2-[2-[4-[2-[2-[1,3-Dihydro-1,1-bis(4-hydroxyphenyl)-3-oxo-5-isobenzofuranthioureidyl]ethylaminocarbonyl]ethyl]phenyl] ethylamino]-5′-N-ethylcarboxamidoadenosine (FITC-APEC): A fluorescent ligand for A2a-adenosine receptors

The fluorescein conjugate, FITC-APEC (2-[2-[4-[2-[2-[1,3-dihydro-1,1-bis(4-hydroxyphenyl)-3-oxo-5-isobenzofuranthioureidyl]ethylaminocarbonyl]ethyl] phenyl]ethylamino]-5-N-ethylcarboxamidoadenosine), is a novel ligand derived from a series of functionalized congeners that act as selective A_2a-adenosine receptor agonists. The binding of FITC-APEC to bovine striatal A_2a-adenosine receptors measured by fluorescence techniques was saturable and of a high affinity, with aB _max of 2.3±0.3 pmol/mg protein andK _D of 57±2 nM. TheK _D value estimated by fluorescence was consistent with theK _i (11±0.3 nM) obtained by competition studies with [³H]CGS 21680. Additionally, theB _max value found by FITC-APEC measurement was in agreement withB _max values obtained using radioligand binding. FITC-APEC exhibited rapid and reversible binding to bovine striatum. The potencies of chemically diverse A_2a-adenosine receptor ligands estimated by inhibition of FITC-APEC binding were in good agreement with their potencies determined using radioligand binding techniques (r=0.97,P=0.0003). FITC-APEC binding was not altered by purine derivatives that do not recognize A_2a-adenosine receptors. These findings demonstrate that the novel fluorescent ligand FITC-APEC can be used in the quantitative characterization of ligand binding to A_2a-adenosine receptors.     

Study of vibrational relaxation of O_3 (001)using photoacoustic technique

I.IntroductionStudyofvibrationalkineticsofozonemoleculesintheatmosphericairisimportantowingtostronginfluenceofthereagent'svibrationalexcitationonratesofchemicalreactionwithparticipationofozone,aproblemreferredtodestructionoftheozonelayerintheatmosphere[1].Majorityofexperimentaldataonvibrationalrelaxationconstantsofozonemoleculeswasobtainedbythelaserfluorescence[2landdoubleresonancel3]techniques.Thesetechniquesallowustomeasuretherateconstantsoflevelpopulationvariationoccurringalloverthepossible…     

A Spectroscopic Study of 2-[4′-(Dimethylamino)phenyl]-benzothiazole Binding to Insulin Amyloid Fibrils

The spectroscopic properties of 2-[4′-(dimethylamino)phenyl]-benzothiazole (BTA-2) in solution and in the presence of amyloid fibrils were investigated using absorption and fluorescence spectroscopy. Solution studies show that BTA-2 forms micelles in aqueous solutions, but that the dye can be solvated upon the addition of acetonitrile (CH₃CN). BTA-2 binds to amyloid fibrils in solution leading to a characteristic blue-shift in the emission spectrum and an increase in fluorescence intensity. However, in solutions with increasing CH₃CN concentration, there was a marked decrease in binding of the BTA-2 to fibrils. Studies demonstrating the effect of BTA-2 concentration on binding were performed. A comparison with the standard amyloid fluorescent marker, thioflavin T (ThT), showed that BTA-2 is more fluorescent, making it an excellent dye to label amyloid samples.     

Study on third-order nonlinear optical properties of a soluble poly(p-phenylene vinylene) derivative

Recently, π-conjugated polymers with large π-electrondelocalization have received much attention because oftheir larger and ultra faster nonlinear optical (NLO)response due to the distortion of π-conjugated elec-tronic charge distribution along the main chain[1-3].Poly(p-phenylene vinylene) (PPV) and its derivativesare typical π-conjugated polymers that have been de-scribed in the literature for the possibility of using themin light-emitting device and large-area multicolor dis-play, whi…     

Superconductivity of κ-(BEDT-TTF)2Cu[N(CN)2]I under pressure

The insulating state of κ-(BEDT-TTF)₂Cu[N(CN)₂]I salt appearing at ambient pressure at low temperatures is suppressed by hydrostatic pressure. The resistive measurements showed that the emerging metallic state reveals superconductivity in high-quality crystals. The superconducting state with the transition temperature of about 8 K is stable at pressures higher than 0.1 GPa.     

Study of the reaction 12C(γ, n 3He)2α

The possibility of separating, with the aid of photoemulsion, channels of the reaction ¹²C(γ, n ³He)2α that involve the formation of ⁷Be and ⁸Be intermediate nuclei in excited states is studied. The experimental energy distributions of these nuclei are obtained. The relative yields from these reaction channels are estimated.     

The electronic structure of oriented poly[2-methoxy-5-(2’-ethyl-hexyloxy)- 1,4-phenylene-vinylene]

Poly[2-methoxy-5-(2-ethyl-hexyloxy)-1,4-phenylene-vinylene] (MEH-PPV) adopts a preferential orientation on indium tin oxide. Although the basic building block of this polymer provides a negligible overall point-group symmetry, the polymer MEH-PPV packs with sufficient order to exhibit band structure. The polymer is fragile with bond cleavage evident following both argon-ion impact and ultraviolet radiation, but annealing leads to the restoration of much of the bond order. PACS 78.40.Me; 73.20.-r; 79.40.+z     

Structure of the product of intracomplex alkylation of target octanucleotide pd[TGTTTGGC] by means of 4-[N-methyl-N-(2-chloro-ethyl)-amino]benzyl-5′-phosphamido derivative of heptanucleotide pd[CCAAACA]: Two-dimensional1H-NMR spectroscopy and restrained molecular mechanics refinement

The spatial structure of a covalent adduct — the product of intracomplex alkylation at N-3-position of dC-8 nucleoside residue of target octanucleotide pd[TGTTTGGC] by means of 4-[N-methyl-N-(2-chloroethyl)amino]benzyl-5′-phosphamido derivative of heptanucleotide pd[CCAAACA] — has been investigated in aqueous solution by two-dimensional (2D)¹H-NMR spectroscopy and restrained molecular mechanics calculations. By using COSY, COSY-DQF and NOESY experiments the assignment of oligonucleotide protons as well as protons of modifying group was carried out. The correlation times of benzylamide fragment protons and those of neighbouring nucleotide residues dC-1 and dC-8 were shown to be equal and shorter thanτ _c of intraduplex nucleotides. The analysis of proton-proton coupling constants for H1′, H2′a, H2′b and H3′ protons showed all sugar residues to be in 2′-endo conformation. The distances between protons closed in the space were determined by means of a set of one-dimensional (1D) NOE experiments. The experimental distances were used as the constraints for energy minimization by molecular mechanics calculations. Eight conformations of benzylamide fragment of the covalent adduct differed with orientations of 4-N-methyl residue of the alkylating group and 1-methyleneamide linker function were constructed as starting structures in energy minimization procedure. Among of the resulting optimized structures only one S(Alk)8^* was found to satisfy both experimental data and energetic criteria. The benzylamide fragment in conformation S(Alk)8^* has been shown to localize in the region of lacked nucleoside residue of the duplex at the end of heptanucleotide chain less than 5 Å apart from the residues dC-1 and alkylated dC-8.     

A Photoelectron Spectroscopic Study of the 2-Azidopyridine ⇋ Tetrazolo [1.5-α]Pyridine Equilibrium between 391 and 533 K

The azido/tetrazole equilibrium has been widely examined^1,2,3 but most of the studies concern the solid state and the solution. The publications dealing with the vapour phase are rare and contain only qualitative information obtained either by IR or MS. However, it is clearly established that the azido form is stabilized at high temperatures. In the particular case of 2-azidopyridine I, according to ¹H NMR and IR data, the equilibrium lies strongly on the side of the tetrazole II in solution.^3,4 In the vapour phase at high temperature, mass spectrometry,⁵ IR,⁶ and the nature of compounds obtained by gas phase pyrolysis^7,8 of tetrazolo [1,5-α]pyridines, shown that the azide form is favoured in those conditions.     

Luminescent Properties of the Hexakis(Nitrito)Europate(Iii) Ion [Eu(No2)6]3−

Abstract

The 12-coordinated hexakis(nitrato)europate(III) ion displays a luminescence spectrum compatible with T_h, symmetry, with essentially a single emission line at 16 873 cm^?1 arising from the ⁵D₀→⁷F₁ transition. At low temperature (4.2 - 170 K), the lifetime of the ⁵D₀ level amounts to 10.9 ms and then sharply decreases because of vibrational de-excitation processes (E_a = 2 250 ± 1 490 cm^?1). The forbidden ⁵D₀→⁷F₀ transition displays an extensive pattern of Stokes and anti Stokes vibrational components and its energy reflects a nephelauxetic parameter for the nitrite ions δO(NO₂) equal to -14.4, slightly larger than the one associated to the nitrate ion in [Eu(NO₃)₆]^3-. The ligand excitation spectrum contains several bands displaying extensive vibrational structure mostly due to the δ(NO₂) vibrational mode.     

Study of the critical current density and the thermodynamic critical field in deuterated κ-(BEDT-TTF)2Cu[N(CN)2]Br organic superconductor

ABSTRACT

We have studied the reversible and irreversible part of the hysteresis loops as a function of slow cooling rate through the order–disorder transformation near 80?K for the deuterated (κ-D₈-Br) κ-(BEDT-TTF)₂Cu[N(CN)₂]Br organic superconductor. We estimated the critical current density J_C and the thermodynamic critical field H_C from the magnetic hysteresis loops. Temperature dependence of the critical current density derived from the irreversible part using Bean’s model. The thermodynamic critical field H_C has been obtained from the reversible part of the hysteresis loops.     

Electron paramagnetic resonance of quasi-one-dimensional crystal [Nd2(Cl3COO)6(H2O)3]n · nH2O

A quasi-one-dimensional single crystal of [Nd₂(Cl₃COO)₆(H₂O)₃]_n · nH₂O in which chains are built up of two alternating neodymium-ion dimer fragments is studied by the EPR technique. It is found that anisotropic interactions between neodymium ions in a chain are responsible for the complex shape of the EPR spectrum. Two groups of EPR signals are distinguished in the spectrum. Each group corresponds to one of the chain dimers disturbed by the interaction with neighbors in the chain. The shape of the EPR spectra is interpreted as a superposition of the spectra of chain fragments which have different lengths and are formed by the alternating magnetic triplet and nonmagnetic singlet states in the chain. Consideration is given to two cases when two alternating dimer fragments are either equivalent or nonequivalent to each other. It is shown that the spectral shape is primarily determined by the superposition of the spectra of an isolated triplet state (S=1), two interacting triplet states, and three interacting triplet states whose weighting contributions differ for the above two cases. The tensors of the anisotropic spin-spin interaction are determined, and the contribution from the isotropic component of the interaction is estimated.     

Synthesis and Analytical Application of a Novel Fluorescent Hg2+ Probe 3′, 6′-Bis(Diethylamino)-2-((2,4-Dimethoxybenzylidene)Amino)Spiro[Isoindoline-1,9′-Xanthene]-3-Thione

A novel probe, 3′,6′ - bis(diethylamino) -2- ((2,4-dimethoxybenzylidene)amino) spiro [isoindoline-1,9′-xanthene]-3-thione (RBS), was designed and synthesized. Its structure was characterized with elemental analysis, IR spectra and ¹H NMR. The probe displayed highly selective and sensitive recognition of Hg²⁺. Reacting with mercury ions in aqueous solution, its fluorescence intensity was enhanced significantly, while its color was changed from colorless to pink. So, a new fluorescence method of detection of Hg²⁺ was proposed. Its dynamic response concentration range and detection limit for Hg²⁺ were 5.00?×?10^?9 M to 1.00?×?10^?6 M detected and 1.83?×?10^?9 M, respectively. Satisfying results were obtained when the probe was applied to detect spiked Hg²⁺ in samples.     

[Cu~ⅡEDTA]~(2-)与[Fe~Ⅱ(CN)_6]~(4-)反应产物的分子光谱研究

按1:1(摩尔比)混合[Cu EDTA]~(2-)和[Fe(CN)_6]~(4-)溶液(pH=8)时,得到一种深红棕色溶液。测定并讨论了此红棕色溶液的电予光谱和红外光谱,据此确定此溶液中生成了不太稳定的氰桥配合物——[EDTA Cu~Ⅱ—NC—Fe~Ⅱ(CN)_5]~(6-)。     

Temperature Dependence of the Critical Field of the Organic Superconductor κ-(BEDT-TTF)2Cu[N(CN)2]Br

JETP Letters - We present upper critical magnetic fields data for κ(BEDT-TTF)2Cu[N(CN)2]Br (hereafter k-Br), single crystals with the magnetic field applied either or perpendicular and...     

Extraction of some trapping parameters from experimental thermoluminescence (TL) signal of alumina (α-Al2O3) using analytical models

The exploitation of thermoluminescence (TL) signals constitutes the background of important and phenomenological methods used for estimating the kinetic parameters such as the activation energy (E), the frequency factor (s) and the general order of kinetics (b). These parameters are, in general, poorly known and all the used methods often diverge on their determined values. In the present paper, we investigate the suitability of the general phenomenological equations used to extract some trapping parameters from experimental TL signals of alumina (α-Al₂O₃). α-Al₂O₃ TL signal exhibits, under hard uv-irradiation (4.8 eV), two TL-main peaks located at 415 nm and 696 nm corresponding to F and Cr³⁺ centers respectively. To this aim, we numerically computed the analytical expression of TL which results from general order kinetic (b) taking into account the trapped charge concentration and the radiative/retrapping yield R. The computed curves for R = 1 fit perfectly the experimental data, allowing the extraction of some TL data as E, b and s from TL bands of alumina.     

(E)-3-[N-(α-苯乙胺)]-2-烯基-1-苯丙酮的合成及其研究

烯胺是一类重要的反应中间体,其在有机合成中有着广泛的应用.采用碳-氮转移法合成了结构稳定、不易转变为亚胺的手性烯胺化合物(E)-3-[N-(α-苯乙胺)]-2烯基-1-苯丙酮,并对产物进行了红外光谱及核磁共振氢分析,结果令人满意.     

Spectroscopic Study of Cyano-Bridged Hetero-Metallic Polymeric Complexes with 2-Methylpyrazine: [M(NH3)(2mpz)Ni(CN)4]·nH2O (M(II) = Cu or Zn)

Journal of Applied Spectroscopy - We have synthesized new cyano-bridged hetero-metallic polymeric complexes [M(NH3)(2mpz)Ni(CN)4]·nH2O in the powder form for the fi rst time. Their structures...     

Crystal structure of cholesteryl 4-[4-(4-n-hexylphenylethynyl)-phenoxy]butanoate – a liquid-crystalline unsymmetric dimer

Cholesteryl 4-[4-(4-n-hexylphenylethynyl)-phenoxy]butanoate, which exhibits the phase sequence: Cr 119.3°C (42.4?J?g^?1) SmA 196.4°C (1.1?J?g^?1) TGB–N* 202.4°C (5.4?J?g^?1) I, crystallizes in the triclinic space group P1 with unit cell parameters: a?=?10.527(1), b?=?13.151(2), c?=?16.991(2)?Å, α?=?86.13(1)°, β?=?98.96(1), γ?=?105.43(1)°, Z?=?2. The crystal structure has been solved by direct methods using single-crystal X-ray diffraction data and refined to R?=?0.0618. There are two crystallographically independent molecules, I and II, in the asymmetric unit. In both the molecules the phenyl rings are planar. The dihedral angle between the two phenyl rings is 12.16° and 18.14° for molecules I and II, respectively. In both the molecules, the six-membered rings of the cholesterol moiety are conformationally very similar. However, pronounced differences are observed in the conformation of the five-membered ring, which is intermediate between half-chair and envelope in molecule I, and half-chair in molecule II. The packing of molecules in the crystalline state is found to be a precursor to the Smectic A phase structure. The molecules in the crystal are held together by van der Waal's interactions.     

Oxygen plasma activation of Cr(CO)6 on α-Fe2O3(0001)

The chemistry of Cr(CO)₆ on the Fe₃O₄(111) surface termination of α-Fe₂O₃(0001) was explored using temperature programmed desorption (TPD), Auger electron spectroscopy (AES), static secondary ion mass spectrometry (SSIMS) and low energy electron diffraction (LEED) both with and without activation from an oxygen plasma source. No thermal decomposition of Cr(CO)₆ was detected on the surface in the absence of O₂ plasma treatment, with first layer molecules desorbing in TPD at 215 K from a close-packed overlayer. The interaction of first layer Cr(CO)₆ with the Fe₃O₄(111)-termination was weak, desorbing only ～ 30 K above the leading edge of the multilayer state. Activation of multilayer coverages of Cr(CO)₆ with the O₂ plasma source at 100 K resulted in complete conversion of the outer Cr(CO)₆ layers, presumably to a disordered Cr oxide film, with Cr(CO)₆ molecules near the surface left unaffected. Absence of CO or CO₂ desorption states suggests that all carbonyl ligands are liberated for each Cr(CO)₆ molecule activated by the plasma. AES and SSIMS both show that O₂ plasma activation of Cr(CO)₆ results in a carbon-free surface (after desorption of unreacted Cr(CO)₆). LEED, however, shows that the Cr oxide film was disordered at 600 K and likely O-terminated based on subsequent water TPD. Attempts to order the film at temperatures above 650 K resulted in dissolution of Cr into the α-Fe₂O₃(0001) crystal based on SSIMS, an observation linked to the Fe₃O₄(111) termination of the surface and not to the properties of α-Cr₂O₃/α-Fe₂O₃ corundum interface. Nevertheless, this study shows that O₂ plasma activation of Cr(CO)₆ is an effective means of depositing Cr oxide films on surfaces without accompanying carbon contamination.