bluuebunny/crossref_metadata_2025_split huggingface dataset:
Restricted Rotation in Unbridged Sandwich Complexes: Rotational Behavior of closo‐[Co(η5‐NC4H4)(C2B9H11)] Derivatives
Authors: Viñas Clara , Llop Jordi , Teixidor Francesc , Kivekäs Raikko , Sillanpää Reijo 
Published: February 2005

AbstractRotation about the centroid/metal/centroid axis in ferrocene is facile; the activation energy is 1–5 kcal mol−1. The structurally similar sandwich complexes derived from closo‐[3‐Co(η5‐NC4H4)‐1,2‐C2B9H11] (1) have a different rotational habit. In 1, the cis rotamer in which the pyrrolyl nitrogen atom bisects the carboranyl cluster atoms is 3.5 kcal mol−1 more stable in energy than the rotamer that is second lowest in energy. This cis rotamer is wide, spanning 216°, and may be split into three rotamers of almost equal energy by substituting the N and the carboranyl carbon atoms adequately. To support this statement, closo‐[3‐Co(η5‐NC4H4)‐1,2‐(CH3)2‐1,2‐C2B9H9] (2), closo‐[3‐Co(η5‐NC4H4)‐1,2‐(μ‐CH2)3‐1,2‐C2B9H9] (3), 2→BF3, and 3→BF3 have been prepared. Two rotamers are found at low temperature for 2→BF3 and 3→BF3. Compounds 2, 3, and 1→BF3 behave similarly to 1. Rotational energy barriers and the relative populations of the different energy states are calculated from 1H DNMR spectroscopy (DNMR, dynamic NMR). These results agree with those of semiempirical calculations. Without exception, the cis rotamer is energetically the more stable. The fixed conformation of 1 assists in elucidating the rotational preferences of the [3,3′‐Co(1,2‐C2B9H11)2]− ion in the absence of steric hindrance; the [3,3′‐Co(1,2‐C2B9H11)2]− ion is commonly accepted to present a cisoid orientation. Complex 1 is electronically similar to the [3,3′‐Co(1,2‐C2B9H11)2]− ion. Both have heteroatoms in the π ligands, and they have the same electronegativity difference between the constituent atoms. This leads to a view of the [NC4H4]− as [7,8‐C2B9H11]2− ion, with no steric implications. Therefore the [3,3′‐Co(1,2‐C2B9H11)2]− ion should be considered to have a cisoid structure, and the different rotamers observed to be the result of steric factors and of the interaction of the counterion with either BH groups and/or ancillary ligands. The rotamer adopted is the one with the atoms holding the negative charges furthest apart.
Intramolecular Pauson–Khand Reactions of Methylenecyclopropane and Bicyclopropylidene Derivatives as an Approach to Spiro(cyclopropanebicyclo[n.3.0]alkenones)
Authors: de Meijere Armin , Becker Heike , Stolle Andreas , Kozhushkov Sergei I. , Bes M. Teresa , Salaün Jacques , Noltemeyer Mathias 
Published: February 2005

AbstractThe trimethylsilyl‐protected enynes 9 a–c and 14 a, b with alkynyl substituents on the three‐membered ring or on the double bond of a methylenecyclopropane or a bicyclopropylidene moiety were prepared in two steps from the alcohols 6 a–c and 12 a, b, respectively, by conversion to the iodides and their coupling with lithium (trimethylsilyl)acetylide (8) in 38–73 % overall yields. The bicyclopropylidene derivative 9 d was synthesized in 49 % yield directly from bicyclopropylidene (3) by lithiation followed by coupling with (5‐iodopent‐1‐ynyl)trimethylsilane (11). Enynes 9 b–d were protiodesilylated by treatment with K2CO3 in methanol to give the corresponding unprotected enynes 10 b–d in 53, 74 and 94 % yield, respectively. Enynes 17 a–c with a carbonyl group adjacent to the acetylenic moiety were synthesized from oxo derivatives 15 a–c by Wittig olefination followed by coupling with 8 in 47, 18 and 12 % overall yield, respectively. Pauson–Khand reactions of the methylenecyclopropane derivatives with a substituent on the ring (9 a,b and 10 a) as well as on the double bond (14 a,b and their in situ prepared protiodesilylated analogues) proceeded smoothly by stirring of the corresponding enyne with [Co2(CO)8] in dichloromethane at ambient temperature followed by treatment of the formed complexes with trimethylamine N‐oxide under an oxygen atmosphere at −78 °C to give tricyclic or spirocyclopropanated bicyclic enones 18 a, b, 19 a, 20 a, b, 21 a, b in good yields. Alkynylbicyclopropylidene derivatives 9 c, d and 10 c, d formed the corresponding cobalt complexes at −78 to −20 °C. Treatment of the latter with N‐methylmorpholine N‐oxide under an argon atmosphere at −20 °C gave the spirocyclopropanated tricyclic enones 18 c, 19 c and 18 d in 31–45 % yields. The structure of 19 c was proved by X‐ray crystal structure analysis. The cyclization of enynones 17 a–c in MeCN at 80 °C gave the spirocyclopropanated bicyclic diketones 22 a–c in 38–65 % yields. Intramolecular PKRs of the enynes 25 a, d with a chiral auxiliary adjacent to the triple bond gave the corresponding products 26 a, d in 70 and 79 % yield, respectively, as 5:1 and 8:1 mixtures of diastereomers, respectively. Addition of lithium dimethylcuprate or higher order cuprates to the double bond of the former furnished bridgehead‐substituted bicyclo[3.3.0]octanones 27 a–c in 57–86% yields. Protiodesilylation of 27 a followed by acetal cleavage gave the enantiomerically pure spirocyclopropanated bicyclo[3.3.0]octanedione (1R,5R)‐ 29 a with [α]${{{20\hfill \atop {\rm D}\hfill}}}$=−148 (c=1.0 in CHCl3) in 55 % overall yield.
High‐Content Photochromic Polymers Based on Dithienylethenes
Authors: Wigglesworth Tony J. , Myles Andrew J. , Branda Neil R. 
Published: February 2005

AbstractDithienylethenes (DTEs) are one of the most promising classes of photochromic compounds for use in optoelectronic devices such as waveguides, memory media and sensors. The development of DTE based polymers that contain a high mass‐content of the photoactive DTE component, that maintain their photochromic activity in the solid‐state and that are easily processed into thin‐films under a variety of conditions is critical for the implementation of the materials into useful applications. This Microreview provides an overview of the current approaches for preparing DTE‐based polymers and discusses some of the problems associated with the resulting materials such as poor solubility, low DTE content and poor photochromic activity. We present specific examples from our own research, which highlight our research group’s contributions. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)
Essential oil composition of six Hypericum species from southern Brazil
Authors: Ferraz A. B. F. , Limberger R. P. , Bordignon S. A. L. , von Poser G. L. , Henriques A. T. 
Published: February 2005

AbstractThe essential oil of six Brazilian Hypericum species (Family Guttiferae) has been obtained by hydrodistillation: H. caprifoliatum Cham. & Schlecht. (0.2%), H. carinatum Griseb. (0.2%), H. connatum Lam. (0.1%), H. myrianthum Cham. & Schlecht. (0.5%), H. polyanthemum Klotzsch ex Reichardt. (0.2%) and H. ternum A. St. Hil. (0.1%). The composition of the oils was determined by GC and GC–MS and 84 compounds in total have been characterized. The principal constituents of each oil are: nonane (56%) in H. caprifoliatum, undecane (21%) in H. myrianthum, β‐caryophyllene (21%) in H. carinatum, caryophyllene oxide (40%) in H. connatum, β‐caryophyllene (12%) in H. ternum and the benzopyran HP1 (6‐isobutyryl‐5,7‐dimethoxy‐2,2‐dimethyl‐benzopyran) (27%) in H. polyanthemum. Copyright © 2005 John Wiley & Sons, Ltd.
The essential oil composition of Phlomis bruguieri Desf. from Iran
Authors: Morteza‐Semnani Katayoun , Saeedi Madjid 
Published: February 2005

AbstractThe composition of the essential oil obtained from the dried flowering aerial parts of Phlomis bruguieri Desf. (Labiatae) was analysed by GC and GC–MS for the first time; 99 components were identified. The major constituents of the essential oil were germacrene D (23.6%), 4‐hydroxy‐4‐methyl‐2‐pentanone (15.0%), α‐pinene (6.8%) and β‐caryophyllene (6.7%). Copyright © 2005 John Wiley & Sons, Ltd.
The duties of a receiver/manager in Nigeria and Ghana
Authors: Nwauche E. S. 
Published: February 2005

AbstractThis paper critically examines the duties of receiver/managers in Nigeria and Ghana with a view to determining their adequacy or otherwise. The paper distinguishes between a receiver/manager appointed pursuant to ownership or management dispute and a receiver/manager appointed pursuant to the realization of security. With respect to the former the paper concludes that the persons appointed thereby are better described as managers and suggests a more detailed elaboration of their duties. To determine the duties of receiver/managers appointed to realize security the paper examines the meaning of the receiver/managers; the capacity to be appointed to that office and the duties of a receiver/manager appointed by the court as well as those appointed out of court by the security holders. The paper also considers the consequences of a breach of duty and concludes that the law on receivership is largely the same in Nigeria and Ghana even though there is more litigation in Nigeria. Furthermore the paper suggests the importance of appointing professionals as receiver/managers; the need for the clarity of rules to enable the receiver/managers effectively discharge their duties to enable an assessment of the adequacy of the duties. In this regard the paper recommends a comprehensive reform of insolvency law in Nigeria and Ghana. Copyright © 2005 John Wiley & Sons, Ltd.
Co‐expression of alternatively spliced forms of PAX3, PAX7, PAX3‐FKHR and PAX7‐FKHR with distinct DNA binding and transactivation properties in rhabdomyosarcoma
Authors: Du Shouying , Lawrence Eric J. , Strzelecki Donna , Rajput Prerna , Xia Shujuan J. , Gottesman Dina M. , Barr Frederic G. 
Published: February 2005

AbstractPAX3 and PAX7 encode transcription factors implicated in the pathogenesis of rhabdomyosarcoma (RMS), including alveolar RMS in which chromosomal translocations generate PAX3‐FKHR and PAX7‐FKHR fusions. Previous studies of wild‐type PAX3 and PAX7 identified alternative splicing events that modify the paired box and generate 2 isoforms of PAX3 (Q+ and Q−) and 4 isoforms of PAX7 (Q+GL+, Q+GL−, Q−GL+, Q−GL−). In our study, we investigated alternative splicing of the wild‐type and fusion forms of PAX3 and PAX7 in alveolar and embryonal RMS and assessed the functional implications. For PAX3 and PAX3‐FKHR, the Q+ and Q− isoforms were consistently co‐expressed in RMS tumors with slightly higher levels of the Q+ isoform. For PAX7 and PAX7‐FKHR, there was a consistent pattern of co‐expression of the 4 isoforms in RMS tumors: Q+GL− > Q+GL+ ≥ Q−GL− > Q−GL+. DNA binding analysis demonstrated that PAX3 and PAX3‐FKHR Q− isoforms exhibit higher affinity than corresponding Q+ isoforms for class I sites and no difference for class II sites. For PAX7 and PAX7‐FKHR, the relative affinity was Q−GL− > Q+GL− > Q−GL+ ≥ Q+GL+ for class I sites and Q−GL−, Q+GL− > Q−GL+, Q+GL+ for class II sites. Finally, the transcriptional activities of the PAX3‐FKHR and PAX7‐FKHR isoforms on reporter plasmids varied over a 5‐fold and 50‐fold range, respectively, in accord with the differences in DNA binding activity. In conclusion, these studies reveal that PAX3, PAX7 and their fusions with FKHR are each expressed in RMS tumors as a consistent mixture of functionally distinct isoforms. © 2005 Wiley‐Liss, Inc.
Transgenic expression of CCK2 receptors sensitizes murine pancreatic acinar cells to carcinogen‐induced preneoplastic lesions formation
Authors: Mathieu Anne , Clerc Pascal , Portolan Ghislaine , Bierkamp Christiane , Lulka Hubert , Pradayrol Lucien , Seva Catherine , Fourmy Daniel , Dufresne Marlène 
Published: February 2005

AbstractIn humans, initial events of pancreatic carcinogenesis remain unknown, and the question of whether this cancer, which has a ductal phenotype, exclusively arises from duct cells has been raised. Previous studies have demonstrated that transgenic expression of the CCK2 receptor in acinar cells of ElasCCK2 mice plays a role in the development of pancreatic neoplasia. The aim of our study was to examine initial steps of carcinogenesis in ElasCCK2 mice, adding a supplementary defect by using a chemical carcinogen, azaserine. Results of posttreatment sequential immunohistochemical examinations and quantifications demonstrate that mice responded to azaserine. Transition of acinar cells into duct‐like cells expressing Pdx1 and gastrin, as well as proliferation of acinar cells, were transiently observed in both transgenic and control mice. The carcinogen also induced formation of preneoplastic lesions, adenomas, exhibiting properties of autonomous growth. Importantly, expression of the CCK2 receptor increased the susceptibility of pancreas to azaserine. Indeed, treated ElasCCK2 mice exhibited larger areas of pancreatic acinar‐ductal transition, increased cellular proliferation as well as larger adenomas areas vs. control mice. These amplified responses may be related to auto/paracrine stimulation of CCK2 receptor by gastrin expressed in newly formed duct‐like cells. Our results demonstrate that activation of CCK2 receptor and azaserine result in cumulative effects to favor the emergence of a risk situation that is a potential site for initiation of carcinogenesis. © 2005 Wiley‐Liss, Inc.
Suppression of oncogenic NRAS by RNA interference induces apoptosis of human melanoma cells
Authors: Eskandarpour Malihe , Kiaii Shahryar , Zhu Chaoyong , Castro Juan , Sakko Andrew J. , Hansson Johan 
Published: February 2005

AbstractThe majority of human melanomas harbor activating mutations in either the BRAF or NRAS gene. To date, the role of oncogenic NRAS in melanoma remains poorly defined and no current therapies are directed at specifically suppressing oncogenic NRAS in human melanoma tumors. The aim of our study, therefore, was to investigate the effects of suppressing oncogenic NRAS in human melanoma cell lines in vitro. Using both small interfering RNA‐ and plasmid based‐RNA interference techniques, oncogenic NRAS was specifically suppressed in 2 human melanoma cell lines, 224 and BL, which harbor a codon 61 CAA (glutamine) to CGA (arginine) NRAS mutation. Suppression of oncogenic NRAS in these cell lines resulted in increased apoptosis. Furthermore, in 224 cells we demonstrated decreased phosphorylation of extracellular signal‐regulated kinase (ERK) and Akt, and reduced expression of NF‐κB and cyclin D1 in the N‐Ras signaling pathway. In contrast, RNA interference directed at wild‐type (WT) NRAS had no significant effect on apoptosis of 224 cells or 2 human melanoma cell lines (A375 and 397) containing WT NRAS but a codon 600 GTG (valine) to GAG (glutamate) mutation in BRAF. These data suggest that oncogenic NRAS is important for avoidance of apoptosis in melanomas that harbor the codon 61 NRAS mutation and emphasizes oncogenic NRAS as a therapeutic target in patients with tumors that harbor this mutation. © 2005 Wiley‐Liss, Inc.
Evidence for inactivation of distinct telomerase repressor genes in different types of human cancers
Authors: Tanaka Hiromi , Horikawa Izumi , Barrett J. Carl , Oshimura Mitsuo 
Published: February 2005

AbstractTelomerase activation, a critical event in human carcinogenesis, may result from defects in telomerase‐repressing mechanisms. Data from microcell‐mediated chromosome transfer (MMCT) suggests the presence of telomerase repressor genes that become inactivated during carcinogenic processes. The transfer of a normal human chromosome 3 represses telomerase activity of both human renal cell carcinoma (RCC) and breast carcinoma (BC) cells. For a genetic complementation analysis of telomerase repression, 2 RCC cell lines (KC12 and RCC23) and a BC cell line (21NT) were used to make somatic cell hybrids. All of the self‐hybrids (KC12×KC12 and 21NT×21NT) and hybrids from 2 RCC cell lines (KC12×RCC23) expressed the telomerase activity similarly to their parental cells, excluding the possibility of a ploidy‐associated change in telomerase activity and suggesting the same genetic defect shared by the 2 RCC cell lines. In contrast, the fusion of BC and RCC cells (21NT×KC12 and 21NT×RCC23) produced a significant number of telomerase‐negative hybrids, suggesting that the RCC and BC cells have different defects in the telomerase repression, which are functionally corrected through genetic complementation in the hybrids. This notion was supported by the mapping of the RCC telomerase repressor gene to a 5.7‐Mb region on 3p21, which is different from the candidate region for the BC telomerase repressor gene on the same chromosomal band. These findings provide direct evidence for inactivation of distinct telomerase repressor genes in different types of human cancers and may have implications in the tissue‐specific regulation of telomerase during human development and carcinogenesis. © 2005 Wiley‐Liss, Inc.
Cancer risk to the gastric corpus in Japanese, its correlation withinterleukin‐1βgene polymorphism (+3953*T) and Epstein‐Barr virus infection
Authors: Sakuma Kazuya , Uozaki Hiroshi , Chong Ja‐Mun , Hironaka Mitsugu , Sudo Makoto , Ushiku Tetsuo , Nagai Hideo , Fukayama Masashi 
Published: February 2005

AbstractPolymorphisms ofinterleukin‐1 (IL‐1)genes have been reported to modify the risk of gastric carcinoma (GC) in Caucasians. The significance ofIL‐1βgene polymorphisms was evaluated in Japanese GC patients with or without infection ofHelicobacter pyloriand Epstein Barr virus (EBV) with special reference to the topographic features of GC.IL‐1βgene polymorphisms at positions ‐511 and +3953 were evaluated by PCR‐RFLP and a penta‐allelic polymorphism ofIL‐1RAby PCR in healthy controls (n= 103) and GC (n=140; corpus 95, antrum 45). EBV‐infection was determined in the neoplastic tissues byEBER1 in situhybridization, andH. pyloriinfection in nonneoplastic gastric mucosa by PCR targeting of theH. pylori urease Agene. GC consisted of EBV‐associated (n= 24) and EBV‐negative (n= 116) patients, whereasH. pyloriinfection was positive in 130 cases. AmongIL‐1βgene polymorphisms, genotypeIL‐1β+3953 C/T was more frequent in the EBV‐negative (21%) and corpus GC (23%) patients, compared to the controls (10%), respectively, although there was no genotypeIL‐1β+3953 T/T in either group. Thus, the effect ofIL‐1β+3953 T was statistically significant in logistic regression models adjusted for age in EBV negativity (odds ratio [OR] 2.27, 95% confidence interval [CI] 1.02–5.05) and in the corpus GC (2.70, 1.19–6.12) with highest OR 3.55 (1.54–8.23) in EBV‐negative corpus GC. There was no significant influence ofIL‐1gene polymorphism in EBV‐associated GC, but it occurred predominantly in the corpus (24/24) compared to EBV‐negative GC (71/116) (p= 0.00002). There was no correlation betweenH. pyloriinfection andIL‐1gene polymorphism in GC. The cancer risk of the gastric corpus in Japanese is influenced byIL‐1β+3953 polymorphisms. On the other hand, the risk of EBV‐associated GC, which occurs predominantly in the corpus, is not influenced by this pro‐inflammatory polymorphism. © 2005 Wiley‐Liss, Inc.
Virus target cell conditioning model to explain some epidemiologic characteristics of childhood leukemias and lymphomas
Authors: zur Hausen Harald , de Villiers Ethel‐Michele 
Published: February 2005

AbstractFrequent infections in early childhood, whole‐day care and a socially unprivileged environment have been reported as protective factors for childhood leukemias and lymphomas. Conversely, a protected social environment, higher level of education and growing up in families with a low number of children are considered as risk factors. Additional risk factors involve agricultural occupation of the parents and exposure to several other occupational factors. These data led to a number of hypotheses that attempted to explain the epidemiologic observations; however, a number of questions are still open. Here we propose a new concept that could explain most of the epidemiologic characteristics. This concept is based on the assumption that persistent infections with TT virus‐like agents increase the risk for specific chromosomal translocations. This risk should correlate with the viral load. Interferon induction by intermittent infections should reduce the viral load and thus decrease the risk for chromosomal modifications. Some virologic observations in support of this model are presented. © 2005 Wiley‐Liss, Inc.
Structures and electron affinities of the di‐arsenic fluorides As2Fn/As2F (n = 1–8)
Authors: Kasalová Veronika , Schaefer Henry F. 
Published: February 2005

AbstractDevelopments in the preparation of new materials for microelectronics are focusing new attention on molecular systems incorporating several arsenic atoms. A systematic investigation of the As2Fn/As2F systems was carried out using Density Functional Theory methods and a DZP++ quality basis set. Global and low‐lying local geometric minima and relative energies are discussed and compared. The three types of neutral‐anion separations reported in this work are: the adiabatic electron affinity (EAad), the vertical electron affinity (EAvert), and the vertical detachment energy (VDE). Harmonic vibrational frequencies pertaining to the global minimum for each compound are reported. From the first four studied species (As2Fn, n = 1–4), all neutral molecules and their anions are shown to be stable with respect to AsAs bond breaking. The neutral As2F molecule and its anion are predicted to have Cs symmetry. We find the trans FAsAsF isomer of C2h symmetry and a pyramidalized vinylidene‐like AsAsF isomer of Cs symmetry to be the global minima for the As2F2 and As2F species, respectively. The lowest lying minima of As2F3 and As2F are vinyl radical‐like structures FAsAsF2 of Cs symmetry. The neutral As2F4 global minimum is a trans‐bent (like Si2H4) F2AsAsF2 isomer of C2 symmetry, while its anion is predicted to have an unusual fluorine‐bridged (C1) structure. The global minima of the neutral As2Fn species, n = 5–8, are weakly bound complexes, held together by dipole–dipole interactions. All such structures have the AsFmAsFn form, where (m,n) is (2,3) for As2F5, (3,3) for As2F6, (4,3) for As2F7, and (5,3) for As2F8. For As2F8 the beautiful pentavalent F4AsAsF4 structure (analogous to the stable AsF5 molecule) lies about 30 kcal/mol above the AsF3 · · · AsF5 complex. The stability of AsF5 depends crucially on the strong AsF bonds, and replacing one of these with an AsAs bond (in F4AsAsF4) has a very negative impact on the molecule's stability. The anions As2F, n = 5–8, are shown to be stable with respect to the AsAs bond breaking, and we predict that all of them have fluorine‐bridged or fluorine‐linked structures. The zero‐point vibrational energy corrected adiabatic electron affinities are predicted to be 2.28 eV (As2F), 1.95 eV (As2F2), 2.39 eV (As2F3), 1.71 eV (As2F4), 2.72 eV (As2F5), 1.79 eV (As2F6), 5.26 eV (As2F7), and 3.40 eV (As2F8) from the BHLYP method. Vertical detachment energies are rather large, especially for species with fluorine‐bridged global minima, having values up to 6.45 eV (As2F7, BHLYP). © 2005 Wiley Periodicals, Inc. J Comput Chem 26: 411–435, 2005