bluuebunny/crossref_metadata_2025 huggingface dataset:
Ligand Exchange Gas Chromatography on PTFE Open Tubular Columns
Authors: Chyueh S. D. , Liu C. Y.
Published: May 2015

Two kinds of capillary columns were prepared and tested as the stationary phases of ligand exchange gas chromatographic separation of dialkyl sulfides. The PTFE column wall‐coated with silane‐DTC‐Cu but without the addition of silicone exhibits significantly better selectivity towards dialkyl sulfides than a column wall‐coated with 10% silane‐DTC‐Cu in silicone. With the first column connected to a microsample injection valve and a microsample loop, the quantitative determination of dialkyl sulfides can be performed. The column also shows great promise for the separation of dialkyl sulfide‐hydrocarbon mixtures.
Diazotization of Methyl 3‐Amino‐7‐Isopropyl‐2‐Methoxyazulene‐1‐Carboxylate and its 5‐Isopropyl Isomer‐ a Convenient Synthesis of 1,2‐Azulenequinone Derivatives
Authors: Huang Tian‐Chyuan , Lin Yun‐Shan , Lin Shih‐Jue , Chu Shu‐Fan
Published: May 2015

Methyl 3‐amino‐2‐methoxy‐7‐isopropylazulene‐l‐carboxylate(8a) and its 5‐isopropyl isomer (8b) were synthesized by reduction of the 3‐nitro derivatives (7a,b) with zinc/acetic acid in excellent yields. 7a and 7b were prepared by nitration and methylation of methyl 7‐isopropyl‐2‐hydroxyazulene‐l‐carboxylate (5a) and methyl 5‐isopropyl‐2‐hydroxyazulene‐l‐carboxylate (5b), respectively. Diazotization of 8a with sodium nitrite in trifluoroacetic acid at 0 °C gave methyl 5‐isopropyl‐1,2‐azulenequinone‐3‐carboxylate (9a) in 91% yield. Similar reaction of 8b gave the corresponding methyl 7‐isopropyl‐1,2‐azulenequinone‐3‐carboxylate (9b) in 93% yield. No evidence for the formation of l‐diazo‐1,2‐azulenequinones was obtained.
The Enantioresolution of n‐Benzoyl and Its Analogs Derivatized Amino Acids on Cyclodextrin Bonded Chiral Stationary Phases Using a Nonaqueous Acetonitrile‐Based Mobile Phase
Authors: Chen Shushi
Published: May 2015

The separation of amino acids into enantiomers while derivatizing with benzoyl chlorides is demonstrated. It was found that enantioselectivity among these reagents tagging with the same amino acid is quite different and is very sensitive to its structural variations. A noninclusion complexation mechanism i.e. external association is thought to involve in the separation carried out with a nonaqueous polar organic mobile phase. Results also indicate that the chiral recognition seems to be controlled either by moieties from tagging reagents or functional groups on all amino acids examined in this study on the basis of competition. The polarity of side‐chain group on peptide backbone can not be ignored in achieving a successful separation. Furthermore, chiral recognition appears to closely rely upon the location of stereogenic center that is simultaneously attached by amino and carboxyl groups. Finally, mechanism involved will be explored structurally with these tagging reagents derivatized amino acids which structures are highly ordered and amine‐containing compounds with structures similar to that of amino acid.
Engineering of Cardiotoxin by Chemical Synthesis: (I) Rapid Synthesis of Fully Active Cardiotoxin II and IV of Taiwan Cobra Venom
Authors: Wu Chi‐Yue , Chen Shui‐Tein , Ho Chewn‐Lane , Wang Kuns‐Tsuns
Published: May 2015

Two 60‐residue snake toxins with four disulfide bridges, cardiotoxin II and IV, of Taiwan cobra (Naja naja atra) have been rapidly prepared in overall yields of 3.9% (cardiotoxin II) and 3.7% (cardiotoxin IV) within three weeks using the chemical method. Physicochemical characterization of these synthetic cardiotoxins was carried out by amino acid analysis, mass spectroscopy, capillary electrophoresis, peptide mapping, circular dichroism spectroscopy, and lethal toxicity. As compared with natural cardiotoxins, the results indicated that the synthetic cardiotoxins possessed the same physicochemical properties as those of natural ones. Therefore, in addition to preparation of various important toxins with satisfactory quantities for biochemical and pharmacological studies within a short lime, this rapid method also provides an important route to obtain many interesting toxins and designed toxin analogues for structure/function relationship studies in the near further.
Tannins from Betel Nuts
Authors: Ma Ying‐Tsun , Hsu Feng‐Lin , Lan Shu‐Jan J. , Chen Chieh‐Fu
Published: May 2015

From the acetone extract of fresh‐betel nuts, two procyanidin pentamers, two procyanidin tetramers and three procyanidin trimers, along with (+)‐catechin, (‐)‐epicatechin, procyanidin A‐l, procyanidin B‐l, procyanidin B‐2, and procyanidin B‐7 were isolated. Based on 1H NMR and 13C NMR spectral data as well as the results of thiolysis degradation, the chemical structures of two series of oligomeric arecatannins A and B have been established. The arecatannins from betel nuts were found to be condensed‐type tannins which possess (‐)‐epicatechin unit and (+)‐catechin units. All arecatannins had C4‐C8 linked (‐)‐epicatechin in the upper units whereas the (+)‐catechin in the terminal unit had C4‐C8 or C4‐C6 linkage.
Synthesis of Novel Tetraacetal Oxa‐Cage Compounds from 2‐Methylthiofurans
Authors: Lin Chu‐Chung , Huang Fang‐Jung , Lin June‐Chieh , Wu Hsien‐Jen
Published: May 2015

Several novel tetraacetal oxa‐cage compounds 9a‐9f were synthesized from the corresponding 2‐methylthiofurans la‐lf by a short sequence. The structures of these tetraoxa‐cage compounds were deduced from their spectral data and proven by X‐ray analysis of 9a. Ozonolysis of the endo adducts 5a‐5f in CH2C12 at −78 °C followed by reduction with dimethyl sulfide gave the tetraoxa‐cages 9a‐9f in 65‐75% yields, respectively. Ozonolysis of the exo adduct 6a under the same reaction conditions gave the tetracarbonyl compound 10. The phenylthio group substituted tetraoxa‐cage 13 and the tetraacetal oxa‐cage 17, with one more carbon atom on the apex position, were also synthesized in a similar sequence.
Synthesis of Novel Triacetal Trioxa‐Cage Compounds by Ozonolysis of Bicyclo[2.2.1]Heptenes and Bicyclo[2.2.2]Octenes
Authors: Wu Chung‐Yi , Lin Chu‐Chung , Lai Ming‐Cheng , Wu Hsien‐Jen
Published: May 2015

Several novel triacetal trioxa‐cage compounds 11a‐11g, 13, 15, 17 and 19 are synthesized in a short sequence. Ozonolysis of bicyclo[2.2.1]heptenes 4a‐4c, 8a‐8c, 10a, 10b and 14 in dichloromethane at −78 °C followed by reduction with dimethyl sulfide gave triacetal oxa‐cages 11a‐11g, 13 and 15 in moderate yields, respectively. Ozonolysis of bicyclo[2.2.2]octenes 16 and 18 under the same reaction conditions gave triacetal oxa‐cages 17 and 19 in moderate yields, respectively.
Synthesis of Tetraacetal Tetraoxa‐Cage Compounds with Alkyl Substituents at Different Sites of the Oxa‐Cage Skeleton
Authors: Lin Rong‐Liang , Wu Chung‐Yi , Chem Jyh‐Haur , Wu Hsien‐Jen
Published: May 2015

Tetraacetal tetraoxa‐cage compounds 3a, 3b, 4a, 4b, 7, 13,14, and 15 were synthesized by a short sequence. They were obtained from ozonolysis of endo adducts la, lb, 2a, 2b, and 6 in dichloromethane at −78 °C followed by reduction with dimethyl sulfide. Ozonolysis of 7‐anti‐trimethylsilyl‐5,6‐bis‐endo‐diacetylnorbornene 8 under the same reaction conditions did not give the tetraoxa‐cage 9. The methylsulfinyl oxa‐cage 13 derived from l‐methylthio‐5,6‐bis‐endo‐diacetylnorbornene 11 was converted to compounds 14 and 15.
Synthesis of Thermally Stable MCM‐41 at Ambient Temperature
Authors: Lin Hong Ping , Cheng Soofin , Mou Chung‐Yuan
Published: May 2015

A new process to synthesize thermally stable mesoporous molecular sieves of MCM‐41 structure based on delayed neutralization at ambient temperature was investigated. All samples synthesized by this new method have BET surface areas of about 1100m2/g and possess high thermal stability up to 900°C. Higher crystallinity and less lattice constriction after calcination were observed for samples with a longer aging period. Those samples with aging time longer than 10 days exhibited four characteristic XRD peaks of MCM‐41 both before and after calcination at 560°C. The N2 adsorption‐desorption isotherms of the calcined samples showed larger average pore size and more homogenous pore size distribution. The method was also successfully applied to the synthesis of MCM‐41 with different surfactants of hydrocarbon length with 10–18 carbons and proves to be a simple route for obtaining thermally stable MCM‐41 at room temperature.
Absorption and Flourescence of a Rigidly‐Bridged Donor‐Acceptor Molecule in Langmuir‐Blodgett Mixed Films
Authors: Amire Olasoji A.
Published: May 2015

Thermodynamic analysis of the pressure‐area isotherms, of solutions of rigidly‐bridged donor‐acceptor molecule, D(10)A, in arachidic acid, indicates that the solutions behave ideally at low concentrations. The surface area per molecule at high dilutions (mf ≤ 0.02) approximates to 27 Å2 from which it is evident that the long axis of the D(10)A molecule is oriented vertically, and the short axis of the 1,4‐dimethoxynaphthalene moiety parallel to the monolayer surface at 25 mN m−1 surface pressure Evidence from electronic absorption, static and time‐resolved fluorescence spectra led us to conclude that D(10)A molecules form ground‐state dimers, intermolecular excimers with very short lifetimes which do not photodimerize in Langmuir‐Blodgett films, and give long‐Jived (τ3 ≈ 29±3ns) charge‐transfer emissions at 440 nm.
Synthesis of 3,5,7‐Trioxapentacyclo[7.2.1.02,8.04,11.06,10]dodecane. A Novel Diacetal Trioxa‐Cage
Authors: Tsai Shih‐Hwa , Wu Hsien‐Jen , Chung Wen‐Sheng
Published: May 2015

3,5,7‐Trioxapentacyclo[7.2.1.02,8.04,11.06,10]dodecane, the parent compound of novel diacetal trioxa‐cages, was synthesized from maleic anhydride cyclopentadiene adduct 1 by a four‐step sequence. Attempts for the synthesis of monoaza dioxa‐cage 12 failed. Ozonolysis of compound 9 in CH2Cl2‐EtOH(1:1) at −78°C followed by reduction with Me2S gave 13 in 65% yield.
Liquid Chromatographic Determination of 3‐Hydroxy‐3‐methylglutaryl Coenzyme A Reductase Inhibitors
Authors: Shen Pei‐Ming , Shiao Ming‐Shi , Chung Huey‐Ru , Lee Kuan‐Rong , Chao Yu‐Sheng , Hunt Vincent M.
Published: May 2015

Reversed‐phase high‐performance liquid chromatography (RP‐HPLC) was used as a tool to explore the retention behavior and separation of four 3‐hydroxy‐3‐methylglutaryl coenzyme A (HMG‐CoA) reductase inhibitors, namely compactin, lovastatin, simvastatin, and pravastatin in their hydroxy acid and lactone forms. The contribution of C‐6 and C‐2′ methyl groups and lactonization to the molecular hydrophobicity among these four structurally related HMG‐CoA reductase inhibitors were elucidated. Eight components (four lactones and four hydroxy acids) could be resolved by RP‐HPLC with isocratic elution. In a binary mobile phase system of acetonitrile‐water containing 0.5% acetic acid, the free hydroxy acids and corresponding lactone forms remained intact and were completely separated. This study demonstrated that RP‐HPLC is suitable for simultaneous determination of active and prodrug forms of these HMG‐CoA reductase inhibitors.
Cuprate‐catalyzed Three‐Component Couplings of Functionalized Organozinc Reagents
Authors: Lipshutz Bruce H. , Gross Tim , Buzard Daniel J. , Tirado Raymond
Published: May 2015

Organozinc reagents FG‐(CH2)nZnX containing electrophilic centers (FG) upon conversion to their corresponding zincates (FG‐(CH2)nZnMe2Li) and in the presence of 5–8 mol % MeCu(CN)Li, undergo 1,4‐additions to cyclic conjugated enones. The intermediate zinc enolates can be trapped with aldehydes to afford products of three‐component couplings.
Formation of Azulenequinone Derivatives from Variously Functionalized Azulenes by Bromine‐oxidation
Authors: Yang Paw‐Wang , Chen Jhy‐An , Wakabayashi Hidetsugu , Shindo Kimio , Kurihara Teruo , Wu Chi‐Phi , Yasunami Masafumi , Nozoe (The Late) Tetsuo
Published: May 2015

Variously functionalized 1,5‐ and 1,7‐azulenequinones were easily derived in one‐pot in 30‐50% yield from the bromine‐oxidation of 2‐methoxyazulene and 2‐methyl derivatives of 1‐cyano‐, 1‐methoxycarbonyl‐ and its 7‐isopropyl derivatives, while 1‐methoxycarbonylazulene afforded several unstable products from which we could not isolate any azulenequinones. 1‐Acetylazulene afforded 3‐bromo‐1,5‐ and ‐1,7‐azulenequinones via side‐chain brominated intermediates in high yield. 1,3‐Dichloroazulene afforded a mixture of 3‐chloro‐1,5‐ and −1,7‐azulenequinones, while 1‐fluoro‐ and 1,3‐diiodoazulene gave a mixture of 3‐bromoazulenequinones. Analogous oxidation of 1,3‐difluoroazulene produced 3‐fluoroazulenequinones, but we could not isolate them due to its instability. Hydroxy group of 2‐(3‐hydroxypropyl)azulene was intact during this quinone formation reaction.
The Analysis of Sulfur Compounds by Solid Adsorbent Tenax GR Preconcentration and Gas Chromatography with Flameless Sulfur Chemiluminescence Detection
Authors: Sye Wen‐Fa , Cheng Mei‐Fang
Published: May 2015

Gas chromatography using flameless sulfur chemiluminescence detection was applied to the analysis of sulfur compounds in air. A trap employing the solid adsorbent Tenax GR was used to enrich ambient levels of volatile sulfur compounds. The sulfur gases were then thermally released according to programmed temperature from the adsorbent trap and re‐collected in a column cooled with liquid nitrogen. The sulfur compounds were revolatilized and directly transferred to the system of PLOT‐column gas chromatograph/flameless sulfur chemiluminescence detector for analysis. The PTV injector has been used as a thermal resorption chamber for analysis of sulfur compounds. The sulfur gaseous compounds known to cause nuisance odors in the air from sewerage treatment works were determined.
A Model Study of Intramolecular Asymmetric Radical Cyclizations of α‐Ester and α‐Amide Radicals
Authors: Yeh Ru‐Long , Jiaang Weir‐Tom , Tsai Yeun‐Min
Published: May 2015

Starting from malonate, a practical route was developed for the synthesis of α‐phenylthio acid 3. Several chiral compounds including (‐)‐menthol, (‐)‐8‐pbenylmenthol and a camphor based oxazolidinone 8 reacted with 3 to give α‐phenylthio esters or amide. These sulfides cyclized efficiently when reacted with tributyltin hydride. Among the chiral auxiliaries used, 8‐phenylmenthyl group displayed moderate asymmetric induction (64% ee for cis‐product and 40% ee for trans‐product). Based on this results, a transition state model was proposed to explain the observed stereoselectivity. In this model, due to π,π‐orbital overlap of the phenyl ring and the carbonyl, the si‐face of the most stable conformer of the radical was shielded. This controlled the carbon‐carbon bond formation to occur from the re‐face.
Constituents of the Bark of Ficus microcarpa Lf.
Authors: Kuo Yueh‐Hsiung , Li Yen‐Cheng
Published: May 2015

The isolation and identification of twenty‐eight crystalline components from the bark of Ficus microcarpa L.f. are described. Their structures were determined on the basis of spectral data and values taken from the literature. These compounds include fourteen triterpenoids, one fatty alcohol, eight steroids, one coumarin, one flavane, two 4‐hydroxybenzoates, and one carotenoid‐like compound.
Chemical Constituents of Heartwood of Bauhinia purpurea
Authors: Kuo Yueh‐Hsiung , Yeh Ming‐Hsi
Published: May 2015

The isolation and identification of twenty‐two components from the heartwood of Bauhinia purpurea are described. Their structures were determined on the basis of spectral evidence as well as direct comparison with authentic samples. Those components included six steroids, two triterpenoids, three fatty alcohol, acid and ester, two glycerols, five flavonoids, two phenols, one chromone, and one sugar. Among these, 6′‐(β‐sitosteryl‐3‐O‐β‐glucopyranosidyl)tetraeicosanoate is a new compound.
Conductometric Flow‐Injection Glucose Biosensing System with an Immobilized Glucose‐Oxidase Mini‐Reactor
Authors: Chen Richie L. C. , Chang Bin‐Wha , Chang Hsien‐Chang
Published: May 2015

A flow‐injection conductometric manifold equipped with an immobilized glucose‐oxidase mini‐reactor was proposed for the determination of glucose concentration. The glucose of the injected sample plug was oxidized enzymatically to its δ‐lactone, and the hydrolysis of the lactone generated a concentration‐dependent flow‐injection signal. The dynamic range was from the tens of μM to the mM order of glucose; the immobilized enzyme reactor was stable for at least several months. The pH of the carrier solution was maintained in a slightly alkaline region (ca. 8.0 by 500 μM of Tris‐HCl) to accelerate the spontaneous hydrolysis of δ‐gluconolactone. The repeatability of the flow‐injection signals was improved (CV < 3%, n = 7) by the addition of Triton X‐100® (0.7% w/v) into the carrier solution.
Efficient, Optimized Applications of p‐Nitrophenyl Active Ester Temporarily Protecting Groups Together with Simultaneous Activation in Synthesis of Special Glu and Lys Peptides
Authors: Szókán Gy. , Almás M. , Kótai A. , Khlafulla A. R.
Published: May 2015

Benzyloxycarbonyl‐glutamylpeptide p‐nitrophenylesters were prepared from protected amino acids, e.g.: p‐nitrophenyl‐glutamate as carboxyl component and aminoacid or peptide p‐nitrophenylesters as amino components by different kinds of peptide coupling methods. Mixed carbonic anhydride and azide methods gave good results. The p‐nitrophenylesters existed as temporary protecting groups, so the peptide couplings proceeded together with simultaneous activation. The conditions and applications of the procedure are discussed. The peptides having one or more active ester groups were used to form amides by their aminolysis with derivatives of ethylamine or were polycondensated (after deprotection) to obtain polypeptides.
Dioxins in Soil and Fish Samples from a Waste Pentachlorophenol Manufacturing Plant
Authors: Soong Der‐Kau , Hou Peter C. C. , Ling Yong‐Chien
Published: May 2015

A method to analyze polychlorinated dibenzo‐p‐dioxins and dibenzofurans (PCDD/DFs, dioxins) and coplanar polychlorinated biphenyls in environmental samples is developed and used to determine the levels of PCDD/DFs in 13 soil and 4 fish samples collected around a waste pentachlorophenol manufacturing plant. The 2,3,7,8‐tetrachlorodioxin toxic equivalents (TEQ) values range from 0.239 ng‐TEQ/g to 1357 ng‐TEQ/g in soil samples and 0.041 ng‐TEQ/g to 0.247 ng‐TEQ/g in fish samples. A broader survey of PCDD/DF contamination in the vicinity around the manufacturing plant is strongly recommended.
Determination of Bismuth in Sediment and Soil by Ultrasonic Slurry Sampling Electrothermal Atomic Absorption Spectrometry
Authors: Mierzwa J. , Sun Y. C. , Yang M. H.
Published: May 2015

The analytical conditions of the direct determination of bismuth in some certified reference material samples (soil and sediment) by slurry sampling Zeeman electrothermal atomic absorption spectrometry (ETAAS) with the use of automated ultrasonic slurry mixing are discussed. Palladium nitrate was used as a chemical modifier. With the use of this modifier it was possible to stabilize bismuth to the pyrolysis temperature of 1300 °C. Platform atomization was performed at 2050 °C. The results of determination are calculated from a simple, aqueous standards based calibration graph.

Statistical evaluation of the results indicate that the slurry sampling method is reproducible and the accuracy of the proposed method is very good. This method is rather simple and its other advantages are good sensitivity and relatively short analysis time.
Selenium Determination in Serum by Graphite Furnace Atomic Absorption Spectrometry
Authors: Yen Cheng‐Chieh , Chen Wen‐Kang , Wang Chin‐Ping , You Jiing‐Nar , You Wei‐Chu , Yu Jya‐Jyun , Lee Yean‐Jang , Chung Chien , Kuo Sheng‐Chu
Published: May 2015

Selenium concentration in serum has been proposed as the most valuable indicator of human selenium status. In this work, the concentration of selenium in serum is measured by GFAAS using longitudinal Zeeman‐effect background correction, a highly sensitive technique that can be used to determine selenium at sub‐ppb level. Standard reference materials are analyzed to verify the accuracy and precision of this technique. The direct method proposed in this study is used for the determination of selenium in human serum collected from healthy people of 19–25 years and women of 21–34 years in the First trimester of pregnancy. The method developed in this study, which can quickly and accurately measure serum selenium, is suitable for applications in clinical diagnosis or biological monitoring.
Synthesis and Characterizations of p‐Xylyl Bridged Dinuclear Complexes of Molybdenum and Tungsten. The Crystal Structure of μ‐p‐xylyl‐bis(1‐Me‐3‐SiMe3‐cyclopentadienyltricarbonylmolybdenum)
Authors: Lin See , Chen Yen‐Hsien
Published: May 2015

The reactions of R1R2CpM(CO)3−Li+ (M = Mo, W) with α, α′‐dichloro‐p‐xylene yielded p‐xylyl bridged dinuclear complexes of R1R2CpM(CO)3 in high yields. All of such new complexes are very stable to air and water. Some of them are stable even in dilute acids and dilute bases. Complex 4 crystallizes in the monoclinic system, space group P21/n, with a = 6.847(5) Å, b = 9.838(2) Å, c = 25.140(10) Å, β = 96.56(5)°, Z = 2, RF=0.077, Rw = 0.105 and V = 1682.4(14) Å3.
Syntheses of New Azo Dyestuff Containing a Sydnone Ring
Authors: Tien Hsien‐Ju , Hwang Yuh‐Ren , Wen Ten‐Chin
Published: May 2015

New azo dyestuffs containing a sydnone ring were prepared by the diazonium coupling of 3‐(p‐/m‐aminophenyl)sydnones with phenol or 1‐/2‐naphthols.
Photophysics of Indocarbocyanine Dyes in Organic Solvents
Authors: Zhifei Dai , Bixian Peng
Published: May 2015

The absorption and fluorescence properties of a series of 18 indocarbocyanine dyes in organic solvents have been determined. The wavelengths of the absorption and fluorescence maxima, the fluorescence lifetimes and the fluorescence quantum yields relative to the benzo‐15‐crown‐5‐substituted phthalocyanine have been measured. The results are discussed in relation to the molecular structures or the dye studied.
NMR Study of the Ligand Interchange of Hexacyclen and Hexamethylhexacyclen Complexes with TI+ Ion in 70% Methanol Solution
Authors: Shamsipur Mojtaba , Alizadeh Naader
Published: May 2015

The exchange kinetics of TI+ complexes with hexacyclen and hexamethylhexacyclen were studied in 70% methanol solution by proton NMR line‐shape analysis. In TI+‐hexacyclen system, a dissociative mechanism is found to be predominant at higher temperatures, while a bimolecular pathway may become more important at lower temperatures. In contrast, the TI+‐hexamethylhexacyclen system solely prefers a dissociative exchange mechanism in entire temperature range studied. The corresponding exchange rates and the activation parameters Ea, ΔH‡, ΔS‡ and ΔG‡ for the exchange have been determined, and the possible parameters controlling the exchange rates and mechanisms are discussed.
New Triterpenes from the Heartwood of Melaleuca leucadendron L.
Authors: Lee Ching‐Kuo
Published: May 2015

Fourteen chemical constituents were isolated from the CHCl3 soluble portion of the heartwood of Melaleuca leucadendron L. These compounds include β‐sitosterol (1), β‐sitostenone (2), 6‐hydroxy‐4,6‐dimethyl‐3‐hepten‐2‐one (3), naphthalene (4), squalene (5), 2α3β‐dihydroxyurs‐12‐en‐28‐oic acid (6), 3β‐hydroxylup‐20(29)‐en‐27,28‐dioic acid (7), 2α,3β‐dihydroxyolean‐12‐en‐28‐oic acid (8), 3β,23‐dihydroxyolean‐12‐en‐28‐oic acid (9), 2α,3β,23‐trihydroxyolean‐12‐en‐28‐oic acid (10), 3β‐trans‐p‐coumaroyloxy‐2α,23‐dihydroxyolean‐12‐en‐28‐oic acid (11), and three novel oleanane derivatives 23‐trans‐p‐coumaroyloxy‐2α,3β‐dihydroxyotean‐12‐en‐28‐oic acid (12), 3β‐trans‐caffeoyloxy‐2α,23‐dihydroxyolean‐12‐en‐28‐oic acid (13), and its isomer 3β‐cis‐caffeoyloxy‐2α,23‐dihydroxyolean‐12‐en‐28‐oic acid (14), The three novel compounds were characterized as the two and three O‐methylated derivatives, respectively.
Photochemistry of p‐Nitroacetophenone in 2‐Propanol
Authors: Lin Yuh‐Nong , Jeng Guang‐Yan , Chan Tung‐Tan , Yen Giann‐Feng , Wong Yin‐Gang
Published: May 2015

Upon irradiation in 2‐propanol, p‐nitroacetophenone 1 was reduced via the triplet state to p‐hydroxyaminoacetophenone 5 which was further reduced to p‐aminoacelophenone 2 and 4,4′‐diacetylazobenzene 4. Similar irradiation of 5 also gave 2 and 4, and its oxidation by oxygen gave 4,4′‐diacetylazoxybenzene 3. Photolysis of monomeric p‐nitrosoacetophenone 6 afforded acetophenone and 3 that were not produced during the irradiation of 1. Possible photoreaction pathways were discussed on the basis of published mechanisms.
Tandem Thermal Reactions for the Synthesis of Jasmonoids
Authors: Ho Tse‐Lok , Shyu Kuo‐Feng
Published: May 2015

A tandem reaction tactic for the preparation of a jasmonoid intermediate consists of pyrolysis of a spiroannulated cyclopentanone. The thermal decomposition actually involves a retro‐Diels‐Alder reaction and a homo‐1,5‐hydrogen shift with cleavage of the cyclopropane unit.
Intramolecular Electronic Energy Transfer in a Supersonic Jet Expansion
Authors: Speiser Shammai
Published: May 2015

Intramolecular electronic energy transfer (intra‐EET) was investigated in an isolated bichromophoric naphthalene (N) and anthracene (A) 1:1 molecular cluster. Investigation of the spectroscopic properties of these chromophores, separately and loosely bound in a van der Waals complex, helps to understand the dependence of the EET rate on the initially excited vibronic level and on the cluster's interchromophoric orientation.

Measurement of fluorescence excitation spectra of anthracene, at different anthracene pressures shows bands that can be assigned to dimers of anthracene. From measurement of the anthracene excitation spectrum at increasing naphthalene pressures one can identify other spectral features, characterized by different spectral shifts from excitations of the bare molecule. Some transitions are probably due to a 13.5 cm−1 progression associated with an interchromophore cluster bond. Pressure dependence of fluorescence intensity gives evidence for 1:1 cluster composition, and for a slow intra‐EET rate that is associated with an unfavoured orientation of the two chromophores in one of the two possible conformers of the A‐N cluster, as supported by a calculation of the cluster geometry and by comparison with a recent study of intra‐EET in the A‐(CH2)n‐N bichromophoric molecules.
Acid‐Base Properties of the Ground and Excited States of Ruthenium(II) Tris(4′‐methyl‐2,2′‐bipyridine‐4‐carboxylic Acid)
Authors: Su Chien‐Hua , Chang I‐Jy
Published: May 2015

The acid dissociation constant, pKa, for the ground and excited states of ruthenium tris(4′‐methyl‐2,2′‐bipyridine‐4‐carboxylic acid) complex have been measured. The ground state pKa obtained from the pH titration curve of the complex absorption at 454 nm was 2.5. The lifetimes of the excited‐state for deprotonated and protonated ruthenium complexes are 595 and 150 ns, respectively. The excited‐state pKa* is obtained from the emission titration curve at 630 nm and corrected for the excited‐state lifetime to be 4.2. The increase of 1.7 pH units in the acid dissociation constant in the excited‐state indicates that the ligand is much more basic in the excited‐state. This result confirms the MLCT assignment for the lowest electronic transition of [Ru(mbpyCOOH)3]2+.
Synthesis, Structure and Magnetic Properties of a Cyclic Heterotetranuclear Co3Fe Complex of 2‐Mercaptophenol (H2mp) with tri‐n‐Butylphosphine Participation
Authors: Chen Zhong‐Ning , Li Wen‐Jie , Rang Bei‐Sheng , Zhang Hua‐Xin , Zhou Zhong‐Yuan , Mak Thomas C. W. , Cai Yuan‐Ba , Hong Mao‐Chun , Liu Han‐Qin
Published: May 2015

Neutral heterotetranuclear complex Co3Fe(mp)4(Hmp)(PBun3)3 2 (PBun3 = tri‐n‐butylphosphine) of 2‐mercaptophenol (H2mp) was synthesized in a molar ratio of CoCl2:FeCl3:H2mp:NaOMe:PBun3 = 0.75:0.25:1:2:1 under anaerobic conditions. It represents partially FeIII‐substituted form of the asymmetric mixed‐valence tetracobalt complex Co4(mp)4(Hmp)(PBun3)3 (1). 2 crystallizes in the triclinic space group Pl̄, with a = 12.373(2) Å, b = 15.677(3) Å, c = 20.571(4) Å, α = 93.59(3)° β = 93.45(3)° γ = 112.30(3)°, V = 3669 Å3, and Z = 2. The molecule exhibits a cyclic skeleton of Co3FeS4O3 with two doubly μ2‐S bridges, one doubly μ2‐O bridge, and one singly μ2‐O bridge. The four mp2− ligands display two different modes, ObSb‐T and OtSb, while the monoanion Hmp− is only terminally chelated to Fe3+ ion in HOtSt fashion (b stands for bridge, t for terminal, and T for trinuclear). The three Co centers are located in approximately square‐based pyramidal environments, and the Fe atom in distorted trigonal bipyramidal geometry. Three types of main fragment ions were observed in the FAB mass spectrum of 2. The dissociation of the fragments follows the order: PBun3 first, then Hmp and mp ligands. Moreover, the dissociation of Fe(Hmp) is first, followed by Co(mp) and Co(mp)2, according with the fact that Fe(Hmp) is only loosely bonded. Variable‐temperature magnetic susceptibility measurements showed that 2 exhibits weak magnetic exchange interactions.
Synthesis and Reactivities of 1,5‐ and 1,7‐Azulenequinone Derivatives. A Highly Convenient, One‐Pot Synthesis of 3‐Bromo‐1,5‐ and −1,7‐Azulenequinones by Bromination of Azulene,
Authors: Wakabayashi Hidetsugu , Kurihara Teruo , Shindo Kimio , Tsukada Masaaki , Yang Paw‐Wang , Yasunami Masafumi , Nozoe Tetsuo
Published: May 2015

A very convenient, one‐pot synthesis (over 80% yield) of 3‐bromo‐1,5‐ and −1,7‐azulenequinones has been developed by bromination of azulene in aqueous tetrahydrofuran. Reduction of 3‐bromo‐1,5‐ and −1,7‐azulenequinones with tin or zinc powder in acetic acid gave the parent 1,5‐ and 1,7‐azulenequinones, and further reduction products.
“Sock‐Ball” Chromatographic Separation of Some Polycyclic Aromatic Hydrocarbons with C60‐Fullerene Stationary Phase
Authors: Chang Cheng‐Shyong , Tsai Hou‐Jen , Den Tschau‐Gan
Published: May 2015

Polycyclic aromatic hydrocarbons (PAHs) of different molecular shapes were tested and compared with a prepared C60‐fullerene‐phase, and with the commercial Amino‐phase or RP‐18‐phase in the mobile phase of methanol/dichloromethane (90/10 — 70/30) or n‐hexane/dichloromethane (80/20). The chromatographic separation results indicate that C60‐fullerene‐phase achieves the special selectivities and performances for the separation of PAHs. Based on the retention mechanism of “π‐π” complex interaction or “Sock‐Ball” shaped combination, PAHs undergo more pronounced interaction with C60 ligand. For example, decacyclene, a sock‐shaped PAH, the structure of which was calculated by means of semi‐empirical molecular orbital methods, possesses stronger retention to give a “Sock‐Ball” chromatographic separation with C60‐fullerene‐phase. However, PAHs with bend, planar, or co‐planar structures eluted on C60‐fullerene‐phase undergo adsorption chromatography, but possess weaker retentions. The retention power of “Sock‐Ball” chromatography can successfully recognize the different molecular shapes of PAHs.
Aggregative Activation in Connection with a Few Reactions Using Transition or Alkali Metal Derivatives as Intermediates
Authors: Caubère Paul
Published: May 2015

Aggregative Activation principles are given. The first application described deals with the preparation of reducing agents used to perform couplings and carbonylations of aryl and hetaryl halides. The second application deals with the preparation of two kind of super bases: sodium amide and butyllithium containing complex bases. The arynic synthesis of indoles is given as an illustration of the use of the first kind of base while the metalation of pyridine derivatives exemplifies the use of the second. In this latter case, a new metalation radical mechanism is proposed.
Interaction of T1 and S1 States of h4‐ and d4‐Acetaldehyde Using a Quantum‐Beat Technique
Authors: Hsu Tsing‐Jung , Lee Shih‐Huang , Tang Kuo‐Chun , Chen I‐Chia
Published: May 2015

Decays of fluorescence of h4‐ and d4‐acetaldehyde are measured. The quantum‐beat structure is observed for both isotopic species. This oscillatory phenomenon is due to interaction of the state S1 (Ã′ A″) and T1. Below the dissociation threshold to form products methyl and formyl radicals, an upper limit of a lifetime is set at 195‐800 ns for perturbed triplet states of CD3CDO; the lifetime is calculated directly from the linewidth of Fourier‐transformed spectra. At excitation wavelength shorter than 316.12 nm, the transformed linewidth increases, indicating the onset of CD3 + DCO formation.
Synthesis and Structures of 1‐(2‐Thienylmethyl)‐2‐(2‐thienyl)bezimidazole and Its Cu(I) and Ag(I) Complexes
Authors: Hwang Wen‐Shu , Hwang Chung‐Jeh , Wang Dong‐Liang , Lee Liang‐Shiu , Chiang Michael Y.
Published: May 2015

N,N′‐1,2‐phenylenebis(2‐thienylideneimine) (PTI) can be obtained via the condensation of o‐phenylenediamine and thiophene‐2‐carboxaldhyde in cyclohexane. It isomerized to its cyclic form 1‐(2‐thienylmethyl)‐2‐(2‐thienyl)benzimidazole (TMTBI) readily in the presence of Fe2(CO)9. Coordination reactions of PTI with cuprous iodide and silver nitrate in acetonitrile resulted in the formation of [Cu(TMTBI)I]2 and [Ag(TMTBI)2]NO3, respectively, in which the PTI ligand had been isomerized to TMTBI. Both PTI, TMTBI, and complexes were characterized by NMR, IR, and Mass spectroscopies as well as elemental analysis. The crystal structures of TMTBI and [Cu(TMTBI)I]2 were determined by single‐crystal X‐ray diffraction. Crystallographic details for X‐ray structures are as follows. TMTBI is crystallized in the monoclinic space group P21/n with a = 8.953(3), b = 9.150(1), c = 17.436(2) Å, β = 93.73(2)°, and Z = 4. The final R factor was 0.050 (Rw = 0.066) for 1337 observed reflections. Complex [Cu(TMTBI)I]2 is crystallized in the triclinic space group \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm P}\bar 1 $\end{document} with a = 9.961 (2), b = 10.825(2), c = 9.184(2) Å, α = 112.98(2), β = 110.78(2), γ = 88.71 (2)°, and Z = 2. The final R factor was 0.056 (Rw = 0.057) for 2363 observed reflections.
Purification, Characterization and Mechanistic Study of β‐Glucosidase from Flavobacterium meningosepticum (ATCC 13253)
Authors: Li Yaw‐Kuen , Chu Shi‐Her , Sung Yu‐Hui
Published: May 2015

A β‐glucosidase (EC 3.2.1.21) from Flavobacterium meningosepticum has been purified and characterized. Purity was enhanced at least 530‐fold from crude cell extract with 16.6% yield. The estimated molecular mass of the purified enzyme is 150 kDa by gel filtration and 78 kDa by SDS‐PAGE. This dimeric enzyme has a pI = 9.0 and an optimal activity at pH 5.0 and temperature of 50 °C. Divalent metal ions (Hg2+, Cu2+, Ca2+, Mg2+) and EDTA have negligible effect on the enzyme activity. The enzyme exhibited a high specificity on the glycon portion of aryl‐β‐D‐glycosides. NMR spectroscopy revealed the enzyme catalyzed hydrolysis of p‐nitrophenyl‐β‐D‐glucopyranoside with the retention of anomeric configuration, indicating that a double displacement mechanism was involved. A preliminary study of the Bronsted relationship showed a concave‐downward plot, which is consistent with the two‐step mechanism.
Lignans and Kauranes from the Stems of Annona cherimola
Authors: Chen Chung‐Yi , Wu Tung‐Ying , Chang Fang‐Rong , Wu Yang‐Chang
Published: May 2015

Four lignans and six kauranes, (+)‐epi‐syringaresinol (1), annocherin A (16β‐hydroxy‐17,19‐diacetoxy‐ent‐kaurane) (2), (+)‐syringaresinol (3), (+)‐dia‐syringaresinol (4), liriodendrin[(+)‐syringaresinol‐di‐O‐β‐D‐glucopyranoside] (5), 16α‐hydro‐17‐acetoxy‐ent‐kauran‐19‐oic acid (6), 16β‐hydro‐17‐hydroxy‐ent‐kauran‐19‐al (7), 16α‐hydro‐17‐hydroxy‐ent‐kauran‐19‐al (8), 16β‐hydro‐17‐hydroxy‐ent‐kauran‐19‐oic acid (9) and 16α‐hydro‐17‐hydroxy‐ent‐kauran‐19‐oic acid (10) were isolated from the stems of Annona cherimola. Among them, 1 is obtained for the first time from natural sources and 2 is a new compound. The structures of these compounds were characterized and identified by spectral analyses.
Studies with Polyfunctionally Substituted Heterocycles: New Synthesis of Pyrido[5′, 4′:2,3][1,3,4]oxadiazolo[3,2‐a]pyridine; Pyridazine; 1,3,4‐Oxadiazote; and Pyrazolo[1,5‐a]Pyrimidine Derivatives
Authors: Barsy Magda A. , Elmaghraby Mohammed A. , Ahmed Salwa M.
Published: May 2015

Cyanoacetohydrazide 1a reacts with 2‐arylhydrazoketons 2a,b and 3a,b in refluxing ethanol to yield pyrido[5′,4′:2,3][1,3,4]oxadiazolo[3,2‐a]pyridine and pyridazine derivatives; in the absence of solvent pyrazolo[1,5‐a]pyrimidine derivatives were obtained. The reaction of 2a,b and 3a,b will) benzoylhydrazine afforded 1,3,4‐oxadiazole and pyrazole derivatives.
Synthesis of 1‐(2‐Carboxyethylbenzyl)‐2‐benzenesulfonamidobicyclo[2.2.1]heptane: A Novel Potent Thromboxane Antagonist
Authors: Kan Wai‐Ming , Chem Ching‐Yuh , Su Sheng‐Fang
Published: May 2015

A potent thromboxane antagonist, 1‐[2‐(2‐carboxyethyl)benzyl)]‐2‐benzenesulfonamidobicyclo‐[2.2.1]heptane was synthesized from norcamphor in 8 steps. It was shown to be a very potent thromboxane antagonist by inhibition of platelet aggregation induced by U46,619 at nanomolar concentration. The key intermediate 3‐[2‐bromomethylphenyl]propyl tetrahydropyran ether may be useful for the synthesis of other interphenylene containing prostaglandin analogs.
Effects of Ligand Chain Length and Terminal N‐Alkylation on the Protonation Constants and Stability Constants of Some Transition Metal Complexes of Linear Tetraaza and Pentaaza Ligands
Authors: Allen Chang C. , Shieh Fa‐Kun , Liu Yuh‐Liang , Chung Chung‐Sun
Published: May 2015

A number of terminal N‐alkylated linear tetraaza and pentaaza ligands were prepared. Their ligand protonation constants and some transition and post‐transition metal (Ni2+, Cu2+, Zn2+, and Cd2+) complex stability constants were determined by potentiometric titration methods. In general, methylation and ethylation at the terminal nitrogen atoms caused the corresponding ligand nitrogen basicity to increase; however, the corresponding metal complex stabilities were decreased compared to the non‐alkylated structural analogs, presumably due to a steric effect.
Studies on 1, 2, 4‐Benzothiadiazine 1, 1‐Dioxide IX.1 Synthesis and Pharmacological Evaluation of 1, 2, 4‐Benzothiadiazine 1, 1‐Dioxide Biphenyl Tetrazoles as Angiotensin II Antagonists
Authors: Chem Ji‐Wang , Lin Hua‐Mei , Cheng Fong‐Chi , Lo Jir‐Chun , Lai Nan‐Yi , Kao Chai‐Lin , Usifoh Cyril O.
Published: May 2015

In the course of our investigations on the development of cardiovascular agents, 3‐butyl‐2‐[2′‐(2H‐tetrazol‐5‐yl)bipheny]‐4‐yl]methyl‐2H‐1, 2, 4‐benzothiadiazine 1, 1‐dioxide (2) was considered as a potential angiotensin II antagonist on the basis of bioisosteric replacement of the quinazoline ring of compound 1 with a 1, 2, 4‐benzothiadiazine 1, 1‐dioxide ring system. Alkylation of 6 with 4 afforded 7 and 8 in 24% and 28% yields, respectively. An attempt to remove the trityl group of compounds 7 and 8 under acidic condition gave the ring opened products 9 and 11 in 28% and 36% yields, respectively. However, compounds 2 and 10 were obtained in 46% and 85% yields when compounds 7 and 8 were refluxed in methanol. Preliminary assays of compounds 9 and 11 against angiotensin II receptors revealed weak activity with IC50 values of 3.6 μM and 5.4 μM, respectively. Compound 10 (IC50 = 87 nM) exhibited stronger binding affinity than compound 2 (IC50 = 750 nM).
Formal Synthesis of (±)‐Mitsugashiwalactone and (±)‐Isodihydronepetalactone from Norborn‐5‐en‐2‐one Involving Shapiro Reaction
Authors: Chang Meng‐Yang , Ciang Nein‐Chen
Published: May 2015

A formal synthesis of (±)‐mitsugashiwalactone (1) and (±)‐isodihydro nepetalactone (2) was accomplished. Baeyer‐Villiger lactonization of ketone 9 followed by acidic treatment led to the rearranged lactone 8, which underwent a series of functional group transformations to give cyclopentanone derivatives 19 and 20. Shapiro reaction on 21 and 22 in the presence of excess dry ice gave lactones 5 and 6. Lactones 5 and 6 previously have been converted to mitsugashiwalactone (1) and isodihydronepetalactone (2), respectively.
Synthesis and Biological Activity of ω‐(5‐Aryl‐1,3,4‐oxadiazol‐2‐thio)‐ and ω‐(5‐Aryl‐1,3,4‐oxadiazol‐2‐thioacetoxyl)‐ω‐(1‐H‐1,2,4‐triazol‐1‐yl)acetophenones
Authors: Chu Chang‐Hu , Sun Xiao‐Wen , Sun Le , Zhang Zi‐Yi , Li Zhi‐Chun , Liao Ren‐An
Published: May 2015

Eighteen novel ω‐(5‐Aryl‐1,3.4‐oxadiazol‐2‐thio)‐ω‐(1‐H‐1,2,4‐triazol‐1‐yl)acetophenones (4a‐4i) and ω‐(5‐Aryl‐1,3,4‐oxadiazol‐2‐thioacetoxyl)‐ω‐(1‐H‐1,2,4‐triazol‐1‐yl)acetophenones (5a‐5i) were synthesized. All the compounds synthesized were confirmed by elemental analyses and spectral data. The biological activity of representative compounds was evaluated.
High Performance Liquid Chromatographic Enantioresolution of Benzoyl Amino Acid, Dipeptides and Tripeptide on β‐Cyclodextrin Bonded Stationary Phase Using Polar‐Organic Acetonitrile as the Mobile Phase
Authors: Chen Shushi
Published: May 2015

The enantiomeric resolution of several dipeptides, amino acid (i.e., isoleucine) and tripeptide (i.e., Leu‐Gly‐Phe) with two stereogenic centers on β‐cyclodextrin bonded chiral stationary phase (β‐CD CSP) using polar‐organic acetonitrile as the mobile phase is examined through pre‐column chemical derivatization with a series of tagging reagents such as benzoyl chloride, benzenesulfonyl chloride and 1‐naphthalenesulfonyl chloride. These tagging reagents are similar in structure; however, the enantioselectivity for the same analyte derivatized with these tagging reagents is quite different and found to be the best with benzoyl chloride. In the reversed‐phase mode or on the γ‐CD CSP under the same chromatographic conditions, the enantioresolution diminishes for all tagged enantiomers that were examined in this study. Dipeptides derivatized by benzoyl chloride appear to be better resolved than by dansyl chloride as reported previously. Interestingly, no enantioresolution for most derivatized amino acids with single stereogenic center was observed. Finally, enantioresolution can be enhanced by replacing the basic additive such as triethylamine with tripropylamine in the polar‐organic mobile phase.
Intramolecular Electron Transfer in CO‐Bound Mixed‐Valence Cytochrome c Oxidase Following CO Photolysis
Authors: He Qizhi , Pan Lian‐Ping , Chan Sunney I.
Published: May 2015

Internal electron transfer in bovine cytochrome c oxidase was initiated by CO photolysis of the CO‐bound mixed‐valence form of the enzyme. Transient absorption spectroscopy was used to monitor changes in the redox states of the metal centers in the enzyme brought about by electron re‐equilibration. Upon CO photodissociation, reduced high spin cytochrome a3 was generated in less than 0.1 μsec, and a portion of the reduced cytochrome a3 was reoxidized with biphasic rate constants of k1 = 1.0 × 106 s−1 and k2 = 7.8 × 104 s−1. Concomitant reduction of cytochrome a was also observed with biphasic rate constants of k1 = 1.6 × 106 s−1 and k2 = 9 × 104 s−1. The stoichiometry of cytochrome a3 oxidized to cytochrome a reduced was found to be close to 1:1. Contrary to similar studies in the literature, no reduction of CuA was observed. As a control, no transient absorption changes corresponding to electron transfer was observed in the CO‐inhibited fully reduced form of the enzyme. These results indicate that there is significant electron reequilibration only between cytochrome a3 and cytochrome a upon photolysis of the CO‐bound mixed‐valence enzyme.
Biochemistry and Molecular Biology of Snake Neurotoxin
Authors: Yang Chen‐Chung , Chang Long‐Sen
Published: May 2015

A review of research on snake neurotoxin is presented, with emphasis on the chemical modification studies and molecular cloning of postsynaptic and presynaptic neurotoxins from Naja naja atra (Taiwan cobra) (Fig. 1a) and Bungarus multicinctus (Taiwan banded krait) (Fig. 1b). Cobrotoxin and α‐bungarotoxin are the primary postsynaptic neurotoxins isolated from the venom of N. naja atra and B. multicinctus, respectively. Although they share a common three‐dimensional structure, the functional elements essential for the manifestation of their toxicity are different. Selective and stepwise chemical modification of cobrotoxin indicate that at least two cationic groups, an ϵ‐amino group of Lys‐47 and a guanidino group of Arg‐33 common to all known postsynaptic neurotoxins, are functionally important for its neuromuscular blocking activity. However, for α‐bungarotoxin, the side chains of several basic amino acid residues are involved in the multipoint contact between the toxin and acetylcholine receptor. Moreover, the conserved Trp residue is essential for the neurotoxicity of cobrotoxin, but not for α‐bungarotoxin. The cDNAs encoding cobrotoxin and α‐bungarotoxin was constructed from the cellular RNA isolated from the venom glands of N. naja atra and B. multicinctus by polymerase chain reaction. The sequence of their 3′‐untranslational region, signal peptide and 5′‐untranslational region share a high degree of homology, suggesting that they are evolutionarily related. Expression of both neurotoxic protein in E. coli generated polypeptide chains for reactions with the antisera against the native neurotoxins.

Presynaptic neurotoxins constitute a different group of neurotoxic proteins in snake venom proteins. These presynaptic neurotoxins are either basic phospholipase A2 (PLA2) per se or contain basic PLA2 as an indispensible part of their structures. Thus, the presynaptic neurotoxins usually show both PLA2 activity and presynaptic neurotoxicity. β‐Bungarotoxin (β‐Bgt), the main presynaptic PLA2 neurotoxin isolated from the venom of B. multicinctus (Taiwan banded krait), consists of two dissimilar polypeptide chains, a PLA2 subunit (A chain) and potassium channel recognition subunit (B chain). Chemical modification studies show that the toxin might possess two functional sites, one responsible for the catalytic activity and the other for its pharmacological properties. Molecular cloning and expression of the A chain and B chain of β‐Bgt reveal that the A chain of β‐Bgt is an active subunit with PLA2 activity, and that the B chain is involved in voltage‐gated potassium channel blocking action observed with β‐Bgt.
Recent New Developments of Steady‐State and Time‐Dependent Density Functional Theories for the Treatment of Structure and Dynamics of Many‐Electron Atomic, Molecular, and Quantum Dot Systems
Authors: Chu Shih‐I , Tong Xiao‐Min , Chu Xi , Telnov Dmitry
Published: May 2015

We present a short account of recent new developments of density‐functional theory (DFT) for accurate and efficient treatments of the electronic structure and quantum dynamics of many‐electron systems. The conventional DFT calculations contain spurious self‐interaction energy and improper long‐range potential, preventing reliable description of the excited and resonance states. We present a new DFT with optimized effective potential (OEP) and self‐interaction‐correction (SIC) to overcome some of the major difficulties encountered in conventional DFT treatments using explicit energy functionals. The OEP‐SIC formalism uses only orbital‐independent single‐particle local potentials and is self‐interaction free, providing a theoretical framework for accurate description of the excited‐state properties and quantum dynamics. Several applications of the new procedure are presented, including: (a) the first successful DFT treatment of the atomic autoionizing resonances, (b) a relativistic extension of the OEP‐SIC formalism for the calculation of the atomic structure with results in good agreement with the experimental data across the periodic table (Z = 2–106), (c) electronic structure calculation of the ionization properties of molecules, and (d) the delicated “shell‐filling” electronic structure in quantum dots. Finally we present also new formulations of time‐dependent DFT for nonperturbative treatment of atomic and molecular multiphoton and nonlinear optical processes in intense and superintense laser fields. Both the time‐independent Floquet approach and the time‐dependent OEP‐SIC technique are introduced. Application of the time‐dependent DFT/OEP‐SIC procedure to the study of multiple high‐order harmonic generation processes in intense ultrashort pulsed laser fields is discussed in detail.