bluuebunny/crossref_metadata_2025_split huggingface dataset:
Tandem mass spectra of divalent metal ion adducts of glycosyl sulfides, sulfoxides and sulfones; distinction among stereoisomers
Authors: Madhusudanan K. P. , Kumar Brijesh , Kanojiya Sanjeev , Agnihotri Geetanjali , Misra Anup Kumar 
Published: October 2006

AbstractThe tandem mass spectra of the divalent metal ion (Mg2+, Ca2+, Sr2+, Ba2+, Mn2+, Ni2+, Co2+ and Zn2+) adducts of acetylated 1,2‐trans‐glycosyl sulfides, sulfoxides and sulfones were examined using low energy collision‐induced dissociation on a Quattro II quadrupole tandem mass spectrometer. Abundant doubly charged ions, such as [3M + Met]2+ and [2M + Met]2+, were observed with alkaline earth metal chlorides. The other ions observed were [M + MetCl]+, [M + MetOAc]+, [M + MetO2SPh]+ and [2M + MetCl]+. The deprotonated metal adducts [M + Met‐H]+ were seen only in the sulfones. The divalent metal ion adducts showed characteristic fragmentation pathways for the glycosyl sulfides, sulfoxides and sulfones, depending on the site of metal attachment. The doubly charged metal ion adducts dissociate to two singly charged ions, [M + MetOAc]+ and [M − OAc]+, in the sulfides and sulfoxides. In the sulfones, the adducts dissociate to [M + MetO2SPh]+ and [M − O2SPh]+. In contrast to the alkaline earth metals, which attach to the acetoxy functions, the transition metals attach to the sulfide and sulfoxide functions. The metal chloride adducts display characteristic fragmentation for the sulfides, sulfoxides and sulfones. The glucosyl, mannosyl and galactosyl sulfides, sulfoxides and sulfones could be differentiated on the basis of the stereochemically controlled MS/MS fragmentations of the metal chloride adducts. Copyright © 2006 John Wiley & Sons, Ltd.
A generic stepwise optimization strategy for liquid chromatography electrospray ionization tandem mass spectrometry methods
Authors: Moberg My , Bergquist Jonas , Bylund Dan 
Published: October 2006

AbstractThe feasibility and advantages of using sophisticated chemometric tools in combination with the execution of thoroughly planned experiments to determine experimental conditions for optimal performance of an LC‐ESI‐MS/MS analysis is demonstrated. A stepwise strategy is proposed, which provides a controlled optimization procedure of the chromatographic quality (in terms of separation among the sample constituents) and maximizes the mass spectrometric signal of the selected product ions. Design of experiments (DOE) and response surface methodology are applied throughout the procedure. The stepwise approach has the advantage of dealing with the different optimization criteria separately, i.e. first ensuring sufficient chromatographic separation, then maximizing the amount of precursor ion entering the mass spectrometer, and finally generating high amounts of selected product ions. The experiments are performed on a linear ion trap mass spectrometer. Retention mapping using the band‐tracking model is applied during LC development, which facilitates the optimization of segmented gradients. A set of different siderophores, strong iron chelates, is used as the model substances. Copyright © 2006 John Wiley & Sons, Ltd.
Current analytical methods for the detection of dityrosine, a biomarker of oxidative stress, in biological samples
Authors: DiMarco Theresa , Giulivi Cecilia 
Published: October 2006

AbstractDityrosine is a fluorescent molecule formed as a result of normal posttranslational processing. In many structural proteins, dityrosine confers resistance to proteolysis and physicochemical trauma as a stabilizing crosslink. Dityrosine has also been found in oxidative/nitrative stress under a variety of conditions and biological systems. In this regard, it has been used as an important biomarker for oxidatively modified proteins during UV and γ‐irradiation, aging, and exposure to oxygen free radicals, nitrogen dioxide, peroxynitrite, and lipid hydroperoxides. Renewed interest in dityrosine and other tyrosine oxidation products as clinical indicators of oxidative modification has driven the development of important techniques for the specific analysis and quantification of these molecules. The presence of elevated levels of dityrosine in mammalian tissue and urine samples has been measured by chromatographic separation followed by mass spectrometry GC‐MS and HPLC‐MS/MS. Increases in dityrosine levels have been associated with pathologies such as eye cataracts, atherosclerosis, acute inflammation, and Alzheimer's disease. The continued development of, and increased accessibility to, improved mass spectrometric instrumentation will expand the capability, feasibility, and sensitivity with which specific biomarkers like dityrosine can be measured. © 2006 Wiley Periodicals, Inc., Mass Spec Rev 26:108–120, 2007
Age at menopause predicts age at onset of Parkinson's disease
Authors: Ragonese Paolo , D'Amelio Marco , Callari Graziella , Salemi Giuseppe , Morgante Letterio , Savettieri Giovanni 
Published: October 2006

AbstractWe investigated the association between age at onset of Parkinson's disease (PD) and fertile life characteristics in 145 women. Linear regression analyses showed a significant correlation between age at PD onset and age at menopause (P = 0.003), between age at PD onset and fertile life duration (P = 0.008), and a nonsignificant correlation between PD onset and cumulative duration of pregnancies (P = 0.23). These results support the possible role of estrogens in PD. © 2006 Movement Disorder Society
Hypoperfusion of the visual pathway in parkinsonian patients with visual hallucinations
Authors: Matsui Hideaki , Nishinaka Kazuto , Oda Masaya , Hara Narihiro , Komatsu Kenichi , Kubori Tamotsu , Udaka Fukashi 
Published: October 2006

AbstractLittle is known about the developing mechanisms of visual hallucinations in Parkinson's disease. This study aimed to investigate perfusion changes in parkinsonian patients with visual hallucinations using n‐isopropyl‐p‐[123I]iodoamphetamine ([123I]IMP) single photon emission computed tomography imaging. A total of 70 consecutive patients, including 31 patients with visual hallucinations, and 39 patients without hallucinations, participated in this study. Patients with severe cognitive impairment (Mini‐Mental State Examination score < 20), nonvisual hallucinations, or confusion were excluded. We compared brain perfusion changes between the two groups. We found that hallucinatory patients had significant perfusion reductions in the bilateral inferior parietal lobule, inferior temporal gyrus, precuneus gyrus, and occipital cortex compared to nonhallucinatory patients. These results suggested that hypoperfusion of the visual pathway was closely related to visual hallucinations in Parkinson's disease. © 2006 Movement Disorder Society
Cellular uptake mechanisms and potential therapeutic utility of peptidic cell delivery vectors: Progress 2001–2006
Authors: Fischer Peter M. 
Published: October 2006

AbstractCell delivery vectors (CDVs) are short amphipathic and cationic peptides and peptide derivatives, usually containing multiple lysine and arginine residues. They possess inherent membrane activity and can be conjugated or complexed with large impermeable macromolecules and even microscopic particles to facilitate cell entry. Various mechanisms have been proposed but it is now becoming clear that the main port of entry into cells of such CDV constructs involves adsorptive‐mediated endocytosis rather than direct penetration of the plasma membrane. It is still unclear, however, how and to what extent CDV constructs are capable of exiting endosomal compartments and reaching their intended cellular site of action, usually the cytosol or the nucleus. Furthermore, although many CDVs can mediate cellular uptake of their cargo and appear comparatively non‐toxic to cells in tissue culture, the utility of CDVs forin vivoapplications remains poorly understood. Whatever the mechanisms of cell entry and disposition, the overriding question as far as potential pharmacological application of CDV conjugates is concerned is whether or not a therapeutic margin can be achieved by their administration. Such a margin will only result if the intracellular concentration in the target tissues necessary to elicit the biological effect of the CDV cargo can be achieved at systemic CDV exposure levels that are non‐toxic to both target and bystander cells. It is proposed that the focus of CDV research now be shifted from mechanisticin vitrostudies with labeled but otherwise unconjugated CDVs toin vivopharmacological and toxicological studies using CDV‐derivatized and other cationized forms of inherently non‐permeable macromolecules of true therapeutic interest. © 2006 Wiley Periodicals, Inc. Med Res Rev, 27, No. 6, 755–795, 2007
Combined use of Overhauser spectroscopy and NMR diffusion experiments for mapping the hydration structure of nucleosides: structure and dynamics of uridine in water
Authors: Seba Hadj B. , Thureau Pierre , Ancian Bernard , Thévand André 
Published: October 2006

AbstractComplementary results from 13C intermolecular nuclear Overhauser effects (NOE), 1H13C heteronuclear Overhauser spectroscopy (HOSEY) and 1H‐NMR diffusion measurements were used for probing the structure of the first solvation shell of uridine in water. It is demonstrated that a cyclic dihydrate is formed. The two water molecules produce two hydrogen bonds with the two oxygen atoms from the pyrimidine ring and accept only one hydrogen bond from the amide proton. The dihydrate has only a short lifetime as compared with the rotational correlation time of the free nucleoside. The chemical exchange constant of the amide proton with water is then estimated by diffusion experiments. The results are consistent with previous data obtained for uracil in water and provide interesting information about water accessibility in nucleic acid bases. Copyright © 2006 John Wiley & Sons, Ltd.
Analytical solution of the harmonic waves diffraction by a cylindrical lined cavity in poroelastic saturated medium
Authors: Karinski Y. S. , Shershnev V. V. , Yankelevsky D. Z. 
Published: October 2006

AbstractThis paper presents a model for the analysis of plane waves diffraction at a cavity in an infinite homogeneous poroelastic saturated medium, lined by a lining composed of four equal segments. An elastic boundary layer is placed between the cavity lining and the infinite porous medium. The boundary layer is simulated by ‘elastic boundary conditions’ in which the bulk matrix stress is proportional to the relative displacement between the lining and the surrounding medium matrix boundary. In addition, fluid impermeability through the intermediate layer is assumed.For the frequencies, that differ from the pseudoresonanse frequencies, the problem was reduced to the problem of an ideal elastic medium.A closed‐form analytical solution of the problem was obtained using Fourier–Bessel series, the convergence of which was proven. It was shown that the number of series terms required to obtain a desired level of accuracy can be determined in advance.The influence of the medium porosity on the medium dynamic stress concentration was studied. Copyright © 2006 John Wiley & Sons, Ltd.
Influence of dipolar species on charge transport in poly[2‐methoxy‐5‐(2′‐ethylhexyloxy)‐p‐phenylene vinylene]
Authors: Toman Petr , Nešpůrek Stanislav , Weiter Martin , Vala Martin , Sworakowski Juliusz , Bartkowiak Wojciech , Menšík Miroslav 
Published: October 2006

AbstractA theoretical study and experimental evidence for a decrease of the charge carrier mobility in poly[2‐methoxy‐5‐(2′‐ethylhexyloxy)‐p‐phenylene vinylene] (MEH‐PPV) under the influence of dipolar species are presented in this paper. The presence of polar species in the vicinity of an MEH‐PPV chain modifies the on‐chain site energies and consequently, due to random mutual positions and orientations, increases the width of the energy distribution of the chain transport states. The influence of energetic disorder of these states on the charge carrier mobility was modeled by means of the Monte Carlo method, based on a numerical solution of the time‐dependent Schrödinger equation in the tight‐binding approximation. It was shown that the increasing disorder destroys the resonance between charge carrier energies on adjacent sites and, therefore, limits the diffusive charge carrier motion. Copyright © 2006 John Wiley & Sons, Ltd.
Synthesis, structural and mechanical properties of porous polymeric scaffolds for bone tissue regeneration based on neat poly(ε‐caprolactone) and its composites with calcium carbonate
Authors: Olah Laszlo , Filipczak Katarzyna , Jaegermann Zbigniew , Czigany Tibor , Borbas Lajos , Sosnowski Stanislaw , Ulanski Piotr , Rosiak Janusz M. 
Published: October 2006

AbstractThe aim of the present study was to develop new materials which could be applicable as bone substitutes or be used in bone tissue engineering. Two types of porous scaffolds based on poly(ε‐caprolactone) (PCL) were investigated. Type 1 scaffolds were prepared by solvent casting/particulate leaching technique, using NaCl with the grain size 250–500 µm as a porogen. In the case of Type 2 scaffolds, the biodegradable polymer was blended with calcium carbonate, which, in contrast to NaCl, is not leached out from the product during manufacture, either in the form of calcite powder or aragonite (needle‐like crystals). Influence of manufacturing technique and initial substrate composition on product properties was investigated. The tests involved porosity measurements, structure analysis by optical and scanning electron microscopy and mechanical studies (determination of compression strength and modulus). The results indicate the important role of the phase exchange process in the formation of micropores. In this process PCL precipitated from its acetone solution in the presence of water creating microporous three‐dimensional polymer structures. The Type 1 scaffolds possessed both micropores and macropores. Good interconnectivity between the pores was observed for samples of the initial porogen content higher than 33%. Microporous samples containing inorganic filler have lower porosity and higher compression strength. For Type 2 scaffolds the shape of filler particles has an important influence on mechanical properties—replacing powder with needle‐like crystals (in the same weight amount) results in a three‐ to five‐fold increase in compression modulus. Copyright © 2006 John Wiley & Sons, Ltd.
Biomacromolecular engineering: design, synthesis and characterization. One‐pot synthesis of block copolymers of arborescent polyisobutylene and polystyrene
Authors: Puskas Judit E. , Kwon Yongmoon 
Published: October 2006

AbstractNovel arborescent block copolymers comprising of an arborescent rubbery polyisobutylene (PIB) midsegment and glassy polystyrene (PSt) end blocks were prepared by sequential addition of monomers. Synthesis was conducted by the use of 4‐(2‐methoxyisopropyl) styrene as an inimer‐type initiator in conjunction with titanium tetrachloride (TiCl4) in 60:40 (v/v) methylcyclohexane/methyl chloride solvent mixture. Isobutylene was polymerized for 1–2 hr and then prechilled styrene in the same solvent mixture was sequentially added with select additives to the reaction flask. The recovered block copolymers were purified and then characterized by 1H‐NMR, size exclusion chromatograph (SEC), tensile test, atomic force Microscopy (AFM) and X‐ray photoelectron spectroscopy (XPS). Samples with 16.4–32.8 wt% PSt and Mn = 47,600–125,900 g/mol (Mw/Mn = 2.02–4.45) displayed thermoplastic elastomeric properties with 5–9.2 MPa tensile strength and 490–920% elongation. The arborescent block copolymers showed surface morphologies ranging from spherical to cylindrical/lamellar nanometer‐sized discreet PSt phases dispersed in a continuous PIB matrix, with a 10 nm PIB layer on the surface. Drug release profiles of paclitaxel from two arborescent blocks were found to be similar to that measured from Translute®. Copyright © 2006 John Wiley & Sons, Ltd.
In situ synthesis of optically transparent interpenetrating organic/inorganic networks
Authors: Widmaier Jean‐Michel , Bonilla Gabriela 
Published: October 2006

AbstractTernary hybrid interpenetrating networks composed of polyurethane (PU), poly(methyl methacrylate) (PMMA) and silica were prepared by in situ bulk polymerization. The inorganic phase was generated from tetraethoxysilane (TEOS) via sol‐gel chemistry. Highly transparent films were successfully synthesized using (trimethoxysilyl)propyl methacrylate (TMSPM) and isocyanatopropyl triethoxy silane (IPTES) as dual coupling agents. In order to minimize undesirable side‐reactions, PU was allowed to prepolymerize first before introduction of water into the reactive medium. According to infrared spectroscopic analysis and thermogravimetric studies of the hybrid materials, the condensation reaction was not complete certainly due to the presence of the organic components. The experimental procedure has to be optimized before any application of these hybrids as damping materials. Copyright © 2006 John Wiley & Sons, Ltd.
Ferrocene containing copolymers with improved electrostatic dissipation properties for advanced applications
Authors: Smith Trent M. , Nelson Gordon L. 
Published: October 2006

AbstractPolyurethane (PU) and polyimide (PI) copolymers containing a ferrocene oligomer (FcOlig) in the backbone were synthesized and characterized. PU materials with the FcOlig in the chain (PU‐FcOlig) demonstrated improved electrostatic dissipation properties and decreased electrical resistance in comparison to the unmodified PU parent material. The surface resistance decreased nearly 30 times and the volume resistance decreased nearly 12 times with a 3.5% FcOlig reacted in with Rubinate® 9272. The same 3.5% PU‐FcOlig material exhibited an average surface potential resulting from charge deposited of 130 ± 4 V down from 1600 ± 65 V for the unmodified PU. The charge dissipation time to 1/e (initial voltage divided by e) was also decreased to 81 ± 7 msec for 1.5% PU‐FcOlig materials from an average of 934 ± 62 msec for the parent PU. Incorporating the FcOlig into the backbone of a PI (BPDA‐ODA PI FcOlig) had no significant effects on the electrical properties in comparison to the unmodified parent PI (BPDA, 3,3′, 4,4′‐biphenyltetracarboxylic dianhydride; ODA, 3,3′‐oxydianiline). The difference in electrical properties between the ferrocene containing PUs and PIs is the lack of FcOlig blocks on or near the surface of the PI. X‐ray photoelectron spectroscopy (XPS) confirms that on the surface of the ferrocene containing PUs iron in the form of ferrocene is detected, but even after etching the PIs to a depth of 50, 100, 500 Å, and finally scraping the surface with a scalpel no iron was observed. Published in 2006 by John Wiley & Sons, Ltd.
Formation and structure of organized molecular films for fluorinated comb copolymers
Authors: Fujimori Atsuhiro , Masuya Ryosuke , Masuko Toru , Ito Eisuke , Hara Masahiko , Kanai Kaname , Ouchi Yukio , Seki Kazuhiko , Nakahara Hiroo 
Published: October 2006

AbstractThe molecular orientation in monolayer and multilayer films of fluorinated comb copolymers with various monomer ratios can be characterized by in‐plane and out‐of plane X‐ray diffraction (XRD), near‐edge X‐ray absorption fine structures (NEXAFS) spectroscopy at the C K‐edges, and atomic force microscopic observation. And further, the fine structure in the solid state and phase transition behavior of newly synthesized comb copolymers having fluorocarbon and hydrocarbon side‐chains were investigated by temperature controlled wide‐angle X‐ray diffraction (WAXD) and differential scanning calorimetry (DSC). From the WAXD profiles, two kinds of short spacing peaks based on the formation of the sub‐cell for fluorinated and hydrogenated side‐chains were confirmed at 5.0 and 4.1 Å, respectively. Furthermore, two kinds of endothermic peaks, which corresponded to melting peaks of both side‐chain crystals, appeared in the heating process of the DSC thermograms. From these experimental findings, the phase separation structure having the independently packed immiscible side‐chain crystalline formed in the whole polymer crystal. In addition, it was found that these comb polymers formed highly ordered (double) layer structures estimated using WAXD and small‐angle X‐ray scattering (SAXS). These fluorinated comb copolymers form the monolayer on the water surface and their transferred film with phase separated structure at nanometer size on the solid. There were hydrogenated domains at 10–20 nm diameter scales in these phase separated surface structures of the monolayers. From these experimental results, these copolymer monolayers are expected to be used as in new molecular devices such as nano‐lithography based on the surface patterning of polymer nano‐materials. Copyright © 2006 John Wiley & Sons, Ltd.
Prediction of peptide structure: How far are we?
Authors: Thomas Annick , Deshayes Sébastien , Decaffmeyer Marc , Van Eyck Marie Hélène , Charloteaux Benoit , Brasseur Robert 
Published: October 2006

AbstractRational design of peptides is a challenge, which would benefit from a better knowledge of the rules of sequence–structure–function relationships. Peptide structures can be approached by spectroscopy and NMR techniques but data from these approaches too frequently diverge. Structures can also be calculated in silico from primary sequence information using three algorithms: Pepstr, Robetta, and PepLook. The most recent algorithm, PepLook introduces indexes for evaluating structural polymorphism and stability. For peptides with converging experimental data, calculated structures from PepLook and, to a lesser extent from Pepstr, are close to NMR models. The PepLook index for polymorphism is low and the index for stability points out possible binding sites. For peptides with divergent experimental data, calculated and NMR structures can be similar or, can be different. These differences are apparently due to polymorphism and to different conditions of structure assays and calculations. The PepLook index for polymorphism maps the fragments encoding disorder. This should provide new means for the rational design of peptides. Proteins 2006. © 2006 Wiley‐Liss, Inc.
A hinge of the endogeneous ATP synthase inhibitor protein: The link between inhibitory and anchoring domains
Authors: Domínguez‐Ramírez L. , Gómez‐Puyou A. , de Gómez‐Puyou M. Tuena 
Published: October 2006

AbstractThe ATP synthase of bovine heart mitochondria possesses a regulatory subunit called the endogenous inhibitory protein (IF1). This subunit regulates the catalytic activity of the F1 sector in the mitochondrial inner membrane. When ΔμH+ falls, IF1 binds to the enzyme and inhibits ATP hydrolysis. On the other hand, the establishment of a ΔμH+ induces the release of the inhibitory action of IF1, allowing ATP synthesis to proceed. IF1 is also involved in the dimerization of soluble F1. Dynamic domain analysis and normal mode analysis of the reported crystallographic structure of IF1 revealed that it has an effective hinge formed by residues 46–52. Molecular dynamics data of a 27 residue fragment confirmed the existence of the hinge. The hinge may act as a regulatory region that links the inhibitory and anchoring domains of IF1. The residues assigned to the hinge are conserved between mammals, but not in other species, such as yeasts. Likewise, unlike the heart inhibitor, the yeast protein does not have the residues that allow it to form stable dimers through coiled‐coil interactions. Collectively, the data suggest that the hinge and the dimerization domain of the inhibitor protein from bovine heart are related to its ability to form stable dimers and to interact with other subunits of the ATP synthase. Proteins 2006. © 2006 Wiley‐Liss, Inc.