at the insulin receptor substrate 1 gene on insulin sensitivity in a healthy young population. Furthermore, we examined whether the presence of this single nucleotide polymorphism (SNP; GR or GG) interacts with dietary fat to modulate insulin sensitivity.

Methods and results: Fifty‐nine healthy volunteers consumed three diets during 4 wk each following a randomized crossover design: a saturated fatty acid diet, a low‐fat and high carbohydrate (CHO) diet or a MUFA diet. For each diet, we investigated peripheral insulin sensitivity with the insulin suppression test. Steady‐state plasma glucose and plasma‐free fatty acids concentrations were significantly lower in GR subjects after the intake of a CHO diet, than did homozygous GG subjects (p<0.05). However, no differences were observed after consuming the two other diets.

Conclusions: Insulin sensitivity increased in GR subjects for the G972R polymorphism at the insulin receptor substrate 1 gene locus, after intake of a CHO diet. Increased knowledge of how these and other genes influence insulin sensitivity should increase the understanding of personalized nutrition.
N‐acetylcysteine counteracts oxidative stress and prevents hCG‐induced apoptosis in rat Leydig cells through down regulation of caspase‐8 and JNK
Authors: Aggarwal Archana , Misro Man Mohan , Maheshwari Ankur , Sehgal Neeta , Nandan Deoki
Published: September 2010

We have earlier reported that following persistent stimulation with hCG, oxidative stress‐induced apoptosis in rat Leydig cells was mainly achieved through the extrinsic pathway. In the present study, the role of N‐acetylcysteine (NAC) in counteracting the oxidative stress and the mechanisms of inhibition of apoptosis under such conditions were investigated. NAC (1 mM) intervention with repeated hCG stimulation (50 ng/ml, four times, each with 30 min challenge) prevented the decline in Leydig cell viability and the rise in lipid peroxidation and reactive oxygen species. Simultaneously, the activities of the enzymes glutathione‐S‐transferase, catalase, superoxide dismutase and the intracellular glutathione and antioxidant capacity of the treated cells improved significantly. Apoptotic markers Fas, FasL, and caspase‐8, up‐regulated following repeated hCG exposure, were significantly down‐regulated following NAC co‐incubation. While Bcl‐2 expression was fully restored, Bax and caspase‐9 remained unchanged. NAC treatment induced down‐regulation of upstream JNK/pJNK and down‐stream caspase‐3 in the target cells. Taken together, the above findings indicate that NAC counteracted the oxidative stress in Leydig cells induced as a result of repeated hCG stimulation, and inhibited apoptosis by mainly regulating the extrinsic and JNK pathways of metazoan apoptosis. Mol. Reprod. Dev. 77:900–909, 2010. © 2010 Wiley‐Liss, Inc.
Broadening the spectrum of controls for skin biopsy in painful neuropathies
Authors: Herrmann David N. , O'Connor Alec B. , Schwid Steven R. , DA Yuwei , Goodman Andrew D. , Rafferty Jennifer , Donahue Suzanne , Dworkin Robert H.
Published: September 2010

Epidermal nerve fiber density (ENFD) is useful in the evaluation of small‐fiber neuropathies (SFSNs). A recent evidence‐based review highlighted the need to broaden the spectrum of ENFD controls to include lower limb pain states other than polyneuropathy. We studied epidermal innervation in multiple sclerosis (MS) and distal lower limb burning pain (DLLBP). Distal‐leg ENFD/morphology in MS DLLBP patients did not differ significantly from that of healthy controls. This study extends the range of ENFD controls and further supports use of ENFD assessment in SFSN. Muscle Nerve, 2010
Proposal for a modified grading system based on mitotic index and Bcl2 provides objective determination of clinical outcome for patients with breast cancer
Authors: Abdel‐Fatah Tarek MA , Powe Desmond G , Ball Graham , Lopez‐Garcia Maria A , Habashy Hany O , Green Andrew R , Reis‐Filho Jorge S , Ellis Ian O
Published: September 2010

We hypothesized that the interaction between mitotic index (M) and Bcl2 could accurately discriminate between low‐ and high‐grade breast cancer (BC) and provide a more objective measure of clinical outcome than histological grade, especially for patients with intermediate histological grade (G2), small size or oestrogen receptor (ER)‐negative cancers. A well‐characterized series of 1650 BCs with long‐term follow‐up was subjected to immunohistochemical analysis for Bcl2. Mitotic index (M) was assessed according to Nottingham Grading System (NGS) guidelines: M1: < 10 mitoses; M2: 10–18 mitoses; M3: > 18 mitoses. Results were validated in an independent series of patients (n = 245) uniformly treated with adjuvant anthracycline‐based chemotherapy. Subsequently, BCs were classified according to the combined M/Bcl2 profile and compared with NGS. Multivariate Cox regression models using validated prognostic factors demonstrated that the subgroups defined by M/Bcl2 profile remained significantly associated with patients' outcome but also performed better than lymph node status and tumour size. Incorporation of the M/Bcl2 profile into the Nottingham Prognostic Index (NPI) reclassified twice as many patients into the excellent prognosis group, potentially improving decision‐making and sparing patients unneeded systemic adjuvant therapy. Patients with M2–3/Bcl2− and M3/Bcl2+ (high risk) had a two‐ to three‐fold increased risk of recurrence when treated with either adjuvant hormone therapy or anthracycline‐based chemotherapy compared with those with M1/Bcl2 ± and M2/Bcl2+ (low risk) [HR = 3.4 (2.8–5.6); p < 0.0001 and HR = 2.3 (1.2–4.3); p = 0.0009]. In conclusion, a grading system defined by mitotic counting and Bcl2 expression accurately reclassified patients with NGS‐G2, small tumour size or ER‐negative cancers into two groups: low risk (NGS‐G1‐like) versus high risk (NGS‐G3‐like) of BC mortality and recurrence, improving prognosis and therapeutic planning. Copyright © 2010 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.
Validated TLC method for simultaneous quantitation of kutkoside and picroside‐I from Kutki extract
Authors: Gaikwad P. S. , Bhope S. G. , Kuber V. V. , Patil M. J.
Published: September 2010

Introduction – The two iridoid glycosides kutkoside and picroside‐I are the active hepatoprotective principles of Picrorhiza kurroa Royle ex Benth (Scrophulariaceae), commonly known as Kutki. Quantitation of these phytoconstituents is important for the routine quality control of Kutki extract.

Objective – To develop and validate a simple, precise and rapid thin‐layer chromatography (TLC) method for the simultaneous quantitation of kutkoside and picroside‐I in Kutki extract.

Methodology – The analysis was performed on a TLC precoated silica gel 60 F254 plate with ethyl acetate:methanol:glacial acetic acid:formic acid (25:5:1:1, v/v/v/v) as mobile phase. Densitometric evaluation of kutkoside and picroside‐I was carried out at 265 nm and the mobile phase showed good resolution with Rf values 0.42 ± 0.03 and 0.61 ± 0.03 for kutkoside and picroside‐I, respectively. The method was validated in terms of specificity, linearity, accuracy and precision.

Results – The content of kutkoside and picroside‐I was found to be 2.18 and 1.90%, respectively, and was comparable with those obtained by HPLC. The linearity was found to be in the range of 80–480 ng/spot for both kutkoside and picroside‐I. The average recovery values were found to be 96.5 and 96.0% for kutkoside and picroside‐I, respectively.

Conclusion – The developed method was found to be relatively simple, precise and reproducible for the simultaneous quantitation of kutkoside and picroside‐I. The method does not employ any derivatisation procedure and can be used as a quality control tool for the routine analysis of commercial Kutki extracts. Copyright © 2010 John Wiley & Sons, Ltd.
Synchronous fluorescence determination of phytic acid in FOODSTUFFS and urine based on replacement reaction
Authors: Cao Shuhong , Dong Nian , Chen Jingwen
Published: September 2010

Introduction – Phytic acid is a ubiquitous and abundant natural component in many plant seeds, fruits and vegetables. Its biological and pharmaceutical functions are still controversial. The examination on the level of phytic acid in foodstuffs and urine can provide valuable information for its dietary intake and metabolism.

Objective – To develop a sensitive and reliable synchronous fluorescence protocol for determination of phytic acid in selected foodstuffs and human urine.

Methodology – Phytic acid efficiently catches Cu2+ ion in previously prepared CuII‐2,2′‐bipyridine complex in aqueous solution, releasing the fluorescent 2,2′‐bipyridine molecule and recovering synchronous fluorescence. The recovered fluorescence is proportional to the added phytic acid, by which the levels of phytic acid in the selected foodstuffs and human urine are quantified.

Results – A calibration curve with a regression equation of If = 37.745 + 39.245c (R2 > 0.9988) showed good linearity over the range 0.18–17.50 mg/L phytic acid. The relative standard deviation at 95% confidence degree was less than 2.04% (n = 5), indicating that the procedures are reproducible. The detection and quantification limit of phytic acid were estimated to be 0.12 and 0.18 mg/L, respectively. By the proposed method, phytic acid in the selected foodstuffs and urine was determined to be 3.25–16.76 and 0.43–1.21 mg/L with recoveries of 96.8%–105.6% and 95.1%–104.2%, respectively. The results are in good agreement with those obtained by the reported HPLC technique.

Conclusion – The developed method is sensitive, reliable and economical, which permits its practical application in quantitative analyses of trace phytic acid in foodstuffs and urine. Copyright © 2010 John Wiley & Sons, Ltd.
Carbon dioxide‐induced crystallization in poly(L‐lactic acid) and its effect on foam morphologies
Authors: Liao Xia , Nawaby Arghavan Victoria , Whitfield Pamela S
Published: September 2010

The effect of carbon dioxide (CO2) on the physical properties of poly(L‐lactic acid) (PLLA) and on the formation of crystalline domains was investigated. The presence of CO2 in the matrix was found to induce crystallization in PLLA, with the crystallinity increasing with increasing CO2 pressure. The combination of saturation conditions and formation of crystalline domains was studied for its effect on the formation of porous morphologies in PLLA. Moreover, the effect of CO2 on PLLA properties and formation of porous structures was further exploited by first creating crystalline domains in samples using CO2 at various pressures at 25 °C and then re‐saturating the same samples with CO2 at a constant pressure of 2.8 MPa and 0 °C. This paper reports on the solubility of CO2 at 25 and 0 °C in PLLA, crystallization and subsequent effect on foam morphologies when processed using different saturation cycles. Unique and intriguing morphologies were obtained by specifically controlling the properties of PLLA. Copyright © 2010 Crown in the right of Canada. Published by John Wiley & Sons, Ltd
Ionic polymers with expanded π‐conjugation systems derived from through‐space interaction in piperazinium and homopiperazinium rings
Authors: Yamaguchi Isao , Matsuda Yukari , Sato Moriyuki
Published: September 2010

Reactions of N‐(2,4‐dinitrophenyl)‐4‐arylpyridinium chlorides (aryl (Ar) = phenyl and 4‐biphenyl) with piperazine or homopiperazine caused opening of the pyridinium ring and yielded polymers that consisted of 5‐piperazinium‐3‐arylpenta‐2,4‐dienylideneammonium chloride (N(CH2CH2)2N+ (Cl−)CHCHC(Ar)CHCH) or 5‐homopiperazinium‐3‐arylpenta‐2,4‐dienylideneammonium chloride (N(CH2CH2CH2)(CH2CH2)N+ (Cl−)CHCHC(Ar)CHCH) units. 1H NMR spectral analysis suggested that the π‐electrons of the penta‐2,4‐dienylideneammonium group of the polymers were delocalized. UV‐visible spectral measurements revealed that the π‐conjugation system expanded along the polymer chains because of the orbital interaction between electrons of the two nitrogen atoms of the piperazinium and homopiperazinium rings. However, the π‐conjugation length depended on the distance between the two nitrogen atoms; that is, the polymers containing the piperazinium ring had a longer π‐conjugation length than those containing the homopiperazinium ring. Conversion of the piperazinium and homopiperazinium rings from the boat to the chair form led to a decrease in the π‐conjugation length. The surface of pellets that were molded from the polymers exhibited metallic luster, and these polymers underwent electrochemical oxidation in solution. Copyright © 2010 Society of Chemical Industry
Synthesis of hybrid nanocomposites based on new triazeno copolymers and montmorillonite used for detecting metal ions
Authors: Melinte Violeta , Buruiana Tinca , Tampu Daniel , Buruiana Emil C
Published: September 2010

The modern synthesis of novel functional materials with improved properties includes that of hybrid nanocomposites composed of inorganic nanoparticles and organic derivatives, where controlling the molecular structure at atomic and macroscopic dimensions is a key factor, with a major effect on performance. An extension of this approach to the field of nanocomposites containing photopolymers with triazene groups attached on a methacrylic backbone could be of great interest in the future development of chemosensors and photoresists, among others. Photopolymer/clay nanocomposites were prepared by in situ free radical copolymerization of 1‐(phenyl)‐3‐(2‐methacryloyloxyethylcarbamoyloxyethyl)‐3‐methyltriazene‐1 or 1‐(p‐methoxyphenyl)‐3‐(2‐methacryloyloxyethylcarbamoyloxyethyl)‐3‐methyltriazene‐1 and vinyl acetate or styrene in solution and in the presence of 3 and 5 wt% of organically modified montmorillonite. The characterization of the nanocomposites and pure copolymers was achieved through 1H NMR and Fourier transform infrared spectroscopy, gel permeation chromatography, thermogravimetric analysis, X‐ray diffraction, atomic force microscopy and fluorescence analysis. The morphologies and properties of the nanocomposites are dependent on the nature of the triazene, on the co‐monomer structure and on the organoclay content. Also, the fluorescence response of these nanocomposites towards certain metal ions (Fe3+, Cu2+, Hg2+, Ni2+) in dimethylformamide solution was investigated. The effect of uranyl ions on the fluorescence intensity of the nanocomposites in solution or as films could be exploited in the development of ‘turn‐off’ or ‘turn‐on’ chemosensors for this type of analyte. Triazeno copolymer/organophilic montmorillonite nanocomposites with exfoliated (not completely exfoliated) or exfoliated and intercalated structures exhibit distinct characteristics concerning their fluorescence behaviour, a higher sensing ability towards certain target compounds (Fe3+, UO22+) being evidenced for those incorporating 3 wt% organoclay in solution and as films. Copyright © 2010 Society of Chemical Industry
Preparation and properties of one‐pack polybenzoxazine‐modified polyurethanes with improved thermal stability and electrical insulating properties
Authors: Jamshidi Sadegh , Yeganeh Hamid , Mehdipour‐Ataei Shahram
Published: September 2010

A novel method has been developed for the combination of polyurethanes and polybenzoxazines. For this purpose, firstly, p‐nitrophenol blocked polyurethanes (BPUs) were prepared via the reaction of poly(tetramethylene ether) glycol of various molecular weights, 2,4‐tolylene diisocyanate and p‐nitrophenol. The BPUs were then mixed with 2,2‐bis(3,4‐dihydro‐3‐phenyl‐2H‐1,3‐benzoxazine)propane (Ba) at various weight ratios. To prepare poly(urethane‐co‐benzoxazine) networks, the BPU/Ba mixtures were subjected to a heating programme derived from detailed differential scanning calorimetry and gel content measurements. Results showed about 30 to 40 °C reduction of polymerization temperature for complete curing of BPU/Ba mixtures in comparison to neat Ba. This phenomenon was related to catalytic action of librated p‐nitrophenol molecules. The thermal, mechanical, viscoelastic and electrical properties of prepared thermoset polymers were measured and correlated with their chemical structures. A significant improvement of thermal stability and dielectric strength in comparison to neat polyurethanes was found. Also, enhancement of tensile properties, ease of curing and ability to be transformed into thin films are fascinating features of these newly developed materials in comparison to neat polybenzoxazines. Therefore, these polymers have potential applicability as high‐performance materials in modern electrical industries. Copyright © 2010 Society of Chemical Industry
Thermo‐ and pH‐sensitive hydrogels based on 2‐(2‐methoxyethoxy)ethyl methacrylate and methacrylic acid
Authors: París Rodrigo , García José , Quijada‐Garrido Isabel
Published: September 2010

Hydrogels based on commercially available 2‐(2‐methoxyethoxy)ethyl methacrylate (MEO2MA), with methacrylic acid (MAA) as comonomer, are studied. The incorporation of an ionizable monomer, such as MAA, in a thermosensitive system leads to the formation of hydrogels able to respond to pH and temperature according to their monomeric composition. Thus, at low pH, the acid groups of MAA are protonated, and they do not contribute to increase the hydrophilic balance, and collapse of the hydrogels occurs around room temperature. For temperatures below that of collapse, the degree of swelling increases with increasing MEO2MA content. In contrast, at neutral or basic pH, the ionization of the acid groups contributes to increase the hydrophilicity and the osmotic pressure, leading to polyelectrolyte behaviour. In this regime, the swelling capacity increases and the thermosensitivity decreases with increasing MAA content in the hydrogels. These properties make poly(MEO2MA‐co‐MAA) hydrogels suitable candidates for use in oral controlled delivery of hydrophobic drugs. This possibility is explored using ibuprofen as a model drug, after a complete study of the swelling kinetics. Copyright © 2010 Society of Chemical Industry
Integrated data management and validation platform for phosphorylated tandem mass spectrometry data
Authors: Lahesmaa‐Korpinen Anna‐Maria , Carlson Scott M. , White Forest M. , Hautaniemi Sampsa
Published: September 2010

MS/MS is a widely used method for proteome‐wide analysis of protein expression and PTMs. The thousands of MS/MS spectra produced from a single experiment pose a major challenge for downstream analysis. Standard programs, such as MASCOT, provide peptide assignments for many of the spectra, including identification of PTM sites, but these results are plagued by false‐positive identifications. In phosphoproteomic experiments, only a single peptide assignment is typically available to support identification of each phosphorylation site, and hence minimizing false positives is critical. Thus, tedious manual validation is often required to increase confidence in the spectral assignments. We have developed phoMSVal, an open‐source platform for managing MS/MS data and automatically validating identified phosphopeptides. We tested five classification algorithms with 17 extracted features to separate correct peptide assignments from incorrect ones using over 2600 manually curated spectra. The naïve Bayes algorithm was among the best classifiers with an AUC value of 97% and PPV of 97% for phosphotyrosine data. This classifier required only three features to achieve a 76% decrease in false positives as compared with MASCOT while retaining 97% of true positives. This algorithm was able to classify an independent phosphoserine/threonine data set with AUC value of 93% and PPV of 91%, demonstrating the applicability of this method for all types of phospho‐MS/MS data. PhoMSVal is available at http://csbi.ltdk.helsinki.fi/phomsval.
Amphiphilic polymer conetworks prepared by controlled radical polymerization using a nitroxide cross‐linker
Authors: Zhao Weijie , Fang Ming , He Junpo , Chen Junyu , Tang Wei , Yang Yuliang
Published: September 2010

Tandem atom transfer radical polymerization (ATRP) and nitroxide‐mediated radical polymerization (NMRP) were used to synthesize a polystyrene‐co‐poly(acrylic acid) (poly(St‐co‐AA)) network, in which the two components were interconnected by covalent bond. First, a specific cross‐linker, 1,4‐bis(1′‐(4″‐acryloyloxy‐2″,2″,6″,6″‐tetramethylpiperidinyloxy)ethyl)benzene (di‐AET), a bifunctional alkoxyamine possessing two acrylate groups, was copolymerized with tert‐butyl acrylate through ATRP to prepare a precursor gel. The gel was then used to initiate the NMRP of styrene to prepare poly(St‐co‐(t‐BA)) conetwork, in which the cross‐linkages are composed of polystyrene segments. Finally, the poly(St‐co‐(t‐BA)) conetwork was hydrolyzed to produce amphiphilic poly(St‐co‐AA) conetwork. The resulting gels show swelling ability in both organic solvent and water, which is characteristic of amphiphilic conetworks. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 4141–4149, 2010
Combination of radical and cationic photoprocesses for the single‐step synthesis of organic‐inorganic hybrid films
Authors: Belon Cindy , Chemtob Abraham , Croutxé‐Barghorn Céline , Rigolet Séverinne , Le Houérou Vincent , Gauthier Christian
Published: September 2010

Nanocomposite materials prepared from radically photocurable hybrid sol–gel precursors have been widely developed within the last decade, especially to devise novel optical devices and coatings. For their synthesis, a preferential route has involved in the successive sol–gel process of acrylate trialkoxysilane precursors followed by radical photopolymerization. In contrast, this work presents an original one‐step synthesis based on the association of two different photoinitiators (PIs) in the same formulation: the photolysis of a hydroxyphenylketone (radical PI) affords polyacrylate chains while that of a diaryl iodonium salt (cationic PI) generates powerful superacids catalyzing the sol–gel reactions of the alkoxy functions. The behavior of methacrylate and acrylate trimethoxysilane precursors was compared to highlight the effect of the organic moiety functionality on the reaction kinetics (Fourier transform infrared spectroscopy) and the film microstructure (13C and 29Si solid‐state nuclear magnetic resonance). Interestingly, evidence of local organization in these hybrid films was also given by X‐ray analysis. In a last part, their thermomechanical properties were discussed thoroughly using a range of techniques: DSC, scratch‐resistance test, nanoindentation. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 4150–4158, 2010
Poly(propylene glycol)‐based ammonium ionenes as segmented ion‐containing block copolymers
Authors: Tamami Mana , Williams Sharlene R. , Park Jong Keun , Moore Robert B. , Long Timothy E.
Published: September 2010

The synthesis and characterization of series of segmented poly(propylene glycol) (PPG)‐based ammonium ionenes is described. Bromine end‐capped oligomers were successfully synthesized using the reaction of 6‐bromohexanoyl chloride with 1000, 2000, and 4000 g/mol PPGs. 1H NMR spectroscopy, titration studies, and matrix‐assisted laser desorption ionization‐time of flight (MALDI‐TOF) mass spectrometry revealed the difunctionality of the oligomers. First, a series of PPG‐based ammonium ionenes was synthesized from bromine end‐capped PPG oligomers and N,N,N′,N′‐tetramethyl‐1,6‐hexanediamine. For this series, a single glass transition temperature (Tg) of approximately −66 °C was observed through differential scanning calorimetry (DSC); dynamic mechanical analysis (DMA) showed the onset of flow ranged from 20 to 80 °C. In addition, a series of PPG‐based ammonium ionenes containing 1,12‐dibromododecane was synthesized to increase the aliphatic hard segment (HS) content and enhance the mechanical properties of the resulting materials. For these, two Tg's were observed using DMA; DMA also showed the onset of flow of ionenes containing higher HS content (33 wt %) occurred in the range of 100–140 °C. Tensile analysis for these ionenes demonstrated an average tensile strength at break ranging from 0.2 to 2.4 MPa. Small angle X‐ray scattering (SAXS) profiles for these ionenes showed that Bragg distances increase linearly with the molecular weight of PPG soft segment. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 4159–4167, 2010
Copolymerization of ethylene with isoprene promoted by titanium complexes containing a tetradentate [OSSO]‐type bis(phenolato) ligand
Authors: Capacchione Carmine , Saviello Daniela , Avagliano Antonietta , Proto Antonio
Published: September 2010

Copolymerization of ethylene with isoprene (IP) catalyzed by 1,4‐dithabutanediyl‐linked bis(phenolato) titanium complexes 1 and 2 and methylaluminoxane (MAO) produced exclusively ethylene‐IP copolymers with good activity. The copolymer microstructure can be varied by changing the ratio between the monomers in the copolymerization feed, affording copolymers with IP content ∼60%. The copolymer microstructure was fully elucidated by 13C‐NMR spectroscopy of the copolymers with various IP content revealing a strong tendency to the alternating microstructure. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 4200–4206, 2010
“Click polyester”: Synthesis of polyesters containing triazole units in the main chain via safe and rapid “click” chemistry and their properties
Authors: Nagao Yu , Takasu Akinori
Published: September 2010

Click Cu(I)‐catalyzed polymerizations of diynes that contained ester linkages and diazides were performed to produce polyesters (click polyesters) of large molecular weights [(∼1.0–7.0) × 104], that contained main‐chain 1,4‐disubstitued triazoles in excellent yields. Incorporation of triazole improved the thermal properties and magnified the even‐odd effect of the methylene chain length. We also found that, by changing the positions of the triazole rings, the thermal properties of the polyesters could be controlled. The use of in situ azidation was a safe reaction, as explosive diazides are not used. In addition, the microwave heating was found to accelerate the polymerization rates. This is the first study that has applied click chemistry for the synthesis of a series of polyesters. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 4207–4218, 2010
The cyanine dye/trichloromethyl‐1,3,5‐triazine/thiols in two‐ and three‐component photoinitiating systems for free radical polymerization
Authors: Kabatc Janina
Published: September 2010

The new photoinitiating systems for free radical polymerization of multifunctional monomers composed of carbocyanine dye, 1,3,5‐triazine derivative and heteroaromatic mercaptan were described. It was shown, that the polymerization abilities of such photoinitiatng systems are comparable with those observed for well‐known cyanine borate two‐component photoinitiating systems. The fluorescence quenching rate constants of tested sensitizer was about 2 × 1010 M−1s−1. Basing on the results of laser flash photolysis, the mechanism of the photochemical reactions occuring in the three‐component photoinitiating system was proposed. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 4243–4251, 2010
Thermo‐responsive fluorescent micelles from amphiphilic A3B miktoarm star copolymers prepared via a combination of SET‐LRP and RAFT polymerization
Authors: Zhang Weidong , Zhang Wei , Zhang Zhengbiao , Cheng Zhenping , Tu Yingfeng , Qiu Yansheng , Zhu Xiulin
Published: September 2010

A novel amphiphilic A3B miktoarm star copolymer poly(N‐isopropylacrylamide)3‐poly(N‐vinylcarbazole) ((PNIPAAM)3(PVK)) was successfully synthesized by a combination of single‐electron transfer living radical polymerization (SET‐LRP) and reversible addition‐fragmentation chain transfer (RAFT) polymerization. First, the well‐defined three‐armed poly(N‐isopropylacrylamide) (PNIPAAM)3 was prepared via SET‐LRP of N‐isopropylacrylamide in acetone at 25 °C using a tetrafunctional bromoxanthate iniferter (Xanthate‐Br3) as the initiator and Cu(0)/PMDETA as a catalyst system. Secondly, the target amphiphilic A3B miktoarm star copolymer ((PNIPAAM)3(PVK)) was prepared via RAFT polymerization of N‐vinylcarbazole (NVC) employing (PNIPAAM)3 as the macro‐RAFT agent. The architecture of the amphiphilic A3B miktoarm star copolymers were characterized by GPC, 1H‐NMR spectra. Furthermore, the fluorescence intensity of micelle increased with the temperature and had a good temperature reversibility, which was investigated by dynamic light scattering (DLS), fluorescent and UV‐vis spectra. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 4268–4278, 2010
Synthesis and hydrolytic degradation of stereoregular aromatic poly(ester amide)s derived from D‐xylose
Authors: Pinilla Inmaculada Molina , Martínez Manuel Bueno , Galbis Juan A.
Published: September 2010

Stereoregular poly(ester amide)s (PEAs) were prepared by the polycondensation method using naturally occurring D‐xylose and aromatic diacids as the starting materials. The polymers were characterized by elemental analysis, GPC, IR, and 1H‐ and 13C NMR spectroscopies. Thermal and X‐ray diffraction studies revealed them to be mainly amorphous. The polymers are hydrophilic and their degradation studies were carried out at 37 and 80 °C in buffered salt solution at pH 8. The degradation study was monitored by mass loss, GPC, IR, and NMR spectroscopies. The hydrolytic degradation of these PEAs occurred rapidly by hydrolysis of the ester functions to a final compound, which maintained the amide functions. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010
Hybrid organic/inorganic epoxy resins prepared by frontal polymerization
Authors: Scognamillo Sergio , Alzari Valeria , Nuvoli Daniele , Mariani Alberto
Published: September 2010

The syntheses of hybrid epoxy resins made from different ratios among bisphenol‐A diglycidyl ether, 3‐glycidoxypropyltrimethoxysilane (GPTMS), and diethylenetriamine were successfully performed by using frontal polymerization. Conversions were always almost quantitative, and, because of the use of this alternative convenient technique, materials were prepared in very short times. Samples were characterized by DSC, TGA, IR spectroscopy, and solvent extraction. It was found that those materials containing a relatively high‐Si amount exhibit two different transition temperatures, with the highest one that increases as the content of GPTMS raises. The analogies and the differences with the analogous samples prepared by the classical batch technique are discussed. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010
Synthesis, photoluminescence, and electrochromism of polyamides containing (3,6‐di‐tert‐butylcarbazol‐9‐yl)triphenylamine units
Authors: Wang Hui‐Min , Hsiao Sheng‐Huei , Liou Guey‐Sheng , Sun Chieh‐Hsiang
Published: September 2010

A new carbazole‐derived, triphenylamine (TPA)‐containing aromatic dicarboxylic acid monomer, 4,4′‐dicarboxy‐4″‐(3,6‐di‐tert‐butylcarbazol‐9‐yl)TPA, was synthesized, and it led to a series of electroactive aromatic polyamides with main‐chain TPA and pendent 3,6‐bis(tert‐butyl)carbazole units by reacting it with various aromatic diamines via the phosphorylation polyamidation technique. The polyamides were amorphous with good solubility in many organic solvents and could be solution‐cast into flexible and strong films. They showed high glass‐transition temperatures (282–335 °C) and high thermal stability (10% weight loss temperatures >480 °C). The electroactive polymer films had well‐defined and reversible redox couples with good cycle stability in acetonitrile solutions. The polymer films also exhibited fluorescent and multielectrochromic behaviors. The anodically electrochromic polyamide films had moderate coloration efficiency (∼100 cm2/C) and high optical contrast ratio of transmittance change (Δ%T) up to 47% at 813 nm and 48% at 414 nm for the green coloring. After hundreds of cyclic switches, the polymer films still retained good redox and electrochromic activity. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010
Oxidation of cellulose fibers mediated by nonpersistent nitroxyl radicals
Authors: Biliuta Gabriela , Fras Lidija , Strnad Simona , Harabagiu Valeria , Coseri Sergiu
Published: September 2010

Three different nonpersistent radicals bearing >NO• moiety have been used to oxidize the viscose fibers at room temperature and alkaline pH. The generation of the free radical species was achieved in situ, from their corresponding OH precursors: 1‐hydroxybenzotriazole, violuric acid, and N‐hydroxy‐3,4,5,6‐tetraphenylphthalimide. Three different routes were used: (i) in the presence of metallic cocatalyst (lead tetraacetate), (ii) under metal‐free conditions (anthraquinone as organic cocatalyst), and (iii) a homolytically scission of OH bond through a 365‐nm UV irradiation. The oxidized fibers were subjected to attenuated total reflection FTIR characterization, potentiometric titration, wide angle X‐ray, energy dispersive X‐ray analyses, microscopic investigations, and solid‐state 13C‐NMR. The patterns of CP/MAS 13C‐NMR spectra revealed that the oxidation occurred at the C6 primary hydroxyl groups of cellulose. Notably, as a result of the introduction of hydrophilic carboxylate groups, the water retention values of the oxidized fibers increased by 35% as compared to the original nonoxidized sample. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010
Mechanism of generation of photoelastic birefringence in methacrylate polymers for optical devices
Authors: Shafiee Houran , Tagaya Akihiro , Koike Yasuhiro
Published: September 2010

We clarified the birefringence properties of poly(methyl methacrylate), poly(ethyl methacrylate), poly(isobutyl methacrylate), poly(cyclohexyl methacrylate), poly(isopropyl methacrylate), and poly(tert‐butyl methacrylate). We demonstrated that the conformational change in polymer molecules that causes orientational birefringence differs from that causing photoelastic birefringence. Orientational birefringence depends mainly on the orientation of the main chains of the methacrylate polymers above Tg. On the other hand, photoelastic birefringence in elastic deformation below Tg depends mainly on the orientation of the side chains while the main chains are scarcely oriented. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 2029–2037, 2010
Optical and two‐photon absorption analysis of radiation‐grafted fluoropolymer
Authors: El‐Diasty Fouad , Aly E. Hassan , El‐Sawy N. M.
Published: September 2010

Grafting by gamma irradiation has a significant influence on the dispersion properties of polymeric materials. Accordingly, we study the effect of grafting on the material electronic structure parameters such as the fundamental absorption edge and bandgap structure. The optical absorption of grafted polymeric films of poly(tetrafluoroethylene‐co‐perfluorovinyl ether) (PFA‐g‐PAAc) is determined in a very wide spectral range of 0.2–3 μm. The nonlinear two‐photon absorption coefficient is determined that showed an increase as a result to the grafting process. Moreover, a significant increase in the optical conductivity for the polymeric films is acquired after grafting. Positron annihilation spectroscopy is used to study polymer structure and volume size of nanoholes of Ps. The data revealed an increase of crosslinking with a smaller average volume size with grafting. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 2045–2051, 2010
pH‐responsive photoluminescence properties of a water‐soluble copolymer containing quinoline groups in aqueous solution
Authors: Kalogianni Aliki , Pefkianakis Eleftherios , Stefopoulos Andreas , Bokias Georgios , Kallitsis Joannis K.
Published: September 2010

The synthesis of a water‐soluble copolymer containing quinoline groups, P(DMAM‐co‐SDPQ), through free radical copolymerization of N,N‐dimethylacrylamide, DMAM, with 2,4‐diphenyl‐6‐(4‐vinylphenyl)quinoline, SDPQ, is presented and the optical properties of the final product are investigated in aqueous solution as a function of pH. It is found that the emission peak of SDPQ is red‐shifted from 411 to 484 nm with decreasing pH, due to the protonation of quinoline groups at low pH, suggesting that this copolymer may function as a luminescent pH‐indicator. Moreover, the copolymer exhibits the characteristics of a luminescent pH‐detector within the pH range 2 < pH < 4, as in this pH region the ratio of the emission intensity at 411 nm over that at 484 nm changes linearly in a logarithmic scale with the pH of the solution. Finally, the formation of less polar quinoline clusters in the aqueous P(DMAM‐co‐SDPQ) solution upon increasing pH was detected through Nile red probing. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 2078–2083, 2010
Role of matrix crystallinity in carbon nanotube dispersion and electrical conductivity of iPP‐based nanocomposites
Authors: Jeon Keesu , Warnock Stephen , Ruiz‐Orta Carolina , Kismarahardja Ade , Brooks James , Alamo Rufina G.
Published: September 2010

A homopolymer iPP and a series of propylene‐ethylene random copolymers with a content of ethylene from 7 to 21 mol % were used as matrices to prepare single‐walled carbon nanotube (SWCNT) nanocomposites in a range of SWCNT concentration from 0.15 to 1 wt %. The solution blending and melt‐ compression molding procedures were kept identical for all nanocomposites. The poly(propylenes) have crystallinities ranging from 70 to 10%, and serve to test the role of SWCNTs acting as nucleants to preserve in the nanocomposites the uniform dispersion of SWCNTs after sonication. The major role of polymer crystallinity is to mediate toward a more open and more connected SWCNT network structure. Fast nucleation and growth of high crystalline matrices on multiple sites along the surface of the nanotubes prevents SWCNT clustering, and entraps the SWCNT network between the semicrystalline structure reducing the driving force of nanotubes to curl and twist. Depletion of crystallites in the less crystalline matrices (<35% crystallinity) leads to curled and poorly connected nanotubes. A consequence of the gradual loss of SWCNT connectivity is a decreased electrical conductivity; however, the change with crystallinity is not linear. Conductivity decreases sharply with decreasing crystallinity for SWCNT contents near the percolation region, while for contents approaching the plateau region the electrical conductivity is less sensitive to matrix crystallinity. The percolation threshold decreases rapidly for polymers with <∼30% crystallinity and slowly levels off at crystallinities >∼40%. At SWCNT concentrations of 0.15 wt %, SEM images of nanocomposites with the highest crystallinity matrix indicate debundled and interconnected nanotubes, whereas more disconnected and curled SWCNTs remain in the lowest crystallinity nanocomposites. Electrical conductivity in the former is relatively high, whereas the latter are insulators. Also discussed is the nucleating effect of nanotubes and restrictions of the filler to polymer chain diffusion in the crystallization of the polymers. SEM images and Raman spectra in the radial breathing modes region (100–400 cm−1) are complementary tools to extract the quality and details of the SWCNT dispersion in the nanocomposites. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 2084–2096, 2010
A molecular dynamics simulation study of three polysulfones in dry and hydrated states
Authors: Marque Grégory , Verdu Jacques , Prunier Valéry , Brown David
Published: September 2010

Molecular dynamics (MD) simulations of three polysulfones (poly(ether sulfone) PESU, poly(phenylene sulfone) PPSU and polysulfone PSU) in dry and hydrated states were undertaken in order to study the specific interactions between water and glassy polymer matrices of the same structural family. Dry polysulfone models were generated using a hybrid pivot Monte Carlo‐MD single‐chain sampling technique and the resulting relaxed densities were found to be in close agreement with experimental data. Hydrated systems are found to reproduce quite well volumetric changes experimentally observed. The concentrations of sulfonic groups can explain qualitatively their different water solubilities. Water is preferentially hydrogen‐bonded to two sites which either link two polymer sites, or one polymer site and another water, or two other waters. A detailed analysis of these water bridges that are formed is presented. Only a small quantity of potential bridging sites are occupied for water contents near the experimental saturation. The free fractional volumes, the probe accessible volumes, the swelling of the polymers, the water‐polymer interactions and the hydrogen bond lifetimes, are also presented for these polysulfones. Water‐water interactions and water clusters are found to be more important in the more hydrophilic PESU in comparison to the less hydrophilic PSU. © 2010 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2010
Conformational regulation of the EGFR kinase core by the juxtamembrane and C‐terminal tail: A molecular dynamics study
Authors: Mustafa Morad , Mirza Amar , Kannan Natarajan
Published: September 2010

The catalytic domain of epidermal growth factor receptor (EGFR) is activated by dimerization, which requires allosteric coupling between distal dimerization and catalytic sites. Although crystal structures of EGFR kinases, solved in various conformational states, have provided important insights into EGFR activation by dimerization, the atomic details of how dimerization signals are dynamically coupled to catalytic regions of the kinase core are not fully understood. In this study, we have performed unrestrained and targeted molecular dynamics simulations on the active and inactive states of EGFR, followed by principal component analysis on the simulated trajectories, to identify correlated motions in the EGFR kinase domain upon dimerization. Our analysis reveals that the conformational changes associated with the catalytic functions of the kinase core are highly correlated with motions in the juxtamembrane (JM) and C‐terminal tail, two flexible structural elements that play an active role in EGFR kinase activation and dimerization. In particular, the opening and closing of the ATP binding lobe relative to the substrate binding lobe is highly correlated with motions in the JM and C‐terminal tail, suggesting that ATP and substrate binding can be coordinated with dimerization through conformational changes in the JM and C‐terminal tail. Our study pinpoints key residues involved in this conformational coupling, and provides new insights into the role of the JM and C‐terminal tail segments in EGFR kinase functions. Proteins 2010. © 2010 Wiley‐Liss, Inc.
Hydrolysis of organophosphate compounds by mutant butyrylcholinesterase: A story of two histidines
Authors: Amitay Moshe , Shurki Avital
Published: September 2010

This study is aimed at understanding the hydrolysis mechanism of organophosphate (OP) compounds by G117H‐BChE. It is a theoretical study that focuses on the role of the G117H mutation in the dephosphorylation step. Various proposed mechanisms are examined. We show that His117 acts as a general base by activating a water molecule, and thus assisting its nucleophilic attack on the phosphate. The calculated reaction energy profile agrees well with the experimental data. Moreover, analysis of the reaction via its two hypothetical elementary steps, proton transfer and hydroxide attack, supports the role of His117 as a general base. Further support to the proposed mechanism is gained by structural comparison of the active site to RNAse A, which has similar composition of substrate and functional groups. The similarity between these enzymes extends beyond the structure and also becomes evident when comparing functionality of various active sites residues as well as rate–pH dependence obtained in the two cases. Moreover, it is demonstrated that an extended form of Bevilacqua's model (Biochemistry 2003;42:2259–2265) may resolve the apparent contradictions between the proposed mechanism and various experimental observations regarding rate–pH dependence. Finally, that same model is shown to rationalize the hydrolase activity of G117D BChE, an observation which is considered puzzling. It is concluded that G117H‐BChE hydrolyzes echothiophate and possibly other OP compounds via a general acid–base mechanism. On the basis of this mechanism, one can now proceed with rational design aimed at improving the enzyme by exploiting both the structural and mechanistic knowledge. Proteins 2011. © 2010 Wiley‐Liss, Inc.
Self‐organized TiO2 nanotubes: Factors affecting their morphology and properties
Authors: Berger Steffen , Hahn Robert , Roy Poulomi , Schmuki Patrik
Published: September 2010

Self‐organized oxide nanostructures grown by controlled anodic oxidation of a metal substrate attracted wide scientific interest due to a broad number of potential applications. The present work gives an overview on growth principles and mechanistic aspects of self‐organized TiO2 nanotubular layers and related transition metal oxide nanostructures. In particular, key electrochemical factors that control tube geometry and routes to fabricate advanced TiO2 nanotube geometries and morphologies are discussed.
Effect of localized states on internal quantum efficiency of III‐nitride LEDs
Authors: Karpov Sergey Yu.
Published: September 2010

A model is suggested accounting for effects of localized electron and hole states formed by composition fluctuations in the InGaN active region of a III‐nitride LED on non‐radiative carrier recombination at threading dislocations. The model enables explanation of the abnormal temperature dependence of internal quantum efficiency (IQE) of a green LED structure recently observed at low current densities. The theoretical predictions are in quantitative agreement with experiment in the temperature range between 200 K and 453 K. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)