bluuebunny/crossref_metadata_2025 huggingface dataset:
Development of NIR-II small animal living fluorescence imaging system
Authors: Wu Dan-Dan , Pan Li , Zhou Zhe , Fu Wei-Wei , Zhu Hai-Long , Dong Yue-Fang ,   Medical Imaging Technology Laboratory, Suzhou Institute of Biomedical Engineering Technology, Chinese Academy of Sciences, Suzhou 215163, China,   Suzhou Guoke Shiqing Medical Technology Co., Ltd, Suzhou 215163, China
Published: January 2024

Fluorescence imaging technology can dynamically monitor gene and cell changing in live animals in real-time, with advantages such as high sensitivity, high resolution, and non-invasion. In recent years, it has been widely used in tumor research, gene expression research, drug development research, etc. The imaging wavelength of traditional fluorescence imaging technology falls in the visible and near-infrared-I region. Due to the absorption and scattering effects of light propagation in biological tissues, and the inherent fluorescence of biological tissues, traditional fluorescence imaging techniques still have significant limitations in penetration depth and image signal-to-noise ratio. In this work, a highly integrated near-infrared-II (NIR-II, 900—1880 nm) small animal living fluorescence imaging system is developed by taking the advantages of NIR-II fluorescence imaging technology, such as low absorption, low scattering, and deep penetration depth in biological tissues. And a method of enhancing and correcting fluorescence image is proposed to optimize fluorescence images. In this work, the biological tissue simulation experiments and live animal experiments are conducted to test the performance and imaging effect of the system. The experimental results show that the system has the advantages of deep penetration depth, high signal-to-noise ratio, and high sensitivity. Combined with commercial indocyanine green reagents and aggregation-induced emission dyes, this system can monitor the distribution of blood vessels in real time and continuously monitor deep tissues and organs in mice, and conduct the dynamically monitoring research in living mice in a conscious state. This helps to promote tumor research and drug development research in the field of biomedical imaging to enter a new stage.
Tracing the substrate translocation mechanism in P-glycoprotein
Authors: Gewering Theresa , Waghray Deepali , Parey Kristian , Jung Hendrik , Tran Nghi NB , Zapata Joel , Zhao Pengyi , Chen Hao , Januliene Dovile , Hummer Gerhard , Urbatsch Ina , Moeller Arne , Zhang Qinghai
Published: January 2024

P-glycoprotein (Pgp) is a prototypical ATP-binding cassette (ABC) transporter of great biological and clinical significance.Pgp confers cancer multidrug resistance and mediates the bioavailability and pharmacokinetics of many drugs (Juliano and Ling, 1976; Ueda et al., 1986; Sharom, 2011). Decades of structural and biochemical studies have provided insights into how Pgp binds diverse compounds (Loo and Clarke, 2000; Loo et al., 2009; Aller et al., 2009; Alam et al., 2019; Nosol et al., 2020; Chufan et al., 2015), but how they are translocated through the membrane has remained elusive. Here, we covalently attached a cyclic substrate to discrete sites of Pgp and determined multiple complex structures in inward- and outward-facing states by cryoEM. In conjunction with molecular dynamics simulations, our structures trace the substrate passage across the membrane and identify conformational changes in transmembrane helix 1 (TM1) as regulators of substrate transport. In mid-transport conformations, TM1 breaks at glycine 72. Mutation of this residue significantly impairs drug transport of Pgp in vivo, corroborating the importance of its regulatory role. Importantly, our data suggest that the cyclic substrate can exit Pgp without the requirement of a wide-open outward-facing conformation, diverting from the common efflux model for Pgp and other ABC exporters. The substrate transport mechanism of Pgp revealed here pinpoints critical targets for future drug discovery studies of this medically relevant system.
A Remarkable Genetic Shift in a Transmitted/Founder Virus Broadens Antibody Responses Against HIV-1
Authors: Jain Swati , Uritskiy Gherman , Mahalingam Marthandan , Batra Himanshu , Chand Subhash , Trinh Hung V. , Beck Charles , Shin Woong-Hee , AlSalmi Wadad , Kijak Gustavo , Eller Leigh A. , Kim Jerome , Kihara Daisuke , Tovanabutra Sodsai , Ferrari Guido , Robb Merlin L. , Rao Mangala , Rao Venigalla B.
Published: January 2024

A productive HIV-1 infection in humans is often established by transmission and propagation of a single transmitted/founder (T/F) virus, which then evolves into a complex mixture of variants during the lifetime of infection. An effective HIV-1 vaccine should elicit broad immune responses in order to block the entry of diverse T/F viruses. Currently, no such vaccine exists. An in-depth study of escape variants emerging under host immune pressure during very early stages of infection might provide insights into such a HIV-1 vaccine design. Here, in a rare longitudinal study involving HIV-1 infected individuals just days after infection in the absence of antiretroviral therapy, we discovered a remarkable genetic shift that resulted in near complete disappearance of the original T/F virus and appearance of a variant with H173Y mutation in the variable V2 domain of the HIV-1 envelope protein. This coincided with the disappearance of the first wave of strictly H173-specific antibodies and emergence of a second wave of Y173-specific antibodies with increased breadth. Structural analyses indicated conformational dynamism of the envelope protein which likely allowed selection of escape variants with a conformational switch in the V2 domain from an α-helix (H173) to a β-strand (Y173) and induction of broadly reactive antibody responses. This differential breadth due to a single mutational change was also recapitulated in a mouse model. Rationally designed combinatorial libraries containing 54 conformational variants of V2 domain around position 173 further demonstrated increased breadth of antibody responses elicited to diverse HIV-1 envelope proteins. These results offer new insights into designing broadly effective HIV-1 vaccines.
FBXO24 ensures male fertility by preventing abnormal accumulation of membraneless granules in sperm flagella
Authors: Kaneda Yuki , Miyata Haruhiko , Xu Zoulan , Shimada Keisuke , Kamoshita Maki , Nakagawa Tatsuya , Emori Chihiro , Ikawa Masahito
Published: January 2024

Ribonucleoprotein (RNP) granules are membraneless electron-dense structures rich in RNAs and proteins, and involved in various cellular processes. Two RNP granules in male germ cells, intermitochondrial cement and the chromatoid body (CB), are associated with PIWI-interacting RNAs (piRNAs) and are required for transposon silencing and spermatogenesis. Other RNP granules in male germ cells, the reticulated body and CB remnants, are also essential for spermiogenesis. In this study, we disrupted FBXO24, a testis-enriched F-box protein, in mice and found numerous membraneless electron-dense granules accumulated in sperm flagella.
Fbxo24
knockout (KO) mice exhibited malformed flagellar structures, impaired sperm motility, and male infertility, likely due to the accumulation of abnormal granules. The amount and localization of known RNP granule-related proteins were not disrupted in
Fbxo24
KO mice, suggesting that the accumulated granules were distinct from known RNP granules. Further studies revealed that RNAs and two importins, IPO5 and KPNB1, abnormally accumulated in
Fbxo24
KO spermatozoa. In addition, IPO5 and KPNB1 were recruited to stress granules, RNP complexes, when cells were treated with oxidative stress or a proteasome inhibitor. These results suggest that FBXO24 plays a critical role in preventing the accumulation of importins and RNP granules in sperm flagella.
Self-inhibiting percolation and viral spreading in epithelial tissue
Authors: Xu Xiaochan , Nielsen Bjarke Frost , Sneppen Kim
Published: January 2024

SARS-CoV-2 induces delayed type-I/III interferon production, allowing it to escape the early innate immune response. The delay has been attributed to a deficiency in the ability of cells to sense viral replication upon infection, which in turn hampers activation of the antiviral state in bystander cells. Here, we introduce a cellular automaton model to investigate the spatiotemporal spreading of viral infection as a function of virus and host-dependent parameters. The model suggests that the considerable person-to-person heterogeneity in SARS-CoV-2 infections is a consequence of high sensitivity to slight variations in biological parameters near a critical threshold. It further suggests that within-host viral proliferation can be curtailed by the presence of remarkably few cells that are primed for IFN production. Thus the observed heterogeneity in defense readiness of cells reflects a remarkably cost-efficient strategy for protection.
Determinants of Green Purchase Behaviour of Consumers in Ernakulam District, Kerala
Authors: Aswathy K. K.  , Ushadevi K. N.
Published: January 2024

Aims: The study aimed to identify the determinants of green purchase behaviour of consumers.

Methodology: Primary data were collected from the consumers (200) who use at least one green product with an eco-label in Ernakulam District. A purposive sampling was employed to select 100 consumers both from Kochi Corporation area and Mulanthuruthy panchayath of Ernakulam district of Kerala, during the month of august and september 2023. Secondary data were collected from websites, government reports, and publications.

Results: The factor analysis revealed that respondents in grama panchayat influenced by three factors like eco consumer insight, concern towards nature and green product value perspective. Whereas the factors like concern towards nature, government intervention, green product value perceptive and green promotion were acting as the major determinants of green purchase behaviour in the corporation area. The overall response of green consumers in Ernakulam district highlighted, three main factors that influence their purchase decision such as eco consumer insight, concern towards nature, and green product value perspective.

Conclusion: The marketers and policymakers need to consider the factors like eco consumer insight, concern towards nature, green product value perspective, green promotion for popularising and increasing the sale of green products.
The Diagnostic Significance of the Holter Monitoring in the Evaluation of Palpitation at Tanta University Hospitals
Authors: Ata Saad Wageh Abo EL , Masry Magdy Mohamed EL , Shedoudy Sahr Abd Allah EL , Nassar Mohamed Bayoumi
Published: January 2024

Background: Palpitations are the second-most common cause of primary healthcare referrals to cardiologists and are linked to long-term morbidity. Despite the absence of a significant underlying cause, a considerable number of patients report fear and anxiety. The purpose of this study was to assess individuals who were evaluated for palpitation in order to ascertain the diagnostic yield of 24 or 48 hours of Holter monitoring.

Methods: 105 participants participated in this prospective observational cross-sectional research, children and adults, with palpitations, dizziness and syncope, with Holter monitoring 24 or 48 hours. Every patient had a thorough medical history, clinical evaluation, and physical assessment, Resting Electrocardiography (ECG), Transthoracic Echocardiography, and Holter monitoring. Patients were further subdivided into two groups: Positive Holter group and Negative Holter group.

Results: Symptoms among positive Holter response showed that 48.6% had palpitations, 34.2% had dizziness and 13.3% had syncope. Higher age, increased frequency of danger factors (Diabetes mellitus, Hypertension, Ischemic heart disease, cardiomyopathy), symptoms (Palpitations, Dizziness, Syncope), Premature ventricular contractions and lower Ejection fraction was observed in patients with positive Holter response compared to patients with negative Holter response. There was no significant association with sex, smoking, Atrial fibrillation, regular sinus rhythm, and premature atrial contractions (P ≤ 0.05).

Conclusions: Holter Monitoring retains its value, despite the appearance of new investigations and considered the first line for assessment of palpitations as it is widespread and not expensive. It has a good outcome if the patient’s symptoms are suggestive for arrhythmia, syncope and dizziness.
The Catalytic Asymmetric Addition of Diethylzinc to N‐(Diphenylphosphinoyl) Imines Catalyzed by Cu(OTf)2‐Chiral N‐(Binaphthyl‐2‐yl)thiophosphoramide Ligands
Authors: Shi Min , Wang Chun‐Jiang
Published: August 2003

Chiral N‐(binaphthyl‐2‐yl)thiophosphoramide L7 [O,O‐diethyl 2′‐(ethylamino)‐1,1′‐binaphthyl‐2‐ylamidothiophosphate] prepared from the reaction of diethyl chlorothiophosphate with (R)‐(+)‐N‐ethyl‐1,1′‐binaphthyl‐2,2′‐diamine was used as a catalytic chiral ligand in the first Cu(OTf)2‐promoted catalytic asymmetric addition of diethylzinc to N‐(diphenylphosphinoyl) imines in which ~85% ee can be realized.
Molecular Basis for the Enantioselective Ring Opening of β‐Lactams Catalyzed by Candida antarctica Lipase B
Authors: Park Seongsoon , Forró Enikö , Grewal Harjap , Fülöp Ferenc , Kazlauskas Romas J.
Published: August 2003

Lipase B from Candida antarctica (CAL‐B) catalyzes the slow, but highly enantioselective (E>200), ring‐opening alcoholysis of two bicyclic and two 4‐aryl‐substituted β‐lactams. Surprisingly, the rate of the reaction varies with the nature of the alcohols and was fastest with either enantiomer of 2‐octanol. A 0.5‐g scale reaction with 2‐octanol as the nucleophile in diisopropyl ether at 60 °C yielded the unreacted β‐lactam in 39–46% yield (maximum yield is 50%) with ≥96% ee. The product β‐amino acid esters reacted further by polymerization (not isolated or characterized) or by hydrolysis due to small amounts of water in the reaction mixture yielding β‐amino acids (7–11% yield, ≥96% ee). The favored enantiomer of all four β‐lactams had similar 3‐D orientation of substituents, as did most previously reported β‐lactams and β‐lactones in similar ring‐opening reactions. Computer modeling of the ring opening of 4‐phenylazetidin‐2‐one suggests that the reaction proceeds via an unusual substrate‐assisted transition state, where the substrate alcohol bridges between the catalytic histidine and the nitrogen of the β‐lactam. Computer modeling also suggested that the molecular basis for the high enantioselectivity is a severe steric clash between Ile189 in CAL‐B and the phenyl substituent on the slow‐reacting enantiomer of the β‐lactam.
Endo‐ und Exotemplate zur Erzeugung von anorganischen Materialien mit großer spezifischer Oberfläche
Authors: Schüth Ferdi
Published: August 2003

Poröse Materialien und Materialien mit großer Oberfläche sind in vielen wissenschaftlichen Bereichen von Interesse. Templatverfahren können genutzt werden, um solche Materialien unter Steuerung ihrer Struktur‐ und Textureigenschaften zu synthetisieren, wobei molekulare oder supramolekulare Einheiten als Template der Synthesemischung hinzugefügt werden. Sie werden in einem wachsenden Festkörper eingeschlossen und hinterlassen nach ihrer Entfernung ein Porensystem. Für solche Template wird der Begriff “Endotemplat” eingeführt. Alternativ können porenhaltige Gerüstmaterialien eingesetzt werden, innerhalb derer ein Feststoff synthetisiert wird. Nach Entfernung des Gerüsts verbleibt je nach Verknüpfung der Poren im Templat entweder ein poröser oder feinteiliger Feststoff. Solche Template werden als “Exotemplate” bezeichnet. Durch geeignete Wahl des Templatverfahrens gelang es in den letzten Jahren, die Steuerung von Struktur und Textur auf der Größenskala zwischen Nanometern und Mikrometern zu optimieren.
Study on the properties of crosslinking of poly(ethylene oxide) and hydroxyapatite–poly(ethylene oxide) composite
Authors: Banat R. , Tinçer T.
Published: August 2003

This study covers the crosslinking of poly(ethylene oxide) (PEO) and its composite with calcium hydroxyapatite (HA), their mechanical and swelling properties, and morphology. Sheets of the composites of PEO (two different grades with Mv: 5 × 106 and 2 × 105) and HA and neat PEO were prepared by compression molding. The prepared composite and PEO (0.1‐mm‐thick) sheets were crosslinked with exposure of UV‐irradiation in the presence of a photoinitiator, acetophenone (AP). This simple method for crosslinking, induced by UV‐irradiation in the presence of AP, yielded PEO with gel content up to 90%. Gel content, equilibrium swelling ratio, and mechanical and morphological properties of the low molecular weight polyethylene oxide (LMPEO)–HA crosslinked and uncrosslinked composites were evaluated. Although the inclusion of HA into LMPEO inhibits the extent of crosslinking, the LMPEO–HA composite with 20% HA by weight shows the highest gel content, with appreciable equilibrium swelling and mechanical strength. The growth of HA in simulated body fluid solutions on fractured surfaces of LMPEO and also LMPEO–HA was found to be very favorable within short times. The dimensional stability of these samples was found to be satisfactory after swelling and deposition experiments. The good compatibility between the filler hydroxyapatite and poly(ethylene oxide) makes this composite a useful tissue‐adhesive material. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 488–496, 2003
Influence of structural parameters on the degradation of ultrahigh‐molecular‐weight vinyl‐type network‐polymer precursors during elution through size exclusion chromatography columns
Authors: Ikeda Jun‐Ichi , Oe Hiroaki , Aota Hiroyuki , Matsumoto Akira
Published: August 2003

Network‐polymer precursors obtained in various crosslinking monovinyl/divinyl copolymerization systems, including benzyl methacrylate/1,6‐hexanediol dimethacrylate, benzyl acrylate (BzA)/1,6‐hexanediol diacrylate (HDDA), and vinyl benzoate/divinyl adipate, were subjected to degradation during elution through size exclusion chromatography (SEC) columns, although the copolymerizations were conducted under specified conditions where the factors for the greatly delayed gelation from the Flory–Stockmayer gelation theory were reduced. The most remarkable degradation was observed for the BzA/HDDA copolymerization, which provided prepolymers with the most flexible backbone chains. Thus, the BzA/HDDA precopolymers were chosen, and their degradation behavior during elution through SEC columns was explored in detail as one of the representatives of vinyl‐type network‐polymer precursors. The results were correlated with the structural parameters of network‐polymer precursors, including primary polymer chain length, branched structure, and multiple crosslink or network structure. The degradation became more remarkable with decreased primary polymer chain length, that is, the increment of branching, whereas reduced degradation was observed with the incorporation of loop and network structures into the prepolymer. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 577–582, 2003
Performance measurement framework for hierarchical text classification
Authors: Sun Aixin , Lim Ee‐Peng , Ng Wee‐Keong
Published: August 2003

Hierarchical text classification or simply hierarchical classification refers to assigning a document to one or more suitable categories from a hierarchical category space. In our literature survey, we have found that the existing hierarchical classification experiments used a variety of measures to evaluate performance. These performance measures often assume independence between categories and do not consider documents misclassified into categories that are similar or not far from the correct categories in the category tree. In this paper, we therefore propose new performance measures for hierarchical classification. The proposed performance measures consist of category similarity measures and distance‐based measures that consider the contributions of misclassified documents. Our experiments on hierarchical classification methods based on SVM classifiers and binary Naïve Bayes classifiers showed that SVM classifiers perform better than Naïve Bayes classifiers on Reuters‐21578 collection according to the extended measures. A new classifier‐centric measure called blocking measure is also defined to examine the performance of subtree classifiers in a top‐down level‐based hierarchical classification method.
Reversible Anion Exchanges between the Layered Organic–Inorganic Hybridized Architectures: Syntheses and Structures of Manganese(II) and Copper(II) Complexes Containing Novel Tripodal Ligands
Authors: Fan Jian , Gan Lu , Kawaguchi Hiroyuki , Sun Wei‐Yin , Yu Kai‐Bei , Tang Wen‐Xia
Published: August 2003

Six noninterpenetrating organic–inorganic hybridized coordination complexes, [Mn(3)2(H2O)2](ClO4)2⋅2 H2O (5), [Mn(3)2(H2O)2](NO3)2 (6), [Mn(3)2(N3)2]⋅2 H2O (7), [Cu(3)2(H2O)2](ClO4)2 (8), [Mn(4)2(H2O)(SO4)]⋅CH3OH⋅5 H2O (9) and [Mn(4)2](ClO4)2 (10) were obtained through self‐assembly of novel tripodal ligands, 1,3,5‐tris(1‐imidazolyl)benzene (3) and 1,3‐bis(1‐imidazolyl)‐5‐(imidazol‐1‐ylmethyl)benzene (4) with the corresponding metal salts, respectively. Their structures were determined by X‐ray crystallography. The results of structural analysis of complexes 5, 6, 7, and 8 with rigid ligand 3 indicate that their structures are mainly dependant on the nature of the organic ligand and geometric need of the metal ions, but not influenced greatly by the anions and metal ions. While in complexes 9 and 10, which contain the flexible ligand 4, the counteranion plays an important role in the formation of the frameworks. Entirely different structures of complexes 5 and 10 indicate that the organic ligands greatly affect the structures of assemblies. Furthermore, in complexes 5 and 6, the counteranions located between the cationic layers can be exchanged by other anions. Reversible anion exchanges between complexes 5 and 6 without destruction of the frameworks demonstrate that 5 and 6 can act as cationic layered materials for anion exchange, as determined by IR spectroscopy, elemental analyses, and X‐ray powder diffraction.
Cyclization Triggered by Deprotonation: The Gas‐Phase Acidity of 1,8‐Chalcogen‐Bridged Naphthalenes
Authors: Sanz Pablo , Yáñez Manuel , Mó Otilia
Published: August 2003

High‐level density functional theory computations have been used to estimate the gas‐phase (intrinsic) acidities of the complete series of 1,8‐chalcogen‐bridged naphthalene derivatives. The existence of a chalcogenchalcogen bond in chalcogen‐bridged naphthalene derivatives plays a crucial role in the intrinsic acidity of the system. For 1,8‐naphthalenediylbis(oxy), where this bond does not exist, theparaCH group is the most acidic site, whereas for the remaining compounds, deprotonation of theorthoCH groups is the most favorable process. Deprotonation of the aromatic rings has a large effect on the strength of the bonds of the five‐membered ring. These effects depend on the nature of the heteroatoms forming the XY bridge, and modulate the acidity of the molecule. Also importantly, when one of the heteroatoms is oxygen,orthoandparadeprotonation lead to cleavage of the XY bridge. This bond fission favors the formation of a CYC (Y=S, Se, Te) three‐membered ring that enhances the stability of the anion and, therefore, increases the acidity of these compounds. We have shown that, whereas this cyclization process is energetically favorable for oxygen‐containing compounds, it is not favorable for the remaining derivatives.
Molecular modeling of various peptide sequences of gliadins and low‐molecular‐weight glutenin subunits
Authors: Yaşar Fatih , Çelik Süeda , Köksel Hamit
Published: August 2003

The contribution of the three‐dimensional structures of one heptapeptide (PQPQPFP) sequence and one pentapeptide (PQQPY) repeat sequence of α/β‐gliadins, one heptapeptide (PQQPFPQ) repeat sequence of γ‐gliadins, two heptapeptide (PQQPPFS and QQQQPVL) repeat motifs of low‐molecular‐weight (LMW) subunits and a tetrapeptide sequence in polyQ region of S‐rich prolamins to their conformations are investigated by using the recently developed multicanonical simulation procedure. Ramachandran plots were prepared and analysed to predict the relative occurrence probabilities of β‐turn, γ‐turn, and helical structures. The probability of inverse γ‐turn was generally higher than that of β‐turns in all sequences investigated. Occurrence probability of helical structure in the repetitive domain of gliadins was low. Structural predictions of QQQQPVL sequence of LMW‐glutenin subunits and QQQQ sequence in the polyQ region of S‐rich prolamins indicate the presence of helical structures with the probability of > 20%. The probability of helical structure significantly decreased around 100°C.
Aren't there two parties in an employment relationship? Antecedents and consequences of organization–employee agreement on contract obligations and violations
Authors: Tekleab Amanuel G. , Taylor M. Susan
Published: August 2003

Past studies have paid little attention to an organization's perspective on reciprocal obligations in the employment relationship, despite its importance to overall satisfaction and the survival of the relationship. This study assesses parties' levels of agreement on the reciprocal obligations of the psychological contract, and their consequences on parties' perceptions of contract violations. Furthermore, the study examines subsequent reactions of both parties to perceived violations. Results indicate that managers and employees tend to disagree on the employee's obligations and violations of the contract but not on the organization's obligations and violations. More importantly, results from multivariate regression analyses indicate that employee tenure with the manager and leader–member exchange (LMX) as reported by the manager were positively related to agreement on employees' obligations. Agreement on employees' obligations was related to perceptions of violation by the manager, but in a direction opposite to that hypothesized. Both managers' perceptions of employee violations and employees' perceptions of organization violations were related to employee outcomes assessed by the managers and the employees. Implications and suggestions for future research are discussed. Copyright © 2003 John Wiley & Sons, Ltd.
Alkane‐ and areneoxodiazonium ions: experimental results leading to an ab initio theoretical investigation
Authors: Eckert‐Maksić Mirjana , Glasovac Zoran , Maskill Howard , Zrinski Irena
Published: August 2003

Alkaneoxodiazonium ions (R—NNO)+ and (R—O—N2)+, which are closely analogous to alkanediazonium ions (R—N2)+, were detected as reactive intermediates in acid‐catalysed reactions of nitrosohydroxylamines and deamination‐type reactions. The isomers were compared by high‐level MO investigations of the reactions of nitrous oxide with cationic electrophiles H+, CH3+, Me3C+ and PhCH2+. Strongly bonded species are formed in reactions with the powerfully electrophilic H+ and CH3+, and the resulting ions differ considerably in stabilities; less stable species are formed with Me3C+ and PhCH2+ and the complexes so formed have similar stabilities. Two isomers of Ph(N2O)+, analogous to phenyldiazonium ion, PhN2+, are calculated to be stable ions with the end‐N‐bonded isomer being preferred over the O‐bonded ion at the MP4(SDQ)/6–311G(d,p)//MP2(fc)/6–31G(d,p) and G3 levels of theory. Both are non‐planar with the phenyl ring at 90° to the non‐linear N2O residue. Syntheses of salts of Ar(N2O)+ are now planned. Copyright © 2003 John Wiley & Sons, Ltd.
Thermolysis of N‐tetramethylpiperidinyl triphenylacetate: homolytic fragmentation of a TEMPO ester
Authors: Henry‐Riyad Huda , Tidwell Thomas T.
Published: August 2003

Thermolysis of N‐tetramethylpiperidinyl triphenylacetate (7, Ph3CCO2T, T=2,2,6,6‐tetramethylpiperidinyl) in benzene at 146°C leads to the formation of triphenylmethane (Ph3CH, 80%), tetramethylpiperidine (TH, 91%), and tetraphenylmethane (Ph4C, 9%). First‐order rate constants for the decomposition at 132.8 and 150.0°C were 2.20 × 10−6 and 2.88 × 10−5 s−1, respectively. In benzene‐d6 solvent the triphenylmethane was formed as Ph3CD to the extent of 20%, as determined by 1H NMR and mass spectrometry. The results are interpreted as showing that Ph3CCO2T undergoes thermolysis by concerted two‐bond scission with formation of Ph3C⋅, tetramethylpiperidinyl radicals and CO2. The formation of Ph4C occurs by addition of Ph3C⋅ to benzene, followed by hydrogen atom abstraction from the resulting adduct. Calculations using DFT methods at the B3LYP/6–311++G** level were used to elucidate the bond fission of HCO2T (2), and indicate that cleavage to HCO2⋅ and T⋅ is favored by 7.8 kcal mol−1 relative to cleavage to HC(•)O and TO⋅, in agreement with the experimental results. Copyright © 2003 John Wiley & Sons, Ltd.
Hepatoprotective and antioxidant activities of Tetracera loureiri
Authors: Kukongviriyapan Veerapol , Janyacharoen Taweesak , Kukongviriyapan Upa , Laupattarakasaem Pisamai , Kanokmedhakul Somdej , Chantaranothai Pranom
Published: August 2003

Tetracera loureiri is one of the most valued herbs in Thai traditional medicine. In this study, we describe its in vitro and in vivo antioxidant and hepatoprotective activities. The ethanol extract of T. loureiri possessed potent antioxidant and strong free radical scavenging properties assayed using ferric reducing antioxidant power (FRAP) and 2,2‐diphenyl‐1‐picrylhydrazyl (DPPH), respectively. The cytoprotective effects of T. loureiri were demonstrated in ethanolic extracts of freshly isolated rat hepatocytes against the chemical toxicants paracetamol and tertiary‐butylhydroperoxide. The cells pretreated with the extract maintained the GSH/GSSG ratio and suppressed lipid peroxidation in a dose dependent manner. Pretreating rats with the ethanol extract orally, one hour prior to intraperitoneal injection of toxic doses of paracetamol, signiﬁcantly prevented elevations of plasma ALT and AST. These results suggest that T. loureiri may be of potential therapeutic value in some liver disorders. Copyright © 2003 John Wiley & Sons, Ltd.
Antiprotozoal activity of the constituents of Teloxys graveolens
Authors: Calzada Fernando , Velázquez Claudia , Cedillo‐Rivera Roberto , Esquivel Baldomero
Published: August 2003

Antiprotozoal activity‐guided fractionation of a methanol extract of the aerial parts of Teloxys graveolens led to the isolation of one coumarinic acid derivative, melilotoside, and five flavonoids, pinocembrine, pinostrobin, chrysin, narcissin and rutin. Among them, melilotoside exhibited the most potent activity toward Entamoeba histolytica and Giardia lamblia (IC50 12.5 and 16.8 µg/mL, respectively). Narcissin showed selectivity against E. histolytlica (IC50 17.2 µg/mL). The results support data for the traditional use of T. graveolens in some gastrointestinal diseases. Copyright © 2003 John Wiley & Sons, Ltd.
Promotion of hair growth by ginseng radix on cultured mouse vibrissal hair follicles
Authors: Matsuda Hideaki , Yamazaki Miho , Asanuma Yusuke , Kubo Michinori
Published: August 2003

A 70% methanol extract from red ginseng (steamed and dried roots of Panax ginseng C. A. Meyer, a kind of Ginseng Radix) had superior activity to that of white ginseng (peeled and dried root of P. ginseng, another kind of Ginseng Radix) in a hair growth promoting assay using mouse vibrissal follicles in organ culture. Of the major constituents of P. ginseng, ginsenoside‐Rb1 (G‐Rb1) exhibited activity, but ginsenoside‐Rg1 (G‐Rg1) and ‐Ro (G‐Ro) were ineffective. Additionally, 20(S)‐ginsenoside‐Rg3 (20(S)‐G‐Rg3) formed by the processing of red ginseng from the crude root of P. ginseng also showed hair growth promoting activity. These results indicate that Ginseng Radix possesses hair growth promoting activity, and its bioactive components are partially attributable to the ginseng saponin components mentioned above. Copyright © 2003 John Wiley & Sons, Ltd.
The Generation of Dihydropyrimidine Libraries Utilizing Biginelli Multicomponent Chemistry
Authors: Kappe C. Oliver
Published: August 2003

With the emergence of high‐throughput screening in the pharmaceutical industry over a decade ago, synthetic chemists were faced with the challenge of preparing large collections of molecules to satisfy the demand for new screening compounds. The unique exploratory power of multicomponent reactions such as the Ugi four‐component reaction was soon recognized to be extremely valuable to produce compound libraries in a time‐ and cost effective manner. The present review article summarizes strategies for the construction of libraries through another multicomponent reaction, the Biginelli dihydropyrimidine synthesis. In this three‐component condensation dating back to 1893, CH‐acidic carbonyl compounds, aldehydes and urea‐type building blocks combine to assemble a multifunctionalized dihydropyrimidine scaffold. Due to the interesting pharmacological properties associated with the privileged DHPM structures, the Biginelli reaction and related procedures have received increasing attention in recent years. This review details synthetic advances for the construction of Biginelli libraries via solution phase and solid‐phase strategies that are amenable to a high‐throughput or combinatorial format.
QSAR of Adenosine Receptor Antagonists II:
Authors: Roy Kunal
Published: August 2003

Considering potential of selective adenosine receptor subtype ligands in the development of prospective drug candidates, A1 and A3 receptor binding affinity data of 2‐arylpyrazolo[3,4‐c]quinoline derivatives have been subjected to QSAR analyses to explore the physicochemical requirements for selective binding. The study has been carried out with Wang‐Ford charges of the common atoms of the molecules calculated from their energy minimized conformations using AM1 technique. Apart from the charge parameters, physicochemical variables like partition coefficient and molar refractivity of the whole molecules have been used along with suitable indicator variables. The study shows that substituents on the appended 2‐phenyl ring and 4‐amino or 4‐keto substitution on the pyrazolo[3,4‐c]quinoline nucleus modulate the selectivity pattern. Further, negative charge on the quinoline nitrogen and volume and lipophilicity of the whole molecules are important contributors to the selectivity.
Structure‐Viscosity Relationships for Thai Rice Starches
Authors: Noosuk Piyarat , Hill Sandra E. , Pradipasena Pasawadee , Mitchell John R.
Published: August 2003

The viscosities of five Thai rice starches with different amylose contents were measured by rotational rheometry and using a Rapid Visco Analyser. The viscosity response was interpreted in terms of the swelling volume and the structural properties of the granule determined by calorimetry, infrared spectroscopy and X‐ray diffraction.

It was found that the waxy rice starches had a higher swelling volume resulting in a higher viscosity than the other rice classes. Critical concentrations for close packing, identified from the concentration where the flow behaviour departs from Newtonian, were 2.5%, 1.5% and 1.10% for the high amylose, medium amylose and waxy rice starch, respectively. An exception to this was a commercial high amylose starch that had a critical concentration similar to the medium amylose category. This was ex‐plained in terms of a relatively higher loss of short‐range molecular order on gelatini‐sation as shown by FTIR for this starch. Medium amylose Jasmine rice starch, extracted from rice that had been aged for 5 months, showed differences in granule size, crystallinity, pasting profile and enthalpy of gelatinisation when compared with the results for starch extracted from freshly harvested rice. This was provisionally interpreted in terms of granule damage during the extraction process, though more work would be required to confirm this interpretation.
Crystal structure of DJ‐1/RS and implication on familial Parkinson's disease1
Authors: Huai Qing , Sun Yingjie , Wang Huanchen , Chin Lih-Shen , Li Lian , Robinson Howard , Ke Hengming
Published: August 2003

DJ‐1 is a protein involved in multiple physiological processes, including cancer, Parkinson's disease, and male fertility. It is unknown how DJ‐1 functions in the apparently different systems. The crystal structure of DJ‐1 at 1.6 Å resolution shows that DJ‐1 is a helix‐strand‐helix sandwich and forms a dimer. The DJ‐1 structure is similar to the members of the intracellular protease PfpI family. However, the catalytic triad of Cys–His–Glu is not strictly conserved in DJ‐1, implying that DJ‐1 has a different catalytic mechanism if it acts as a protease or DJ‐1 serves as a regulatory protein in the physiological processes. The structure shows that Leu166 positions in the middle of a helix and thus predicts that the L166P mutation will bend the helix and impact the dimerization of DJ‐1. As a result, the conformational changes may diminish the DJ‐1 binding with its partner, leading to the familial Parkinson's disease caused by the single L166P mutation.
Polyphosphates strongly inhibit the tRNA dependent synthesis of poly(A) catalyzed by poly(A) polymerase from Saccharomyces cerevisiae
Authors: Günther Sillero Marı́a A , de Diego Anabel , Silles Eduardo , Osorio Hugo , Sillero Antonio
Published: August 2003

Polyphosphates of different chain lengths (P3, P4, P15, P35), (1 μM) inhibited 10, 60, 90 and 100%, respectively, the primer (tRNA) dependent synthesis of poly(A) catalyzed poly(A) polymerase from Saccharomyces cerevisiae. The relative inhibition evoked by p4A and P4 (1 μM) was 40 and 60%, respectively, whereas 1 μM Ap4A was not inhibitory. P4 and P15 were assayed as inhibitors of the enzyme in the presence of (a) saturating tRNA and variable concentrations of ATP and (b) saturating ATP and variable concentrations of tRNA. In (a), P4 and P15 behaved as competitive inhibitors, with K
i values of 0.5 μM and 0.2 μM, respectively. In addition, P4 (at 1 μM) and P15 (at 0.3 μM) changed the Hill coefficient (n
H) from 1 (control) to about 1.3 and 1.6, respectively. In (b), the inhibition by P4 and P15 decreased V and modified only slightly the K
m values of the enzyme towards tRNA.
Long‐term restitution of 4‐aminopyridine‐sensitive currents in Kv1DN ventricular myocytes using adeno‐associated virus‐mediated delivery of Kv1.5
Authors: Kodirov S.A , Brunner M , Busconi L , Koren G
Published: August 2003

Overexpression of a dominant‐negative truncated Kv1.1 (Kv1DN) polypeptide in the mouse heart resulted in marked attenuation of a 4‐aminopyridine (4‐AP)‐sensitive current, I
K,slow1. We used recombinant adeno‐associated virus (rAAV) as a vector for direct delivery of Kv1.5 into the mouse myocardium in order to normalize the action potential duration (APD) 6 months after injection. The injection of rAAV‐Kv1.5 reconstituted the 4‐AP‐sensitive outward potassium currents, shortened the APD, and eliminated spontaneous early afterdepolarizations. Immunoblots detected the FL‐Kv1.5 polypeptides only in rAAV‐Kv1.5‐infected hearts. These data demonstrate long‐term expression of 4‐AP‐sensitive potassium currents in ventricular myocytes by gene transfer using rAAV vector encodes Kv1.5.
Evidence for the negative cooperativity of the two active sites within bovine somatic angiotensin‐converting enzyme
Authors: Binevski Peter V , Sizova Elena A , Pozdnev Vladimir F , Kost Olga A
Published: August 2003

The somatic isoform of angiotensin‐converting enzyme (ACE) consists of two homologous domains (N‐ and C‐domains), each bearing a catalytic site. We have used the two‐domain ACE form and its individual domains to compare characteristics of different domains and to probe mutual functioning of the two active sites within a bovine ACE molecule. The substrate Cbz‐Phe‐His‐Leu (N‐carbobenzoxy‐L‐phenylalanyl‐L‐histidyl‐L‐leucine; from the panel of seven) was hydrolyzed faster by the N‐domain, the substrates FA‐Phe‐Gly‐Gly (N‐(3‐[2‐furyl]acryloyl)‐L‐phenylalanyl‐glycyl‐glycine) and Hip‐His‐Leu (N‐benzoyl‐glycyl‐L‐histidyl‐L‐leucine) were hydrolyzed by both domains with equal rates, while other substrates were preferentially hydrolyzed by the C‐domain. The inhibitor captopril ((2S)‐1‐(3‐mercapto‐2‐methylpropionyl)‐L‐proline) bound to the N‐domain more effectively than to the C‐domain, whereas lisinopril ((S)‐N
α‐(1‐carboxy‐3‐phenylpropyl)‐L‐lysyl‐L‐proline) bound to equal extent with all ACE forms. However, active site titration with lisinopril assayed by hydrolysis of FA‐Phe‐Gly‐Gly revealed that 1 mol of inhibitor/mol of enzyme abolished the activity of either two‐domain or single‐domain ACE forms, indicating that a single active site functions in bovine somatic ACE. Neither of the k
cat values obtained for somatic enzyme was the sum of k
cat values for individual domains, but in every case the value of the catalytic constant of the hydrolysis of the substrate by the two‐domain ACE represented the mean quantity of the values of the corresponding catalytic constants obtained for single‐domain forms. The results indicate that the two active sites within bovine somatic ACE exhibit strong negative cooperativity.
Pi2 pulsations and substorm onsets: A review
Authors: Olson John V.
Published: August 2003

Pi2 pulsations have been the subject of continuous study since they were recognized to be an integral part of the magnetospheric substorm. With the advent of arrays of ground instruments the nature of the Pi2 has begun to be understood. As adopted by the 13th General Assembly of the International Union of Geodesy and Geophysics in 1963, Pi2 is a designation that includes impulsive pulsations in the period range from 40 to 150 s. The Pi2 signal encompasses a class of pulsations that represents two fundamental processes. The first process is the sudden generation of field‐aligned currents in association with the disruption of cross‐tail currents in the plasma sheet and their subsequent effects on the ionosphere. The ionosphere appears to be something more than a passive load for this electrodynamic impulse. It responds, sending currents back into a magnetosphere whose topology is changing and, perhaps producing the feedback necessary to cause the explosive growth of the substorm current system. Oscillations of these currents are detected across the nightside of the Earth at onset as the midlatitude and high‐latitude portions of Pi2. The second process is the impulse response of the inner magnetosphere to the compressional waves that are generated at substorm onset. Traveling inward, they stimulate field line resonances and surface waves at the plasmapause and excite global oscillations in the inner magnetosphere. The two processes produce wave modes that couple and cross‐couple threading energy into the inner magnetosphere and ultimately to the ground. The purpose of this review is to construct a phenomenological overview of the Pi2.
Solar wind ionic charge states during the Ulysses pole‐to‐pole pass
Authors: Ko Yuan‐Kuen , Gloeckler George , Cohen Christina M. S. , Galvin Antoinette B.
Published: August 2003

We analyze and compare the ionic charge composition data for different types of the solar wind (slow wind from equatorial regions, fast wind from low‐latitude coronal hole and fast wind from both south and north polar coronal hole) which the Solar Wind Ion Composition Spectrometer (SWICS) on Ulysses observed during the pole‐to‐pole pass of its primary mission. The implications on the electron temperature, electron density, and ion outflow velocity from the corresponding solar wind source regions are also discussed. We find that the electron temperature in the source region of the slow solar wind is higher than that in the coronal hole. We also find a possible north‐south asymmetry in the electron temperature that may be correlated to the north–south asymmetry in the solar wind speed found in the SWOOPS/Ulysses data. In particular, we make extensive discussions on the latitudinal variations in the polar coronal hole. On the basis of our data without clear constraints from other coronal observations, the preliminary result is that the electron density may be higher, or the heavy ion outflow velocities may be lower toward lower heliographic latitude.
Bridging the gap between ground‐based and space‐based observations of the night airglow
Authors: Broadfoot A. L. , Bellaire Paul J.
Published: August 2003

Data sets from most satellite experiments focus on global dynamics by integrating daily conditions over long periods, rather than local dynamics over short timescales. Reports from the ground‐based 1993 airborne lidar and observations of the Hawaiian airglow/airborne noctilucent cloud campaigns (ALOHA/ANLC‐93), with their high temporal and spatial resolution, have described the dynamic nature of the night airglow, or nightglow. Recognizing this dynamic activity, we note that space‐based observations currently made from satellites will only poorly complement ground‐based observations. Space‐based observations that can be correlated to observations over a ground‐based site are possible for only a few minutes per day. Ground‐based observations can be complemented by space‐based observations only by experiments operating in snapshot mode and using a high‐performance instrumentation during the limited flight time over a ground station. The only space platform currently capable of supporting such experimentation is the space shuttle, or Space Transportation System (STS). In the future, appropriate payloads should be planned and deployed on the International Space Station to take advantage of its similar capabilities. The night airglow layer at the Earth's limb was monitored by the Arizona Airglow Experiment (GLO) from the space shuttle Endeavour throughout its 12‐day STS 69 mission in September 1995. When the nightglow was observed from above, the O2 atmospheric band system was conspicuous. Patches of enhanced emission 2500–5000 km in lateral extent were observed. Intensity changes by a factor of 4 were common. Similar activity has been reported in data from the Upper Atmosphere Research Satellite (UARS) remote sensing experiments high‐resolution Doppler imager (HRDI) and wind imaging inferometer (WINDII). The O2(0,0) band emission cannot be observed from the ground because the intervening O2 atmosphere overhead is optically thick to this emission. However, the O2(0,0) band emission is the brightest in the nightglow spectrum observed from orbit. It is 22 times brighter than the O2(0,1) band, which is monitored regularly by ground‐based observers. Thus the intense signature of the O2(0,0) band can be used as an indicator of dynamic activity in the nightglow emission layer.
Magnetostatically equilibrated plasma sheet with developed medium‐scale turbulence: Structure and implications for substorm dynamics
Authors: Antonova Elizabeth E. , Ovchinnikov Ilya L.
Published: August 2003

A simple theory of the magnetostatic equilibrium of the magnetospheric plasma sheet is proposed. It takes into consideration the effects of the large‐scale dawn‐to‐dusk electric field and developed medium‐scale turbulence. This makes it possible to describe the main features of the plasma sheet dynamics. The suggested model assumes that the magnetic field lines are not equipotential and that the regular velocity of a plasma parcel is much lower than the chaotic velocity. Hence the plasma is intensely mixed. One of the main consequences of such mixing is the experimentally observed temperature equalization across the plasma sheet. The obtained dependence of plasma pressure on the magnetic vector potential permits one to solve the Grad‐Shafranov equation and reconstruct, in the tail approximation, the magnetic field line configuration for the case of inhomogeneous distribution of the dawn‐to‐dusk electric field along the tail. The thickness of the plasma sheet in the model is determined by the magnitudes of the regular and stochastic electric fields, their scales, and plasma temperature. A quasi three‐dimensional model of the plasma sheet is developed. The substorm dynamics of the plasma sheet is analyzed. The model can explain the thinning of the plasma sheet without variations in the plasma pressure at the tail axis (thinning without compression) during the substorm growth phase. The plasma sheet expansion during substorm expansion phase is related to the growth of turbulent fluctuations.