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Kinds of Ions Terms modified by Ions Selected AbstractsDeafferentation-induced apoptosis of neurons in thalamic somatosensory nuclei of the newborn rat: critical period and rescue from cell death by peripherally applied neurotrophinsEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 7 2000Alfonso Baldi Abstract This study shows that unilateral transection of the infraorbital nerve (ION) in newborn (P0) rats induces apoptosis in the contralateral ventrobasal thalamic (VB) complex, as evidenced by terminal transferase-mediated deoxyuridine triphosphate-biotin nick end labelling (TUNEL) and electron miscroscopy. Double-labelling experiments using retrograde transport of labelled microspheres injected into the barrel cortex, followed by TUNEL staining, show that TUNEL-positive cells are thalamocortical neurons. The number of TUNEL-positive cells had begun to increase by 24 h postlesion, increased further 48 h after nerve section, and decreased to control levels after 120 h. Lesion-induced apoptosis in the VB complex is less pronounced if ION section is performed at P4, and disappears if the lesion is performed at P7. This time course closely matches the critical period of lesion-induced plasticity in the barrel cortex. Nerve growth factor (NGF) or brain-derived neurotrophic factor (BDNF), applied on the ION stump alone or in combination, are able to partially rescue thalamic neurons from apoptosis. Total cell counts in the VB complex of P7 animals that underwent ION section at P0 confirm the rescuing effect of BDNF and NGF. Blockade of axonal transport in the ION mimics the effect of ION section. These data suggest that survival-promoting signals from the periphery, maybe neurotrophins, are required for the survival of higher-order neurons in the somatosensory system during the period of fine-tuning of neuronal connections. We also propose that anterograde transneuronal degeneration in the neonatal rat trigeminal system may represent a new animal model for studying the pathways of programmed cell death in vivo. [source] Ecological correlates of infraorbital foramen area in primatesAMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY, Issue 1 2010Magdalena N. Muchlinski Abstract The infraorbital foramen (IOF) transmits the infraorbital nerve (ION) to specialized sensory cells (mechanoreceptors) in the maxillary region. The size of the IOF has been used in numerous paleoecological interpretations of the fossil record. However, these interpretations have been applied without an explicit analysis of the relationship between ecological variables and the IOF. ION and IOF cross-sectional area show a strong positive correlation. As a result, IOF area can be a proxy for ION area, and it is hypothesized that IOF area may be a good measure for maxillary somatosensory acuity. Differences in diet, substrate preference, and/or activity pattern have been shown to correlate with differences in maxillary somatosensory acuity among mammals. This study examines how IOF area covaries with different ecological variables. IOF area was measured for 89 primate species. Ecological profiles were also created for each species and used to evaluate interspecific variation in relative IOF area within each ecological category. The results show a significant relationship between relative IOF area and diet, but not substrate preference or activity pattern. Frugivores have significantly larger relative IOFs than either folivores or insectivores, but the relative IOFs of folivores and insectivores do not differ significantly from one another. These results partially support the hypothesis that maxillary mechanoreception is a critical sensory cue for primates within a feeding context. Results for this study suggest the IOF can be used as an informative character in some paleoecological interpretations of the primate fossil record. Am J Phys Anthropol, 2010. © 2009 Wiley-Liss, Inc. [source] A PSYCHOANALYTICAL READING OF EURIPIDES, ION: REPETITION, DEVELOPMENT AND IDENTITYBULLETIN OF THE INSTITUTE OF CLASSICAL STUDIES, Issue 1 2008NAOMI WEISS First page of article [source] CASE REPORT: Clinical application of mfERG/VEP in assessing superior altitudinal hemifield lossCLINICAL AND EXPERIMENTAL OPTOMETRY, Issue 4 2005Dr Henry Ho-lung Chan PhD FAAO Multifocal ERG (mfERG) and multifocal VEP (mfVEP) have been used widely in the investigation of pathological changes or functional variations in the visual system. Altitudinal hemifield loss is a visual field defect that is usually found in patients with ischaemic optic neuropathy (ION). Anterior ischaemic optic neuropathy (AION) is a complex multi-factorial disease and it is difficult to diagnose according to clinical symptoms and signs alone. AION is believed to be caused by an infarction of the optic nerve due to the occlusion of the posterior ciliary arteries. The current report presents a patient diagnosed with non-arteritic AION. In this report, the mfERG findings did not match the results of the visual field test but those of the mfVEP did. After consideration of the visual electrophysiological and visual field results, the defect arises from neither the retina nor the visual pathway behind the optic chiasma. Hence, the optic nerve is the most likely location of the lesion, causing the superior altitudinal hemi-field loss. This report shows that the mfERG and mfVEP techniques can be used for objective visual field assessment to supplement the conventional visual field testing. [source] Improved Voltammetric Response of L -Tyrosine on Multiwalled Carbon Nanotubes-Ionic Liquid Composite Coated Glassy Electrodes in the Presence of Cupric IonELECTROANALYSIS, Issue 19 2008Liqin Liu Abstract L -Tyrosine can exhibit a small anodic peak on multiwalled carbon nanotubes (MWCNTs) coated glassy carbon electrodes (GCE). At pH,5.5 its peak potential is 0.70,V (vs. SCE). When an ionic liquid (i.e., 1-octyl-3-methylimidazolium hexafluorophosphate, [omim][PF6]) is introduced on the MWCNT coat, the peak becomes bigger. Furthermore, in the presence of Cu2+ ion the anodic peak of L -tyrosine increases further due to the formation of Cu2+ - L -tyrosine complex, while the peak potential keeps unchanged. Therefore, a sensitive voltammetry based on the oxidation of Cu2+ - L -tyrosine complex on MWCNTs-[omim][PF6] composite coated electrode is developed for L -tyrosine. Under the optimized conditions, the anodic peak current is linear to L -tyrosine concentration in the range of 1×10,8,5×10,6 M, and the detection limit is 8×10,9 M. The modified electrode shows good reproducibility and stability. In addition, the voltammetric behavior of other amino acids is explored. It is found that among them tryptophan (Trp) and histidine (His) can also produce sensitive anodic peak under same experimental conditions, and their detection limits are 4×10,9 M and 4×10,6 M, respectively. [source] Electrocatalytic Reduction of Nitrite Ion on a Toluidine Blue Sol-Gel Thin Film Electrode Derived from 3-Aminopropyl Trimethoxy SilaneELECTROANALYSIS, Issue 22 2007K. Thenmozhi Abstract An organically modified sol-gel electrode using 3-aminopropyltrimethoxy silane for covalent immobilization of a redox mediator namely toluidine blue has been reported. Cyclic voltammetric characterization of the modified electrode in the potential range of 0.2,V to ,0.6,V exhibited stable voltammetric behavior in aqueous supporting electrolyte with a formal potential of ,0.265,V vs. SCE, corresponding to immobilized toluidine blue. The electrocatalytic activity of the modified electrode when tested towards nitrite ion exhibited a favorable response with the electrocatalytic reduction of nitrite occurring at a reduced potential of ,0.34,V. A good linear working range from 2.94×10,6,M to 2.11×10,3,M with a detection limit of 1.76×10,6,M and quantification limit of 5.87×10,6,M was obtained for nitrite determination. The stable and quick response (4,s) of the modified electrode towards nitrite under hydrodynamic conditions shows the feasibility of using the present sensor in flow systems. Significant improvements in the operational stability by overcoming the leachability problem and repeatability with a relative standard deviation of 1.8% of the TB thin film sensor have been obtained by the strategy of immobilization of the mediator in the sol-gel matrix. [source] Disposable Screen-Printed Edge Band Ultramicroelectrodes for the Determination of Trace Amounts of Nitrite IonELECTROANALYSIS, Issue 10 2006Jen-Lin Chang Abstract The application of linear scan voltammetry for sensitive determination of nitrite by using a disposable screen-printed edge band carbon ultramicroelectrode (designated as SPUME) was reported in this study. The measurement with the SPUME can be performed in solutions of low ionic strength, e.g., natural waters, because the ohmic loses are negligible. The limiting oxidation current of nitrite showed a wide linear range up to 3,mM at the SPUME. A relative standard deviation of 2.46% (n=5) for analyzing 5,,M nitrite indicated a detection limit (S/N=3) of 0.38,,M. Real sample analysis of mineral and ground water samples as well as bratwurst food product showed satisfactory results. Since the SPUME is low cost and easy for mass production, the disposable nature further offers to application in diverse field of electroanalytical chemistry. [source] A Bis-Oxime Derivative of Diaza-18-Crown-6 as an Ionophore for Silver IonELECTROANALYSIS, Issue 11 2005Michael Abstract A new pendant-arm derivative of diaza-18-crown-6, containing two oxime donor groups, has been synthesized and incorporated into a polyvinyl chloride (PVC) membrane ion-selective electrode. The electrode shows selectivity for Ag+ ion, with a near Nernstian response. Pb2+, Cu2+, Hg2+, and Tl+ are major interfering ions, with Cd2+ having minor interference. The electrode shows no potentiometric response for the ions Mg2+, Al3+, K+, Ca2+, Ni2+, Fe3+, and La3+, and is responsive to H+ at pH<6. [source] Mixed Aza-Thioether Crowns Containing a 1,10-Phenanthroline Sub-Unit as Neutral Ionophores for Silver IonELECTROANALYSIS, Issue 24 2002Mojtaba Shamsipur Abstract Three different recently synthesized aza-thioether crowns containing a 1,10-phenanthroline sub-unit (L1,L3) and a corresponding acyclic ligand (L4) were studied to characterize their abilities as silver ion ionophores in PVC-membrane electrodes. Novel conventional silver-selective electrodes with internal reference solution (CONISE) and coated graphite-solid contact electrodes (SCISE) were prepared based on one of the 15-membered crowns containing two donating S atoms and two phenanthroline-N atoms (L1). The electrodes reveal a Nernstian behavior over wide Ag+ ion concentration ranges (1.0×10,5,1.0×10,1,M for CONISE and 5.0×10,8,4.0×10,2,M for SCISE) and very low limits of detection (8.0×10,6,M for CONISE and 3.0×10,8,M for SCISE). The potentiometric response is independent from pH of the solution in the pH range 3.0,8.0. The electrodes manifest advantages of low resistance, very fast response and, most importantly, good selectivities relative to a wide variety of other cations. The electrodes can be used for at least 2 months (for CONISE) and 4 months for (SCISE) without any appreciable divergence in potentials. The electrodes were used as an indicator electrode in the potentiometric titration of Ag+ ion and in the determination of silver in photographic emulsions and in radiographic and photographic films. [source] Design of Neutral Metallomesogens from 5,5-Dimethyldipyrromethane: Metal Ion Mediated Control of Folding and Hairpin StructuresEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 32 2008Kelly A. Ames Abstract New ligands derived from 5,5-dimethyldipyrromethane and their corresponding neutral complexes with ZnII and PdII are described. The ligands incorporate either a hexacatenar [H2(1n), n = 1, 10, 12, 14 and 16], tetracatenar [H2(2n), n = 1 and 16] or an extended dicatenar structure [H2(3n), n = 1and 16]. Single-crystal X-ray structure determinations of [Zn2(11)2] and [Zn2(31)2] confirm a distorted tetrahedral geometry at ZnII to afford double-stranded helical structures, while the PdII species [Pd(31)] shows a distorted square-planar geometry with the ligand adopting an alternative hairpin conformation. The metal-free hexacatenar ligands H2(1n) (n = 10, 12, 14, 16) and the corresponding complexes [Zn2(116)2] and [Pd(1n)] (n = 12, 14, 16) are not mesomorphic. However, the tetracatenar complex [Zn2(216)2] generates a smectic mesophase, as confirmed by X-ray diffraction, while [Pd(216)] and the metal-free ligand H2(216) show no mesomorphic behaviour. Two of the extended dicatenar compounds, H2(316) and [Zn2(316)2] are non-mesomorphic, while [Pd(316)] displays a smectic A phase.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] Stabilization of Long Cationic EMACs by Reduction or Loss of One Metal IonEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 27 2008Rayyat H. Ismayilov Abstract The new pyrimidyl- and naphthyridyl-modulated pentapyridyltetramine ligand (H3N9 -2pm) and its linear nona- and octanickel chain complexes were successfully synthesized. The nonanickel complex [Ni9(,9 -N9 -2pm)4Cl2](PF6)2 (1) contains two fully delocalized, mixed-valence [Ni2(napy)4]3+ units. Magnetic measurements performed on the defective octanuclear complex [Ni8(,8 -N9 -2pm)4Cl2](PF6)2 (2) demonstrate that the metal chain provides a pathway of magnetic superexchange coupling over the extended metal atom chain (EMAC). (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] Tripyrrinatocadmium Complexes: Enforcing Supramolecular Aggregation by a Large IonEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 7 2007Martin Bröring Abstract A newly developed method for the preparation of free base tripyrrin ligands HTrpy by cyanide-promoted demetalation of nickel chelates TrpyNiNCO was used in order to explore the chemistry of cadmium tripyrrins TrpyCdX with a variety of anionic co-ligands X. The introduction of the large CdII ion into the tripyrrin N3 coordination site was accomplished by the use of cadmium acetate as the metal precursor. Ligand exchange experiments using sodium salts of different anions disclose a marked tendency for pentacoordination, which is achieved either by the formation of chelates or of 1D coordination polymers that form as a consequence of the size of the central metal. The attempted introduction of chlorido, iodido, or cyanato ligands thus leads mainly to decomposed material, while the use of 1,1,1-trifluoracetylacetonate, salicylate, and acetate ligands results in stable, pentacoordinate and monomeric complexes with the external ligand bound as a four- or six-membered O,O -chelate ring. With the pseudohalogenido ligands thiocyanate, selenocyanate, and azide as well as with the weakly coordinating trifluoroacetate 1D coordination polymers with a variety of chain structures were obtained and investigated by X-ray diffraction studies. Interestingly TrpyCdN3 is present in the crystal as a coordinatively and hydrogen-bonded methanol adduct with a dimeric repeating subunit. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Kinetics and Mechanism of Oxidation of Fe2+ by the Tris(biguanide)manganese(IV) Ion in Aqueous Acid MediaEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 14 2004Basab Bijayi Dhar Abstract Tris(biguanide)manganese(IV), [Mn(LH2)3]4+ (LH2 = biguanide, C2N5H7), quantitatively oxidises Fe2+ to Fe3+ and is itself reduced to Mn2+ with almost quantitative (> 95%) release of biguanide. The reaction rate strongly depends on added Fe3+; in the presence of externally added Fe3+, the reaction shows a clear first-order dependence in [MnIV], whereas in the absence of any added Fe3+, an initial quick loss of MnIV is associated with a subsequent very sluggish decay. Two consecutive one-electron transfer inner-sphere steps are proposed for the entire redox process where [Mn(LH2)3]3+, the initial one-electron-reduced product of MnIV, is believed to be a steady-state intermediate. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source] Enantioselective Synthesis of Functionalized 1-Benzoxepines by Phenoxide Ion Mediated 7- endo - tet Carbocyclization of Cyclic Sulfates,,EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 2 2009Sajal Kumar Das Abstract A new asymmetric synthesis of 2,3-disubstituted 1-benzoxepines is described. Key steps include Sharpless asymmetricdihydroxylation of trans -,,,-unsaturated esters and phenoxide ion mediated intramolecular 7- endo - tet carbocyclization of syn -2,3-dihydroxy ester derived cyclic sulfates. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source] Stable Ion and Electrophilic Substitution (Nitration and Bromination) Study of A-Ring Substituted Phenanthrenes: Novel Carbocations and Substituted Derivatives; NMR, X-ray Analysis, and Comparative DNA BindingEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 3 2007Cédric Brulé Abstract Persistent carbocations were generated from five A-ring mono- and di-substituted phenanthrenes [3-OMe; 4-OMe, 1,3-bis(OMe), 2,4-bis(OMe), and 1,3-bis(Me)]. In all cases protonation occurs in the A-ring, ortho/para relative to methoxy or methyl substituent(s). Complete NMR assignments of the resulting carbocations are reported and their charge delocalization modes are discussed. Mild nitration (with 20,50,% aqueous HNO3 at ,10 °C or at room temp.) and bromination (NBS/MeCN/room temp.) of these substrates resulted in the synthesis of several novel mononitro-/dinitro- as well as monobromo/dibromo derivatives, including those with nitro or bromo substituent in the bay-region. Correspondence between the site of attack in low-temperature protonation study and nitro substitution in ambient mild nitrations are examined. Complete NMR assignments for the new derivatives are reported as well as X-ray structures for 2,4-dimethoxy-1-nitro- and 1,3-dimethyl-4-nitrophenanthrenes. A comparative DNA binding study with MCF cells on three of the synthesized mononitro and one dinitro derivative showed that 1,3-dimethyl-9-nitro- (nitro at the meso position), 3-methoxy-4-nitro- (nitro in bay-region), and 1,3-dimethoxy-4,9-dinitrophenanthrenes (nitro in both meso and bay-regions) formed DNA adducts. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Encapsulation and Stabilization of Reactive Aromatic Diazonium Ions and the Tropylium Ion Within a Supramolecular HostEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 24 2004Julia L. Brumaghim Abstract Supramolecular assemblies with internal cavities are being developed as nanoscale reaction vessels to protect or modify the reactivity of guest species through encapsulation. Diazonium cations and the tropylium cation were examined for their ability to encapsulate in the tetrahedral [Ga4L6]12, supramolecular assembly. The 4-(diethylamino)benzenediazonium cation 1 readily formed a 1:1 host,guest complex with this assembly, and this encapsulation prevented 1 from reacting with 2,4-pentanedione in D2O. The tropylium cation also formed a 1:1 host,guest complex with the [Ga4L6]12, assembly, greatly slowing its decomposition in D2O. Encapsulation in the protected environment of this host cavity alters the reactivity of these guest molecules, giving them greater stability. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004) [source] Spectroscopic Investigation of the Europium(3+) Ion in a New ZnY4W3O16 MatrixHELVETICA CHIMICA ACTA, Issue 11 2009bieta Tomaszewicz Abstract A new Zn and Eu tungstate was characterized by spectroscopic techniques. This tungstate, of the formula ZnEu4W3O16, crystallized in the orthorhombic system and was synthesized by a solid-state reaction. It melts incongruently at 1330°. The luminescent properties, including excitation and emission processes, luminescent dynamics, and local environments of the Eu3+ ions in ZnEu4W3O16 and ZnY4W3O16,:,Eu3+ diluted phases (1, 5, and 10,mol-% of Eu3+ ion) were studied basing on the f6 -intraconfigurational transitions in the 250,720,nm spectral range. The excitation spectra of this system (,em 615 and 470,nm) show broad bands with maxima at 265 and 315,nm related to the ligand-to-metal charge-transfer (LMCT) states. The emission spectra under excitation at the O,W (265,nm) and O,Eu3+ (315,nm) LMCT states present the blue-green emission bands. The emission of tungstate groups mainly originate from the charge-transfer state of excited 2p orbitals of O2, to the empty orbitals of the central W6+ ions. On the other hand, in the emission of the Eu3+ ions, both the charge transfer from O2, to Eu3+ and the energy transfer from W6+ ions to Eu3+ are involved. The emission spectra under excitation at the 7F0,5L6 transition of the Eu3+ ion (394,nm) of ZnY4W3O16,:,Eu3+ diluted samples show narrow emission lines from the 5D3, 5D2, and 5D1 emitting states. The effect of the active-ion (Eu3+) concentration on the colorimetric characteristic of the emissions of the compound under investigation are presented. [source] Micellar Effects on the Reaction between an Arenediazonium Ion and the Antioxidants Gallic Acid and Octyl GallateHELVETICA CHIMICA ACTA, Issue 1 2008Losada Barreiro, Sonia Abstract The effect of sodium dodecyl sulfate (SDS) micelles on the reaction between the 3-methylbenzenediazonium (3MBD) ion and either the hydrophilic antioxidant gallic acid (GA) or the hydrophobic analogue octyl gallate (OG) have been investigated as a function of pH. Titration of GA in the absence and presence of SDS micelles showed that the micelles do not alter the first ionization equilibrium of GA. Analysis of the dependence of the observed rate constant (kobs) with pH shows that the reactive species are GA2, and OG,. Kinetics results in the absence and presence of SDS micelles suggest that SDS aggregates do not alter the expected reaction pathway. SDS Micelles inhibit the spontaneous decomposition of 3MBD as well as the reaction between 3MBD and either GA or OG, and upon increasing the SDS concentration, with kobs approaching the value for the thermal decomposition of 3MBD in the presence of SDS. Our results are consistent with the prediction of the pseudophase model and show that the origin of the inhibition for the reaction with GA is different to that for the reaction with OG; in the former case, the observed inhibition can be rationalized in terms of the micelle-induced electrostatic separation of reactants in the micellar Stern layer, whereas the observed inhibition in the reaction with OG is a consequence of the dilution effect caused by increasing SDS concentration, decreasing the local OG, concentration in the Stern layer. [source] Methoxycarbonylation of Aliphatic Diamines with Dimethyl Carbonate Promoted by in situ Generated Hydroxide Ion: A Mechanistic ConsiderationADVANCED SYNTHESIS & CATALYSIS (PREVIOUSLY: JOURNAL FUER PRAKTISCHE CHEMIE), Issue 2-3 2010Dae Won Kim Abstract The methoxycarbonylation reactions of aliphatic diamines with dimethyl carbonate are accelerated greatly in the presence of water. Theoretical investigations on the mechanistic aspects of the methoxycarbonylation of 1,6-hexanediamine strongly suggest that the hydroxide ion, generated in situ from the interaction of 1,6-hexanediamine with water, is an active catalytic species and plays a pivotal role in the rate-determining hydrogen abstraction step from the amino group. [source] Physicochemical Properties of Cellulose Selectively Oxidized with the 2,2,6,6-Tetramethyl-1-Piperidinyl Oxoammonium IonJOURNAL OF FOOD SCIENCE, Issue 5 2007D.S. Suh ABSTRACT:, This study examined the characteristics of the oxidation reaction on the primary alcohol groups in cellulose involving the 2,2,6,6-tetramethyl-1-piperidinyl oxoammonium ion (TEMPO) and determined the optimum conditions for the preparation of oxidized cellulose (OC). The applicability of OC in polysaccharide systems was also investigated. The effects of TEMPO, sodium bromide (NaBr), and temperature on the oxidation reaction time, yield, and selectivity for primary alcohol groups were examined using response surface methodology (RSM). The reaction time decreased with increases in the temperature and the levels of TEMPO and NaBr. The yield increased with the level of NaBr and decreased as the temperature increased. Selectivity increased with the temperature and decreased as the levels of TEMPO and NaBr increased. The optimum levels of TEMPO and NaBr and the optimum temperature for the production of OC were determined as 0.3 mM/100 mM anhydroglucose unit (AGU), 50 mM/100 mM AGU, and 25 °C, respectively. The water and oil binding capacity and viscosity of cellulose increased with oxidation. Wheat starch containing OC exhibited a decreased initial pasting temperature and setback, but increased peak viscosity, gelatinization, and retrogradation enthalpy (,H). The hardness of the wheat starch gel decreased significantly upon the addition of OC. [source] Gas-phase tautomers of protonated 1-methylcytosine.JOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 11 2005Preparation, dissociation mechanisms, energetics Abstract Tautomers of 1-methylcytosine that are protonated at N-3 (1+) and C-5 (2+) have been specifically synthesized in the gas phase and characterized by tandem mass spectrometry and quantum chemical calculations. Ion 1+ is the most stable tautomer in aqueous and methanol solution and is likely to be formed by electrospray ionization of 1-methylcytosine and transferred in the gas phase. Gas-phase protonation of 1-methylcytosine produces a mixture of 1+ and the O-2-protonated tautomer (3+), which are nearly isoenergetic. Dissociative ionization of 6-ethyl-5,6-dihydro-1-methylcytosine selectively forms isomer 2+. Upon collisional activation, ions 1+ and 3+ dissociate by loss of ammonia and [C,H,N,O], whose mechanisms have been established by deuterium labeling and ab initio calculations. The main dissociations of 2+ following collisional activation are losses of CH2CNH and HNCO. The mechanisms of these dissociations have been elucidated by deuterium labeling and theoretical calculations. Copyright © 2005 John Wiley & Sons, Ltd. [source] Reactions of BBrn+ (n = 0,2) at fluorinated and hydrocarbon self-assembled monolayer surfaces: observations of chemical selectivity in ion,surface scatteringJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 7 2001Nathan Wade Abstract Ion,surface reactions involving BBrn+ (n = 0,2) with a fluorinated self-assembled monolayer (F-SAM) surface were investigated using a multi-sector scattering mass spectrometer. Collisions of the B+ ion yield BF2+ at threshold energy with the simpler product ion BF+· appearing at higher collision energies and remaining of lower abundance than BF2+ at all energies examined. In addition, the reactively sputtered ion CF+ accompanies the formation of BF2+ at low collision energies. These results stand in contrast with previous data on the ion,surface reactions of atomic ions with the F-SAM surface in that the threshold and most abundant reaction products in those cases involved the abstraction of a single fluorine atom. Gas-phase enthalpy data are consistent with BF2+ being the thermodynamically favored product. The fact that the abundance of BF2+ is relatively low and relatively insensitive to changes in collision energy suggests that this reaction proceeds through an entropically demanding intermediate at the vacuum,surface interface, one which involves interaction of the B+ ion simultaneously with two fluorine atoms. By contrast with the reaction of B+, the odd-electron species BBr+· reacts with the F-SAM surface to yield an abundant single-fluorine abstraction product, BBrF+. Corresponding gas-phase ion,molecule experiments involving B+ and BBr+· with C6F14 also yield the products BF+· and BF2+, but only in extremely low abundances and with no preference for double fluorine abstraction. Ion,surface reactions were also investigated for BBrn+ (n = 0,2) with a hydrocarbon self-assembled monolayer (H-SAM) surface. Reaction of the B+ ion and dissociative reactions of BBr+· result in the formation of BH2+, while the thermodynamically less favorable product BH+· is not observed. Collisions of BBr2+ with the H-SAM surface yield the dissociative ion,surface reaction products, BBrH+ and BBrCH3+. Substitution of bromine atoms on the projectile by hydrogen or alkyl radicals suggests that Br atoms may be transferred to the surface in a Br-for-H or Br-for-CH3 transfer reaction in an analogous fashion to known transhalogenation reactions at the F-SAM surface. The results for the H-SAM surface stand in contrast to those for the F-SAM surface in that enhanced neutralization of the primary ions gives secondary ion signals one to two orders of magnitude smaller than those obtained when using the F-SAM surface, consistent with the relative ionization energies of the two materials. Copyright © 2001 John Wiley & Sons, Ltd. [source] Enhanced permeation of methotrexate in vitro by ion pair formation with L -arginineJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 10 2009Vijay D. Ivaturi Abstract Ion paired solutions of methotrexate in L -arginine/water/propylene glycol systems were evaluated for their potential to enhance the permeation of methotrexate across rabbit nasal mucosa in vitro. The partition coefficient of methotrexate in the methotrexate: L -arginine ion paired systems was observed to be 24 times greater than that of the methotrexate system without L -arginine. The ion pair formation between methotrexate and L -arginine was confirmed by a decrease in the conductivity of the systems in the presence of propylene glycol, a dielectric constant reducing agent. The permeation of methotrexate across the rabbit nasal mucosa from the ion paired systems was observed to be significantly greater (p,<,0.05) as compared to control systems of methotrexate solution in water and a sodium salt. Furthermore, a threefold increase in the flux of methotrexate was observed when propylene glycol was added to the ion paired systems. These results suggest that methotrexate: L -arginine ion paired systems have potential in improving the permeation of methotrexate across rabbit nasal mucosa and may form the basis for further development of an intranasal therapeutic system of methotrexate. © 2008 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 98:3633,3639, 2009 [source] Ion imprinted polymer particles for separation of yttrium from selected lanthanidesJOURNAL OF SEPARATION SCIENCE, JSS, Issue 9 2006Ramakrishnan Kala Abstract Lanthanide(III) (Dy, Gd, Tb and Y) ion imprinted polymer (IIP) materials were synthesized via single pot reaction by mixing lanthanide imprint ion with 5,7-dichloroquinoline-8-ol, 4-vinylpyridine, styrene, divinylbenzene and 2,2,-azobisisobutyronitrile in 2-methoxyethanol porogen. The imprint ion was removed by stirring the above materials (after powdering) with 6 mol/L HCl to obtain the respective lanthanide IIP particles. Y-Dy, Y-Gd and Dy-Gd polymer particles were obtained by physically mixing equal amounts of the respective leached individual lanthanide(III) particles. Control polymer (CP) particles were similarly prepared without imprint ion. Application of the above synthesized polymer particles was tested for separation of Y from Dy, Gd and Tb employing batch and column SPE methods using inductively coupled plasma atomic emission spectrometry for the determination. Optimization studies show that Y present in 500 mL can be preconcentrated using Dy-Gd IIP particles and eluted with 20 mL of 1.0 mol/L of HCl, providing an enrichment factor of , 25. Dy-Gd IIP particles offer higher selectivity coefficients for Y over other lanthanides compared to other IIP particles and commercial liquid,liquid extractants. Selectivity studies for Y over other coexisting inorganic species (other than lanthanides) were also conducted and the results obtained show a quantitative separation of Y from other inorganics other than Cu(II) and Fe(III). Furthermore, both batch and column studies indicate the purification of yttrium concentrate from 55.0 ± 0.2 to 65.2 ± 0.2% in a single stage of operation. [source] Studies on Preparation and Fluorescent Properties of a Novel Photo-Sensitive Nanoparticle Composed of Europium Ion and Cinnamic Acid DerivativeMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 23 2009Dongjian Shi Abstract A novel fluorescent and photo-sensitive nanoparticle was self-assembled from an europium-based random copolymer, europium coordinated poly(methylacrylic acid)- co -poly(cinnamyl acrylate) (PMCFA-Eu3+), which was synthesized from methylacrylic acid (MAA), and Eu3+ -cinnamyl acrylate derivative (CFA) by radical polymerization. DLS and TEM results indicated the formation of spherical nanoparticles with 120,nm in diameter. The PMCFA-Eu3+ complex showed stronger fluorescence than Eu3+, indicating the effective energy transferred from the ligand to Eu3+. Moreover, the photo-crosslinking of the cinnamate groups induced a decrease in the diameter and an increase in the fluorescent properties of the PMCFA-Eu3+ nanoparticles. This functional nanoparticle might be useful as a carrier and a fluorescence probe in biomedical and fluorescent fields. [source] Cluster ion beam profiling of organics by secondary ion mass spectrometry , does sodium affect the molecular ion intensity at interfaces?RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 24 2008Felicia M. Green The use of cluster ion beam sputtering for depth profiling organic materials is of growing technological importance and is a very active area of research. At the 44th IUVSTA Workshop on "Sputtering and Ion Emission by Cluster Ion Beams", recent results were presented of a cluster ion beam depth profile of a thin organic molecular layer on a silicon wafer substrate. Those data showed that the intensity of molecular secondary ions is observed to increase at the interface and this was explained in terms of the higher stopping power in the substrate and a consequently higher sputtering yield and even higher secondary ion molecular sputtering yield. An alternative hypothesis was postulated in the workshop discussion which may be paraphrased as: "under primary ion bombardment of an organic layer, mobile ions such as sodium may migrate to the interface with the inorganic substrate and this enhancement of the sodium concentration increases the ionisation probability, so increasing the molecular ion yield observed at the interface". It is important to understand if measurement artefacts occur at interfaces for quantification as these are of great technological relevance , for example, the concentration of drug in a drug delivery system. Here, we evaluate the above hypothesis using a sample that exhibits regions of high and low sodium concentration at both the organic surface and the interface with the silicon wafer substrate. There is no evidence to support the hypothesis that the probability of molecular secondary ion ionisation is related to the sodium concentration at these levels. © Crown copyright 2008. Reproduced with the permission of Her Majesty's Stationery Office. Published by John Wiley & Sons, Ltd. [source] Ion Dynamics in Confined Spaces: Sodium Ion Mobility in Icosahedral Container Molecules,ANGEWANDTE CHEMIE, Issue 41 2010Maren Podewitz Gefangen und doch mobil: Ein zentrales PH2, -Ion (siehe Bild; magenta) ist in einem Behälter von zwölf tert -Butoxidanionen (rot und schwarz) in ikosaedrischer Anordnung verkapselt. Die 12 oder 13 Natriumgegenionen sind dynamisch über die 20 Ecken eines regulären Dodekaeders (blau) fehlgeordnet. Die Aktivierungsbarrieren für den Natriumaustausch sind bemerkenswert niedrig (10,30,kJ,mol,1) und liegen im Bereich schneller Lithiumionenleiter. [source] A Bowl-Shaped ortho -Semiquinone Radical Anion: Quantitative Evaluation of the Dynamic Behavior of Structural and Electronic Features,ANGEWANDTE CHEMIE, Issue 36 2010Akira Ueda Dr. Elegant aufgetischt: Das erste ,schüsselförmige" o -Semichinonradikal (siehe Bild; mit einem Na+ -Ion) wurde synthetisiert und bezüglich seiner elektronischen Eigenschaften charakterisiert. Das dynamische Verhalten (konkav,konvex) wurde mit EPR- und ENDOR/TRIPLE-Messungen sowie DFT-Rechnungen ebenfalls quantitativ untersucht. [source] Solving the Hydration Structure of the Heaviest Actinide Aqua Ion Known: The Californium(III) Case,ANGEWANDTE CHEMIE, Issue 22 2010Elsa Galbis Schwergewicht: Röntgenabsorptionsspektroskopie (schwarze Punkte) und Monte-Carlo-Simulationen (blaue Linie) von CfIII in wässriger Lösung wurden kombiniert, um den Ligandenabstand und die Koordinationszahl (CN) im CfIII -Aqua-Ion, dem schwersten bislang gemessenen und simulierten Kation, zu bestimmen (siehe Bild). Die Ergebnisse stützen das Vorliegen einer Kontraktion in der Actinoidreihe wie in der Lanthanoidreihe. [source] Adhesion Effects of a Guanidinium Ion Appended Dendritic "Molecular Glue" on the ATP-Driven Sliding Motion of Actomyosin,ANGEWANDTE CHEMIE, Issue 17 2010Kou Okuro Festgeklebt: Ein heterotropes Konjugat aus Actin und Myosin , Actomysin , wird durch einen wasserlöslichen ,molekularen Klebstoff", ein Dendrimer mit neun Guanidinium-Resten, stabilisiert (siehe Bild; ATP=Adenosintriphosphat, ADP=Adenosindiphosphat). Während das Dendrimer erster Generation die ATP-getriebene Gleitbewegung von Actinfilamenten auf dem Myosin-funktionalisierten Deckglas bremst oder zum Stillstand bringt, ist ein verwandtes Dendrimer nullter Generation dazu nicht in der Lage. [source] | ||||||||||||||||||||||||||||||||||||||||||||||||||||