bluuebunny/crossref_metadata_2025_split huggingface dataset:
Applications of Highly Sulfated Cyclodextrins for Enantiomeric Separation by Capillary Electrophoresis
Authors: Chen Fu‐Tai A. , Evangelista Ramon A. 
Published: May 2015

AbstractSeparation of enantiomeric pairs of compounds by capillary electrophoresis (CE) was performed using highly sulfated α‐, β‐ and γ‐cyclodextrins (HS‐CDs). CE analysis of the HS‐CDs using indirect absorbance detection showed that the new class of chiral selectors has substantially higher degrees of sulfation and narrower heterogeneity than those used in previous reports. Elemental analyses showed that the average number of sulfate groups per cyclodextrin was 11, 12, and 13, for HS‐α, β and γCD, respectively. Our earlier 13C NMR data of HS‐CDs were consistent with the structural assignment of complete sulfation at the C‐6 primary hydroxyl groups, greater than 70% sulfation at the C‐2 secondary hydroxyls and absence of substitution at the C‐3 hydroxyls. CE‐based chiral separations were performed using a generalized procedure with phosphate buffer (pH 2.5) containing 5% (w/v) HS‐CD in a 50 μm I.D. × 31 cm (total length) fused silica capillary. Quantitation of enantiomeric impurity of less than 1% was demonstrated for pseudoephedrine and phenylpropanolamine. The HS‐α, β and γCD complement each other by exhibiting different chiral selectivity. The combination of HS‐α, β and γCD resolved more than 140 chiral compounds of neutral, acidic and basic drugs with very different structural features. The HS‐CDs were synthesized under conditions of controlled sulfation to produce chiral reagents with consistent composition, making them excellent chiral selectors for capillary electrophoretic analysis of enantiomeric impurities.
The Leaving Group Effect in Free Radical SH2′ Reactions
Authors: Wu Yuh‐Wern , Tseng Ming‐Chung , Lu Cheng‐Yi , Chou Hsueh‐Hsun , Tseng Yeong‐Fuh , Hsieh Hui‐Joan 
Published: May 2015

AbstractThe relative rates of the leaving groups in free radical SH reactions have been determined. The order of the relative elimination rates of the leaving group is: I > Br (14) > SPh (2) > Cl (1) » OPh, SiMe3. This is consistent with the bond dissociation energy of the C‐X bond. The less the bond dissociation energy value is, the better the leaving group is.
Determination of Magnesium Ascorbyl Phosphate in Cosmetic Bleaching Products Using a Disposable Screen‐Printed Carbon Electrode
Authors: Shih Ying , Zen Jyh‐Myng 
Published: May 2015

AbstractA preanodized screen‐printed carbon electrode is used for the determination of magnesium ascorbyl phosphate in cosmetic bleaching products. The preanodization process exhibits a marked enhancement of the current response of magnesium ascorbyl phosphate at the screen‐printed carbon electrode. The linear range is up to 240 (correlation coefficient = 0.999) in pH 2.0 citrate buffer with a detection limit (S/N = 3) of 0.33 μM. The electrode has the advantages of low cost and easy of handling and can be either disposable or reused since the renewal gives a good reproducible surface. Quantitative analysis was performed by the standard addition method for magnesium ascorbyl phosphate content in cosmetic products.
Studies on the Synthesis of New 3‐(3,5‐Diamino‐1‐substituted‐pyrazol‐4‐yl)azo‐thieno[2,3‐b]pyridines and 3‐(2‐Amino‐5,7‐disubstituted‐pyrazolo[1,5‐a]pyrimidine‐3‐yl)azothieno[2,3‐b]pyridines
Authors: Ho Yuh‐Wen 
Published: May 2015

AbstractCoupling the diazonium salt of 3‐amino‐2‐cyano‐4,6‐dimethylthieno[2,3‐b]pyridine 1 with malononitrile 2 gave 2‐cyano‐3‐(hydrazonomalononitrile)‐4,6‐dimethylthieno[2,3‐b]pyridine 3 which then reacted with hydrazine compounds 4a‐4h to yield corresponding 2‐cyano‐3‐(3,5‐diamino‐1‐substituted‐pyrazol‐4‐yl)azo‐4,6‐dimethylthieno[2,3‐b]pyridines 5a‐5h. The 2‐cyano‐3‐(2‐amino‐5,7‐disubstituted‐pyrazolo‐[1,5‐a]pyrimidine‐3‐yl)azo‐4,6‐dimethylthieno[2,3‐b]pyridines 7a‐7f were obtained in good yield by the cyclocondensation reaction of 2‐cyano‐3‐(3,5‐diamino‐pyrazol‐4‐yl)azo‐4,6‐dimethylthieno[2,3‐b]pyridine 5a with the appropriate 1,3‐diketones 6a‐6f under acidic condition.
Siderophores and Iron‐Transport in Microorganisms
Authors: Pattus Franc , Abdallah Mohamed A. 
Published: May 2015

AbstractIron is an essential element in many biological systems, and in spite of its abundance (5% of the earth crust), its availability is dramatically limited by the very high insolubility of iron(III) at physiological pHs where the concentration of free iron(III) is less than 10−17 M, a value which is much too low to allow any possible growth to aerobic microorganisms.Iron metabolization by the microorganisms necessitates generally the biosynthesis of low molecular weight compounds (300 to 2000 Da) called siderophores. These molecules which are generally excreted into the culture medium, chelate very strongly iron(III), solubilize it and transport it into the cells using an ATP‐dependent high affinity transport system.For nearly fourty years, the structural studies on siderophores have shown a great diversity of structures for these iron‐chelating molecules synthesized by microorganisms. These structures are characterized by the presence of one, two and in most cases, three bidentate chelating groups, generally oxygenated, necessary for the formation of very stable hexacoordinated octahedric complexes between the siderophores and iron(III). These groups are generally either catecholates, or hydroxamates or hydroxyacids, but can be any other bidentate groupsIn what follows several typical examples of siderophores belonging to each of these categories are given. It is clear that considering the very high number of siderophores having so many different structures so far isolated and characterized (more than 200), we have restricted this report to the most representative structures of each category, with a special emphasis to pyoverdins, the fluorescent peptidic siderophores of the fluorescent pseudomonads.Similarly the siderophore‐mediated iron‐transport mechanisms of Gram‐negative bacteria described therafter will report mainly on those of Escherichia coli with a special emphasis to Pseudomonas when information is available.The pyoverdin‐mediated iron‐transport in fluorescent pseudomonads implies biochemical mechanisms which involve signal and energy exchanges between the two membranes across the periplasmic space. The energy transduction mechanism in the case of the pyoverdin‐mediated active transport in P. aeruginosa has not been completely elucidated so far. Nevertheless from the data obtained for ferric enterobactin and ferrichrome in E. coli, it is plausible that a common mechanism of transport can take place for all the enterobacteria. The key element of this mechanism is protein TonB in E. coli, head of a series of TonB proteins having a very close structure and characterized in P. putida WCS358 and P. aeruginosa ATCC 156942. The striking similarities existing between the various iron‐transport steps in these different bacterial species is highly in favour of a common energy‐dependent siderophore‐mediated iron‐transport mechanism in microorganisms.
Piezoelectric Crystal Membrane Chemical Sensors Based on Fullerene and Macrocyclic Polyethers
Authors: Shih Jeng‐Shong 
Published: May 2015

AbstractVarious reusable and sensitive piezoelectric (PZ) quartz crystal membrane sensors with home‐made computer interfaces for signal acquisition and data processing were developed to detect organic/inorganic vapors and organic/inorganic/biologic species in solutions, respectively. Fullerene(C60), fullerene derivatives and artificial macrocyclic polyethers, e.g., crown ethers and cryptands, were synthesized and applied as coating materials on quartz crystals of the PZ crystal sensors. The oscillating frequency of the quartz crystal decreased due to the adsorption of organic or inorganic species onto coating material molecules on the crystal surface. The crown ether‐coated PZ crystal gas detector exhibited high sensitivity with a frequency shift range of 10–340 Hz/(mg/L) for polar organic gases, a short response time (< 2.0 min.), good selectivity, and good reproducibility. The Ag(I)/crptand22 and Ru(III) / crptand22 coated PZ gas detectors were also prepared for nonpolar organic vapors, e.g., alkynes and alkenes. The frequency shifts of the nonpolar PZ sensors were in the order: alkynes > alkenes > alkanes. A Ti(IV)/Cryptand22‐coated PZ crystal sensor was also developed to detect the inorganic air pollutants, e.g., CO and NO2. A piezoelectric gas sensor for both polar/nonpolar organic vapors based on C60‐cryptand22 was also prepared. The cryptand22‐coated PZ gas sensor was also employed as a GC detector for organic molecules. The cryptand22‐coated piezoelectric GC detectors compared well with the commercial thermal conductivity detector (TCD). The interaction between fullerene C60 and organic molecules was studied with a fullerene coated PZ gas detector. A multi‐channel PZ organic gas detector with PCA(Principal Component Analysis) and BPN (Back Propagation Neural) analysis methods was developed. Various liquid piezoelectric crystal sensors based on long‐chain macrocyclic polyethers, e.g., C10H21‐dibenzo‐16‐crown‐5, C18H37‐benzo‐15‐crown‐5, (C17CO)2‐cyptand22 and fullerene derivatives, e.g., C60‐NH‐cryptand22 and dibenzo‐16‐crown‐5‐C60, were also developed as HPLC detectors for metal ions, anions, and various organic compounds in solutions. The sensitive and highly selective PZ bio‐sensors based on enzymes, polyvinylaldehyde, polycinnaldehyde‐C60 and C60‐cryptand22 were developed to detect various biologic species, e.g., proteins, glucose, and urea. A quite sensitive EQCM (Electrochemical Quartz Crystal Micro‐balance) detection system was also developed for detection of trace heavy metal ions.
Theoretical Study Of β2,3‐Peptide Models
Authors: Wu Yun‐Dong , Wang De‐Ping 
Published: May 2015

AbstractConformational features of α,β‐disubstituted β2,3‐dipeptide models have been studied with quantum mechanics method. Geometries were optimized with the HF/6‐31G** method, and energies were evaluated with the B3LYP/6‐31G** method. Solvent effect was evaluated with the SCIPCM method. For (2S,3S)‐β2,3‐dipeptide model 1, a six‐membered‐ring hydrogen bonded structure is most stable. However, the conformation corresponding to the formation of the 14‐helix is only about 1.7 kcal/mol less stable in methanol solution, indicating that the 14‐helix is favored if a (2S,3S)‐β2,3‐polypeptide contains more than 5 residues. On the other hand, the conformation corresponding to the formation of β‐sheet is most stable for (2R,3S)‐β2,3‐dipeptide model 2, suggesting that this type of β‐peptides is intrinsically favored for the formation of β‐sheet secondary structure.
Computational Study of Vertical Ionization Potentials Using Density Functional Theory and Green's Function Methods
Authors: Hu Ching‐Han , Chong Delano P. 
Published: May 2015

AbstractOver one hundred vertical ionization potentials (VIPs) were computed using density functional theory (DFT) and Green's function (GF) based methods. The DFT approaches include the unrestricted transition state (uTS) and unrestricted diffuse ionization (uDI) approximations using the Becke88‐Perdew86 exchange‐correlation functional. Green's function methods include the outer‐valence GF (OVGF) approach, the parametrized GF2 (pGF2), and the parametrized GF2 times screened interaction (pGW2) approximations. DFT computations of IPs using the uTS approximation was found to be nearly as accurate as those predicted using the elaborate OVGF method. The much more computationally efficient uDI approximation provides predictions of moderate accuracy and is recommended for computing IPs for larger molecules. We have observed that the average absolute deviations from a uDI calculation using poorer basis set (DZVP) and poorer geometry (AM1 optimization) is only slightly larger.
Determination of Molecular Weight of PDPS Modified Copolymers
Authors: Hwang Yeun‐Hsing , Yang Mei‐Hui 
Published: May 2015

AbstractMolecular weight (MW) determinations of polydiphenylsiloxane‐co‐polydimethylsiloxane (PDPS/PDMS), polydiphenylsiloxane‐co‐polymethylphenylsiloxane (PDPS/PMPS) and polydiphenylsiloxane‐co‐polymethyl(3,3,3‐trifluoropropyl)siloxane (PDPS/PMFPS) statistical copolymers by gel permeation chromatography (GPC), GPC coupled differential viscometer (GPC‐DV) and light scattering (LS) techniques have been compared and discussed. The MW obtained by GPC‐DV in the PDPS/PDMS and the PDPS/PMPS series agreed with that obtained by LS very well. In PDPS/PDMS copolymers, it was found that the MW obtained by GPC was much lower than that obtained by GPC‐DV and LS, as Ph2SiO) content is higher than 50 mol%. In PDPS/PMFPS copolymers, the MW obtained by GPC was far different from that obtained by GPC‐DV and the deviation decreased with increasing Ph2SiO) mol%. The α values of the copolymers can be explained by the structure of the polymer in tetrahydrofuran (THF). Based on the relatively soluble copolymers, not only the differential refractive index increments (dn/dc) of PMPS, PDMS and PMFPS homopolymers but also that of the PDPS homopolymer in THF could be calculated by their corresponding copolymers.
Covalent Interaction of Ru(terpy)(tmephen)Cl+ with DNA: A Potential Ruthenium‐Based Anticancer Drug
Authors: Cheng Chien‐Chung , Lee Wen‐Li , Su Jyan‐Gwo , Liu Chen‐Lun 
Published: May 2015

AbstractThe use of ruthenium complexes in antitumor therapy was launched two decades ago. In view of their low toxicity and good selectivity for solid tumor metastasis, ruthenium complexes have great potential as alternative drugs to cisplatin in cancer chemotherapy. A series of monochloro ruthenium complexes, Ru(terpy) (NN)Cl+ (NN, bidentate nitrogen ligand), containing different electron‐donating groups were prepared. The reactivity towards the formation of Ru‐DNA adduct were revealed by gel mobility shift assay. Their DNA binding sites of Ru(terpy)(tmephen)Cl+ were located predominantly at the purine residues i.e., guanine and adenine, by terminating DNA elongation in vitro using PCR and primer extension techniques. Surprisingly, the ability of Ru(terpy)(tmephen)Cl+ to inhibit cell growth was found to be approximately two times better than that of a known cross‐linking agent, Ru(bpy)2Cl2. Therefore, the increase in liability of the chloro ligand was demonstrated to improve the reactivity of these ruthenium complexes towards the covalent bond formation in Ru‐DNA adducts and result also in a significant inhibition of cell growth. Based on our results, these ruthenium complexes modified with electron‐rich groups provide new consideration in the tune of ruthenium‐based drugs in cancer chemotherapy.
Copper(ll) Complexes of Diamino Diamide and Diamino Diamine in Aqueous Solution
Authors: Chao Min‐Shiun , Huang Shih‐Liang 
Published: May 2015

AbstractIn order to study the difference on the equilibrium, spectral properties of copper(II) complexes of diamino diamide and diamino diamine, new tetradentate ligands, 4,7‐dimethyl‐4,7‐diazadecanediamide (4,7‐N,N′‐Me2‐L‐2,2,2) and 1,10‐diamino‐4,7‐dimethyl‐4,7‐diazadecane (4,7‐N,N′‐Me2‐3,2,3‐tet), have been synthesized. Synthetic procedures for these new ligands are described. Their protonation constants have been determined potentiometrically in 0.10 MKC1 at 25.0°C. The formation of their copper(II) complexes have been investigated quantitatively by the potentiometric technique and by the measurement of their electronic spectra.
Studies with Polyfunctionally Substituted Heteroaromatics: The Reaction of Heterocyclic Enaminonitriles with α‐β‐Unsaturated Nitriles
Authors: Hussein A. M. , Hafez I. S. Abdel , Elnagdi M. H. 
Published: May 2015

Abstract5‐Amino‐4‐cyano‐3‐phenylpyrazole (1) reacts with cinnamonitriles (2) to yield the pyrazolo[1,5‐a]pyrimidines (3). Also, 5‐amino‐4‐cyano‐1‐phenylpyrazole (4) reacts with cinnamonitriles (2) to yield the pyrazolo[3,4‐b]pyridine derivatives (5). In contrast to this reaction, enaminothiophene (6) reacts with cinnamonitriles (2) to yield compound (7) not (8). The enaminopyrane (9) reacts with cinnamonitriles (2) to yield (10). Finally we have attempted to add cinnamonitriles (2) to thiopyrane (13); only rearrangement and aromatization product (14) was isolated.
The Constituents of Lindera Glauca
Authors: Chang Yuh‐Chwen , Chang Fang‐Rong , Wu Yang‐Chang 
Published: May 2015

AbstractTwenty‐eight compounds including seven alkaloids, (+)‐3‐chloro‐N‐formylnornantenine (1), (+)‐N‐formylnornantenine (2), (+)‐boldine (3), (+)‐norboldine (4), (‐)‐norboldine (5), lycicamine (6), and tetrahydroberberine (7); four flavonoids, kaempferol (8), kaempferol‐3‐O‐arabinoside (9), quercetin (10), and quercetin‐3‐O‐rhamnoside (11); one butanolide, akolactone A (12); one p‐quinone, 2,6‐dimethoxy‐p‐quinone (13); one cyclohex‐2‐en‐1‐one, blumenol A (14); six benzenoids, methylparaben (15), p‐hydroxybenzoic acid (16), vanillic acid (17), syringic acid (18), 3,4,5‐trimethoxybenzoic acid (19), and 3‐(3,4‐dihydroxyphenyl) propionic acid (20); one diterpene, phytol (21); one triterpene, squalene (22); six steroids, (3‐sitosterol (23), β‐sitostenone (24), stigmasta‐4,22‐dien‐3‐one (25), 6β‐hydroxy‐β‐sitostenone (26), 6β‐hydroxystigmasterone (27), and β‐sitosteryl‐D‐glucoside (28) were isolated from the aerial part of Lindera glauca. These compounds were characterized and identified by physical and spectral method. All compounds were isolated for the first time from this plant. Among them, (+)‐3‐chloro‐N‐formylnornantenine (1) is a new one.
Synthesis, Absorption Spectra Studies and Biological Activity of Some Novel Conjugated Dyes
Authors: El‐Aal R. M. Abd , Koraierm A. I. M. 
Published: May 2015

AbstractNovel monomethine 2a‐f, dimethine 4a‐f and tetramethine 6a‐h cyanine dyes were prepared as conjugated dyes. Such dyes incorporating coumarin and/or quinoline derivatives 1a‐d. These dyes were synthesized to study their spectral behavior, solvatochromism and biological activity. These dyes are characterized by elemental analysis, IR, 1H NMR and mass‐spectra.
Analysis of Dichlorobenzene in Water by Solid‐Phase Microextraction
Authors: Liu Yah‐Ping , Ho Wu‐Hsiung 
Published: May 2015

AbstractThe solid‐phase microextraction (SPME) technique using a 100 μm film polydimethylsiloxane (PDMS) coated fiber has been examined with the aim to determine dichlorobenzene in aqueous samples. The feasibility of SPME‐GC‐ECD analysis has been evaluated. Absorption time of 30 min was selected and 1 min was long enough for complete desorption of the analytes in the injection port of the gas chromatograph. Linear ranges from 0.03 to 5 μg/L and method detection limits between 7 and 9 ng/L for dichlorobenzenes were obtained. The relative standard deviations were less than 12% for a spiking level of 3 μg/L. The proposed method was applied to determine dichlorobenzenes in spiked deionized water, ground water, and in industrial effluent samples.
Nickel(II) Complexes of N‐Alkyl‐Substituted Diamino Diamides in Aqueous Solution
Authors: Chao Min‐Shiun , Ou Chang‐Fang , Huang Shih‐Liang 
Published: May 2015

AbstractIn order to study the steric, inductive, and ring‐strain effects of diamino diamides on the equilibrium and spectral properties of nickel(II)‐diamino diamides complexes, four tetradentate ligands, 4‐methyl‐4,7‐diazadecanediamide(4‐Me‐L‐2,2,2), 4,7‐dimethyl‐4,7‐diazadecanediamide(4,7‐N,N'‐Me2‐L‐2,2,2), 4‐ethyl‐4,7‐diazadecanediamide (4‐Et‐L‐2,2,2), and 4‐methyl‐4,8‐diazaundecanediamide (4‐Me‐L‐2,3,2), have been synthesized. Their protonation constants have been determined potentiometrically in 0.1M KCl at 25.0°C The formation of their nickel(II)‐complexes and the Ni‐O to Ni‐N bond rearrangements at the two amide sites of these complexes have been investigated quantitatively by potentiometric and spectrophotometric techniques under the same conditions. Electronic spectra of the nickel(II)‐complexes of these ligands and their deprotonated species formed in aqueous solution were measured and discussed.
Determination of Organochlorine Pesticides in Milk by Electron Capture Capillary Gas Chromatography
Authors: Ho Wu‐Hsiung , Yu Li‐Jun 
Published: May 2015

AbstractThe goal of this study was to develop an analytical method to determine the organochlorine pesticides residues in milk. The samples were loaded onto the self‐packed diatomaceous earth columns, then eluted with 25 mL solvent mixture of n‐hexane‐acetone‐ethyl acetate (4+2+1, v/v/v). After collection and concentration, the extracts were cleaned up by the C18 solid‐phase extraction cartridges. Gas chromatograph/electron capture detector was used for determination. The average recoveries of milk which were spiked with 10 ng/mL of α‐BHC, lindane, heptachlor, dieldrin, p,p'‐DDD, and p,p'‐DDT were above 92%. Limits of detection between 0.5‐1.8 ng/mL were achieved.
Synthesis of Some 7H‐s‐Triazolo[3,4‐b]‐1,3,4‐thiadiazine Derivatives
Authors: Dong Heng‐Shan , Wei Kun , Wang Qing‐Lian , Quan Bin 
Published: May 2015

AbstractThe cyclization of 1‐amino‐2‐mercapto‐5‐[5‐methyl‐1‐(4‐methylphenyl)‐1,2,3‐triazol‐4‐yl]‐1,3,4‐triazole with various α‐haloketone in absolute ethanol yields 7H‐3‐[5‐methyl‐1‐(4‐methylphenyl)‐1,2,3‐triazol‐4‐yl]‐6‐substituted‐s‐triazolo[3,4‐b]‐1,3,4‐thiadiazines and their structures are established by elemental analysis, MS, IR and 1H NMR spectral data.
Diagram Technique for Nonlinear Optical Spectroscopy in the Fast Electronic Dephasing Limit
Authors: Fainberg B. D. 
Published: May 2015

AbstractWe show that applying the double‐sided Feynman diagrams to systems with fast electronic dephasing opens up new possibilities for using this technique in resonance nonlinear optical spectroscopy. The novel potentials are including non‐perturbative system‐bath interactions (non‐Markovian relaxation) and the summation of diagrams. The last procedure enables us to obtain new equations for a nonperturbative description of the light‐matter interaction.
Concentration Dependence of the Fifth‐Order Two‐Dimensional Raman Signal
Authors: Tominaga Keisuke , Yoshihara Keitaro 
Published: May 2015

AbstractThe concentration dependence of the fifth order two‐dimensional Raman signal intensity is reexamined. The instantaneous response of the fifth order signal comes from the fifth order susceptibility. The delayed response of the fifth order signal is consistent with a genuine fifth order Raman rather than a cascading process of the third order nonlinearity.
Ultrafast Coherent Control in the Electronic Ground State of a Molecule
Authors: Heid Mario , Chen Tao , Pausch Roman , Schwoerer Heinrich , Kiefer Wolfgang 
Published: May 2015

AbstractWe report on a coherent control experiment to selectively excite a well localized nuclear probability density in the electronic ground state of isolated, jet cooled potassium dimer molecules. The basic idea of this control scheme is to take advantage of the motion of a vibrational wave packet created in an intermediate excited electronic state, from which a Franck‐Condon window to the desired final state in the ground state emerges. To realize this concept we apply a resonant stimulated Raman process, in which the two involved laser pulses are separated by a time delay τ1 and their wavelengths are independently tunable. The method enables us to excite ground state vibrational wave packets, whereby the vibrational energy of the wave packet and the position of its generation along the internuclear separation coordinate of the ground state potential energy surface can in principle be freely chosen by the experimentalist. The results we present for the chosen model system K2 strongly support the idea that this control concept might be one possible approach to selectively populate a desired chemical reaction channel in the electronic ground state of a molecule.