bluuebunny/crossref_metadata_2025_split huggingface dataset:
Chemistry and Biology of Roseophilin and the Prodigiosin Alkaloids: A Survey of the Last 2500 Years
Authors: Fürstner Alois 
Published: August 2003

AbstractThe pyrrole alkaloids of the prodigiosin family make up an unusual chapter in the chemistry of natural products. Owing to the characteristic red color of these secondary metabolites, colonies of the Gram‐negative‐producing bacteria may strikingly resemble droplets of blood. This phenomenon caused considerable confusion in the past and was likely responsible for many seemingly miraculous (prodigious) events. After the eventual transition from superstition to science, the prodigiosins started to attract considerable attention because of their promising physiological properties. Most interesting are the immunosuppressive activities at doses that are not cytotoxic, in particular since in vivo studies suggest that the prodigiosins act synergistically with cyclosporine A or FK 506, which are presently the dominant drugs in clinical immunosuppressive regimens. Furthermore, the chemistry of the closely related and structurally rather unique alkaloid roseophilin is summarized, a cytotoxic agent that recently became the focal point of many innovative total syntheses.
Synthesis and characterization of thiol‐terminated poly(ethylene oxide) for chemisorption to gold surface
Authors: Du Ying Jun , Brash John L. 
Published: August 2003

AbstractThiol‐terminated poly(ethylene oxide) (PEO) was synthesized using two different approaches: esterification of terminal hydroxyl groups with mercaptoacetic acid and amidation using N‐hydroxysuccinimidyl PEO (NHS–PEO) and cysteine. The reaction of hydroxyl‐terminated PEO with mercaptoacetic acid was carried out in boiling toluene. Different thiolated PEOs, including linear PEOs of varying molecular weights and end‐group types, and star‐type PEOs were synthesized. Nuclear magnetic resonance and infrared spectroscopy were used to characterize the products. The reaction kinetics were also briefly investigated. Gel permeation chromatography was used to investigate the relative amounts of the mono‐ and disubstituted products in the α,ω‐dihydroxy PEOs. NHS–PEO was used both to attach terminal thiol groups via reaction with cysteine and to conjugate other amino acids (and potentially any amino‐containing molecule) to PEO. Reactions using NHS–PEO were carried out at room temperature in water. The chemisorption of these thiolated PEOs to gold was expected to yield surfaces resistant to biofouling, in particular to unwanted protein adsorption. Chemisorption of amino acid–, peptide‐, or protein‐terminated PEOs in addition may yield surfaces having specific biological activity. Work on these aspects will be reported elsewhere. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 594–607, 2003
Viscometric behavior of quaternized polysulfones
Authors: Ghimici Luminita , Avram Ecaterina 
Published: August 2003

AbstractThe effects of the quaternary ammonium group size and the solvent nature and composition on the viscometric behavior of several quaternized polysulfones (PSFs) were investigated. The solution viscosity of the cationic PSFs was determined over a wide concentration range in N,N‐dimethylformamide (DMF). The experimental data were plotted in the terms of the Fedors equation. It was found that the intrinsic viscosity values were strongly dependent on the size of quaternary ammonium groups. The viscosity of PSF quaternized with N,N‐dimethylbutylamine (PSF‐DMBA) was also measured in the mixed solvents consisting of DMF/methanol and DMF/diethylether. Polyelectrolyte behavior was observed for PSF‐DMBA in the mixtures of DMF/methanol for all compositions employed and in the mixtures of DMF/diethylether with the diethylether content as high as 25 vol %. The viscosity decrease and precipitation in the polymer solution with increasing diethylether content was attributed to the dipole–dipole attraction between ion pairs formed in a less polar medium. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 465–469, 2003
Vibrational overtone initiated photopolymerization of acrylonitrile
Authors: Gu Hua , Snavely D. L. 
Published: August 2003

AbstractVibrational overtone activated polymerization of acrylonitrile (AN) has been demonstrated using two initiators, benzoyl peroxide (BP), and 2,2′‐(azobis)isobutyronitrile (AIBN). Excitation of the fifth vibrational overtone of the CH stretch of AIBN at 627 nm and BP at 604 nm initiates the reaction. Monomer conversions were monitored by a gravimetric method. In both cases, the wavelength selectivity was investigated by irradiating the monomer/initiator mixtures at the absorption maximum of the initiator, the absorption maximum of the monomer, and at a wavelength (580 nm for AN/AIBN and 625 nm for AN/BP) where neither the initiator nor the monomer absorbs light. For the AN/AIBN mixture, after 48 h the monomer conversion for the irradiation on the peak absorption of AIBN (627 nm) is about twice as large as the irradiation at 580 nm. For the AN/BP mixture, after 48 h the monomer conversion for the irradiation on the peak absorption of BP (604 nm) is about a factor of 2.2 larger than for the irradiation at 625 nm. The overall quantum yields of both polymerizations were estimated. After 48 h the overall quantum yield for the AN/AIBN mixture irradiated at the initiator absorption (Φ627 = 21083) is about 10 times larger than for the sample irradiated at the pure monomer absorption (Φ595 = 1942). For the AN/BP mixture, the 604 nm quantum yield (Φ604 = 1096) is about 2.4 times larger than the 595 nm quantum yield (Φ595 = 448). The influence of the initiator concentration is also presented. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 565–571, 2003
TROPDAD: A New Ligand for the Synthesis of Water‐Stable Paramagnetic [16+1]‐Electron Rhodium and Iridium Complexes
Authors: Breher Frank , Böhler Carsten , Frison Gilles , Harmer Jeffrey , Liesum Lorenz , Schweiger Arthur , Grützmacher Hansjörg 
Published: August 2003

AbstractThe new tetradentate ligand 1,4‐bis(5 H‐dibenzo[a,d]cyclohepten‐5‐yl)‐1,4‐diazabuta‐1,3‐diene (Htropdad) allows the syntheses of the 16‐electron cationic rhodium complexes [M(Htropdad)](O3SCF3) (M=Rh, Ir). The structure of the rhodium complex was determined by X‐ray analysis and points to a description of these as [M+1(Htropdad)0] with short CN bonds (av 1.285 Å) and a long CC bond (1.46 Å) in the diazabutadiene (dad) moiety, that is the M→dad charge‐transfer is negligible. Both [Rh(Htropdad)]+and [Ir(Htropdad)]+are reduced at very low potentials (E11/2= −0.56 V andE11/2=−0.35 V, respectively) which allowed the quantitative synthesis of the neutral paramagnetic complexes [M(Htropdad)]0(M=Rh, Ir) by reacting the cationic precursor complexes simply with zinc powder. The [M(Htropdad)]0complexes are stable against protic reagents in organic solvents. Continuous wave and pulse EPR spectroscopy was used to characterize the paramagnetic species and the hyperfine coupling constants were determined: [Rh(Htropdad)]0:Aiso(14N)=11.9 MHz,Aiso(1H)=14.3 MHz,Aiso(103Rh)= −5.3 MHz; [Ir(Htropdad)]0:Aiso(14N)=11.9 MHz,Aiso(1H)=14.3 MHz. In combination with DFT calculations, the experimentally determinedgand hyperfine matrices could be orientated within the molecular frame and the dominant spin density contributions were determined. These results clearly show that the complexes [M(Htropdad)]0are best described as [M+1(Htropdad).−] with a [16+1] electron configuration.
Thermodynamics and Kinetics of the Hydride‐Transfer Cycles for 1‐Aryl‐1,4‐dihydronicotinamide and Its 1,2‐Dihydroisomer
Authors: Zhu Xiao‐Qing , Cao Lei , Liu Yang , Yang Yuan , Lu Jin‐Yong , Wang Jian‐Shuang , Cheng Jin‐Pei 
Published: August 2003

AbstractFive 1‐(p‐substituted phenyl)‐1,4‐dihydronicotinamides (GPNAH‐1,4‐H2) and five 1‐(p‐substituted phenyl)‐1,2‐dihydronicotinamides (GPNAH‐1,2‐H2) were synthesized, which were used to mimic NAD(P)H coenzyme and its 1,2‐dihydroisomer reductions, respectively. When the 1,4‐dihydropyridine (GPNAH‐1,4‐H2) and the 1,2‐dihydroisomer (GPNAH‐1,2‐H2) were treated with p‐trifluoromethylbenzylidenemalononitrile (S) as a hydride acceptor, both reactions gave the same products: pyridinium derivative (GPNA+) and carbanion SH− by a hydride one‐step transfer. Thermodynamic analysis on the two reactions shows that the hydride transfer from the 1,2‐dihydropyridine is much more favorable than the hydride transfer from the corresponding 1,4‐dihydroisomer, but the kinetic examination displays that the former reaction is remarkably slower than the latter reaction, which is mainly due to much more negative activation entropy for the former reaction. When the formed pyridinium derivative (GPNA+) was treated with SH−, the major reduced product was the corresponding 1,4‐dihydropyridine along with a trace of the 1,2‐dihydroisomer. Thermodynamic and kinetic analyses on the hydride transfer from SH− to GPNA+ all suggest that the 4‐position on the pyridinium ring in GPNA+ is much easier to accept the hydride than the 2‐position, which indicates that when the 1,4‐dihydropyridine is used the hydride donor to react with S, the formed pyridinium derivative GPNA+ may return to the 1,4‐dihydropyridine by a hydride transfer cycle; but when the 1,2‐dihydropyridine is used as the hydride donor, the formed pyridinium derivative can not return to the 1,2‐dihydropyridine by the hydride reverse transfer from SH− to GPNA+. These results clearly show that the hydride‐transfer cycle is favorable for the 1,4‐dihydronicotinamides, but unfavorable for the corresponding 1,2‐dihydroisomers.
Chemical and Biochemical Sensing with Modified Single Walled Carbon Nanotubes
Authors: Davis Jason J. , Coleman Karl S. , Azamian Bobak R. , Bagshaw Claire B. , Green Malcolm L. H. 
Published: August 2003

AbstractThe nano dimensions, graphitic surface chemistry and electronic properties of single walled carbon nanotubes make such a material an ideal candidate for chemical or biochemical sensing. Carbon nanotubes can be nondestructively oxidized along their sidewalls or ends and subsequently covalently functionalized with colloidal particles or polyamine dendrimers via carboxylate chemistry. Proteins adsorb individually, strongly and noncovalently along nanotube lengths. These nanotube–protein conjugates are readily characterized at the molecular level by atomic force microscopy. Several metalloproteins and enzymes have been bound on both the sidewalls and termini of single walled carbon nanotubes. Though coupling can be controlled, to a degree, through variation of tube oxidative pre‐activation chemistry, careful control experiments and observations made by atomic force microscopy suggest that immobilization is strong, physical and does not require covalent bonding. Importantly, in terms of possible device applications, protein attachment appears to occur with retention of native biological structure. Nanotube electrodes exhibit useful voltammetric properties with direct electrical communication possible between a redox‐active biomolecule and the delocalized π system of its carbon nanotube support.
Coordination Algorithms Control Molecular Architecture: [CuI4(L2)4]4+ Grid Complex Versus [MII2(L2)2X4]y+ Side‐By‐Side Complexes (M=Mn, Co, Ni, Zn; X=Solvent or Anion) and [FeII(L2)3][Cl3FeIIIOFeIIICl3]
Authors: Lan Yanhua , Kennepohl Dietmar K. , Moubaraki Boujemaa , Murray Keith S. , Cashion John D. , Jameson Geoffrey B. , Brooker Sally 
Published: August 2003

AbstractThe synthesis and characterisation of a pyridazine‐containing two‐armed grid ligand L2 (prepared from one equivalent of 3,6‐diformylpyridazine and two equivalents of p‐anisidine) and the resulting transition metal (Zn, Cu, Ni, Co, Fe, Mn) complexes (1–9) are reported. Single‐crystal X‐ray structure determinations revealed that the copper(I) complex had self‐assembled as a [2×2] grid, [CuI4(L2)4][PF6]4⋅(CH3CN)(H2O)(CH3CH2OCH2CH3)0.25 (2⋅(CH3CN)(H2O)(CH3CH2OCH2CH3)0.25), whereas the [Zn2(L2)2(CH3CN)2(H2O)2][ClO4]4⋅CH3CN (1⋅CH3CN), [NiII2(L2)2(CH3CN)4][BF4]4⋅(CH3CH2OCH2CH3)0.25 (5 a⋅(CH3CH2OCH2CH3)0.25) and [CoII2(L2)2(H2O)2(CH3CN)2][ClO4]4⋅(H2O)(CH3CN)0.5 (6 a⋅(H2O)(CH3CN)0.5) complexes adopt a side‐by‐side architecture; iron(II) forms a monometallic cation binding three L2 ligands, [FeII(L2)3][FeIIICl3OCl3FeIII]⋅CH3CN (7⋅CH3CN). A more soluble salt of the cation of 7, the diamagnetic complex [FeII(L2)3][BF4]2⋅2 H2O (8), was prepared, as well as two derivatives of 2, [CuI2(L2)2(NCS)2]⋅H2O (3) and [CuI2(L2)(NCS)2] (4). The manganese complex, [MnII2(L2)2Cl4]⋅3 H2O (9), was not structurally characterised, but is proposed to adopt a side‐by‐side architecture. Variable temperature magnetic susceptibility studies yielded small negative J values for the side‐by‐side complexes: J=−21.6 cm−1 and g=2.17 for S=1 dinickel(II) complex [NiII2(L2)2(H2O)4][BF4]4 (5 b) (fraction monomer 0.02); J=−7.6 cm−1 and g=2.44 for S= 3/2 dicobalt(II) complex [CoII2(L2)2(H2O)4][ClO4]4 (6 b) (fraction monomer 0.02); J=−3.2 cm−1 and g=1.95 for S= 5/2 dimanganese(II) complex 9 (fraction monomer 0.02). The double salt, mixed valent iron complex 7⋅H2O gave J=−75 cm−1 and g=1.81 for the S= 5/2 diiron(III) anion (fraction monomer=0.025). These parameters are lower than normal for FeIIIOFeIII species because of fitting of superimposed monomer and dimer susceptibilities arising from trace impurities. The iron(II) centre in 7⋅H2O is low spin and hence diamagnetic, a fact confirmed by the preparation and characterisation of the simple diamagnetic iron(II) complex 8. Mössbauer measurements at 77 K confirmed that there are two iron sites in 7⋅H2O, a low‐spin iron(II) site and a high‐spin diiron(III) site. A full electrochemical investigation was undertaken for complexes 1, 2, 5 b, 6 b and 8 and this showed that multiple redox processes are a feature of all of them.
Pairing of Isolated Nucleobases: Double Resonance Laser Spectroscopy of Adenine–Thymine
Authors: Plützer Christian , Hünig Isabel , Kleinermanns Karl , Nir Eyal , de Vries Mattanjah S. 
Published: August 2003

AbstractThe vibronic spectrum of the adenine–thymine (A–T) base pair was obtained by one‐color resonant two‐photon ionization (R2PI) spectroscopy in a free jet of thermally evaporated A and T under conditions favorable for formation of small clusters. The onset of the spectrum at 35 064 cm−1 exhibits a large red shift relative to the π–π* origin of 9H‐adenine at 36 105 cm−1. The IR–UV spectrum was assigned to cluster structures with HNH⋅⋅⋅OC/N⋅⋅⋅HN hydrogen bonding by comparison with the IR spectra of A and T monomers and with ab initio calculated vibrational spectra of the most stable A–T isomers. The Watson–Crick A–T base pair is not the most stable base‐pair structure at different levels of ab initio theory, and its vibrational spectrum is not in agreement with the observed experimental spectrum. Experiments with methylated A and T were performed to further support the structural assignment.
Detecting instabilities in flows of viscoelastic fluids
Authors: Fiétier N. 
Published: August 2003

AbstractThere is a growing interest in developing numerical tools to investigate the onset of physical instabilities observed in experiments involving viscoelastic flows, which is a difficult and challenging task as the simulations are very sensitive to numerical instabilities. Following a recent linear stability analysis carried out in order to better understand qualitatively the origin of numerical instabilities occurring in the simulation of flows viscoelastic fluids, the present paper considers a possible extension for more complex flows. This promising method could be applied to track instabilities in complex (i.e. essentially non‐parallel) flows. In addition, results related to transient growth mechanism indicate that it might be responsible for the development of numerical instabilities in the simulation of viscoelastic fluids. Copyright © 2003 John Wiley & Sons, Ltd.
Occurrence of certain mycotoxins in corn and corn‐based products and thermostability of fumonisin B1 during processing
Authors: El‐Sayed A. M. Abd Alla , Soher E. Aly , Sahab A. F. 
Published: August 2003

AbstractA total of 57 samples of corn and corn‐based products collected from various districts of Egypt were analyzed for Fusarium mycotoxins (T‐2, diacetoxyscripenol (DAS( deoxynivalenol (DON) and fumonisin B1 (FB1) and aflatoxins. FB1 was detected in about 80%, 53.85%, 33.3%, and 28.57% of yellow corn, corn meal, white corn, and popcorn samples, respectively. The levels of FB1 ranged from 10 to 780 μg/kg. T‐2 and DAS were detected in 5% and 10% of yellow corn samples, respectively, and DON was detected in white corn and popcorn samples at levels of 28.8 and 10.1 μg/kg, respectively. Starch samples were found to be free from Fusarium mycotoxins. Baking balady bread at 450°C/min reduced FB1 to 72.4% while baking Franco bread at 250°C/20 min reduced FB1 to 57.4%. Boiling of macaroni and corn in water completely removed FB1 from contaminated samples. On the other side, corn flakes samples were found to be contaminated with aflatoxins B1 and G1 at levels ranging from 6 to 10 ppm, whereas 2.9% of samples were contaminated with aflatoxin B1 > 35 ppm and G1 > 16 ppm.
Effects of different emulsifier types, fat contents, and gum types on retardation of staling of microwave‐baked cakes
Authors: Seyhun Nadide , Sumnu Gülüm , Sahin Serpil 
Published: August 2003

AbstractThe effects of different types of emulsifiers, gums, and fat contents on the retardation of staling of microwave‐baked cakes were investigated. First, different types of emulsifiers (DATEM, Lecigran, and Purawave) at three different fat contents (50%, 25%, and 0%) were added to cake formulations to retard staling of microwave‐baked cakes. Then, three types of gums (guar gum, xanthan gum, and methylcellulose) were added to the optimum formulations chosen. As a control, cakes formulated without any emulsifier or gum addition and baked in an conventional oven at 175°C for 25 min was used. Weight loss, firmness, soluble starch and amylose content of the cakes were used as the indicators of staling criteria. Cakes were baked in a microwave oven for 1.5 min at 100% power. Variation of staling parameters during storage of cakes followed zero‐order kinetics. Use of emulsifiers and gums helped to retard staling of microwave‐baked cakes. Fat content was found to be a significant factor in affecting variation of firmness and weight loss of the cakes during storage. DATEM and Purawave were the most effective emulsifier types. Using gums in combination with emulsifiers gave better moisture retention and softer cakes than using gums alone.
Effect of processing on the protein nutritional value of Canavalia gladiata seeds
Authors: Ekanayake Sagarika , Nair Baboo , Radcliff Jansz Errol , Asp Nils‐Georg 
Published: August 2003

AbstractEvaluation of protein true digestibility (TD( biological value (BV( and net protein utilization (NPU) of diets containing mature sword bean (Canavalia gladiata( seed flour and grits were carried out with male Sprague‐Dawley rats. The seed flour and grits were processed by soaking, cooking, soaking and cooking, autoclaving, and roasting. The TD of processed flour (cooked (84.8( soaked and cooked (76.2( autoclaved (82.0( roasted grits (64.5( and roasted flour (61.2)) were significantly higher (p < 0.05) than in the raw (51.4) and the soaked only grits (35.8). Soaking the grits decreased the TD. The BV of cooked grits and grits cooked after soaking were significantly higher than that of the other processed samples (p < 0.05). However, the BV of the diets containing cooked and soaked and cooked grits were not significantly different. The NPU of the cooked grits (39.4) and grits cooked after soaking (37.6) were significantly higher (p < 0.05) than that of the other processed samples (autoclaved grits (31.0( roasted grits (19.5( roasted flour (10.8( and soaked only grits (1.6)). The NPU of all the processed samples were significantly lower than the reference casein (p < 0.05). The highest protein nutritional quality was obtained by either cooking the grits or by soaking and cooking the grits. In vitro protein digestibility measurements were not well correlated to the true digestibility.
Application of Bayesian spatial statistical methods to analysis of haplotypes effects and gene mapping
Authors: Molitor John , Marjoram Paul , Thomas Duncan 
Published: August 2003

AbstractWe propose a method to analyze haplotype effects using ideas derived from Bayesian spatial statistics. We assume that two haplotypes that are similar to one another in structure are likely to have similar risks, and define a distance metric to specify the appropriate level of closeness between the two haplotypes. Through the choice of distance metric, varying levels of population genetics theory can be incorporated into the modeling process, including some that allow estimation of the location of the disease causing mutation(s). This location can be estimated, along with the other parameters of the model, using Markov chain Monte Carlo (MCMC) estimation methods. We demonstrate the effectiveness of the model on two real datasets, a well‐known dataset used to fine‐map the gene for cystic fibrosis, and one used to localize the gene for Friedreich's ataxia. Genet Epidemiol 25:95–105, 2003. © 2003 Wiley‐Liss, Inc.
Pedigree disequilibrium tests for multilocus haplotypes
Authors: Dudbridge Frank 
Published: August 2003

AbstractAssociation tests of multilocus haplotypes are of interest both in linkage disequilibrium mapping and in candidate gene studies. For case‐parent trios, I discuss the extension of existing multilocus methods to include ambiguous haplotypes in tests of models which distinguish between thecisandtransphase. A likelihood‐ratio test is proposed, using the expectation‐maximization (E‐M) algorithm to account for haplotype ambiguities. Assumptions about the population structure are required, but realistic situations, including population stratification, which violate the assumptions lead to conservative tests. I describe a permutation procedure for the null hypothesis of interest, which controls for violation of the assumptions. For general pedigrees, I describe extensions of the pedigree disequilibrium test to include uncertain haplotypes. The summary statistics are replaced by their expected values over prior distributions of haplotype frequencies. If prior distributions are not available, a valid test is possible by using the E‐M algorithm to estimate the null distribution of haplotype frequencies. Similar methods are available for quantitative traits. Exact permutation tests are difficult to construct in small samples, but an approximate procedure is appropriate in large samples, and can be used to account for dependencies between tests of multiple haplotypes and loci.Genet Epidemiol25:115–121, 2003. © 2003 Wiley‐Liss, Inc.