bluuebunny/crossref_metadata_2025_split huggingface dataset:
A rapid method for fractionation and puriﬁcation of a 92 kDa cartilage glycoprotein
Authors: Roussidis Andreas E. , Anagnostides Stavros T. 
Published: April 2004

AbstractMatrix glycoproteins are among the main components that contribute to the properties of cartilage. In this article we report on the development of a rapid method for the fractionation and puriﬁcation of a 92 kDa glycoprotein from chick sternal cartilage. The developed procedure involves ion‐exchange chromatography on DEAE‐Sephacel, gel permeation chromatography on Sepharose CL‐6B and semi‐preparative SDS‐polyacrylamide gel electrophoresis. Identiﬁcation of protein was performed by western blotting using speciﬁc antibodies and purity by capillary electrophoresis. The proposed method is superior to those previously published since it eliminates the step of density gradient centrifugation. Copyright © 2003 John Wiley & Sons, Ltd.
Stability indicating reversed‐phase high‐performance liquid chromatographic and thin layer densitometric methods for the determination of ziprasidone in bulk powder and in pharmaceutical formulations
Authors: El‐Sherif Zeinab A. , El‐Zeany Badr , El‐Houssini Ola M. , Rashed Mohamed S. , Aboul‐Enein Hassan Y. 
Published: April 2004

AbstractTwo sensitive and reproducible methods were developed and validated for the determination of ziprasidone (ZIP) in the presence of its degradation products in pure form and in pharmaceutical formulations. The ﬁrst method was based on reversed‐phase high‐performance liquid chromatography (HPLC), on a Lichrosorb RP C18 column using water:acetonitrile:phosphoric acid (76:24:0.5 v/v/v) as the mobile phase at a ﬂow rate of 1.5 mL min−1 at ambient temperature. Quantiﬁcation was achieved with UV detection at 229 nm over a concentration range of 10–500 µg mL−1 with mean percentage recovery of 99.71 ± 0.55. The method retained its accuracy in presence of up to 90% of ZIP degradation products. The second method was based on TLC separation of ZIP from its degradation products followed by densitometric measurement of the intact drug spot at 247 nm. The separation was carried out on aluminium sheet of silica gel 60 F254 using choloroform:methanol:glacial acetic acid (75:5:4.5 v/v/v) as the mobile phase, over a concentration range of 1–10 µg per spot and mean percentage recovery of 99.26 ± 0.39. Both methods were applied successfully to laboratory prepared mixtures and pharmaceutical capsules. Copyright © 2003 John Wiley & Sons, Ltd.
The Effect of Pressure on Hydrogen Transfer Reactions with Quinones
Authors: Wurche Frank , Sicking Wilhelm , Sustmann Reiner , Klärner Frank‐Gerrit , Rüchardt Christoph 
Published: April 2004

AbstractThe effect of pressure on the oxidation of hydroarenes3–9with 2,3‐dichloro‐5,6‐dicyano‐1,4‐quinone (DDQ;1 a) oro‐chloranil (10), leading to the corresponding arenes, has been investigated. The activation volumes were determined from the pressure dependence of the rate constants of these reactions monitored by on‐line UV/Vis spectroscopic measurements in an optical high‐pressure cell (up to 3500 bar). The finding that they are highly negative and only moderately dependent on the solvent polarity (ΔV≠= −13 to −25 in MTBE and −15 to −29 cm3 mol−1in MeCN/AcOEt, 1:1) rules out the formation of ionic species in the rate‐determining step and is good evidence for a hydrogen atom transfer mechanism leading to a pair of radicals in the rate‐determining step, as was also suggested by kinetic measurements, studies of kinetic isotope effects, and spin‐trapping experiments. The strong pressure dependence of the kinetic deuterium isotope effect for the reaction of 9,10‐dihydroanthracene5/5‐9,9,10,10‐D4with DDQ (1 a) can be attributed to a tunneling component in the hydrogen transfer. In the case of formal 1,3‐dienes and enes possessing two vicinal CH bonds, which have to be cleaved during the dehydrogenation, a pericyclic hydrogen transfer has to considered as one mechanistic alternative. The comparison of the kinetic deuterium isotope effects determined for the oxidation of tetralin9/9‐1,1,4,4‐D4/9‐2,2,3,3‐D4/9‐D12either with DDQ (1 a) or with thymoquinone1 cindicates that the reaction with DDQ (1 a) proceeds in a stepwise manner through hydrogen atom transfer, analogously to the oxidations of 1,4‐dihydroarenes, whereas the reaction with thymoquinone1 cis concerted, following the course of a pericyclic hydrogen transfer. The difference in the mechanistic courses of these two reactions may be explained by the effect of the CN and Cl substituents in1 a, which stabilize a radical intermediate better than the alkyl groups in1 c. The mechanistic conclusions are substantiated by DFT calculations.
Preparation and Reactions of 1,3‐Diphosphacyclobutane‐2,4‐diyls That Feature an Amino Substituent and/or a Carbonyl Group
Authors: Sugiyama Hiroki , Ito Shigekazu , Yoshifuji Masaaki 
Published: April 2004

AbstractThe preparation and properties of a 1‐amino‐1,3‐diphosphacyclobutane‐2,4‐diyl and a 1‐benzoyl‐1,3‐diphosphacyclobutane‐2,4‐diyl, which can be regarded as functionalized cyclic biradical derivatives, were investigated. Hydrolysis of 1‐diisopropylamino‐3‐methyl‐2,4‐bis(2,4,6‐tri‐tert‐butylphenyl)‐1,3‐diphosphacyclobutane‐2,4‐diyl (7), which is formed by reaction of Mes*CP (4; Mes*=2,4,6‐tBu3C6H2) with lithium diisopropylamide and iodomethane, resulted in ring‐opening of the 1,3‐diphosphacyclobutane‐2,4‐diyl skeleton, as well as de‐aromatization of one of the Mes* rings. 3‐Oxo‐1,3‐diphosphapropene 8 and 7‐phosphabicyclo[4.2.0]octa‐1(8),2,4‐triene 9 were the resultant products, and these were subsequently characterized. Isomerization and oxidation of 7 occurred in the presence of TEMPO (2,2,6,6‐tetramethyl‐1‐piperidinoxy) to give the first example of a cyclic dimethylenephosphorane derivative, namely 3‐oxo‐1,3‐diphospha‐1,4‐diene 10. 1‐Benzoyl‐3‐tert‐butyl‐2,4‐bis(2,4,6‐tri‐tert‐butylphenyl)‐1,3‐diphosphacyclobutane‐2,4‐diyl (12) was isolated and characterized from the reaction of 4 with tert‐butyllithium and benzoyl chloride. Compound 12 was subsequently heated and underwent rearrangement of the benzoyl group and ring‐expansion to afford 1‐oxo‐1H‐[1,3]diphosphole 13. Reaction of 4 with lithium diisopropylamide and benzoyl chloride afforded the 2H‐[1,2,4]oxadiphosphinine 15, which was probably formed through the 1,3‐diphosphacyclobutane‐2,4‐diyl intermediate 14. Thermolysis of 15 afforded 1‐oxo‐1H‐[1,3]diphosphole 16 in an Arbuzov‐type rearrangement.
The Ground and Excited States of Polyenyl Radicals C2n−1H2n+1 (n=2–13): A Valence Bond Study
Authors: Luo Yan , Song Lingchun , Wu Wei , Danovich David , Shaik Sason 
Published: April 2004

AbstractThe semiempirical valence bond (VB) method, VBDFT(s), is applied to the ground states and the covalent excited states of polyenyl radicals C2n−1H2n+1 (n=2–13). The method uses a single scalable parameter with a value that carries over from the study of the covalent excited states of polyenes (W. Wu, D. Danovich, A. Shurki, S. Shaik, J. Phys. Chem. A, 2000, 104, 8744). Whenever comparison is possible, the VB excitation energies are found to be in good accord with sophisticated molecular orbital (MO)‐based methods like CASPT2. The symmetry‐adapted Rumer structures are used to discuss the state‐symmetry and VB constitution of the ground and excited states, and the expansion to VB determinants is used to gain insight on spin density patterns. The theory helps to understand in a coherent and lucid manner the properties of polyenyl radicals, such as the makeup of the various states, their geometries and energies, and the distribution of the unpaired electrons (the neutral solitons).
Hybrid Integral‐Equation/Simulation Models: From Complexation Thermodynamics to Direct Free Energies
Authors: Kast Stefan M. 
Published: April 2004

AbstractStatistical‐mechanical integral equation theory, an approximate methodology for computing distribution functions and thermodynamic properties of the liquid state, can be advantageously combined with molecular simulations to overcome inherent limitations of both approaches. This Concept discusses a number of conceptual applications that illustrate the capabilities of hybrid models: A study of complex formation in solution by explicit simulation of only the solute molecules, the correction of artefacts induced by truncated potentials, and an approach to the direct computation of free energies from a simulation of a single state.
Simulated Annealing Study of Diblock Copolymer Thin Films Confined between Two Homogeneous Surfaces
Authors: Yin Yuhua , Sun Pingchuan , Chen Tiehong , Li Baohui , Jin Qinghua , Ding Datong , Shi An‐Chang 
Published: April 2004

AbstractThin films of symmetric diblock copolymers confined between two parallel surfaces have been systematically investigated by means of simulated annealing on a simple cubic lattice. The study was carried out for systems with different film thicknesses and surface–polymer interactions. Very regular equilibrium morphologies of lamella are formed in almost all cases. The dependence of lamellar orientations, total energy, chain‐conformation entropy, and free energy of the confined films on the film thickness and the strength of surface–polymer interactions has been studied systematically. The influence of packing frustration on morphology is observed and the mechanisms of lamellar orientations are investigated.
Solvate‐Supported Proton Transport in Zeolites
Authors: Franke Marion E. , Simon Ulrich 
Published: April 2004

AbstractSolvate‐supported proton transport in zeolite H‐ZSM‐5 was studied by means of complex impedance spectroscopy. The zeolite shows enhanced proton mobility in the presence of NH3 and H2O that depends on the concentration of the solvate molecule, temperature (298–773 K), and the SiO2/Al2O3 ratio of the zeolite (30–1000). In general, proton conductivity in H‐ZSM‐5 is most effectively supported in the presence of NH3 and H2O at high concentrations, low temperatures, and low SiO2/Al2O3 ratios (≤80). For the aluminum‐rich samples desorption measurements reflect different transport mechanisms that depend on the respective temperature range. Up to about 393 K a Grotthus‐like proton transport mechanism is assumed, whereas at higher temperatures (393–473 K) vehiclelike transport seems to dominate. The activation energies for NH4+ and H3O+ vehicle conductivity depend on the SiO2/Al2O3 ratio, and the values are in the range of 49–59 and 39–49 kJ mol−1, respectively, and thus significantly lower than those for “pure” proton conduction in solvate‐free samples.
Ground and Excited‐State Electronic Interactions in Poly(propylene amine) Dendrimers Functionalized with Naphthyl Units: Effect of Protonation and Metal Complexation
Authors: Pina Fernando , Passaniti Paolo , Maestri Mauro , Balzani Vincenzo , Vögtle Fritz , Gorka Marius , Lee Sang‐Kyu , van Heyst Jeroen , Fakhrnabavi Hassan 
Published: April 2004

AbstractWe report the absorption spectra and the photophysical properties (fluorescence spectrum, quantum yield, and lifetime) of four dendrimers of the poly(propylene amine) family (POPAMs) functionalized at the periphery with naphthylsulfonamide (hereafter called naphthyl) units. Each dendrimer Gn, where n=1 to 4 is the generation number, comprises 2n+1 (i.e., 32 for G4) naphthyl functions in the periphery and 2n+1−2 (i.e., 30 for G4) tertiary amine units in the branches. All the experiments have been carried out in acetonitrile solutions. Comparison with two reference compounds (N‐methyl‐naphthalene‐2‐sulfonamide, A, and N‐(3‐dimethylamino‐propyl)‐2‐naphthalene‐1‐sulfonamide, B) has shown that the absorption spectra of the dendrimers are significantly different from those expected from the component units. Furthermore, the intense fluorescence band of the naphthyl unit (λmax=343 nm; Φ=0.15, τ=8.5 ns) is strongly quenched in the dendrimers. The quenching effect increases with increasing generation and is accompanied by the appearance of a weak and broad emission tail at lower energy. Protonation of the amine units of the dendrimers by addition of CF3SO3H (triflic) acid causes a strong increase in the intensity of the naphthyl luminescence and a change in the form of the emission tail. The shapes of the titration curves depend on dendrimer generation, but in any case, the effect of the acid can be fully reversed by successive addition of a base (tributylamine). The results obtained show that in the dendrimers there are interactions (both in the ground and excited states) between naphthyl units as well as between naphthyl units and amine units of the branches; this gives rise to dimer/excimer and charge‐transfer/exciplex excited states. Titration with Zn(CF3SO3)2 has the same effect as acid titration, as far as the final emission spectrum is concerned, but a much higher concentration of Zn(CF3SO3)2 has to be used and the shapes of the titration plots are very different. Titration with Co(NO3)2.6H2O causes a much smaller increase in the intensity of the naphthyl fluorescence compared with Zn(CF3SO3)2 . The results obtained have shown that protonation and metal coordination can reveal the presence of ground and excited state electronic interactions in functionalized poly(propylene amine) dendrimers, and that the presence of photoactive units in the dendrimers can be useful to reveal some peculiar aspects of the protonation and metal coordination processes.
Hydrogen Bonding in Mimics of Watson–Crick Base Pairs Involving CH Proton Donor and F Proton Acceptor Groups: A Theoretical Study
Authors: Guerra Célia Fonseca , Bickelhaupt F. Matthias , Baerends Evert Jan 
Published: April 2004

AbstractWe have theoretically analyzed mimics of Watson–Crick adenine–thymine (AT) and guanine–cytosine (GC) base pairs in which NH⋅⋅⋅O and N⋅⋅⋅HN hydrogen bonds are replaced by NH⋅⋅⋅F and N⋅⋅⋅HC, respectively, by using the generalized gradient approximation of density functional theory at BP86/TZ2P. The general effect of the above substitutions is an elongation and weakening of the hydrogen bonds that hold together the base pairs. However, the precise effects depend on how many and, in particular, on which hydrogen bonds are substituted in AT and GC. Another purpose of this work is to clarify the relative importance of electrostatic attraction versus orbital interaction in the weak hydrogen bonds involved in the mimics, by using a quantitative bond‐energy decomposition scheme. At variance with widespread believe, the orbital interaction component in these weak hydrogen bonds is found to contribute 34–42 % of the attractive interactions and is thus of the same order of magnitude as the electrostatic component, which provides the remaining attraction component.
Electrocatalysis of Nitrate Reduction at Copper‐Nickel Alloy Electrodes in Acidic Media
Authors: Simpson Brett K. , Johnson Dennis C. 
Published: April 2004

AbstractThe cathodic reduction of NO$\rm{ {_{3}^{-}}}$ in 1.0 M HClO4 is investigated by voltammetry at pure Ni and Cu electrodes, and three Cu‐Ni alloy electrodes of varying composition, all configured as rotated disks. Voltammetric data obtained using these hydrodynamic electrodes demonstrate significantly improved activity for NO$\rm{ {_{3}^{-}}}$ reduction at Cu‐Ni alloy electrodes as compared to the pure Ni and Cu electrodes. This observation is explained on the basis of the synergistic benefit of different surface sites for adsorption of H‐atoms, generated by cathodic discharge of H+ at Ni‐sites, and adsorption of NO$\rm{ {_{3}^{-}}}$ at Cu‐sites on these binary alloy electrodes. Koutecky‐Levich plots indicate that the cathodic response for NO$\rm{ {_{3}^{-}}}$ at a Cu75Ni25 electrode corresponds to an 8‐electron reduction, which is consistent with production of NH3. In comparison, the cathodic response at Cu50Ni50 and Cu25Ni75 electrodes corresponds to a 6‐electron reduction, which is consistent with production of NH2OH. Flow injection data obtained using Cu50Ni50 and Cu25Ni75 electrodes with 100‐μL injections exhibit detection limits for NO$\rm{ {_{3}^{-}}}$ of ca. 0.95 μM (ca. 95 pmol) and 0.60 μM (ca. 60 pmol), respectively.
Voltammetric Study of Some Synthetic Antioxidants on Platinum Microelectrodes in Acetic Acid Medium
Authors: Michalkiewicz Slawomir , Mechanik Monika , Malyszko Jan 
Published: April 2004

AbstractThe electrochemical oxidation of the antioxidants tert‐butylhydroquinone (BHQ), tert‐butyl‐4‐hydroxyanisole (BHA) and butylated hydroxytoluene (BHT) has been investigated by voltammetry at platinum microelectrodes in glacial acetic acid containing sodium perchlorate or sodium acetate as a background electrolyte. BHQ, a compound with para‐diphenyl groups, was typically found to have lower oxidation potential than isolated phenols BHA and BHT. Particular attention has been devoted to the mechanism of the electrode processes. Linear scan voltammograms recorded under steady‐state conditions showed well‐defined oxidation waves of the compounds studied even at relatively high concentrations (2 mM), due to a low proclivity for adsorption of the oxidation products on the electrode surface in acetic acid. The optimal conditions for the voltammetric determination of BHQ, BHA and BHT have also been studied. The results reveal that sensitive response for all the oxidants studied can be obtained in solution containing 0.1 M NaClO4 and 0.1 M CH3COONa by using the differential pulse voltammetry and square‐wave voltammetry. Peak currents were found to vary linearly with the antioxidant concentration over the range 3×10−5−1×10−3 M.
Lead Sulfide Nanoparticle as Oligonucleotides Labels for Electrochemical Stripping Detection of DNA Hybridization
Authors: Zhu Ningning , Zhang Aiping , Wang Qingjiang , He Pingang , Fang Yuzhi 
Published: April 2004

AbstractWe report a method for the detection of DNA hybridization in connection to lead sulfide (PbS) nanoparticle tags and electrochemical stripping measurement of the lead. A kind of lead sulfide nanoparticle with free carboxyl groups on its surface was synthesized in aqueous solution. The nanoparticle was used as a marker to label a sequence‐known oligonucleotide, which was then employed as a DNA probe for identifying a target ssDNA immobilized on a PPy modified electrode based on a specific hybridization reaction. The hybridization events were monitored by the oxidation dissolution of the lead sulfide anchored on the hybrids and the indirect determination of the lead ions by anodic stripping voltammetry (ASV). The detection limit is 0.3 pmol L−1 of target oligonucleotides. The PbS nanoparticle combining its easy conjugation to the DNA molecule with the highly sensitive stripping voltammetry detection of lead shows its promising application in the electrochemical DNA hybridization analysis assay.
The Mediated Reduction of Lindane in DMF
Authors: Birkin P. R. , Evans A. , Milhano C. , Montenegro M. I. , Pletcher D. 
Published: April 2004

AbstractThe direct and mediated reductions of the hexachlorocyclohexane, lindane, in DMF are reported. 9,10‐diphenylanthracene (DPA) is a particularly effective mediator. The reaction of DPA− with lindane is a very fast reaction and, indeed, with ratios of [lindane]/[DPA]<5, the mediated reduction of lindane is mass transfer limited with respect to lindane. During the mediated reduction, light emission can be seen even in an undarkened laboratory; this is due to the formation of DPA*.
Power calculations for familial aggregation studies
Authors: Rabbee Nusrat , Betensky Rebecca A. 
Published: April 2004

AbstractFamily studies are frequently undertaken as the first step in the search for genetic determinants of disease. Significant familial aggregation of disease is suggestive of a genetic etiology for the disease, and may lead to more focused genetic analyses. Many methods have been proposed in the literature for the analysis of family studies. One model that is appealing for its simplicity of computation and the conditional interpretation of its parameters is the quadratic exponential model (e.g., Zhao and Prentice [1990] Biometrika 77:642–648; Betensky and Whittemore [1996] Appl. Stat. 45:422–429; Hudson et al. [2001a] Am. J. Epidemiol. 153:500–514). However, a limiting factor in its application, as well as that of the other proposed methods, is that power and sample size calculations have not been derived. These calculations are essential for investigators who are designing family studies. Here we derive analytic approximations for power for testing for familial aggregation, for both randomly sampled and nonrandomly sampled families. We also present simulation studies of power for both single‐ and two‐disease cases, both under random and nonrandom sampling. © 2004 Wiley‐Liss, Inc.
Accuracy of fine‐needle aspiration cytology of salivary gland lesions in the netherlands cancer institute
Authors: Postema Rolf J. , van Velthuysen Mari‐Louise F. , van den Brekel Michiel W. M. , Balm Alfons J. M. , Peterse Johannes L. 
Published: April 2004

AbstractBackground.To evaluate the accuracy of fine‐needle aspiration cytology (FNAC) in salivary gland lesions in a tertiary referral center.Methods.A cytohistologic correlation study was performed using an automated pathology database of 1023 patients diagnosed with a salivary gland lesion.Results.In 388 cases, both cytology and histology were available. Using cytologic confirmation of malignancy as the starting point, the sensitivity, specificity, and accuracy of FNAC in this study were 88%, 99%, and 96%, respectively. Exact type‐specific concordance of the malignant diagnosis was achieved in 66 (88%) of 75 cases and in 211 (95%) of 223 benign cases. Of the 19 cases with a cytologic diagnosis “cyst,” four proved to be malignant. A non‐neoplastic lesion at cytology proved to be correctly classified in 53 (68%) of 80 patients.Conclusions.Our data show that cytology is a reliable and accurate technique to assess lesions of the salivary glands. The cytologic diagnosis of “cysts” and “non‐neoplastic lesions” should be interpreted with caution. © 2004 Wiley Periodicals, Inc. Head Neck 26: 418–424, 2004
Promising results with chemoradiation in patients with sinonasal undifferentiated carcinoma
Authors: Rischin Danny , Porceddu Sandro , Peters Lester , Martin Jarad , Corry June , Weih LeAnn 
Published: April 2004

AbstractBackground.Sinonasal undifferentiated carcinoma (SNUC) is an uncommon malignancy associated with poor prognosis. The optimal treatment approach for SNUC has not been established was performed.Methods.A retrospective review of all patients with SNUC seen at the Peter MacCallum Cancer Centre over a 12‐year period.Results.Ten patients with SNUC were identified, with nine having locally advanced disease (T4). Seven were treated with three cycles of platinum and 5‐fluorouracil followed by radiation with two cycles of concurrent platinum. In these seven patients, the 2‐year progress on‐free survival was 43% (95% CI, 11% to 82%) and 2‐year overall survival was 64% (95% CI, 23% to 91%). One patient with a T1N0 nasal cavity tumor treated with radiation alone has not relapsed. Two patients who were treated with initial surgical resection, prior to referral to our institution, received postoperative radiation, but they subsequently had relapses and died.Conclusion.Induction chemotherapy followed by concurrent chemoradiation is promising treatment strategy for SNUC. © 2004 Wiley Periodicals, Inc. Head Neck 26: 435–441, 2004.