bluuebunny/crossref_metadata_2025 huggingface dataset:
Chemical Constituents from the Root Bark of Formosan Zanthoxylum Ailanthoides
Authors: Cheng Ming‐Jen , Tsai Ian‐Lih , Chen Ih‐Sheng
Published: May 2015

Two new N‐isobutylamides, hydroxy lanyuamide I (1) and hydroxy lanyuamide II (2), together with one hundred and ten known compounds, have been isolated from the root bark of Formosan Zanthoxylum ailanthoides. These known compounds include twenty coumarins, twenty‐one benzo[c]phenanthridines, ten quinoline derivatives, one aporphine, one purine, seven amides, twelve benzenoids, one lactone, four flavonoids, nine lignans, eight steroids, two chlorophylls, eleven terpenoids and three other compounds, which were determined by means of spectral analyses.
Evaluation of Multicenter Electric Multipole Moment Integrals over Integer and Noninteger n‐STOs
Authors: Özdoǧan Telhat
Published: May 2015

Multicenter electric multipole moment integrals over Slater type orbitals with integer and noninteger principal quantum numbers are expressed in terms of overlap integrals. The computer results for the integer case agree best with the prior literature. The accuracy of the computer results for noninteger case is not compared with the literature due to the lack of relevant literature, but the limit of the noninteger case is compared with the integer case and good agreement is achieved for wide changes in the relevant molecular parameters.
Catalytic Oxidation of Methane to C2‐C4 Hydrocarbons over CeO2 Promoted W‐Mn/SiO2 Catalysts at Higher Pressure
Authors: Chou Lingjun , Cai Yingchun , Zhang Bing , Niu Jianzhong , Ji Shengfu , Li Shuben
Published: May 2015

CeO2‐promoted Na‐Mn‐W/SiO2 catalyst has been studied for catalytic oxidation of methane in a micro‐stainless‐steel reactor at elevated pressure. The effect of operating conditions, such as GHSV, pressure and CH4/O2 ratio, has been investigated. 22.0% CH4 conversion with 73.8% C2‐C4 selectivity (C2/C3/C4 = 3.8/1.0/3.6) was obtained at 1003 K, 1.5 × 105 h−;1 GHSV and 1.0 MPa. The results show: Elevated pressure disadvantages the catalytic oxidation of methane to C2‐C4 hydrocarbons. Large amounts of C3 and C4 hydrocarbons are observed. The unfavorable effects of elevated pressure can be overcome by increasing GHSV; the reaction is strongly dependent on the operating conditions at elevated pressure, particularly dependent on GHSV and ratio of CH4/O2. Analyses by means of XRD, XPS and CO2‐TPD show that CO2 produced from the reaction makes a weakly poisoning capacity of the catalyst; information of changeful valence on Ce and Mn was detected over the near‐surface of the Ce‐Na‐W‐Mn/SiO2 catalyst; the existence of Ce3+/Ce4+ and Mn2+/Mn3+ ion couple supported that the reaction over the catalyst followed the Redeal‐Redox mechanism. Oxidative re‐coupling of C2H6 and CH4 in gas phase or over surface of catalyst produces C3 or C4 hydrocarbons.
Synthesis of New Fused and Spiro Heterocyclic Systems from 3,5‐Pyrazolidinediones
Authors: Abdel‐Rahman M. A. , Khodairy A. , Ghattas A.‐B. A. G. , Younes S.
Published: May 2015

4‐Bromo‐1‐phenyl‐3,5‐pyrazolidinedione 2 reacted with different nucleophilic reagents to give the corresponding 4‐substituted derivatives 3–8. The cyclized compounds 9–11 were achieved on refluxing compounds 3, 4 or 6a in glacial acetic acid or diphenyl ether. 4,4‐Dibromo‐1‐phenyl‐3,5‐pyrazolidinedione 12 reacted with the proper bidentates to give the corresponding spiro 3,5‐pyrazolidinediones 13–15, respectively. The 4‐aralkylidine derivatives 16a‐c, were subjected to Mannich reaction to give Mannich bases 17a‐c‐22a‐c, respectively. 4‐(p‐Methylphenylaminomethylidine)‐1‐phenyl‐3,5‐pyrazolidinedione 23 or 4‐(p‐methylphenylazo)‐1‐phenyl‐3,5‐pyrazolidinedione 29 were prepared and reacted with active nitriles, cyclic ketones and N,S‐acetals to give pyrano[2,3‐c]pyrazole, pyrazolo[4′,3′:5,6]pyrano[2,3‐c]pyrazole, spiropyrazole‐4,3′‐pyrazole and spiropyrazole‐4,3′‐[1,2,4]triazolane derivatives 24–34, respectively.
Potent Antipsoriatic Agents: A Facile Preparation of Acylated Derivatives from Dithranol in a Mild Basic Reaction
Authors: Liang David Woei‐Ming , Du Chun‐Jian
Published: May 2015

Treatment of dithranol 1 with various equivalents of acetyl chloride and Et3N in THF at room temperature afforded the corresponding acylated derivatives, such as 1‐acetyloxy‐ and 1,8‐diacetyloxy‐9(10H)‐anthracenones, 6a, and 6b, as well as 1,8,9‐triacetyloxyanthracene 7a, and 1,8,9‐triacetyloxy‐10‐acetylanthracene 7b. 1,8‐Bis(trimethylacetyloxy)‐9(10H)‐anthracenone 6c was also obtained in high yield by using pivaloyl chloride during the mild acylation.
Syntheses of Hitherto Unknown Thiazole, Ylidene and Pyridinethione Derivatives Having a Piperidin‐1‐yl Moiety and Their Use as Antimicrobial Agents
Authors: El‐Gaby Mohamed Sayed A.
Published: May 2015

The novel hydrazone derivatives 2a‐c were prepared by treatment of aldehydes 1a,b with some hydrazines. Thiocarbamoyl functional group in compound 2a was subjected to cyclization reactions with some α‐halocarbonyl reagents and furnished the novel thiazoles 4‐6, 8 and 9. Enaminonitrile 10 and pyridinone 13 derivatives were synthesized by interaction of active methylene compound 2b with N,N‐dimethylformamide‐dimethylacetal and ketene dithioacetal 11, respectively. Aliphatic, aromatic and heteroaromatic active methylene compounds were condensed with aldehydes 1a,b to afford the new ylidenes 15a‐d, 19a,b, 20 and 21. Substituted pyridinethiones 22 and 23 were prepared in high yields by cyclocondensation of 15c with malononitrile and ethyl cyanoacetate, respectively. Indeno[1,2‐b]pyridines 26a,b were obtained by the reaction of ylidenes 19a,b with cyanothioacetamide in ethanol and in the presence of sodium ethoxide under reflux. The structures of the synthesized compounds were established from their analytical and spectral data. The prepared compounds were also screened for their antimicrobial activity.
Synthesis, Reactions and Antimicrobial Activity of Some New Indolyl‐1,3,4‐Oxadiazole, Triazole and Pyrazole Derivatives
Authors: Abdel‐Rahman  , Farghaly A. H.
Published: May 2015

Indole‐3‐carboxylic acid hydrazide 3 was prepared and was treated with aromatic aldehydes in ethanol to give the corresponding hydrazone derivatives 4–7 in good yields. The indole carbohydrazide was incorporated into the 3‐indolyloxadiazoles 8–11 and 18, 3‐indolyltriazoles 13–17 and 35, 3‐indolylpyrazole derivatives 19–23 and carbamate derivatives 26–27. Furthermore, interaction of the carboazide 24 with hydrazine hydrate in refluxing toluene afforded the corresponding semicarbazide derivative 30. The thiadiazine derivative 34 was also prepared. Some of these compounds were screened in vitro for their antibacterial and antifungal activity.
Synthesis of 3‐Halogenated Flavonoids via Electrophile‐Promoted Cyclization of 2‐(3‐Aryl‐2‐propynoyl)anisoles
Authors: Lin Chi‐Fong , Duh Tsai‐Hui , Lu Wen‐Der , Lee Jeng‐Lin , Lee Chia‐Ying , Chen Chin‐Chau , Wu Ming‐Jung
Published: May 2015

Treatment of 2‐(1‐aryl‐3‐propynoyl) anisoles 1 with N‐chlorosuccinimide (NCS) or N‐bromosuccinimide (NBS) gave the 3‐halogenated flavones and their related molecules in moderate yields.
A Sensitive Spectrophotometric Determination of Nitrite in Water and Soil
Authors: Chatterjee Sukumar , Pillai Ajai K. , Gupta V. K.
Published: May 2015

A highly sensitive spectrophotometric method for the determination of nitrite in water and soil has been developed. The reaction of nitrite with acidified potassium iodide to liberate iodine which oxidizes leuco‐crystal violet (LCV) to form crystal violet having absorption maxima at 590 nm forms the bases of this method. In aqueous medium the system obeys Beer's law in the range of 0.1 to 1.0 μg per 25 mL (0.004–0.04 ppm), while in an extractive system the range is 0.025–0.25 μg in 100 mL (0.00025–0.0025 ppm). The molar absorptivity and Sandell's sensitivity were found to be 1.54 × 106 1 mol−1 cm−1 and 44 pg cm−2, respectively.
Pregnane‐Based Steroids from a Formosan Gorgonian Subergorgia Mollis
Authors: Wu Shwu‐Li , Wang Guey‐Horng , Dai Chang‐Feng , Sheu Jyh‐Horng
Published: May 2015

A new steroid, 11α, 15α‐diacetoxy‐17α‐pregna‐4,20‐dien‐3‐one (1), and a known one, 17α‐pregna‐4,20‐dien‐3‐one (2), have been isolated from a Formosan gorgonian Subergorgia mollis. The structures of both compounds were determined on the basis of extensive NMR experiments, including HMQC, HMBC, 1H‐1H COSY and NOESY. Metabolite 2 has not been isolated from a natural source before. The detailed 1H and 13C NMR spectral data of 2 are reported for the first time.
DNA‐Surfactant Interactions. Compaction, Condensation, Decompaction and Phase Separation
Authors: Dias Rita , Rosa Mónica , Pais Alberto Canelas , Miguel Maria , Lindman Björn
Published: May 2015

Recent investigations of the interaction between DNA and alkyltrimethylammonium bromides of various chain lengths are reviewed. Several techniques have been used such as phase map determinations, fluorescence microscopy, and electron microscopy. Dissociation of the DNA‐surfactant complexes, by the addition of anionic surfactant, has received special attention.

Precipitation maps for DNA‐cationic surfactant systems were evaluated by turbidimetry for different salt concentrations, temperatures and surfactant chain lengths. Single‐stranded DNA molecules precipitate at lower surfactant concentrations than double‐helix ones. It was also observed that these systems precipitate for very low concentrations of both DNA and surfactant, and that the extension of the two‐phase region increases for longer chain surfactants; these observations correlate well with fluorescence microscopy results, monitoring the system at a single molecule level.

Dissociation of the DNA‐cationic surfactant complexes and a concomitant release of DNA was achieved by addition of anionic surfactants. The unfolding of DNA molecules, previously compacted with cationic surfactant, was shown to be strongly dependent on the anionic surfactant chain length; lower amounts of a longer chain surfactant were needed to release DNA into solution. On the other hand, no dependence on the hydrophobicity of the compacting agent was observed. The structures of the aggregates formed by the two surfactants, after the interaction with DNA, were imaged by cryogenic transmission electron microscopy. It is possible to predict the structure of the aggregates formed by the surfactants, like vesicles, from the phase behaviour of the mixed surfactant systems.

The compaction of a medium size polyanion with shorter polycations was furthermore studied by means of Monte Carlo simulations. The polyanion chain suffers a sudden collapse as a function of the condensing agent concentration and of the number of charges on the molecules. Further increase of the concentration gives an increase of the degree of compaction. The compaction was found to be associated with the polycations promoting bridging between different sites of the polyanion. When the total charge of the polycations was lower than that of the polyanion, a significant translational motion of the compacting agent along the polyanion was observed, producing only a small‐degree of intrachain segregation. However, complete charge neutralization was not a prerequisite to achieve compacted forms.
Synthesis and Spectroscopic Characterization of Some Ferrocenyl Schiff Bases Containing Pyridine Moiety and Their Complexation with Cobalt, Nickel, Copper and Zinc
Authors: Abd‐Elzaher Mokhles M.
Published: May 2015

Three novel ferrocenyl Schiff base ligands containing pyridine moiety have been formed by 1:2 molar condensation of 1,1′‐diacetylferrocene with 2‐aminopyridine, 2‐amino‐5‐picoline or 2‐amino‐5‐chloropyridine, respectively. The ligands are 1,1′‐bis[1‐(pyridyl‐2‐imino)‐ethyl]ferrocene (L1); 1,1′‐bis[1‐(5‐methyl‐pyridyl‐2‐imino)ethyl]ferrocene (L2) and 1,1′‐bis[1‐(5‐chloropyridyl‐2‐imino)ethyl]ferrocene (L3). These ligands form 1:1 complexes with Co(II), Cu(II), Ni(II) and Zn(II) ions. The prepared ligands and their complexes have been characterized by IR, 1H NMR, 13C NMR, UV/Vis spectra as well as elemental analysis. The spectral data of the ligands and their complexes are discussed in connection with the structural changes due to complexation.
Flavones and Cytotoxic Constituents from the Stem Bark of Muntingia Calabura
Authors: Chen Jih‐Jung , Lin Ru‐Wei , Duh Chang‐Yih , Huang Hung‐Yi , Chen Ih‐Sheng
Published: May 2015

Two new flavones, 8‐hydroxy‐7,3′,4′,5′‐tetramethoxyflavone and 8,4′‐dihydroxy‐7,3′,5′‐trimethoxyflavone, together with thirteen known compounds have been isolated from the stem bark of Muntingia calabura. The structures of two new compounds were determined through spectral analyses. Among the isolates, 8‐hydroxy‐7,3′,4′,5′‐tetramethoxyflavone, 8,4′‐dihydroxy‐7,3′,5′‐trimethoxyflavone, and 3‐hydroxy‐1‐(3,5‐dimethoxy‐4‐hydroxyphenyl)propan‐1‐one exhibited effective cytotoxicities (ED50 values = 3.56, 3.71, and 3.27 μg/mL, respectively) against the P‐388 cell line in vitro.
Treated Rice Bran for Scavenging Cr(III) and Hg(II) from Acidic Solution
Authors: Farajzadeh Mir Ali , Monji Akbar Boviery
Published: May 2015

The purpose of this study was to examine the efficiency with which rice bran (treated or untreated) removes heavy metals, especially Cr(III) and Hg(II), from acidic solution. Sorption assays were done in shaken flasks in the presence of rice bran. Different experimental conditions such as pH, volume of solution, bran weight, particle size, exchange time and stirring time were improved. The efficiency of bran was studied before and after treatments. For treatment, solutions of acid, alkali and salt were used. The results show that after treating with 4 M sodium chloride solution, its efficiency in removal of Cr(III) and Hg(II) was improved. Kinetic measurements of chromium and mercury removal by bran have revealed that sorption equilibrium was obtained after 10 min of contact. Sorption experiments done with various granulometric fractions of rice bran have shown that this sorbent has the same efficiencies in meshes higher than 20. Further research is necessary in order to determine a mechanism for cations removal by the bran. It is mentioned that the process of making polished rice from brown rice discharges rice bran; therefore, it is very inexpensive, with a cost of 1/50 − 1/40 of that of synthetic sorbent, and thus its use would significantly lower the cost of wastewater treatment.
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

The 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

New 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

The 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

A 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

The 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

The 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

This 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

In 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

One 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

How 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

Multiphoton 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

Ruthenium‐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

The 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

This 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

The 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

The 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

In 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

The 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

An 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

Two 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

Collision 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.
Photochemistry in Phototropin, a Blue Light Sensor Protein in Plants
Authors: Iwata Tatsuya , Kandori Hideki
Published: May 2015

Phototropin (phot) is a blue‐light receptor in plants. The protein molecule has two FMN (Flavin MonoNucleotide) binding domains named LOV (Light‐, Oxygen‐, and Voltage‐sensing), which is a subset of the PAS (Per‐Arnt‐Sim) superfamily. Illumination of the phot‐LOV domains produces a covalent C(4a) flavin‐cysteinyl adduct (S390 intermediate) via a triplet‐excited state, which reverts to the original state in the dark. Chemical structure of the S‐H group of the reactive cysteine is important for the adduct formation, and several models have been proposed for efficient reaction. By means of Fourier‐transform infrared (FTIR) spectroscopy of the LOV2 domain of Adiantum phytochrome3 (phy3‐LOV2), a fusion protein of phot containing the phytochrome chromophoric domain, we have studied protonation state of the reactive cysteine (Cys966). Although it was proposed that the cysteine is deprotonated in LOV domains, we observed an S‐H stretch at ˜2570 cm−1. Since phy3‐LOV2 possesses only one cysteine at position 966, this observation clearly indicates that Cys966 is protonated. While transfer reaction of proton, hydrogen, or electron has been proposed from the cysteine in the triplet‐excited state, we also detected the S‐H stretch at 2537 cm−1 in the triplet‐excited state of phy3‐LOV2. This excludes the possibility of proton and hydrogen transfer reactions. These frequencies imply that the S‐H group is free from hydrogen bond in the unphotolyzed state, while it forms a strong hydrogen bond in the triplet‐excited state. We infer the hydrogen‐bonding acceptor to be the N(5) atom of FMN, and such strong interaction presumably drives adduct formation in a microsecond timescale.
Enhanced Energy Transfer Efficiency in Star‐Shaped Light‐Harvesting Block Copolymers Prepared by RAFT Polymerization
Authors: Chen Ming , Ghiggino Kenneth P. , Thang San H. , Wilson Gerard J.
Published: May 2015

Reversible addition‐fragmentation chain transfer (RAFT) polymerization has been used to synthesize a star‐shaped light‐harvesting polymer comprising six diblock copolymer arms of styryl coumarin (St‐Coumarin) and methyl acrylate (MA) surrounding a ruthenium (II) trisbipyridyl energy trap core. The efficiency of excitation energy transfer from the styryl coumarin units to the Ru(II) core is increased to 90% compared to 60% for the analogous star polymer without MA blocks. The enhanced excitation energy transfer efficiency arises from the role of the MA blocks in diminishing the competitive quenching of photoexcited St‐coumarin chromophores by dithiobenzoyl polymer end groups present from the RAFT polymerization procedure.
Theoretical Studies on Photophysical Properties and Mechanism of Phosphorescence in [fac‐Ir(2‐phenylpyridine)3]
Authors: Nozaki Koichi
Published: May 2015

The photophysical properties of [fac‐Ir(ppy)3] have been studied using time‐dependent density functional theory with one‐center spin‐orbit coupling approximation. The phosphorescent state of [fac‐Ir(ppy)3] was characterized by a mixture of 40%3MLCT and 58% intra‐ and inter‐ligand3ππ*with charge distribution being partially localized to a single ligand. Zero‐field splittings and oscillator strengths calculated for the sublevels of the lowest triplet state were in agreement with the observed values. The spin components in the sublevels and the mechanism of phosphorescence were well rationalized using a localized model for a hypothetical M‐LL unit withC2vsymmetry similarly to the cases for [Ru(bpy)3]2+or [Os(bpy)3]2+. Furthermore, it was revealed that the excited states were characterized by both high density‐of‐state (approximately 70 states per eV) and considerable mixing between singlet and triplet states due to strong spin‐orbit coupling.
Formation of Trititanate Nanotubes by Non‐Hydrothermal Methods: Optical Properties and Surface‐Exciton Dynamics Studied by Photoluminescence Spectroscopy
Authors: Jang Joon Hee , Jeon Ki Seok , Park Tae Sook , Lee Ki Whan , Yoon Minjoong
Published: May 2015

Trititanate (H2Ti3O7) nanotubes were prepared by a non‐hydrothermal digestion of TiO(OH)2 solution with 5 M NaOH, and their optical properties and exciton dynamics were studied by using steady‐state and time‐resolved photoluminescence (PL) spectroscopy. Based on TEM, AFM and XRD measurements, the tubular structure was identified to be the same as that of trititanate crystalline multi‐walled scroll nanotubes prepared hydrothermally, which has intershell d‐spacing of 0.79 nm with inner diameters of 5 nm and the lengths of several tens of nanometers. The UV‐absorption spectrum of trititanate nanotubes showed weak surface‐state absorption at 425 nm as well as the absorption maximum band around 350 nm with onset energy 3.03 eV corresponding to the indirect band gap energy. The steady‐state PL spectra of the trititanate nanotubes showed a band‐edge emission band around 360 nm as well as a broad surface emission band originating from widely dispersed surface‐state energy levels (2.84, 2.65, 2.41 2.21 2.03 eV), exhibiting higher relative intensity ratio of the band‐edge emission to the surface emission as compared to that of TiO2 nanoparticles. These results with PL excitation spectra indicate that the density of the surface states was found to be higher in the nanotubes than in TiO2 nanoparticles. The PL decay profiles were measured by using the time correlated single photon counting system (TCSPC) adopting fs‐Ti‐Sappire laser at 350 nm, and they were analyzed to fit a tri‐exponential equation. The decay times depend on monitoring emission wavelength, and at least four different decay time components (˜28 ps, ˜70 ps, ˜700 ps and ˜4 ns) were resolved, implying the existence of charge‐carriers trapping surface states with different energy levels. The two longer decay times are attributed to the deep‐trap surface states of trititanate nanotubes, which are much longer than those of TiO2 nanoparticles. These results suggest that the nonradiative route to the surface excitons recombination is more dominant in trititanate nanotubes than in titania nanoparticles because of strong coupling of excitons wave functions with lattice phonons.
Förster Energy Transfer in Thin Films of Conjugated Polymers and in Solution
Authors: Mukherjee Arnab , Bagchi Biman
Published: May 2015

Fluorescence resonance energy transfer (FRET) is routinely used to study equilibrium and dynamical properties of polymers and biopolymers in the condensed phases. It is now being widely used in conjunction with single molecule spectroscopy where one usually employs the Förster expression which predicts (1/R6) distance dependence of the energy transfer rate. However, critical analysis shows that this expression can be of rather limited validity in many cases. We demonstrate this by explicitly considering a donor‐acceptor system, polyfluorene (PF6)‐tetraphenylporphyrin (TPP), where their sizes are comparable to the distance separating them. In such cases, one may expect much weaker distance (as 1/R2 or even weaker) dependence. We also discuss recent application of FRET to study biopolymer conformational dynamics. We show that the well‐known Wilemski‐Fixman theory needs to be generalized to treat FRET at short separations. The utility of FRET in studying protein folding is also discussed.
Solvation Dynamics in Biological Systems and Organized Assemblies
Authors: Sen Pratik , Pal Subrata , Bhattacharyya Kankan , Bagchi Biman
Published: May 2015

Solvation dynamics of a polar probe in many biological systems and organized assemblies displays a surprising ultraslow component. The origin of this anomalous ultraslow component is investigated using experiments, theory and computer simulations. We first summarize some recent experimental results on solvation dynamics, e.g., temperature dependence, site dependence at active site of an enzyme and red edge excitation shift (REES). Then we propose two new theoretical models to explain the ultraslow component. The first one involves the motion of the ‘buried water’ molecules (both translation and rotation) accompanied by cooperative relaxation (‘local melting’) of several surfactant chains. An estimate of the time is obtained by using an effective Rouse chain model of chain dynamics, coupled with a mean first passage time calculation. The second explanation invokes self‐diffusion of the (di)polar probe (created by optical excitation) itself from a less polar to a more polar region. This may also involve cooperative motion of the surfactant chains in the hydrophobic core, if the probe has a sizeable distribution inside the core prior to excitation. It may also involve escape of the probe to the bulk from the surface of the self‐assembly. The second mechanism should result in the narrowing of the full width of the emission spectrum with time, which has indeed been observed in recent experiments. It is argued that both the two mechanisms may give rise to an ultraslow time constant and may be applicable to different experimental situations. The effectiveness of solvation as a dynamical probe in such complex systems has been discussed. Finally, we give a brief overview of recent results on computer simulations on dynamics of water molecules around a protein and a micelle.
Solvothermal Synthesis of Self‐Assembled Free‐Based Porphyrin Wires
Authors: Li Lu‐Lin , Chuang Hui‐Ju , Lin Kuan‐Jiuh
Published: May 2015

A family of well‐defined prophyrin wires, 5,10,15,20‐tetrakis(4‐N‐ethylpyridyl)porphyrin salts [H2TEPyP4+·A] (A = 2CdI42− 1; 6I− 2; 4I− 3), has been synthesized by hydrothermal methods and was structurally characterized by X‐ray single‐crystal diffraction. Controlling the packing of π‐π stacking backbones was achieved by means of adjusting the counterbalanced anions: tetragonal packing for 1 and 2; hexagonal‐like for 3. The optical properties related to the packing structures were studied by solid‐state diffuse reflectance spectra. The blue‐shift of Soret band demonstrated the H‐aggregate form in the porphyrin wires.