bluuebunny/crossref_metadata_2025_split huggingface dataset:
Determination of the C4H Bond Dissociation Energies of NADH Models and Their Radical Cations in Acetonitrile
Authors: Zhu Xiao‐Qing , Li Hai‐Rong , Li Qian , Ai Teng , Lu Jin‐Yong , Yang Yuan , Cheng Jin‐Pei 
Published: February 2003

AbstractHeterolytic and homolytic bond dissociation energies of the C4H bonds in ten NADH models (seven 1,4‐dihydronicotinamide derivatives, two Hantzsch 1,4‐dihydropyridine derivatives, and 9,10‐dihydroacridine) and their radical cations in acetonitrile were evaluated by titration calorimetry and electrochemistry, according to the four thermodynamic cycles constructed from the reactions of the NADH models with N,N,N′,N′‐tetramethyl‐p‐phenylenediamine radical cation perchlorate in acetonitrile (note: C9H bond rather than C4H bond for 9,10‐dihydroacridine; however, unless specified, the C9H bond will be described as a C4H bond for convenience). The results show that the energetic scales of the heterolytic and homolytic bond dissociation energies of the C4H bonds cover ranges of 64.2–81.1 and 67.9–73.7 kcal mol−1 for the neutral NADH models, respectively, and the energetic scales of the heterolytic and homolytic bond dissociation energies of the (C4H).+ bonds cover ranges of 4.1–9.7 and 31.4–43.5 kcal mol−1 for the radical cations of the NADH models, respectively. Detailed comparison of the two sets of C4H bond dissociation energies in 1‐benzyl‐1,4‐dihydronicotinamide (BNAH), Hantzsch 1,4‐dihydropyridine (HEH), and 9,10‐dihydroacridine (AcrH2) (as the three most typical NADH models) shows that for BNAH and AcrH2, the heterolytic C4H bond dissociation energies are smaller (by 3.62 kcal mol−1) and larger (by 7.4 kcal mol−1), respectively, than the corresponding homolytic C4H bond dissociation energy. However, for HEH, the heterolytic C4H bond dissociation energy (69.3 kcal mol−1) is very close to the corresponding homolytic C4H bond dissociation energy (69.4 kcal mol−1). These results suggests that the hydride is released more easily than the corresponding hydrogen atom from BNAH and vice versa for AcrH2, and that there are two almost equal possibilities for the hydride and the hydrogen atom transfers from HEH. Examination of the two sets of the (C4H).+ bond dissociation energies shows that the homolytic (C4H).+ bond dissociation energies are much larger than the corresponding heterolytic (C4H).+ bond dissociation energies for the ten NADH models by 23.3–34.4 kcal mol−1; this suggests that if the hydride transfer from the NADH models is initiated by a one‐electron transfer, the proton transfer should be more likely to take place than the corresponding hydrogen atom transfer in the second step. In addition, some elusive structural information about the reaction intermediates of the NADH models was obtained by using Hammett‐type linear free‐energy analysis.
Fluorogenic Stereochemical Probes for Transaldolases
Authors: González‐García Eva , Helaine Virgil , Klein Gérard , Schuermann Melanie , Sprenger Georg A. , Fessner Wolf‐Dieter , Reymond Jean‐Louis 
Published: February 2003

AbstractTransaldolase catalyzes the transfer of dihydroxyacetone from, for example, fructose 6‐phosphate to erythrose 4‐phosphate. As a potential probe for assaying fluorescent transaldolase, 6‐O‐coumarinyl‐fructose (1) was prepared in six steps from D‐fructose. The corresponding 6‐O‐coumarinyl‐5‐deoxy derivative 2 was prepared stereoselectively from acrolein and tert‐butyl acetate by a chemoenzymatic route involving Amano PS lipase for the kinetic resolution of tert‐butyl 3‐hydroxypent‐4‐enoate (7) and E. coli transketolase for assembly of the final product. The corresponding stereoisomer related to D‐tagatose was obtained by a chemical synthesis starting from D‐ribose. Indeed, transaldolases catalyze the retro‐aldolization of substrate 1 to give dihydroxyacetone and 3‐O‐coumarinyl‐glyceraldehyde. The latter primary product undergoes a β‐elimination in the presence of bovine serum albumin (BSA) to give the strongly fluorescent product umbelliferone. A similar reaction is obtained with the 5‐deoxy analogue 2, but there is almost no reaction with its stereoisomer 3. The stereoselectivity of transaldolases can be readily measured by the relative rates of fluorescence development in the presence of the latter pair of diastereomeric substrates.
Hierarchical Self‐Assembly, Coassembly, and Self‐Organization of Novel Liquid Crystalline Lattices and Superlattices from a Twin‐Tapered Dendritic Benzamide and Its Four‐Cylinder‐Bundle Supramolecular Polymer
Authors: Percec Virgil , Bera Tushar K. , Glodde Martin , Fu Qiongying , Balagurusamy Venkatachalapathy S. K. , Heiney Paul A. 
Published: February 2003

AbstractThe synthesis and structural analysis of the twin‐dendritic benzamide 10, based on the first‐generation, self‐assembling, tapered dendrons 3,4,5‐tris(4′‐dodecyloxybenzyloxy)benzoic acid and 3,4,5‐tris(4′‐dodecyloxybenzyloxy)‐1‐aminobenzene, and the polymethacrylate, 20, which contains 10 as side groups, are presented. Benzamide 10 self‐assembles into a supramolecular cylindrical dendrimer that self‐organizes into a columnar hexagonal (Φh) liquid crystalline (LC) phase. Polymer 20 self‐assembles into an imperfect four‐cylinder‐bundle supramolecular dendrimer, and creates a giant vesicular supercylinder that self‐organizes into a columnar nematic (Nc) LC phase which displays short‐range hexagonal order. In mixtures of 20 and 10, 10 acts as a guest and 20 as a host to create a perfect four‐cylinder‐bundle host–guest supramolecular dendrimer that coorganizes with 10. A diversity of Φh, simple rectangular columnar (Φr‐s) and centered rectangular columnar (Φr‐c), superlattices are produced at different ratios between 20 and 10. This diversity of LC lattices and superlattices is facilitated by the architecture of the twin‐dendritic building block, polymethacrylate, the host–guest supramolecular assembly, and by hydrogen bonding along the center of the supramolecular cylinders generated from 10 and 20.
Finite‐Element Analysis of Magnetic Field Driven Transport at Inlaid Platinum Microdisk Electrodes
Authors: Mehta Dipesh , White Henry S. 
Published: February 2003

AbstractWe describe a computer‐assisted analysis of three‐dimensional magnetohydrodynamic (MHD) fluid flow resulting from the passage of electrochemically generated charge through a uniform magnetic field. Magnetic field driven molecular transport in electrochemical systems offers a number of emerging opportunities in research and technology. For instance, electrochemical microfluidic transport1 and molecule trapping2 using magnetic fields and field gradients have been demonstrated in recent reports from this laboratory. A key limitation of these investigations is the difficulty in analyzing magnetic field driven flow and transport, due to the complexity of the governing equations of fluid mechanics, electrochemical molecular transport, and magnetic forces. In general, quantitative expressions describing the distribution and fluxes of electroactive species under the influence of a magnetic field cannot be obtained by a direct analytical solution.
Maxwell's equations in periodic chiral structures
Authors: Ammari Habib , Bao Gang 
Published: February 2003

AbstractConsider a time–harmonic electromagnetic plane wave incident on a biperiodic structure in ℝ3. The periodic structure separates two homogeneous regions. The medium inside the structure is chiral and heterogeneous. In general, wave propagation in the chiral medium is governed by Maxwell's equations together with the Drude– Born–Fedorov (constitutive) equations. In this paper, the diffraction problem is formulated in a bounded domain by introducing a pair of transparent boundary conditions. It is then shown that for all but possibly a discrete set of parameters, there is a unique quasi–periodic weak solution to the diffraction problem. Our proof is based on the Hodge decomposition, a compact imbedding result, and the Lax–Milgram Lemma. In addition, an energy conservation for the weak solution is also shown.
Solutions with internal jump for an autonomous elliptic system of FitzHugh–Nagumo type
Authors: Reinecke Carolus , Sweers Guido 
Published: February 2003

AbstractSystems of elliptic partial differential equations which are coupled in a noncooperative way, such as the FitzHugh–Nagumo type studied in this paper, in general do not satisfy order preserving properties. This not only results in technical complications but also yields a richer solution structure. We prove the existence of multiple nontrivial solutions. In particular we show that there exists a solution with boundary layer type behaviour, and we will give evidence that this autonomous system for a certain range of parameters has a solution with both a boundary and an internal layer. The analysis uses results from bifurcation theory, variational methods, as well as some pointwise a priori estimates. The final section contains some numerically obtained results.
Effect of the crosslinking level on the properties of temperature‐sensitive poly(N‐isopropylacrylamide) hydrogels
Authors: Zhang Xian‐Zheng , Wu Da‐Qing , Chu Chih‐Chang 
Published: February 2003

AbstractIn this study, the effect of the level of crosslinking on the properties of poly(N‐isopropylacrylamide) (PNIPAAm) hydrogels was investigated in terms of their lower critical solution temperature (LCST), interior morphology, equilibrium swelling, and deswelling and swelling kinetics. The thermal analysis showed that PNIPAAm hydrogels, having a wide range of crosslinking levels, exhibited almost the same LCSTs, and this was different from what the conventional theory would have predicted. Scanning electron micrographs revealed that the interior network structure of the PNIPAAm matrix became more porous with an increase in the level of crosslinking. This more porous matrix provided numerous water channels for water diffusion in or out of the matrix and, therefore, an improved response rate to the external temperature changes during the deswelling process and the swelling process. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 582–593, 2003
Splitting of energy of dispersive waves in a star‐shaped network
Authors: Mehmeti F. Ali , Régnier V. 
Published: February 2003

AbstractWe study wave and Klein‐Gordon equations in a star‐shaped network. In the wave case we state a d'Alembert‐type solution formula generalizing the formula obtained in Ali Mehmeti [1] and [4] for four branches. In the Klein‐Gordon case (dispersive waves) we solve the problem using the Laplace transform with respect to time. We state a continuity equation linking the energy density and the energy flow for the Klein‐Gordon equation in a star‐shaped network. We observe that the splitting of energy at the central node is the same for propagating waves with and without dispersion.
Shelters for houseless youth: a follow‐up evaluation☆
Authors: Dekel Rachel , Peled Einat , Spiro Shimon E 
Published: February 2003

ABSTRACTThis study followed 345 Israeli youngsters who had been residents of two shelters for runaway and homeless youths, 6–12 weeks after their departure. Telephone interviews were conducted with the youngsters, their parents, and social workers in the community. A majority of the youngsters had either returned to their family homes, or had been placed out of home. Their residential stability was found to be low. Post‐shelter place of residence was related to length of stay at the shelter, amount of contact with their family while at the shelter, and manner of departure. Our findings lead to a typology of shelter uses, and also raise questions about the extent to which shelters achieve their declared goals.
Simian Virus 40 Small Tumor Antigen Induces Deregulation of the Actin Cytoskeleton and Tight Junctions in Kidney Epithelial Cells
Authors: Nunbhakdi-Craig Viyada , Craig Leonard , Machleidt Thomas , Sontag Estelle 
Published: February 2003

ABSTRACTThere is increasing evidence that the transforming DNA tumor virus simian virus 40 (SV40) is associated with human malignancies. SV40 small tumor antigen (small t) interacts with endogenous serine/threonine protein phosphatase 2A (PP2A) and is required for the transforming activity of SV40 in epithelial cells of the lung and kidney. Here, we show that expression of SV40 small t in epithelial MDCK cells induces acute morphological changes and multilayering. Significantly, it also causes severe defects in the biogenesis and barrier properties of tight junctions (TJs) but does not prevent formation of adherens junctions. Small t-induced TJ defects are associated with a loss of PP2A from areas of cell-cell contact; altered distribution and reduced amounts of the TJ proteins ZO-1, occludin, and claudin-1; and marked disorganization of the actin cytoskeleton. Small t-mediated F-actin rearrangements encompass increased Rac-induced membrane ruffling and lamellipodia, Cdc42-initiated filopodia, and loss of Rho-dependent stress fibers. Indeed, these F-actin changes coincide with elevated levels of Rac1 and Cdc42 and decreased amounts of RhoA in small t-expressing cells. Notably, these cellular effects of small t are dependent on its interaction with endogenous PP2A. Thus, our findings provide the first evidence that, in polarized epithelial cells, expression of small t alone is sufficient to induce deregulation of Rho GTPases, F-actin, and intercellular adhesion, through interaction with endogenous PP2A. Because defects in the actin cytoskeleton and TJ disruption have been linked to loss of cell polarity and tumor invasiveness, their deregulation by PP2A and small t likely contributes to the role of SV40 in epithelial cell transformation.
Subcellular Localization of Herpes Simplex Virus Type 1 UL51 Protein and Role of Palmitoylation in Golgi Apparatus Targeting
Authors: Nozawa Naoki , Daikoku Tohru , Koshizuka Tetsuo , Yamauchi Yohei , Yoshikawa Tetsushi , Nishiyama Yukihiro 
Published: February 2003

ABSTRACT

The herpes simplex virus type 1 (HSV-1) UL51 gene products are virion-associated phosphoproteins with apparent molecular masses of 27, 29, and 30 kDa in HSV-1-infected cells. In this study, we have investigated the intracellular localization and distribution of UL51 protein both in infected cells and in transfected cells expressing only UL51. We found that this protein colocalized closely with Golgi marker proteins such as the Golgi-58K protein and GM130 in transfected cells expressing only UL51. However, in infected cells, the UL51 protein localized to the juxtanuclear region but only partially colocalized with the Golgi maker proteins. Mutant protein analysis revealed that the N-terminal 15 amino acid residues of the UL51 protein sufficed for this Golgi localization property. The UL51 protein redistributed on addition of brefeldin A. This was prevented by pretreatment with 2-deoxyglucose and sodium azide, which results in ATP depletion, but not by pretreatment with NaF and AlCl
3
, which activates heterotrimeric G proteins. Moreover, we found that palmitoylation of the UL51 protein through the N-terminal cysteine at position 9 was necessary for its Golgi localization. Protease digestion analysis suggested that the UL51 protein localized on the cytoplasmic face of the membrane in UL51-transfected cells, while in infected cells it localized mainly to the inside of cytoplasmic vesicles and/or the viral envelope. Transmission immunoelectron microscopy revealed an association of UL51 protein-specific labeling with cytoplasmic virions and also with some membranous structure. We infer from these observations that internalization of UL51 protein into the cytoplasmic vesicle and/or virion may occur in association with viral envelopment in HSV-infected cells.
Nontransmissible Virus-Like Particle Formation by F-Deficient Sendai Virus Is Temperature Sensitive and Reduced by Mutations in M and HN Proteins
Authors: Inoue Makoto , Tokusumi Yumiko , Ban Hiroshi , Kanaya Takumi , Tokusumi Tsuyoshi , Nagai Yoshiyuki , Iida Akihiro , Hasegawa Mamoru 
Published: February 2003

ABSTRACT

The formation of nontransmissible virus-like particles (NTVLP) by cells infected with F-deficient Sendai virus (SeV/ΔF) was found to be temperature sensitive. Analysis by hemagglutination assays and Western blotting demonstrated that the formation of NTVLP at 38°C was about 1/100 of that at 32°C, whereas this temperature-sensitive difference was only moderate in the case of F-possessing wild-type SeV. In order to reduce the NTVLP formation with the aim of improving SeV for use as a vector for gene therapy, amino acid substitutions found in temperature-sensitive mutant SeVs were introduced into the M (G69E, T116A, and A183S) and HN (A262T, G264R, and K461G) proteins of SeV/ΔF to generate SeV/M
ts
HN
ts
ΔF. The use of these mutations allows vector production at low temperature (32°C) and therapeutic use at body temperature (37°C) with diminished NTVLP formation. As expected, the formation of NTVLP by SeV/M
ts
HN
ts
ΔF at 37°C was decreased to about 1/10 of that by SeV/ΔF, whereas the suppression of NTVLP formation did not cause either enhanced cytotoxicity or reduced gene expression of the vector. The vectors showed differences with respect to the subcellular distribution of M protein in the infected cells. Clear and accumulated immunocytochemical signals of M protein on the cell surface were not observed in cells infected by SeV/ΔF at an incompatible temperature, 38°C, or in those infected by SeV/M
ts
HN
ts
ΔF at 37 or 38°C. The absence of F protein in SeV/ΔF and the additional mutations in M and HN in SeV/M
ts
HN
ts
ΔF probably weaken the ability to transport M protein to the plasma membrane, leading to the diminished formation of NTVLP.
Dispersion effects in unreplicated factorial designs
Authors: Wiklander Kerstin , Holm Sture 
Published: February 2003

AbstractMethods for estimation of dispersion effects in two‐level unreplicated factorial designs are studied. The consequences of non‐constant variance are discussed. A natural assumption concerning the form of the covariance of location effects leads to a particular normal model. Some linear combinations of the response variables are constructed in order to make a simple structure for inference. The precision of point estimators of dispersion effects, where one is based on experiments with replicates, are compared. A numerical example is given as an illustration of a test. Finally, estimations in fractional designs are described and discussed. Copyright © 2002 John Wiley & Sons, Ltd.
A simple method for nicardipine hydrochloride quantification in plasma using solid‐phase extraction and reversed‐phase high‐performance liquid chromatography
Authors: Fernandes Catarina Marques , Veiga Francisco José Baptista 
Published: February 2003

AbstractA simple and sensitive reversed‐phase liquid chromatography method was developed and validated for the determination of nicardipine hydrochloride (NC) in rabbit plasma. Nicardipine hydrochloride and nimodipine, used as internal standard, were initially extracted from plasma by a rapid solid‐phase extraction using C18 cartridges. After extraction, nicardipine hydrochloride was separated by HPLC on a C18 column and quantified by ultraviolet detection at 254 nm. A mixture of acetonitrile–0.02 M sodium phosphate buffer–methanol (45:40:15) with 0.2% of triethylamine of pH of 6.1 was used as mobile phase. The mean (±SD) extraction efficiency of NC was 77.56 ± 5.4, 84.23 ± 4.32 and 83.94 ± 3.87% for drug concentrations of 5, 25 and 100 ng/mL, respectively. The method proved to be linear in the range of 5–100 ng/mL with a regression coefficient of 0.9993. The relative standard deviations of intra‐ and inter‐day analysis for NC in plasma were 3.26–6.52% (n = 5) and 4.71–9.38% (n = 5), respectively. The differences of the mean value measured from the concentration prepared, expressed in percentages (bias percentage), were only − 5.2, 0.4 and 0.8% at NC 5, 25 and 50 ng/mL, which confirmed the accuracy of the method. The analytical technique was used to determine NC plasma concentration after drug oral administration to rabbits. The results inferred that NC is rapidly absorbed in rabbits and has a short half‐life (t1/2 = 1.34 h). Copyright © 2003 John Wiley & Sons, Ltd.
Synthesis and Crystal Structure of IM‐6, a New Open Framework Cobalt–Gallium Phosphate with Ten‐ and Twelve‐Membered Pore Openings
Authors: Josien Ludovic , Simon‐Masseron Angélique , Gramlich Volker , Patarin Joël , Rouleau Loïc 
Published: February 2003

AbstractA new three‐dimensional microporous cobalt–gallium phosphate, named IM‐6, has been synthesized under solvothermal conditions with an N‐substituted piperazine as organic template. The structure was solved by single‐crystal X‐ray diffraction (triclinic, P$\bar 1$, a=9.848(20), b=12.470(32), c=12.603(28) Å, α=63.47(16)°, β=74.56(16)°, γ=76.03(17)°). IM‐6 exhibits a new framework topology. The inorganic framework is built up of MO4 (M=Co, Ga) and PO4 tetrahedra. It displays a two‐dimensional interconnected channel system running along the [0 $\bar 1$ 1] and [1 0 0] directions and delimited by ten‐ and twelve‐membered ring openings, respectively.
Elektrisch leitfähige Kunststoffe: Der Weg zu einer neuen Materialklasse
Authors: Rehahn Matthias 
Published: February 2003

AbstractKonventionelle gesättigte Polymere sind typische Isolatoren. Anders verhält es sich bei den konjugierten Polymeren: Liegen lange Ketten vor, die alternierend aus C‐C‐Doppel‐und C‐C‐Einfachbindungen bestehen, könnte es prinzipiell zu einer Delokalisierung der π‐Elektronen entlang des Polymerrückgrates kommen. Aufgrund der Peierls‐Instabilität ist dies aber nicht der Fall. Vielmehr bedarf es zusätzlich der Dotierung. Metallähnliche intrinsische Leitfähigkeit bei organischen Polymeren ist Ausgangspunkt für breite Anwendungen.
Electrochemical Approaches for Chemical and Biological Analysis on Mars
Authors: Kounaves Samuel P. 
Published: February 2003

AbstractObtaining in situ chemical data from planetary bodies such as Mars or Europa can present significant challenges. The one analytical technique that has many of the requisite characteristics to meet such a challenge is electroanalysis. Described here are three electroanalytical devices designed for in situ geochemical and biological analysis on Mars. The Mars Environmental Compatibility Assessment (MECA) was built and flight qualified for the now cancelled NASA Mars 2001 Lander. Part of MECA consisted of four “cells” containing arrays of electrochemical based sensors for measuring the ionic species in soil samples. A next‐generation MECA, the Robotic Chemical Analysis Laboratory (RCAL), uses a carousel‐type system to allow for greater customization of analytical procedures. A second instrument, proposed as part of the 2007 CryoScout mission, consists of a flow‐through inorganic chemical analyzer (MICA). CryoScout is a torpedo‐like device designed for subsurface investigation of the stratigraphic climate record embedded in Mars' north polar cap. As the CryoScout melts its way through the ice cap, MICA will collect and analyze the meltwater for a variety of inorganics and chemical parameters. By analyzing the chemistry locked in the layers of dust, salt, and ice, geologists will be able to determine the recent history of climate, water, and atmosphere on Mars and link it to the past. Finally, electroanalysis shows its abilities in the detection of possible microorganism on Mars or elsewhere in the solar system. To identify an unknown microorganism, one that may not even use Earth‐type biochemistry, requires a detection scheme which makes minimal assumptions and looks for the most general features. Recent work has demonstrated that the use of an array of electrochemical sensors which monitors the changes in a solution via electrical conductivity, pH, and ion selective electrodes, can be used to detect minute chemical perturbations caused by the growth of bacteria and with the correct methodology provide unambiguous detection of such life forms.