bluuebunny/crossref_metadata_2025 huggingface dataset:
Reversible Double‐Helix–Random‐Coil Transition Process of Bis{hexa(ethynylhelicene)}s
Authors: Sugiura Hiroki , Amemiya Ryo , Yamaguchi Masahiko
Published: January 2008

Two compounds with two hexa(ethynylhelicene) parts connected by a flexible haxadecamethylene and a rigid butadiyne linker were synthesized. The 1H NMR spectroscopic and CD analyses and vapor‐pressure osmometry (VPO) of these two compounds revealed intramolecular double‐helix formation. Upon heating a 5‐μM solution in toluene, the double‐helix structure unfolded to form a random coil, and on cooling it folded again into a double helix. The thermodynamic stabilities of both structures were dependent on temperature, and the structural change in both compounds is due to the large enthalpies and entropies under equilibrium. The rate constants of their unfolding were obtained by assuming a pseudo‐first‐order reaction; the compound with a rigid linker unfolded slower than that with a flexible linker. The former has a larger activation energy, and its double‐helix and random‐coil conformers were separated by chromatography. The rate of folding was also faster for the flexible‐linker compound with larger activation energy. The rate constants for the folding of both compounds slightly decreased with increasing temperature, which was ascribed to the presence of exothermic pre‐equilibrium and rate‐determining steps. The folding was markedly accelerated with increasing random‐coil concentration, which suggests the involvement of self‐catalysis. A mechanism of folding was proposed. The involvement of different mechanisms of folding and unfolding was suggested by the kinetic studies, and it was confirmed by the presence of hysteresis in the melting profiles. The difference in linker structure also affected the thermal‐switching profiles of the double‐helix–random‐coil structural changes.
Total Synthesis of 2‐Hydroxytetracosanolide and 2‐Hydroxy‐24‐oxooctacosanolide By Using an Effective Lactonization
Authors: Shiina Isamu , Sasaki Akane , Kikuchi Takaaki , Fukui Hiroki
Published: January 2008

We have developed effective methods for the total synthesis of 2‐hydroxytetracosanolide and 2‐hydroxy‐24‐oxooctacosanolide, the defensive salivary secretions of termites. The former natural product isolated from Armitermes neotenicus, a species of termite that inhabits Guyana, contains a 25‐membered lactone backbone, and the latter, extracted from Pseudacanthoterme springer, an African termite, includes a 29‐membered lactone moiety. The key cyclization to produce the 25‐ or 29‐membered lactone core is performed by using 2‐methyl‐6‐nitrobenzoic anhydride (MNBA) with a stoichiometric amount of 4‐(dimethylamino)pyridine (DMAP) or a catalytic amount of 4‐(dimethylamino)pyridine N‐oxide (DMAPO).
The Catalytic Acylcyanation of Imines
Authors: Pan Subhas Chandra , List Benjamin
Published: January 2008

The catalytic acylcyanation of aldimines with acylcyanides and a direct three‐component variant involving the generation of an imine in situ have been developed. Furthermore, a highly enantioselective version has been established, culminating in the first organocatalytic asymmetric three‐component Strecker reaction. Jacobsen thiourea catalysts were found to catalyze the reaction with excellent enantioselectivities, whereas binol phosphates (binol=1,1′‐bi‐2,2′‐naphthol) proved to be catalytically active but only modestly enantioselective. A large number of different substrates could be used in the processes described, thus illustrating the potential of our reaction for the generation of diversity within the attractive α‐amino carbonyl framework. Furthermore, a novel cyclic amidine was obtained from the reaction of acetyl cyanide with ketimines.
Asymmetric 1,3‐Dipolar Cycloadditions of N‐Benzyl and N‐Diphenylmethyl Nitrones and α,β‐Unsaturated Aldehydes Catalyzed by Bis‐Titanium Chiral Lewis Acids
Authors: Hashimoto Takuya , Omote Masato , Hato Yoshio , Kano Taichi , Maruoka Keiji
Published: January 2008

Bis‐titanium chiral Lewis acids that contain two oxygen‐bridged titanium centers were successfully applied to the asymmetric 1,3‐dipolar cycloaddition of nitrones and α,β‐unsaturated aldehydes. The introduction of the diphenylmethyl group as the N substituent on the nitrones, with the aim of destabilizing the nitrone–Lewis acid complex, led to the drastic enhancement of not only the reactivity but also the enantioselectivity. By employing this approach, 1,3‐dipolar cycloadditions of nitrones and the rather unreactive methacrolein were facilitated to give cycloadducts that bear one all‐carbon quaternary center with unique regioselectivity and excellent stereoselectivity.
Quantification of reduced glutathione by HPLC‐UV in erythrocytes of hemodialysis patients
Authors: Garcia Solange Cristina , Schott Karen , Charão Mariele , Moro Angela , Bulcão Rachel , Grotto Denise , Valentini Juliana , Bohrer Denise , Cardoso Simone , Pomblum Valdeci
Published: January 2008

Reduced glutathione (GSH) is a well‐known multifunctional antioxidant. Its depletion is linked to a number of pathologies, such as renal insufficiency. Feasible methodologies in clinical chemistry are vital. Therefore a methodology for GSH quantification was optimized and validated by HPLC‐UV. Important aspects such as acid deproteinization and GSH stability were established. The erythrocytes were hemolyzed, deproteinized, derivatized with 5,5‐dithio‐bis (2‐nitrobenzoic) acid and analyzed using HPLC, on an RP18 gradient elution, λ = 330 nm. The method was applied to hemodialysis patients (n = 75) compared with healthy subjects (n = 40). The assay was linear from 0.5 to 3.0 mm (r2 > 0.99). The intra‐ and inter‐run reproducibilities were obtained with CV% < 10%. The accuracy (bias %) ranged from 1.32 to –6.38%, and the recovery was >94%. The derivatized sample was stable for 60 days at –20°C. The GSH levels in hemodialysis patients showed a significant increase compared with healthy subjects (p < 0.05) and an inverse correlation with age (r = –0.286; p = 0.013) was found. This method used UV detection, reduction of the phosphate concentration in the mobile phase and effective protein removal with trichloroacetic acid. The method proved to be reproducible, precise, accurate and stable. Thus, it can be suggested for routine laboratory tests for the verification of physiopathological conditions. Copyright © 2007 John Wiley & Sons, Ltd.
Correlation between the genetic diversity and variation of total phenolic acids contents in Fructus Xanthii from different populations in China
Authors: Han Ting , Hu Yuan , Zhou Shan‐Yong , Li Hui‐Liang , Zhang Qiao‐Yan , Zhang Hong , Huang Bao‐Kang , Rahman Khalid , Zheng Han‐Chen , Qin Lu‐Ping
Published: January 2008

Fructus Xanthii (Cang‐Er‐Zi) is a traditional Chinese medicine that is used in curing nasal diseases and headache according to the Chinese Pharmacopoeia. For the effective quality control of its medicinal values, reflected by chemical variation patterns, in addition to the relationship with genetic diversity, analyses based on UV spectrophotometry, HPLC fingerprinting and inter‐simple sequence repeat (ISSR) molecular markers were carried out, involving 16 Xanthium populations from different locations in China. The HPLC data showed considerable variation of chemical constituents among the 16 Xanthium populations, and they were classified to three chemotypes by hierarchical clustering analysis. Abundant genetic diversity was detected among the Xanthium populations, which were also clustered into three groups based on their ISSR data and varied according to different species. Combining the genetic divergence and chemical differences showed an important result that, in the two chemotypes, the higher contents of total phenolic acids (TPA) in Fructus Xanthii showed greater genetic diversity (I). We suggest that genetic diversity affects the contents of TPA. Since variable phenolic acid contents may affect therapeutic efficacy, it is important to point out that combining the use of genetic base with chemotype will help control the favourable chemotypes and breed new cultivars with more desirable chemical constituents. Copyright © 2007 John Wiley & Sons, Ltd.
Novel molecularly imprinted monolithic column for selective on‐line extraction of ciprofloxacin from human urine
Authors: Yan Hongyuan , Row Kyung Ho
Published: January 2008

Water‐compatible ciprofloxacin‐imprinted monolithic columns were synthesized in water‐containing systems for selective extraction of ciprofloxacin from human urine samples. Methanol–water (10:3, v/v) was used as a porogenic solvent and the obtained monolithic imprinted polymers reveal high selectivity to ciprofloxacin in an aqueous environment; the affinity can be easily controlled by adjusting the pH of the mobile phase. Owing to the unique porous structure and flow‐through channels existing in the network skeleton of the monolithic MIP, urine samples could be directly injected into the column, proteins and other biological matrix were quickly washed out and ciprofloxacin was selectively retained and enriched. Good linearity was obtained from 0.08 to 400 mg/L (r = 0.998) with the relative standard deviations less than 3.6%. The limit of detection of the method was 0.04 mg/L and the recoveries were more than 94.5% at three different concentrations. Moreover, by increasing the injection volume to 2.0 mL, the sensitivity of the method could be improved 100‐fold according to the peak height of ciprofloxacin. This expedient greatly simplified the overall procedure, resulting in a rapid and efficient sample analysis while maintaining precision and accuracy. Copyright © 2007 John Wiley & Sons, Ltd.
Measurement of reduced and total mercaptamine in urine using liquid chromatography with ultraviolet detection
Authors: Kuśmierek Krzysztof , Bald Edward
Published: January 2008

A simple liquid chromatographic method for the determination of reduced and total mercaptamine in human urine is described. The method is based on derivatization with 2‐chloro‐1‐methylquinolinium tetrafluoroborate followed by ion‐pairing reversed‐phase liquid chromatography separation and ultraviolet‐absorbance detection at 355 nm. Total mercaptamine was determined by reductive conversion of its oxidized fraction to the thiol form before the derivatization step. Baseline separation was achieved on an analytical Zorbax SB C18 (5 µm, 150 × 4.6 mm) column with a mobile phase consisting of pH 2.0 0.05 mol L−1 trichloroacetic acid buffer (component A) and acetonitrile (component B) pumped at 1.2 mL min−1. Gradient elution was used: 0–3 min 12% B, 3–9 min 12–30% B, 9–12 min 30–12% B. The response of the detector was linear within the ranges studied, from 0.1 to 50 µmol L−1 for reduced mercaptamine and from 0.4 to 400 µmol L−1 for total mercaptamine. The imprecision ranges for reduced and total mercaptamine were within 1.45–11.71 and 0.73–10.61%, respectively. The analytical accuracy for determined compounds was from 98.79 to 109.77%. The lower limits of detection and quantitation were 0.05 and 0.1 µmol L−1 of urine for reduced mercaptamine, and 0.2 and 0.4 µmol L−1 of urine for total mercaptamine, respectively. This method can be used for routine clinical monitoring of the title thiol‐drug and its reduced and oxidized fractions. Moreover, cysteine and cysteinylglycine can be measured concurrently, if needed. Copyright © 2007 John Wiley & Sons, Ltd.
Separation of different forms of proteose peptone 3 by hydrophobic interaction chromatography with a dual salt system
Authors: Sousa A. , Passarinha L. A. , Rodrigues L. R. , Teixeira J. A. , Mendonça A. , Queiroz J. A.
Published: January 2008

A panel of four hydrophobic adsorbents (butyl‐, octyl‐, phenyl‐ and epoxy‐Sepharose) was used to examine the selectivity and fractionation of several proteose peptone 3 (PP3) forms from a freeze‐dried extract of whey bovine milk. In particular, the effects of altering the ligand type and salt were investigated. The chromatographic studies suggest that PP3 strongly interacts among the three commercial hydrophobic resins leading to a drop off in selectivity, while a complete binding was achieved at low salt concentrations (below 0.5 m) and total elution only with phosphate buffer and/or water stepwise conditions. Only in epoxy–Sepharose was an appreciably selectivity of the several fractions of PP3 present in the initial feedstock attained. Despite the high salt concentration for a complete binding of PP3 (above 1.5 m ammonium sulfate) onto this support, the dual salt system (ammonium sulfate 1 m and sodium citrate 0.8 m) led to a high separation degree of high and low molecular weight forms of PP3. Copyright © 2007 John Wiley & Sons, Ltd.
Determination of lovastatin in human plasma by ultra‐performance liquid chromatography/electrospray ionization tandem mass spectrometry
Authors: Wang Dong , Wang Dongmei , Qin Feng , Chen Lingyun , Li Famei
Published: January 2008

A fast and sensitive ultra‐performance liquid chromatography tandem mass spectrometry (UPLC‐MS/MS) method was developed for the determination of lovastatin in human plasma. With simvastatin as internal standard, sample pretreatment involved one‐step extraction with n‐hexane–methylene dichloride–isopropanol (20:10:1, v/v/v) of 0.5 mL plasma. Chromatographic separation was carried out on an Acquity™ UPLC BEH C18 column with mobile phase consisting of acetonitrile–water (containing 5 mmol/L ammonium acetate; 85:15, v/v) at a flow‐rate of 0.35 mL/min. The detection was performed on a triple‐quadrupole tandem mass spectrometer by multiple reaction monitoring (MRM) via electrospray ionization source with positive mode. The analysis time was shorter than 1.7 min per sample. The standard curve was linear (r2 ≥ 0.99) over the concentration range 0.025–50.0 ng/mL with a lower limit of quantification of 0.025 ng/mL. The intra‐ and inter‐day precision values were below 11% and the accuracy (relative error) was within 6.0% at three quality control levels. This is the first method of MS with MRM coupled to UPLC for the determination of lovastatin, which showed great advantages of high sensitivity, selectivity and high sample throughput. It was fully validated and successfully applied to the pharmacokinetic study of lovastatin tablets in healthy Chinese male volunteers after oral administration. Copyright © 2007 John Wiley & Sons, Ltd.
Optimization and validation of RP‐HPLC‐UV method with solid‐phase extraction for determination of buparvaquone in human and rabbit plasma: application to pharmacokinetic study
Authors: Venkatesh Gantala , Majid M. I. A. , Ramanathan S. , Mansor S. M. , Nair N. K. , Croft Simon L. , Navaratnam V.
Published: January 2008

A simple, sensitive and specific reversed‐phase high‐performance liquid chromatographic method with UV detection at 251 nm was developed for quantitation of buparvaquone (BPQ) in human and rabbit plasma. The method utilizes 250 µL of plasma and sample preparation involves protein precipitation followed by solid‐phase extraction. The method was validated on a C18 column with mobile phase consisting of ammonium acetate buffer (0.02 m, pH 3.0) and acetonitrile in the ratio of 18:82 (v/v) at a flow rate of 1.1 mL/min. The calibration curves were linear (correlation coefficient ≥0.998) in the selected range. The method is specific and sensitive with limit of quantitation of 50 ng/mL for BPQ. The validated method was found to be accurate and precise in the working calibration range. Stability studies were carried out at different storage conditions and BPQ was found to be stable. Partial validation studies were carried out using rabbit plasma and intra‐ and inter‐day precision and accuracy were within 7%. This method is simple, reliable and can be routinely used for preclinical pharmacokinetic studies for BPQ. Copyright © 2007 John Wiley & Sons, Ltd.
A stereospecific high‐performance liquid chromatographic assay for the determination of ketoconazole enantiomers in rat plasma
Authors: Hamdy Dalia A. , Brocks Dion R.
Published: January 2008

A stereospecific high‐performance liquid chromatographic assay was developed for the quantitation of ketoconazole enantiomers (KTZ) in rat plasma. After protein precipitation of 100 µL plasma using acetonitrile, a wash step was performed using hexane. The supernatant was removed and KTZ enantiomers and amiodarone, the internal standard, were extracted using liquid–liquid extraction with tert‐butyl methyl ether. After transfer and evaporation of the organic layer, the residue was reconstituted in mobile phase and injected into the HPLC through a chiral column. The mobile phase consisted of hexane:ethanol:2‐propanol with diethyl amine, pumped at 1.5 mL/min. All components eluted within 18 min. KTZ enantiomers were baseline resolved and peaks were symmetrical in appearance with no interferences. Calibration curves were linear over the range 62.5–5000 ng/mL of enantiomer. The intraday and interday CV% assessments were ≤19 and <13%, respectively, and mean error was <4% for both enantiomers. The lower limit of quantitation was 62.5 ng/mL for each enantiomer based on 100 µL rat plasma. In rats, plasma concentrations of (+)‐KTZ were higher than those of antipode after single oral doses. The assay was shown to be sensitive and appropriate for use in pharmacokinetics study of KTZ in rat. Copyright © 2008 John Wiley & Sons, Ltd.
Oxidative stress increases 6‐nitronorepinephrine and 6‐nitroepinephrine concentrations in rat brain
Authors: Tsunoda Makoto , Uchino Erika , Imai Kazuhiro , Funatsu Takashi
Published: January 2008

6‐Nitronorepinephrine (nitroNE) and 6‐nitroepinephrine (nitroE) are reaction products of nitric oxide and norepinephrine and epinephrine, respectively. The authors have previously reported a method for determination of nitroNE and nitroE in rat brain using high‐performance liquid chromatography–peroxyoxalate chemiluminescence reaction detection. In this study, the effect of oxidative stress on nitroNE and nitroE concentrations in rat brain was examined using this method. After kainic acid administration in rats for 2 days, the concentrations of both nitroNE and nitroE in rat brains were found to have increased by 400–600%, which was partly suppressed by the co‐administration of a superoxide dismutase mimetic. This indicates that oxidative stress might increase nitroNE and nitroE concentrations in rat brains. Copyright © 2008 John Wiley & Sons, Ltd.
Development of extraction procedures for the determination of imidacloprid: application to residue analysis and dynamics of two formulations in Chinese cabbage
Authors: Khay Sathya , Abd El‐Aty A. M. , Cho Soon‐Kil , Choi Jeong‐Heui , Mamun M. I. R. , Goudah Ayman , Shin Ho‐Chul , Shim Jae‐Han
Published: January 2008

This study was undertaken to investigate whether an additional column clean‐up procedure can affect the accuracy of an analytical method developed for the determination of imidacloprid residues in Chinese cabbage. Thereafter, the residue levels and the degradation rates of imidacloprid were investigated in experimental Chinese cabbage plots after treatment with two different commercial formulations: emulsifiable concentrate (EC) and wettable powder (WP). The analyte was determined using high‐performance liquid chromatography–ultraviolet detection (HPLC‐UVD) and confirmed by high‐performance liquid chromatography–mass spectrometry (HPLC‐MS) in the select ion‐monitoring mode. The mean recoveries ranged from 75.34 to 98.00% and 96.95 to 100.97%, with relative standard deviations of 0.86–4.14 and 1.22–3.52%, in samples treated with and without additional column clean‐up procedures, respectively. The minimum detectable amount of imidacloprid was 4 ng, while the limits of detection and quantitation were 0.2 and 0.5 ppm, respectively. The degradation of pesticide was monitored throughout a period of 13 days under greenhouse conditions. Although the behaviors of the EC and WP formulations appear to be similar, the absolute residue levels obtained with EC and WP treatments differed slightly. When imidacloprid formulations were applied (as foliar treatments) according to the recommended rate, the final residues (13 days post‐treatment) in Chinese cabbage were much lower than the maximum residue limit (MRL = 3.5 ppm) established by the Korean Food and Drug Administration. Taken together, our study suggests that the analysis of imidacloprid can be performed without an additional column clean‐up procedure, and the decline curve and the residue levels in Chinese cabbage could change if the same active ingredient is used in different formulations. Copyright © 2008 John Wiley & Sons, Ltd.
Analysis of hairy root culture of Rauvolfia serpentina using direct analysis in real time mass spectrometric technique
Authors: Madhusudanan K. P. , Banerjee Suchitra , Khanuja Suman P. S. , Chattopadhyay Sunil K.
Published: January 2008

The applicability of a new mass spectrometric technique, DART (direct analysis in real time) has been studied in the analysis of the hairy root culture of Rauvolfia serpentina. The intact hairy roots were analyzed by holding them in the gap between the DART source and the mass spectrometer for measurements. Two nitrogen‐containing compounds, vomilenine and reserpine, were characterized from the analysis of the hairy roots almost instantaneously. The confirmation of the structures of the identified compounds was made through their accurate molecular formula determinations. This is the first report of the application of DART technique for the characterization of compounds that are expressed in the hairy root cultures of Rauvolfia serpentina. Moreover, this also constitutes the first report of expression of reserpine in the hairy root culture of Rauvolfia serpentina. Copyright © 2008 John Wiley & Sons, Ltd.
Chemical and Principal‐Component Analyses of the Essential Oils of Apioideae Taxa (Apiaceae) from Central Balkan
Authors: Kapetanos Chrysostomos , Karioti Anastasia , Bojović Srdjan , Marin Petar , Veljić Milan , Skaltsa Helen
Published: January 2008

The volatile constituents of the essential oils of 23 taxa belonging to the Apioideae subfamily were studied in detail. The investigated taxa were Pimpinella serbica (Vis.) Bentham & Hooker, Libanotis montana Cr., Cnidium silaifolium (Jacq.) Simk. ssp. orientale (Boiss.) Tutin, Bupleurum praealtum L., B. sibthorpianum S. S. var. diversifolium (Roch.) Hay, Aegopodium podagraria L., Torilis anthriscus (L.) Gmel., Orlaya grandiflora (L.) Hoffm., Laserpitium siler L., Laser trilobum (L.) Brokh., Chaerophyllum aureum L., C. hirsutum L., C. temulum L., Pastinaca sativa L., P. hirsuta Pancic., Tordylium maximum L., Physospermum cornubiense (L.) DC., Peucedanum alsaticum L., P. oreoselinum (L.) Moench, P. cervaria (L.) Cuss., P. austriacum (Jacq.) Koch, P. longifolium W. et K., and P. officinale L. All of these species grow wild in the central part of the Balkan Peninsula. The essential oils were found to be complex mixtures of various compounds, more than 100 constituents being in each taxon, with contributions of main products never exceeding 25% of the total content. Sesquiterpene hydrocarbons were found to be the main group of constituents of all taxa, except for Peucedanum species, where monoterpene hydrocarbons were identified as the main components. The chemotaxonomic value of the essential‐oil composition is discussed according to results of principal‐component analysis (PCA). The essential‐oil composition mainly reflects current taxonomic relationships between the investigated taxa.
Total Synthesis of Junionone, a Natural Monoterpenoid from Juniperus communis L., and Determination of the Absolute Configuration of the Naturally Occurring Enantiomer by ROA Spectroscopy
Authors: Lovchik Martin A. , Fráter Georg , Goeke Andreas , Hug Werner
Published: January 2008

Recently, we reported a novel access to 2,2‐diethyl‐3‐[(E/Z)‐prop‐1‐en‐1‐yl]cyclobutanone by an intramolecular nucleophilic substitution with allylic rearrangement (SNi′) of (E)‐6‐chloro‐3,3‐diethylhept‐4‐en‐2‐one. The ring closure reaction was found to proceed with selective syn‐displacement of the leaving group. This method was now applied to the total synthesis of junionone, an olfactorily interesting cyclobutane monoterpenoid isolated from Juniperus communis, L. SNi′ Ring closure of the ketone enolate of (E)‐3,3‐dimethyl‐5‐[(2R,3R)‐3‐methyloxiran‐2‐yl]pent‐4‐en‐2‐one (R,R)‐(E)‐4′ proceeded only after the epoxide moiety had been activated by Lewis acid and led to the junionone precursors (3R)‐ and (3S)‐3‐[(1E,3R)‐3‐hydroxybut‐1‐en‐1‐yl]‐2,2‐dimethylcyclobutanone (S/R,R)‐(E)‐3. The ratio of syn‐ and anti‐conformers in the transitory molecular arrangement was found to depend on the nature of the Lewis acid. The absolute configuration of both the synthetic as well as the natural junionone, isolated from juniper berry oil, was determined by Raman Optical Activity (ROA) spectroscopy. Our experiments led to a novel synthetic route to both (+)‐ and (−)‐junionone, the first determination of the absolute configuration of natural junionone, and to the development of a practical ROA procedure for measuring milligram quantities of volatile liquids.
Synthesis and DNA‐Recognition and ‐Cleavage Properties of Multiply Charged Porphyrin Esters
Authors: Wu Lin , Hu Peng , Xiao Ying , Zhang Ming , Zhang Lixia , Weng Xiaocheng , Wu Xiaojun , Zhou Xiang , Cao Xiaoping
Published: January 2008

A series of systematically modified porphyrin esters, compounds 1–6, with multiple, permanent positive charges introduced at the meso‐positions via N‐methylated 4‐, 3‐, or 2‐pyridyl moieties, were prepared and characterized. Their singlet‐oxygen production, CT‐DNA‐binding properties, and plasmid‐DNA photocleavage propensities were determined spectroscopically and by gel electrophoresis, and compared to those of the known, fourfold‐charged parent porphyrin 4,4′,4″,4′′′‐porphyrin‐5,10,15,20‐tetrayltetrakis(1‐methylpyridinium) (TMPyP4). Some interesting structure–activity relationships could be established to rationalize effects affecting DNA binding mode and cleavage ability.
New Bioactive Clerodane Diterpenoids from the Roots of Casearia membranacea
Authors: Chen Ching‐Yu , Cheng Yuan‐Bin , Chen Shun‐Ying , Chien Ching‐Te , Kuo Yao‐Haur , Guh Jih‐Hwa , Khalil Ashraf Taha , Shen Ya‐Ching
Published: January 2008

Bioassay‐guided fractionation of the acetone extract of the roots of Casearia membranacea furnished three new clerodane diterpenes, caseamembrins S–U (1–3) and the known caseamembrin Q (4). Their structures were established by extensive spectroscopic analyses, especially 2D‐NMR. Compounds 1–4 were tested against human tumor cells, including HeLa (cervical epitheloid carcinoma), DLD‐1 (colon carcinoma), Daoy (medulloblastoma), and KB (oral epidermoid carcinoma) cell lines. Caseamembrin T (2) exhibited the most potent activity against Daoy cells (ED50=10 ng/ml), superior to that of the standard drug mitomycin.
Variability in Essential‐Oil Composition of Piper marginatum sensu lato
Authors: Andrade Eloisa Helena A. , Carreira Léa Maria M. , da Silva Milton Helio L. , da Silva João Domingos , Bastos Cleber N. , Sousa Pergentino José C. , Guimarães Elsie F. , Maia José Guilherme S.
Published: January 2008

This paper contains data on the chemical composition of the essential oils of 22 leaf samples of Piper marginatum Jacq. collected in different areas and ecosystems of the brazilian Amazon, as well as an overview of the available literature. The species presents a large synonymy based on their different leaf characteristics and distinct scents where some of them smell like anise or very close compounds. By GC, GC/MS, and cluster analysis, we identified seven chemotypes for the leaf oils. The main components found in chemotype I were safrole (1) and 3,4‐(methylenedioxy)propiophenone (2). The chemotype II was dominated by 3,4‐(methylenedioxy)propiophenone (2) and p‐mentha‐1(7),8‐diene (10). The major compounds identified in chemotype III were 3,4‐(methylenedioxy)propiophenone (2), myristicin (3), (E)‐β‐ocimene (11), and γ‐terpinene (12). In the chemotype IV, the principal constituents were β‐caryophyllene (13), α‐copaene (14), and 3,4‐(methylenedioxy)propiophenone (2). The chemotype V was dominated by (E)‐isoosmorhizole (6), (E)‐anethole (8), and isoosmorhizole (7). The main compounds found in the chemotype VI were 2‐methoxy‐4,5‐(methylenedioxy)propiophenone (4), methoxy‐4,5‐(methylenedioxy)propiophenone isomer 5, and (E)‐isoosmorhizole (6). The major constituents in chemotype VII were β‐caryophyllene (13), bicyclogermacrene (15), and (E)‐asarone (9).
Phytochemical and Biological Studies of Abies Species
Authors: Yang Xian‐Wen , Li Su‐Mei , Shen Yun‐Heng , Zhang Wei‐Dong
Published: January 2008

In the present review, the literature data on the phytochemical and biological investigations on the genus of Abies are summarized with 110 references. Up to now, 277 compounds were isolated from 19 plants of Abies species. The chemical constituents are mostly terpenoids, flavonoids, and lignans, together with minor constituents of phenols, steroids, and others. The crude extracts and metabolites have been found to possess various bioactivities including insect juvenile hormone, antitumor, antimicrobial, anti‐ulcerogenic, anti‐inflammatory, antihypertensive, antitussive, and CNS (central nervous system) activities.
Synthesis, Spectroscopy, and Biological Properties of Vanadium(IV)–Hydrazide Complexes
Authors: Ashiq Uzma , Ara Rifat , Mahroof‐Tahir Mohammad , Maqsood Zahida T. , Khan Khalid M. , Khan Shamsun N. , Siddiqui Hina , Choudhary Muhammad I.
Published: January 2008

The synthesis, spectroscopic, enzyme‐inhibition, and free‐radical‐scavenging properties of a series of vanadium(IV) complexes, compounds 1–10, were investigated. These complexes exhibit a dimeric structure with hydrazide ligands coordinated in a bidentate fashion. All complexes are stable in the solid state, but exhibit varying degrees of stability in solution. In coordinating solvent such as DMSO, stepwise binding of two solvent molecules at the 6th positions trans to the VO bond of the dimeric unit is observed. The dimeric compounds are converted to monomeric species in which both solvent molecules and the hydrazide ligands are coordinated to the VIV center. The free hydrazide ligands 11–20 were inactive against α‐glucosidase, but the VIV complexes showed varying degrees of inhibition, depending on the type of ligand. The DPPH‐radical‐scavenging activities of 1–20 were determined, which indicated that steric and/or electronic effects responsible for changes in geometry play important roles in terms of antioxidant potential.
Isolation, Structure Elucidation, and Antimycobacterial Properties of Dimeric Naphtho‐γ‐pyrones from the Marine‐Derived Fungus Aspergillus carbonarius
Authors: Zhang Yapeng , Ling Sun , Fang Yuchun , Zhu Tianjiao , Gu Qianqun , Zhu Wei‐Ming
Published: January 2008

Two new dimeric naphtho‐γ‐pyrones, compounds 1 and 2, were isolated from the AcOEt extract of the fungal strain WZ‐4‐11 of Aspergillus carbonarius, together with eight known analogues, including 10,10′‐bifonsecin B (3), 6′‐O‐demethylnigerone (4), nigerone (5), isonigerone (6), fonsecin (7), rubrofusarin B (8), TMC 256A1 (9), and flavasperone (10). Their structures were elucidated by means of UV, CD, IR, and 1D‐ and 2D‐NMR spectroscopy, in combination with HR‐MS analysis. The fully assigned 1H‐ and 13C‐NMR data of 3, and the 13C‐NMR data of 6 are reported for the first time. Compounds 1 and 2 showed weak antimycobacterial activities against Mycobacterium tuberculosis H37Rv, with MIC values of 43.0 and 21.5 μM, resp.
Highly Effective Acyclic Carbohydrate Receptors Consisting of Aminopyridine, Imidazole, and Indole Recognition Units
Authors: Mazik Monika , Kuschel Matthias
Published: January 2008

Neutral imidazole/aminopyridine‐ and indole/aminopyridine‐based receptors, 1 and 2, have been established as highly effective and selective carbohydrate receptors. These receptors effectively recognise neutral carbohydrates through multiple interactions, including neutral hydrogen bonds and CH⋅⋅⋅π interactions between the sugar CH groups and the aromatic rings of the receptors. The design of these receptors was inspired by the binding motifs observed in the crystal structures of protein–carbohydrate complexes. The formation of very strong complexes with β‐glucopyranoside 5, β‐maltoside 8, and α‐maltoside 9 in organic media has been characterised by 1H NMR spectroscopy and confirmed by a second, independent technique, namely fluorescence spectroscopy. The syntheses, molecular‐modelling studies, binding properties of the receptors 1 and 2 toward selected mono‐ and disaccharides as well as comparative binding studies with receptors 3 and 4 are described.
Electron Exchange in Conformationally Restricted Donor–Spacer–Acceptor Dyads: Angle Dependence and Involvement of Upper‐Lying Excited States
Authors: Benniston Andrew C. , Harriman Anthony , Li Peiyi , Patel Pritesh V. , Sams Craig A.
Published: January 2008

The rate constant for triplet energy transfer (kTET) has been measured in fluid solution for a series of mixed‐metal Ru–Os bis(2,2′:6′,2′′‐terpyridine) complexes built around a tethered biphenyl‐based spacer group. The length of the tether controls the central torsion angle for the spacer, which can be varied systematically from 37 to 130°. At low temperature, but still in fluid solution, the spacer adopts the lowest‐energy conformation and kTET shows a clear correlation with the torsion angle. A similar relationship holds for the inverse quantum yield for emission from the Ru–terpy donor. Triplet energy transfer is more strongly activated at higher temperature and the kinetic data require analysis in terms of two separate processes. The more weakly activated step involves electron exchange from the first‐excited triplet state on the Ru–terpy donor and the size of the activation barrier matches well with that calculated from spectroscopic properties. The pre‐exponential factor derived for this process correlates remarkably well with the torsion angle and there is a large disparity in electronic coupling through π and σ orbitals on the spacer. The more strongly activated step is attributed to electron exchange from an upper‐lying triplet state localized on the Ru–terpy donor. Here, the pre‐exponential factor is larger but shows the same dependence on the geometry of the spacer. Strangely, the difference in coupling through π and σ orbitals is much less pronounced. Despite internal flexibility around the spacer, kTET shows a marked dependence on the torsion angle computed for the lowest‐energy conformation.
Covalent Tethering of Organic Functionality to the Surface of Glassy Carbon Electrodes by Using Electrochemical and Solid‐Phase Synthesis Methodologies
Authors: Chrétien Jean‐Mathieu , Ghanem Mohamed A. , Bartlett Philip N. , Kilburn Jeremy D.
Published: January 2008

Organic linkers such as (N‐Boc‐aminomethyl)phenyl (BocNHCH2C6H4) and N‐Boc‐ethylenediamine (Boc‐EDA) have been covalently tethered onto a glassy carbon surface by employing electrochemical reduction of BocNHCH2C6H4 diazonium salt or oxidation of Boc‐EDA. After removal of the Boc group, anthraquinone as a redox model was attached to the linker by a solid‐phase coupling reaction. Grafting of anthraquinone to electrodes bearing a second spacer such as 4‐(N‐Boc‐aminomethyl)benzoic acid or N‐Boc‐β‐alanine was also performed by following this methodology. The surface coverage, stability and electron transfer to/from the tethered anthraquinone redox group through the linkers were investigated by cyclic voltammetry. The effects of pH and scan rate were studied, and the electron‐transfer coefficient and rate constant were determined by using Laviron's equation for the different types of linker. The combination of electrochemical attachment of protected linkers and subsequent modifications under the conditions of solid‐phase synthesis provides a very versatile methodology for tailoring a wide range of organic functional arrangements on a glassy carbon surface.
Switchable Antenna: A Star‐Shaped Ruthenium/Osmium Tetranuclear Complex with Azobis(bipyridine) Bridging Ligands
Authors: Otsuki Joe , Imai Arata , Sato Katsuhiko , Li Dong‐Mei , Hosoda Mayumi , Owa Masao , Akasaka Tetsuo , Yoshikawa Isao , Araki Koji , Suenobu Tomoyoshi , Fukuzumi Shunichi
Published: January 2008

A star‐shaped Ru/Os tetranuclear complex, in which a central Os unit is linked to three peripheral Ru units by 4,4′′‐azobis(2,2′‐bipyridine) (azobpy) bridging ligands, was prepared to examine the unique photodynamics regulated by its redox state. The Ru/Os tetranuclear complex exhibits Ru‐based luminescence at 77 K, whereas the three‐electron reduction (one for each azobpy) of the Ru/Os complex results in luminescence from the Os unit. The photoexcited state of the Ru/Os complex rapidly decays into low energy metal‐to‐ligand charge‐transfer states, in which the excited electron is localized in the azobpy ligand in the form of azobpy.−. Upon the one‐electron reduction of the azobpy ligands, the above‐mentioned low‐energy states become unavailable to the photoexcited complex. As a result, an energy transfer from the Ru‐based excited state to the Os‐based excited state becomes possible. Ultrafast transient absorption measurements revealed that the energy transfer process consists of two steps; intramolecular electron transfer from the terminal bipyridine ligand (bpy.−) to form azobpy2− followed by a metal‐to‐metal electron transfer. Thus, the Ru/Os tetranuclear complex collects light energy into the central Os unit depending on the redox state of the bridging ligands, qualifying as a switchable antenna.
Axoneme‐dependent tubulin modifications in singlet microtubules of the Drosophila sperm tail
Authors: Hoyle Henry D. , Turner F. Rudolf , Raff Elizabeth C.
Published: January 2008

Drosophila melanogaster sperm tubulins are posttranslationally glutamylated and glycylated. We show here that axonemes are the substrate for these tubulin C‐terminal modifications. Axoneme architecture is required, but full length, motile axonemes are not necessary. Tubulin glutamylation occurs during or shortly after assembly into the axoneme; only glutamylated tubulins are glycylated. Tubulins in other testis microtubules are not modified. Only a small subset of total Drosophila sperm axoneme tubulins have these modifications. Biochemical fractionation of Drosophila sperm showed that central pair and accessory microtubules have the majority of poly‐modified tubulins, whereas doublet microtubules have only small amounts of mono‐ and oligo‐modified tubulins. Glutamylation patterns for different β‐tubulins experimentally assembled into axonemes were consistent with utilization of modification sites corresponding to those identified in other organisms, but surrounding sequence context was also important. We compared tubulin modifications in the 9 + 9 + 2 insect sperm tail axonemes of Drosophila with the canonical 9 + 2 axonemes of sperm of the sea urchin Lytichinus pictus and the 9 + 0 motile sperm axonemes of the eel Anguilla japonica. In contrast to Drosophila sperm, L. pictus sperm have equivalent levels of modified tubulins in both doublet and central pair microtubule fractions, whereas the doublets of A. japonica sperm exhibit little glutamylation but extensive glycylation. Tubulin C‐terminal modifications are a prevalent feature of motile axonemes, but there is no conserved pattern for placement or amount of these modifications. We conclude their functions are likely species‐specific. Cell Motil. Cytoskeleton 2008. © 2008 Wiley‐Liss, Inc.
Changes in the magnitude and distribution of forces at different dictyostelium developmental stages
Authors: Delanoë‐Ayari H. , Iwaya S. , Maeda Y. T. , Inose J. , Rivière C. , Sano M. , Rieu J.‐P.
Published: January 2008

The distribution of forces exerted by migrating Dictyostelium amebae at different developmental stages was measured using traction force microscopy. By using very soft polyacrylamide substrates with a high fluorescent bead density, we could measure stresses as small as 30 Pa. Remarkable differences exist both in term of the magnitude and distribution of forces in the course of development. In the vegetative state, cells present cyclic changes in term of speed and shape between an elongated form and a more rounded one. The forces are larger in this first state, especially when they are symmetrically distributed at the front and rear edge of the cell. Elongated vegetative cells can also present a front‐rear asymmetric force distribution with the largest forces in the crescent‐shaped rear of the cell (uropod). Pre‐aggregating cells, once polarized, only present this last kind of asymmetric distribution with the largest forces in the uropod. Except for speed, no cycle is observed. Neither the force distribution of pre‐aggregating cells nor their overall magnitude are modified during chemotaxis, the later being similar to the one of vegetative cells (F0 ∼ 6 nN). On the contrary, both the force distribution and overall magnitude is modified for the fast moving aggregating cells. In particular, these highly elongated cells exert lower forces (F0 ∼ 3 nN). The location of the largest forces in the various stages of the development is consistent with the myosin II localization described in the literature for Dictyostelium (Yumura et al.,1984. J Cell Biol 99:894–899) and is confirmed by preliminary experiments using a GFP‐myosin Dictyostelium strain. Cell Motil. Cytoskeleton, 2008. © 2008 Wiley‐Liss, Inc.
Inhibition of HIV‐1 by a Peptide Ligand of the Genomic RNA Packaging Signal Ψ
Authors: Dietz Julia , Koch Joachim , Kaur Ajit , Raja Chinnappan , Stein Stefan , Grez Manuel , Pustowka Anette , Mensch Sarah , Ferner Jan , Möller Lars , Bannert Norbert , Tampé Robert , Divita Gilles , Mély Yves , Schwalbe Harald , Dietrich Ursula
Published: January 2008

The interaction of the nucleocapsid NCp7 of the human immunodeficiency virus type 1 (HIV‐1) Gag polyprotein with the RNA packaging signal Ψ ensures specific encapsidation of the dimeric full length viral genome into nascent virus particles. Being an essential step in the HIV‐1 replication cycle, specific genome encapsidation represents a promising target for therapeutic intervention. We previously selected peptides binding to HIV‐1 Ψ‐RNA or stem loops (SL) thereof by phage display. Herein, we describe synthesis of peptide variants of the consensus HWWPWW motif on membrane supports to optimize Ψ‐RNA binding. The optimized peptide, psi‐pepB, was characterized in detail with respect to its conformation and binding properties for the SL3 of the Ψ packaging signal by NMR and tryptophan fluorescence quenching. Functional analysis revealed that psi‐pepB caused a strong reduction of virus release by infected cells as monitored by reduced transduction efficiencies, capsid p24 antigen levels, and electron microscopy. Thus, this peptide shows antiviral activity and could serve as a lead compound to develop new drugs targeting HIV‐1.
High‐precision measurement of internuclear distances using solid‐state NMR
Authors: Lee Jae‐Seung , Khitrin Anatoly K.
Published: January 2008

Today, nuclear magnetic resonance (NMR) is among the most efficient tools in structural studies. Measurement of interatomic distances is the most common way of determining high‐resolution structures of molecules using NMR techniques. In this article, we describe NMR techniques for static powder samples, based on a two‐dimensional single‐echo scheme, enhanced with adiabatic cross‐polarization. They can significantly increase the accuracy of measuring internuclear distances and turn NMR into a high‐precision crystallographic technique, complementing the X‐ray, and neutron‐scattering methods. Experimental examples are presented for intramolecular CN and CC distances in α‐crystalline form of glycine. © 2008 Wiley Periodicals, Inc. Concepts Magn Reson Part A 32A: 56–67, 2008.
NMR and the uncertainty principle: How to and how not to interpret homogeneous line broadening and pulse nonselectivity. II. The Fourier connection
Authors: Szántay Csaba
Published: January 2008

By building on the nomenclature introduced and the fundamental ideas discussed in Part I, I now continue my preliminary review of the basic concepts we need for exploring the issues surrounding the uncertainty principles in the context of our “Two NMR Problems” (namely: both the essense of homogeneous NMR line broadening, as well as the fact that a short monochromatic RF pulse exhibits a polychromatic spectral bandwidth, and consequently gives a broad off‐resonance NMR excitation band, are often rationalized in terms of a superficial and/or misguided use of the “uncertainty principle”). To that end, in Part II, I discuss Fourier theory in a way that is hoped to offer a number of delicate, important, and interesting insights that are usually not readily available from more conventional texts. © 2008 Wiley Periodicals, Inc. Concepts Magn Reson Part A 32A: 1–33, 2008.
Natural killer cells infiltrating human nonsmall‐cell lung cancer are enriched in CD56brightCD16− cells and display an impaired capability to kill tumor cells
Authors: Carrega Paolo , Morandi Barbara , Costa Roberta , Frumento Guido , Forte Giuseppe , Altavilla Giuseppe , Ratto Giovanni Battista , Mingari Maria Cristina , Moretta Lorenzo , Ferlazzo Guido
Published: January 2008

BACKGROUND.

Despite natural killer (NK) cells being originally identified and named because of their ability to kill tumor cells in vitro, only limited information is available on NK cells infiltrating malignant tumors, especially in humans.

METHODS.

NK cells infiltrating human nonsmall cell lung cancers (NSCLC) were analyzed with the aim of identifying their potential protective role in an antitumor immune response. Both relevant molecule expression and functions of NK cells infiltrating NSCLC were analyzed in comparison with autologous NK cells isolated from either peritumoral normal lung tissues or peripheral blood.

RESULTS.

The CD56brightCD16− NK cell subset was consistently observed as being highly enriched in tumor infiltrate and displayed activation markers, including NKp44, CD69, and HLA‐DR. Remarkably, the cytolytic potential of NK cells isolated from cancer tissues was lower than that of NK cells from peripheral blood or normal lung tissue, whereas no difference was observed regarding their capability of producing cytokines. With regard to their localization within tumor, NK cells were found in tumor stroma, whereas they were not in direct contact with cancer cells.

CONCLUSIONS.

For the first time NK cells infiltrating NSCLC have been characterized and it is shown that they are mainly capable of producing relevant cytokines rather than exerting direct cancer cell killing. Cancer 2008. © 2008 American Cancer Society.