bluuebunny/crossref_metadata_2025_split huggingface dataset:
What governs nitrogen configuration in substituted aminophosphines?
Authors: Wodrich Matthew D. , Vargas Alfredo , Morgantini Pierre‐Yves , Merino Gabriel , Corminboeuf Clémence 
Published: August 2008

AbstractThe trigonal planar geometry of the nitrogen atom in commonly used phosphoramidite ligands is not in line with the traditional valence shell electron pair repulsion (VSEPR) model. In this work, the effects governing nitrogen configuration in several substituted aminophosphines, A2PNB2 (A or B = H, F, Cl, Br, Me, OMe, BINOP), are examined using modern computational analytic tools. The electron delocalization descriptions provided by both electron localization function (ELF) and block localized wavefunction analysis support the proposed relationships between conformation and negative hyperconjugative interactions. In the parent H2PNH2, the pyramidal nitrogen configuration results from nitrogen lone pair electron donation into the σ* PH orbital. While enhanced effects are seen for F2PNMe2, placing highly electronegative fluorine substituents on nitrogen (i.e., Me2PNF2) eliminates delocalization of the nitrogen lone pair. Understanding and quantifying these effects can lead to greater flexibility in designing new catalysts. Copyright © 2008 John Wiley & Sons, Ltd.
Quinoline formation via a modified Combes reaction: examination of kinetics, substituent effects, and mechanistic pathways
Authors: Sloop Joseph C. 
Published: August 2008

AbstractThis is the first reported investigation of the Combes condensation employing 19F NMR spectroscopy to monitor intermediate consumption and product formation rates. The reaction was found to be first order in both the diketone and aniline. Product regioselectivity and reaction rates were found to be influenced by substituents on the diketones and anilines with rates varying as much as five fold. The consumption rate of key imine and enamine intermediates mirrored quinoline formation rates, in accord with rate determining annulation. A ρ of −0.32 was determined for this cyclization. While the sign of the reaction constant is consistent with rate limiting electrophilic aromatic substitution (EAS), the magnitude is likely a composite value, resulting from opposing substituent effects in the nucleophilic addition and EAS steps. Mechanistic details and reaction pathways supporting these findings are proposed. Copyright © 2008 John Wiley & Sons, Ltd.
Syntheses, characterization, and functionalization of poly(ester amide)s with pendant amine functional groups
Authors: De Wit Matthew A. , Wang Zixi , Atkins Katelyn M. , Mequanint Kibret , Gillies Elizabeth R. 
Published: August 2008

AbstractPoly(ester amide)s (PEAs) comprising α‐amino acids, diols, and diacids are promising materials for biomedical applications such as tissue engineering and drug delivery because of their tunability and potential for either hydrolytic or enzymatic degradation. Although a number of PEAs of different compositions have been reported, there is a significant need for the incorporation of amino acids with functional side chains. This will allow for the conjugation of drugs or cell signaling molecules in tissue engineering scaffolds, thus expanding the potential applications of these materials. The objective of this work was the incorporation of l‐lysine into PEAs to provide functionalizable pendant amine groups. Thus, varying percentages of lysine were incorporated into PEAs comprised of l‐phenylalanine, 1,4‐butanediol, and succinic acid by tuning the ratio of ε‐protected‐l‐lysine and l‐phenylalanine derived monomers. The polymers were characterized by nuclear magnetic resonance spectroscopy, infrared spectroscopy, size exclusion chromatography, and differential scanning calorimetry. The lysine ε‐protecting group was removed, then the reactivity of the pendant amines was demonstrated by reaction with amino acid and tri(ethylene glycol) derivatives. The degradation of thin films of polymers were studied using scanning electron microscopy and the incorporation of lysine was found to significantly accelerate both the hydrolytic and enzymatic degradation. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6376–6392, 2008
Ethylene‐based copolymers with tunable content of polymerizable hindered phenols as nonreleasing macromolecular additives
Authors: Menichetti Stefano , Viglianisi Caterina , Liguori Francesca , Cogliati Clelia , Boragno Luca , Stagnaro Paola , Losio Simona , Sacchi Maria Carmela 
Published: August 2008

AbstractFour comonomers bearing a highly efficient phenolic antioxidant unit and different methylene spacers between the aromatic ring and the double bond have been prepared and tested in copolymerization with ethylene using metallocene‐based catalysts. The possibility of obtaining a “masterbatch” suitable for melt blending with commercial polyolefins has been evaluated by modifying: (i) the structure of the functionalized comonomer, (ii) the kind of catalyst, and (iii) the polymerization conditions. Characterization of monomers and copolymers was accomplished by using 1H and 13C NMR, size exclusion chromatography (SEC), differential scanning calorimetry (DSC), and thermal gravimetric analysis (TGA). Using the comonomer with the longest methylene spacer between the aromatic ring and the double bond, and rac‐(EBTHI)ZrCl2 as catalyst, adjustable amounts of the antioxidant moiety can be incorporated into the polyethylene chains. TGA analysis carried out on some of the copolymers containing the antioxidant group showed no oxygen uptake before decomposition. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6393–6406, 2008
Synthesis and characterization of well‐defined cyclodextrin‐centered seven‐arm star poly(ε‐caprolactone)s and amphiphilic star poly(ε‐caprolactone‐b‐ethylene glycol)s
Authors: Gou Peng‐Fei , Zhu Wei‐Pu , Xu Ning , Shen Zhi‐Quan 
Published: August 2008

AbstractPer‐2,3‐acetyl‐β‐cyclodextrin with seven primary hydroxyl groups was synthesized by selective modification and used as multifunctional initiator for the ring‐opening polymerization of ε‐caprolactone (CL). Well‐defined β‐cyclodextrin‐centered seven‐arm star poly(ε‐caprolactone)s (CDSPCLs) with narrow molecular weight distributions (≤1.15) have been successfully prepared in the presence of Sn(Oct)2 at 120 °C. The molecular weight of CDSPCLs was characterized by end group 1H NMR analyses and size‐exclusion chromatography (SEC), which could be well controlled by the molar ratio of the monomer to the initiator. Furthermore, amphiphilic seven‐arm star poly(ε‐caprolactone‐b‐ethylene glycol)s (CDSPCL‐b‐PEGs) were synthesized by the coupling reaction of CDSPCLs with carboxyl‐terminated mPEGs. 1H NMR and SEC analyses confirmed the expected star block structures. Differential scanning calorimetry analyses suggested that the melting temperature (Tm), the crystallization temperature (Tc), and the crystallinity degree (Xc) of CDSPCLs all increased with the increasing of the molecular weight, and were lower than that of the linear poly(ε‐caprolactone). As for CDSPCL‐b‐PEGs, the Tc and Tm of the PCL blocks were significantly influenced by the PEG segments in the copolymers. Moreover, these amphiphilic star block copolymers could self‐assemble into spherical micelles with the particle size ranging from 10 to 40 nm. Their micellization behaviors were characterized by dynamic light scattering and transmission electron microscopy. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6455–6465, 2008
Efficient initiators for the ring‐opening polymerization of L‐lactide: Synthesis and characterization of NNO‐tridentate Schiff‐base zinc complexes
Authors: Hung Wen‐Chou , Huang Yong , Lin Chu‐Chieh 
Published: August 2008

AbstractA series of efficient catalysts, based on zinc alkoxides coordinated with NNO‐tridentate Schiff‐base ligands (L1H‐L6H), for ring opening polymerization of L‐lactide have been prepared. The reactions of diethyl zinc (ZnEt2) with L1H‐L6H yielded [(μ‐L)ZnEt]2 (1a–6a), respectively. Further reaction of compounds 1a–6a with benzyl alcohol (BnOH) produced the corresponding compounds of [LZn(μ‐OBn)]2 (1b–6b), respectively. X‐ray crystal structural studies reveal that all of these compounds 1a–6a are dimeric bridging through the phenolato oxygen atoms of the Schiff‐base ligand. However, the molecular structures of 1b–6b show a dimeric character bridging through the benzylalkoxy oxygen atoms. Ring‐opening polymerization of L‐lactide, initiated by 1b–6b, proceeds rapidly with good molecular weight control and yields polymer with a very narrow molecular weight distribution. Experimental results show that the substituents on the imine carbon of the NNO‐ligand affect the reactivity of zinc complexes dramatically. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6466–6476, 2008
Novel fluorescent (p‐phenylene ethynylene)‐calix[4]arene‐based polymer: Design, synthesis, and properties
Authors: Costa Alexandra I. , Ferreira Luís F. V. , Prata José V. 
Published: August 2008

AbstractA novel fluorescent (p‐phenylene ethynylene)‐calix[4]arene‐based polymer (CALIX‐PPE) has been successfully synthesized by cross‐coupling polymerization of bis‐calix[4]arene 1 with 1,4‐diethynylbenzene. The polycondensation was carried out in toluene/NEt3 at 35 °C for 24 h, using PdCl2(PPh3)2/CuI as the catalytic system, furnishing CALIX‐PPE in excellent isolated yields (higher than 95%, several runs). The yellow polymer is freely soluble in several nonprotic organic solvents. The GPC trace of the isolated polymer showed a monomodal distribution and a number‐average molecular weight of 23,300 g mol−1 (Mw/Mn = 2.05). No evidence was found in the structural analysis (FTIR and 1H/13C NMR) regarding the formation of alkyne homocoupled segments along the polymer chain. For comparative purposes, the synthesis of an analogous poly(p‐phenylene ethynylene) containing p‐t‐butyl‐phenoxymethyl side chains (TBP‐PPE) was also undertaken. A great similarity was found between the photophysical properties of CALIX‐PPE and TBP‐PPE in solution (UV–vis and laser induced luminescence), clearly demonstrating their unique dependence on the structure and conformation of the conjugated PPE backbone. The fluorescence spectra of polymers are of nearly identical shape, displaying their maximum emission around 420 nm. The calculated solution photoluminescence quantum yields of CALIX‐PPE and TBP‐PPE are of similar magnitude (ϕF(CALIX‐PPE) = 0.43; ϕF(TBP‐PPE) = 0.51). © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 6477–6488, 2008
Viscometric measurement of the thermodynamics of PAN terpolymer/DMSO/water system and effect of fiber‐forming conditions on the morphology of PAN precursor
Authors: Dong Ruijiao , Keuser Marcus , Zeng Xiaomei , Zhao Jiongxin , Zhang Youwei , Wu Chengxun , Pan Ding 
Published: August 2008

AbstractThe thermodynamics of polyacrylonitrile (PAN) terpolymer/dimethyl sulphoxide (DMSO)/water system was investigated by viscometric method. Fourier transform infrared (FTIR) measurement of the temperature dependence of polymer/solvent interaction was performed in the range of 25–80 °C, which was in good agreement with viscometric results. Meanwhile, the upper critical solution temperature (UCST) for PAN terpolymer/DMSO/water system, which is proved to be stable one, was determined from the temperature dependence of the expansion factor αη3. The morphology of PAN precursor prepared by dry‐jet‐wet spinning with different fiber‐forming conditions was examined with a scanning electron microscope (SEM). Judging from SEM photographs, not only the number and size of microvoids of PAN precursor gradually increase, with increasing the temperature of coagulation bath, but also the cross‐section shape of PAN precursor changes from nephroid shape to elliptical shape or circular shape. Therefore, PAN precursor with different microstructures can be fabricated at different quenching‐depths, suggesting that the final microstructure of the PAN precursor greatly depends on the phase separation in the fiber‐forming process. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 1997–2011, 2008
Effect of side groups of polymer glycol on microphase‐separated structure and mechanical properties of polyurethane elastomers
Authors: Kojio Ken , Nakamura Sadaharu , Furukawa Mutsuhisa 
Published: August 2008

AbstractThe effect of side methyl and dimethyl groups of the soft segment component on the microphase‐separated structure and mechanical properties of polyurethane elastomers (PUEs) was investigated. Poly(oxytetramethylene) glycol (PTMG), and PTMG incorporating dimethyl groups (PTG‐X) and methyl side groups (PTG‐L) were used as a polymer glycol, which forms a soft segment in the PUEs. The PUEs were synthesized with 4,4′‐dipheylmethane diisocyanate [1,1′‐methylenebis(4‐isocyanatobenzene)], 1,4‐butane diol, and 1,1,1‐trimethylol propane by a prepolymer method. The degree of microphase separation of the PUEs became weaker with increasing side group content in polymer glycols. Dynamic viscoelastic properties measurement showed reorganized‐crystallization and melting of the soft segment for the PUEs based on PTMG, PTG‐L, and PTG‐X with a lower content of the side groups, but not for a PTG‐L and PTG‐X with higher content of the side groups. Tensile testing revealed that increasing methyl group concentration made the PUEs soften and weaken. The PTMG‐based PUEs obviously exhibited strain‐induced crystallization of the soft segment chains during elongation process. In contrast, for the PTG‐L and PTG‐X‐based PUEs, crystallinity decreased with increasing side group content, and the PUEs with PTG‐L and PTG‐X with highest methyl group content did not crystallize even at a large strain. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 2054–2063, 2008
Validation of proteomic‐based discovery with tissue microarrays
Authors: Hewitt Stephen M. , Takikita Mikiko , Abedi‐Ardekani Behnoush , Kris Ylaya , Bexfield Kathryn , Braunschweig Till , Chung Joon‐Yong 
Published: August 2008

AbstractProteomics is routinely utilized for biomarker discovery above and beyond its general use in basic science. Multiple platforms provide a robust pipeline of candidates that require verification and validation as biomarkers of disease. Within the field of oncology, tissue biomarkers are in high demand as tools of diagnosis, prognosis and prediction of response to therapy. By examining the proteome, rather than the transcriptome, there is the potential to directly interrogate the drug targets and define biomarkers at the most proximate level. Toward these ends, the tissue microarray has become a common platform for verification of results and validation of clinically relevant biomarkers. Immunohistochemistry remains the most common analytical method applied to TMA and provides a direct channel toward clinical application. The TMA stands at the crossroads of proteomics and pathology, combining formalin‐fixed paraffin‐embedded tissue as an analyte and IHC as a method of assay.
Neuroproteomics and systems biology‐based discovery of protein biomarkers for traumatic brain injury and clinical validation
Authors: Kobeissy Firas H. , Sadasivan Shankar , Oli Monika W. , Robinson Gillian , Larner Stephen F. , Zhang Zhiqun , Hayes Ronald L. , Wang Kevin K. W. 
Published: August 2008

AbstractThe rapidly growing field of neuroproteomics has expanded to track global proteomic changes underlying various neurological conditions such as traumatic brain injury (TBI), stroke, and Alzheimer's disease. TBI remains a major health problem with approximately 2 million incidents occurring annually in the United States, yet no affective treatment is available despite several clinical trials. The absence of brain injury diagnostic biomarkers was identified as a significant road‐block to therapeutic development for brain injury. Recently, the field of neuroproteomics has undertaken major advances in the area of neurotrauma research, where several candidate markers have been identified and are being evaluated for their efficacy as biological biomarkers in the field of TBI. One scope of this review is to evaluate the current status of TBI biomarker discovery using neuroproteomics techniques, and at what stage we are at in their clinical validation. In addition, we will discuss the need for strengthening the role of systems biology and its application to the field of neuroproteomics due to its integral role in establishing a comprehensive understanding of specific brain disorder and brain function in general. Finally, to achieve true clinical input of these neuroproteomic findings, these putative biomarkers should be validated using preclinical and clinical samples and linked to clinical diagnostic assays including ELISA or other high‐throughput assays.
Evaluation of a bio‐coating as a solution to improve barrier, friction and optical properties of plastic films
Authors: Farris Stefano , Introzzi Laura , Piergiovanni Luciano 
Published: August 2008

AbstractThe present research dealt with evaluating barrier, friction and optical properties of three different plastic films after deposition of a gelatin‐based bio‐coating. The composite films showed improved barrier properties against oxygen and UV radiation. The oxygen transmission rate decreased in the order of 73% for oriented polypropylene (OPP), 56% for low‐density polyethylene (LDPE) and 40% for polyethylene terephthalate (PET). The increased UV barrier characteristics ranged from 20% for OPP to 12% for both LDPE and PET. Static and kinetic coefficients of friction significantly decreased both in the film‐to‐film and in the film‐to‐metal tests, leading to a desirable value for many applications. However, bio‐coated films showed lower optical performances in terms of transparency and haze. Transparency decreased mainly for LDPE (36%), whereas the haze index increased especially for OPP (85%). Non‐significant differences were observed as far as the water vapour permeability was concerned, except for a slight reduction for PET (from 15.78 to 13.53 cm3/m2/day at 23°C and 90% of relative humidity), suggesting that non‐meaningful effects arose from the addition of a hydrophobic component in the original formulation. Finally, the solubility of the coating in water was around 25% for all the three plastic substrates. The obtained data suggest that the lipid protein coating tested in this study, in spite of its great potential for enhancing some characteristics of plastic packaging films, still exhibits negative aspects which necessitate further improvement. Copyright © 2008 John Wiley & Sons, Ltd.
Ion mobility adds an additional dimension to mass spectrometric analysis of solution‐phase hydrogen/deuterium exchange
Authors: Iacob Roxana E. , Murphy James P. , Engen John R. 
Published: August 2008

AbstractThe goal of this study was to determine the utility of adding ion mobility spectrometry to studies probing the solution‐phase hydrogen/deuterium exchange (HX) of proteins. The HX profile of the Hck SH3 domain was measured at both the intact protein and the peptic peptide levels in the Waters Synapt HDMS system which uses a traveling wave to accomplish ion mobility separation prior to time‐of‐flight (Tof) m/z analysis. The results indicated a similar loss of deuterium with or without use of mobility in the Synapt and a level of deuterium loss comparable with a non‐mobility Q‐Tof instrument. The drift time of this small protein and its peptic peptides did not noticeably change due to solution‐based deuterium incorporation. Importantly, ion mobility separations provided an orthogonal dimension of separation in addition to the reversed‐phase high‐performance liquid chromatography (RP‐HPLC). The additional dimension of separation allowed for the deconvolution of overlapping isotopic patterns for co‐eluting peptides and extraction of valuable deuterium incorporation data for those peptides. Taken together, these results indicate that including ion mobility separation in HX MS analyses further improves the mass spectrometry portion of such experiments. Copyright © 2008 John Wiley & Sons, Ltd.
Effect of age and food intake on dietary carbon turnover recorded in sheep wool
Authors: Zazzo Antoine , Moloney Aidan P. , Monahan Frank J. , Scrimgeour Charlie M. , Schmidt Olaf 
Published: August 2008

AbstractWe present the results of a series of controlled feeding experiments with sheep, designed to investigate the effects of age and level of food intake on the kinetics of incorporation of the dietary carbon signal into wool. Four different groups of three sheep each, ranging in age from 6 to 78 months, were fed a C3 diet and switched to a C4 diet for up to 250 days. Different quantities of the same C4 diet were provided to each group, in order to achieve different growth rates (high, low, and no growth). Wool was repeatedly shorn from each animal and processed for δ13C analyses. Results show that newly grown wool does not start recording the isotope composition of the new diet immediately after the diet‐switch. The time‐lag varies according to the age of the animal, from 6 ± 1 days in lambs to up to 15 ± 4 days in the older ewes. Wool from fast‐growing lambs approached equilibrium faster than that from slow‐growing lambs and young ewes, with old ewes being the slowest. However, 3 weeks after the diet‐switch, the differences in wool δ13C values between the four different groups of animals were relatively small and represented less than 15% of the isotopic difference between the two diets. These results suggest that a single equation can be used to reconstruct previous diets for animals of different age, provided that the diet is similar and all individuals are in positive protein balance. Copyright © 2008 John Wiley & Sons, Ltd.
Effects of acidification on carbon and nitrogen stable isotopes of benthic macrofauna from a tropical coral reef
Authors: Kolasinski Joanna , Rogers Karyne , Frouin Patrick 
Published: August 2008

AbstractStable isotope analyses are widely used to determine trophic levels in ecological studies. We have investigated the effects of carbonate removal via acidification on the stable carbon and nitrogen isotopic composition of 33 species of tropical benthic macrofauna, and we report guidelines for standardizing this procedure for higher taxa in tropical coral reef ecosystems. Many tropical benthic invertebrates are small in size, and therefore body tissue isolation (separating organic carbon from inorganic structures) is difficult and time‐consuming. Literature reviews of invertebrate studies show a lack of consistent procedures and guidelines for preparation techniques, especially for carbonate removal via acidification of whole individuals. We find that acidification decreases the δ13C values of samples containing carbonate, with shifts ranging from 0.21 to 3.20‰, which can be related to CaCO3 content (assessed by a carbonate proxy), justifying acid pre‐treatment. Carbonate‐containing taxa benefiting from acidification included Amphinomida, Terebellida (Annelida), Anomura, Brachyura, Caridea, Amphipoda, Tanaidacea (Arthropoda) and Edwardsiida (Cnidaria). The δ13C shifts of samples containing no carbonate varied up to 0.02 ± 0.20‰. As this induced δ13C shift was lower than the range of an average trophic level shift (0.5 to 1‰), we conclude that acid pre‐treatment is unnecessary. Carbonate‐free taxa consisted of Eunicida, Phyllodocida (Annelida) and Mollusca. We note minimal impact of acidification on δ15N values except for Brachyura, which showed a shift of 0.83 ± 0.46‰, which is still lower than a single trophic level shift (2.9–3.8‰). We conclude that for trophic level studies, both the δ13C and the δ15N of carbonate‐rich macrofauna can be determined from the same acidified sample. Copyright © 2008 John Wiley & Sons, Ltd.