bluuebunny/crossref_metadata_2025_split huggingface dataset:
Synthesis of Several Polyfunctionally Substituted Fused Pyrimidines Incorporating Quinone Compounds
Authors: Khalafallah A. K. , Abd El‐Aal R. M. , El‐Kanzi N. A. A. 
Published: May 2015

AbstractThe synthesis of several new polyfunctionally substituted fused pyrimidines via reaction of 2‐amino 1,4‐naphthoquinone 2 with different reagents is described.
New Synthesis of Pyrazolo[3,4‐b][1,4,5]benzothiadiazepine, ‐[1,4,5]benzoxadiazepine, ‐[1,4,5]benzotriazepine and Pyrazolo[3,4‐b]quinoxaline Derivatives
Authors: El‐Rady Eman A. 
Published: May 2015

AbstractNew pyrazolo[3,4‐b][1,4,5]benzothiadiazepine and its analogues 3 have been obtained by reaction of 4‐nitrosopyrazoles 1 with 2‐aminothiophenol 2a and its analogues 2b,c. Under fused conditions, dipyrazolyl derivatives 7a was obtained with a trace amount of quinoxaline 5a. On the other hand, 5b and 7b were obtained in equal amounts. A proposed pathway is presented.
Accurate Determination of Dimerization Constants from IR Study of Monomer‐Dimer Self‐Association: 3‐Ethyl‐2‐Methyl‐3‐Pentanol in Carbon Tetrachloride as an Example
Authors: Chen Jenn‐Shing , Kao Dah‐Yu 
Published: May 2015

AbstractThe monomer‐dimer self‐association of 3‐ethyl‐2‐methyl‐pentanol in CCl4 at four different temperatures has been studied using IR spectroscopy. The spectral band of the OH fundamental stretching for a free monomer and that for a hydrogen‐bonded dimer were resolved, and their respective integrated absorbances were calculated. The integrated absorbances of the monomer band for various concentrations at a given temperature were then employed based on Eq. 9 to obtain the molar absorptivity of the monomer band and the dimerization constant at that temperature. Similarly, those of the dimer band were employed based on Eq. 13 to determine the molar absorptivity of the dimer band and the dimerization constant at that temperature. Since the same dimerization constant can be determined independently either from the monomer band or from the dimer band, the discrepancy between the two determined values can serve as a criterion of the goodness of the determination. The standard enthalpy and entropy of the dimerization were also obtained from a van't Hoff plot for dimerization constants at different temperatures.
Preparation, Spectral Characterization and Antimicrobial Activities of Schiff Base Complexes Derived from 4‐Aminoantipyrine. Mixed Ligand Complexes with 2‐Aminopyridine, 8‐Hydroxyquinoline and Oxalic Acid and Their Pyrolytical Products
Authors: Mashaly Mahmoud M. , Abd‐Elwahab Zinab H. , Faheim Abeer A. 
Published: May 2015

AbstractA series of biologically active mononuclear complexes of Cu(II), Ni(II), Zn(II), and Fe(III) were prepared. The reactions of the Schiff base ligand 1‐phenyl‐2,3‐dimethyl‐4‐salicylalidene pyrazole‐5‐one, (HL), with the previous metals in the presence of LiOH as a deprotonating agent, yielded different types of complexes. The binary complexes react with the mixed ligands 2‐aminopyridine (2‐ampy), 8‐hydroxyquinoline (8‐OHqu) and Oxalic acid (Ox) to form the mixed ligand complexes. All the binary and mixed ligand complexes have octahedral configurations. The Schiff base ligand (HL) is coordinated to the central metal as monoanionic terdentate ONO ligand. Thermal studies explored the possibility of obtaining new complexes, which can not be prepared from solutions. Five coordinate Ni(II) and Zn(II) complexes were prepared pyrolytically. Also, the binuclear Fe(III) complex was prepared through the thermal transformation of its mononuclear complex to the binuclear one. All complexes and the corresponding thermal products were isolated and their structures were elucidated by elemental analyses, conductance, IR and electronic absorption spectra, magnetic moments, 1H NMR and TG‐DSC measurements. The free ligand (HL) and its metal complexes showed higher antibacterial effects than that of some investigated antibiotics.
Samarium Diiodide Reduction of Cinnamic Acids
Authors: Lin Tzuen‐Yeuan , Fuh Ming‐Ren , Tsau Chi‐Yu 
Published: May 2015

AbstractThe method for measuring SmI2 reduction rates is expanded to a wider range of organic compounds by using not only GC or GC/MS, but also HPLC as the detecting tool. The reduced substrates are not only confined to water insoluble compounds or low boiling compounds only. Water soluble cinnamic acid derivatives of high boiling points are chosen for this application.The absolute rate constants of SmI2 reduction of cinnamic acid in the presence of hexamethylphosphoramide or t‐butanol is considered as a suitable proton source in this reaction. The rates are dependent on substrates and additives as:Rate ∞ [t‐BuOH][Cinnamic acid]and Rate ∞ [HMPA][Cinnamic acid]The reduction rates of α‐methylcinnamic acid, 2‐methylcinnamic acid, 4‐methylcinnamic acid, 2‐methoxycinnamic acid, 3‐methoxycinnamic acid, 4‐methoxycinnamic acid, 2‐hydroxycinnamic acid, 3‐hydroxycinnamic acid, 4‐hydroxycinnamic acid, 2‐chlorocinnamic acid, 3‐chlorocinnamic acid, 4‐chlorocinnamic acid were carefully measured to study the substituent effect.
Determination of Aqueous Butachlor Using Solid‐phase Microextraction and Gas Chromatography
Authors: Tsai Huey‐Ling , Wong Yih‐Gang , Ho Wu‐Hsiung 
Published: May 2015

AbstractThe solid‐phase microextraction (SPME) technique using a 100 μm film poly(dimethylsiloxane) (PDMS) has been examined with the aim to determine butachlor in aqueous samples. The feasibility of SPME gas chromatography‐electron capture detection (GC‐ECD) analysis has been evaluated. From this study the equilibrium distribution constant between PDMS coating and water for butachlor obtained was 1.9 × 103 with a 5.3% RSD. Extraction time of 40 min, desorption time of 3 min and desorption temperature of 250 °C were selected. The effect of salt addition was examined. The inhibitions of methanol and humic acid to the extraction of butachlor were observed. A standard addition method for calibration was recommended to reduce the deviation from matrix interference. Linear ranges from 0.1 to 12 μg/L and limits of detection of 0.007 μg/L for deionized water, 0.010 μg/L for ground water, and 0.016 μg/L for irrigated water were obtained. The proposed method was applied to determine butachlor in irrigated water. The degradation of butachlor in aqueous solution under the irradiation of 253.7 nm light has been measured by the developed SPME‐GC‐ECD procedure. The half‐life of the aqueous butachlor found was 208 seconds.
EPR Studies of Poly(o‐Phenetidine)‐Poly(Styrenesulfonic Acid) and Poly(2‐Ethylaniline)‐Poly(Styrenesulfonic Acid) Complexes
Authors: Lin Der Shyu , Yang Sze Ming 
Published: May 2015

AbstractThis study relates to electron paramagnetic resonance (EPR) of the poly(o‐phenetidine)‐poly(styrenesulfonic acid) [P(O‐P)‐PSSA] and poly(2‐ethylaniline)‐poly(styrenesulfonic acid) [P(2‐E)‐PSSA] complexes; the polyaniline [PANI], poly(o‐phenetidine) [POP], poly(2‐ethylaniline) [P2E], and polyaniline‐poly(styrenesulfonic acid) [PANI‐PSSA] were prepared to be the reference samples; the EPR spectra results were recorded at both 298 K and 77 K, and were analyzed on the basis of the polaron‐bipolaron model, which is typical for non‐degenerate systems. The EPR spectra results of the substituted polyaniline complexes P(O‐P)‐PSSA and P(2‐E)‐PSSA, show temperature‐dependent paramagnetism; the narrow line‐width arises due to polarons, and the charge transport takes place through both polarons and bipolarons. The narrower line‐width of the substituted polyaniline complexes can be attributed to the lower degree of structural disorder, the oxygen absorption of the polymer molecular complexes, and the steric effect by the alkyl group of the polyaniline; the reduced line‐widths were consistent with the lower molecular weight of the complexes.
Efficient Coupling of Allylstannane with Diels‐Alder Cycloadducts Derived from 4‐Bromo‐substituted Masked o‐Benzoquinones: Synthesis of 5‐Allyl‐oxatricyclo[m.3.1.0]decenones and Undecenones
Authors: Lin Ken‐Ching , Chittimalla Santhosh Kumar , Peddinti Rama Krishna , Liao Chun‐Chen 
Published: May 2015

AbstractIn the presence of a catalytic amount of Pd(PPh3)4, allylstannane coupled efficiently with oxatricyclic [m.3.1.0] bromo‐decenones and bromo‐undecenones to afford the corresponding 1,4‐dienes in excellent yields.
Chemical and Antiplatelet Constituents from the Stem of Zanthoxylum Beecheyanum
Authors: Cheng Ming‐Jen , Wu Chin‐Chung , Tsai Ian‐Lih , Chen Ih‐Sheng 
Published: May 2015

AbstractOne new cinnamamide, beecheyamide (1) and one new lignan, (+)‐beechenol (2), together with fifty‐six known compounds, have been isolated from the stem of Zanthoxylum beecheyanum. The known compounds included seven coumarins, six benzo[c]phenanthridines, ten quinoline derivatives, five benzenoids, three aporphines, four amides, seven lignans, four steroids, one chlorophyll, five terpenoids, and five other compounds. The structures of these compounds were determined by means of spectral analyses. Several isolates exhibited significant antiplatelet activities.
Modular Assembly Revealed by Tryptophan and Other Optical Probes in Staphylococcal Nuclease Folding
Authors: Su Zheng‐Ding , Wu Jiun‐Ming , Tsong Tian Yow , Chen Hueih Min 
Published: May 2015

AbstractHow do different molecular events amalgamate to form kinetic funnels for protein folding? To probe local events and dissect folding of sub‐domains new tryptophan probes have been implanted in two locations of staphylococcal nuclease (SNase): the β‐barrel (W140F+L25W) and the C‐helix (W140F+L125W). 8‐Anilino‐l‐naphthalensulfonate (ANS) was also used to trace a transient appearance of hydrophobic clusters. By use of these fluorescence probes in addition to the CD222nm signal of protein, several molecular events for the folding of SNase and its mutants have been resolved and activation barriers for these reactions determined. Folding from a GdmHCl unfolded state begins a burst with the formation of 20% of the secondary structure (< 20 ms in CD mode). The next event (55 ms) is the clustering of hydrophobic side chains in the C‐ and the oligonucleotide binding (OB)‐domains. These hydrophobic clusters are capable of binding ANS and they continue to grow in 500–700 ms. ANS binding sites subsequently sequester and become inaccessible to ANS in a 1.7‐s reaction. Merging of the OB‐ and the C‐domains that follows is a complex tri‐phasic process (134 ms, 457 ms, and 31.3 s). Global folding measured by the CD222nm signal unveils yet another slow reaction (1,600 s) which was shown to originate from the trans/cis isomerization of Pro117. A modular assembly model depicting protein folding‐by‐parts or origami of folding is proposed and discussed in light of these observations.
Imaging Condition Optimization in Multiphoton Microscopy of Three‐Dimensional Collagen Fiber Structures
Authors: Hsiao Chih‐Yuan , Sun Yen , Lo Wen , Lin Sung‐Jan , Jee Shiou‐Hwa , Jan Gwo‐Jen , Dong Chen‐Yuan 
Published: May 2015

AbstractMultiphoton generated autofluorescence and second harmonic signals are useful luminescent signatures for probing the structural and spectral properties of collagen fibers. However, optimization of image formation deep within a three‐dimensional collagen sample may be hindered by index‐mismatch induced spherical aberration. In this work, we examined this issue by comparing the axial multiphoton luminescence profiles of bovine tendon under water, glycerin, and oil immersion conditions. Our results show that, although in general, oil immersion imaging resulted in the slowest decay of measured axial luminescence profile, other immersion conditions can perform better at specific locations within the tendon, indicating the existence of local variations of refractive indices within the collagen‐filled tendon. Our results suggest that optimizing multiphoton imaging of collagen requires acquiring and comparing imaging results using different immersion fluids and that the results may be used to infer the spatial distribution of refractive indices in biological specimens.
Preparative and Structural Studies on Ruthenium(II)‐Thiolate Cyanocarbonyls: Comparison to the [Fe(CO)x(CN)y(SR)z]n− Coordination Modes of Active Sites of Hydrogenases
Authors: Chen Chien‐Hong , Wang Li‐Chun , Liaw Wen‐Feng 
Published: May 2015

AbstractRuthenium‐thiolate cyanocarbonyl compounds [Na·2THF][Ru(CO)(CN)(S‐C5H4N)2] (2), and [PPN] [Ru(CO)(CN)(S‐C5H4N)2] (3) were prepared from reactions of [Na][N(SiMe3)2] and cis‐[Ru(CO)2(S‐C5H4N)2] (1) obtained from reaction of Ru3(CO)12, Me3NO2H2O, and 2‐mercaptopyridine in THF. Complexes 1, 2 and 3 were characterized by IR and single‐crystal X‐ray diffraction. The IR spectrum of complex 2 in the aprotic solvent THF reveals two weak absorption bands for the CN− ligands at 2098 w and 2086 w cm−1 and one strong absorption band 1931 s cm−1 assigned to the carbonyl stretching frequency that support the dimeric architecture with two [Ru(CO)(CN)(S‐C5H4N)2]− units connected through CN‐Na+‐NC interactions, as observed in the single‐crystal X‐ray structure. Ethylation of complex 3 by electrophile [Et3O][BF4] occurring initially at the more accessible, delicately balanced nucleophilic site to yield the charge‐controlled, collision product 4 (Scheme II), and subsequently isomerizing to neutral [Ru(CO)(CNEt)(S‐C5H4N)2] (5) demonstrated the enhanced nucleophilicity toward electrophiles with replacement of carbonyl ligand with cyanide ligand in complex 1, indicative of the strong σ‐donor role of the cyanide vs CO ligand. In comparison with displaying a reversible redox process of complex [Fe(CO)(CN)(S‐C4H3N2)2]−, the electrochemistry of complex 3 reveals an irreversible oxidation at 0.29 V (vs Ag/AgNO3).
Echindoderm Gametes Make PAF; Artificial Activation by External PAF Bipasses Calcium Channels Regulated by 2APB Unlike Jelly Activation of Sperm
Authors: Sparling Mary Lee 
Published: May 2015

AbstractThe search for lipid changes at fertilization shows production of PAF, a phospholipid known as Platelet Activating Factor. Effects on gametes by externally applied PAF suggest it may be involved in several less understood calcium dependent events of fertilization. PAF artificially activates both echinoderm eggs and sperm. Calcium channel drugs 2APB, ruthenium red, nitrendipine and nifedipine and pH 5 SW do not prevent it, but external calcium must be present. 2APB does prevent normal jelly activation of sperm. Egg PAF activation includes cortical reaction or cell shape change. Sperm PAF activation increases adhesivity, the sperm winds up on itself, or dissociates the acrosome, nucleus and mitochondria. Natural PAF produced could alter cell activation, adhesion, fusion, fertilization cone and sperm nuclear changes after entry into egg. Positive effects of PAF and its receptor on capacitation, activation of sperm and embryo viability have been known from in vitro fertilization studies, but mechanisms remain mysterious.
Biologically Potent L‐Hexoses and 6‐Deoxy‐L‐Hexoses: Their Syntheses and Applications
Authors: Kulkarni Suvarn S. , Chi Fa‐Chen , Hung Shang‐Cheng 
Published: May 2015

AbstractThis account describes our recent work in the development of new methodologies to prepare rare and biologically potent L‐hexoses and 6‐deoxy‐L‐hexoses, from cheapest D‐glucose, via L‐hexofuranoses and 1,6‐anhydro‐β‐L‐hexopyranoses as key building blocks. Their applications in the syntheses of heparin oligosaccharides, the carbohydrate moiety of bleomycin A2, and L‐acovenose are also summarized here.
Investigation of the Functional Role of Ca2+ in the Oxygen‐Evolving Complex of Photosystem II: A pH‐Dependence Study of the Substitution of Ca2+ by Sr2+
Authors: Lee Cheng‐I , Brudvig Gary W. 
Published: May 2015

AbstractThe oxygen‐evolving complex (OEC) of photosystem II (PSII) is the catalytic site for the oxidation of water to O2 in photosynthesis. The OEC consists of a tetranuclear manganese (Mn4) cluster with calcium and chloride ions functioning as essential cofactors. Previous studies have shown that substitution of Ca2+ in the OEC by various divalent and trivalent metal ions results in the loss of oxygen‐evolution activity of PSII. Sr2+ is the only ion that has been found to restore the oxygen‐evolving activity in PSII. Although several models have been proposed for the mechanism of water oxidation in PSII, the functional role of Ca2+ remains unclear. In order to test the proposal that Ca2+ functions as a Lewis acid in water oxidation chemistry, the pH dependence of the oxygen‐evolution activity of intact Ca2+‐containing PSII and Sr2+‐substituted PSII has been investigated. In both samples, the pH dependence exhibits a bell‐shaped curve. Sr2+ substitution shifts the peak of the curve to higher pH in comparison to Ca2+‐containing PSII. The pH‐dependent O2‐evolving rates of these two samples are fit to a diprotic model in which protonation of an essential basic group at acidic pH inhibits activity (pKa1) and deprotonation of an essential acidic group at higher pH inhibits activity (pKa2). Sr2+ substitution has no effect on pKa2. This result suggests that the high pH inhibition may be on the electron‐acceptor side of PSII. On the other hand, Sr2+ substitution causes pKa1 to be shifted to higher pH by 1.0 pH unit. This pH‐shift indicates a direct role of Ca2+/Sr2+ in the OEC. The functional role of Ca2+ in oxygen evolution in PSII is discussed based on these results.
The Catalytic Copper Clusters of the Particulate Methane Monooxygenase from Methanotrophic Bacteria: Electron Paramagnetic Resonance Spectral Simulations
Authors: Hung Shao‐Ching , Chen Chang‐Li , Chen Kelvin H.‐C. , Yu Steve S.‐F. , Chan Sunney I. 
Published: May 2015

AbstractThe particulate methane monooxygenase (pMMO) from Methylococcus capsulatus contains 14–15 reduced copper ions, and it has been proposed that these copper ions are arranged in the form of trinuclear clusters. Two of these clusters have been referred to as catalytic clusters (C‐clusters) and have been implicated in dioxygen activation and alkane hydroxylation. The remaining copper ions appear to provide a “reservoir” of reducing equivalents to replenish the electrons at the C‐clusters following dioxygen activation at the C‐clusters during turnover. Accordingly, they are normally reduced and have been called electron‐transfer clusters (E‐clusters). For pMMO prepared in highly enriched membranes, or purified as the pMMO‐detergent complex from these membranes, only the C‐cluster copper ions are oxidized. Recently, the low temperature EPR spectrum of as‐isolated pMMO was deconvoluted into a type 2 Cu(II) signal and a broad, but nearly isotropic EPR signal centered at g ˜ 2.1. Earlier magnetization and magnetic susceptibility measurements have suggested that the latter EPR signal, which is not sensitive to microwave power saturation, might arise from a ferromagnetically exchange‐coupled trinuclear Cu(II) cluster with J ≈ 20 cm−1 and D ≤ 0.05 cm−1. Toward confirming these results, several triangular model Cu(II) complexes, both antiferromagnetically and ferromagnetically coupled and with well‐defined structural and ligand information, were reviewed to gain insights into magneto‐structural correlations. Spectral simulations of the pMMO cluster EPR signals were then performed based on the structural and spectroscopic information provided by the ferromagnetic model complexes. We show that only Cu(II) ions with proper g‐tensors and appropriate relative orientations between them can give rise to the unique EPR signal observed for the C‐cluster(s) in pMMO. The putative C‐cluster EPR signal observed for the as‐isolated pMMO at 3 K was best fitted by a triad of ferromagnetically coupled Cu(II) ions with the following sets of g‐values: (1.983, 2.030, 2.218), (1.983, 2.029, 2.218) and (2.000, 2.033, 2.207); and zero‐field splitting parameters D = 0.017 ± 0.002 cm−1 (175 ± 25 Gauss) and E/D = 0.15. The fit was not sensitive to the value of J so long as the exchange interaction was much larger than the Zeeman interaction (J » gβH).
The Kinetics of Analcime Synthesis in Alkaline Solution
Authors: Fang Jiann‐Neng , Lin I‐Chieh , Lo Huann‐Jih , Song Sheng‐Rong , Chen Yaw‐Lin 
Published: May 2015

AbstractIn this study glass has been used as a starting material in order to increase the resolution of the experiment and establish the kinetics of analcimes during hydrothermal synthesis. The experimental results show that the crystal growth curves represent two‐stage linear growth. The first stage is marked by rapid crystal growth whilst the second stage indicates much slower growth. The nuclei appear before the crystals start growing. The crystal growth rate is dependent on the experimental conditions. The nucleation rate increases as the glass dissolves and reaches a maximum when the glass is completely dissolved. Thereafter, the concentration decreases with the consumption of nutrients, and both nucleation and crystal growth stops when supersaturation occurs.
Synthesis of Imidazo[2,1‐a]isoquinolines from α‐Tosyloxyketones and 1‐Aminoisoquinoline in Ionic Liquid Solvent
Authors: Hou Rei‐Sheu , Wang Huey‐Min , Huang Hsin‐Yu , Chen Ling‐Ching 
Published: May 2015

AbstractThe room temperature ionic liquid n‐butylpyridinium tetrafluoroborate (BPyBF4) is used as a ‘green’ recyclable alternative to classical molecular solvents for the cyclocondensation of α‐tosyloxyketones with 1‐aminoisoquinoline to prepare imidazo[2,1‐a]isoquinolines in good yields.
Photoinduced Spectral Diffusion and Diffusion‐Controlled Electron Transfer Reactions in Fluorescence Intermittency of Quantum Dots
Authors: Tang Jau , Marcus R. A. 
Published: May 2015

AbstractAn overview is given for the experimental and theoretical development on fluorescence intermittency (blinking) in semiconductor crystalline nanoparticles. We consider a model with photoinduced spectral diffusion and diffusion‐controlled electron transfer processes as the underlying mechanism for intermittency in quantum dots. Depending on the frequency response of a dielectric medium, anomalous/normal diffusion in energy space leads to power‐law intermittency for single quantum dots and quasi‐stretched exponential decay in ensemble‐averaged fluorescence intensity. Intricate relationship between single particle and ensemble behavior is discussed. Some kinetic and energetic parameters are linked to the temporal behavior of blinking statistics and ensemble fluorescence decay.
Two Dimensional Electronic Spectroscopy of Molecular Complexes
Authors: Cho Minhaeng , Brixner Tobias , Stiopkin Igor , Vaswani Harsha , Fleming Graham R. 
Published: May 2015

AbstractTwo dimensional (2D) heterodyne‐detected electronic photon echo spectroscopy is introduced and described. We give an intuitive description of the origin and information content of 2D electronic spectra, focusing on molecular complexes. We identify two important quantities—the transition dipole term, and the transition frequency cross correlation function that controls the appearance of 2D electronic spectra.We also show how the transition frequency cross correlation function controls the rate of exciton relaxation. These concepts are illustrated with experimental data on the seven bacteriochlorophyll FMO complex of a green sulfur bacterium, showing how the pathways and mechanisms of energy flow can be elucidated by combining 2D spectra with theoretical modeling.
Collision Relaxation of Highly Vibrationally Excited SO2 by CO in A Supersonic Beam
Authors: Zhang Min , Ma Jian‐Qiang , Han Jun , Dai Hai‐Lung 
Published: May 2015

AbstractCollision relaxation cross sections of a single, highly vibrationally excited level in the ground electronic state of SO2 at 44877.52 cm−1 above the zero‐point by the collision partner CO has been measured in a supersonic expansion using the kinetic quantum beat spectroscopic technique. The depopulation cross section at 14.5 K for this SO2*‐CO system has been determined to be 75 Å2, while the dephasing cross section is 22 Å2. Comparison with previously measured cross sections for the SO2*‐SO2, SO2*‐inert gases systems at room temperature using a similar spectroscopic approach reveals both the long range interaction and repulsive force contributions to the relaxation cross sections of highly vibrationally excited molecules.