bluuebunny/crossref_metadata_2025_split huggingface dataset:
Reactivity of Polyiodides Towards 1,3‐Bis(4‐pyridyl)propane (bpp): A New CuI Cluster Polycatenane Framework and a Novel 2D AgI Cluster Motif
Authors: Niu Yunyin , Song Yinglin , Zhang Ning , Hou Hongwei , Che Deji , Fan Yaoting , Zhu Yu , Duan Chunying 
Published: March 2006

AbstractThe solution‐phase reactions of metal iodides or iodine with 1,3‐bis(4‐pyridyl)propane (bpp) yields four new organic–inorganic hybrid frameworks, namely [(CuI)4(bpp)4]n(1), [(AgI)6(bpp)]n (2), [PbI2(bpp)]n (3), and [I3(bppH)] (4), each of which adopts a different structural motif. For example, complex 1 is a 2D “open” coordination polymeric cluster consisting of a CuI2Cu rhomboid cluster core coordinated by anti‐anti and anti‐gauche bpp interactions to produce an interpenetrating 2D (4,4) polycatenane net; 2 is a novel bpp inclusion compound with a unique 2D polymeric hexagonal prism‐shaped [Ag6I6]n cluster motif; compound 3 is also a 2D “open” supramolecular cluster made from [PbI2]n “ribbons” and bpp bridges; compound 4 is a triiodide made up of organic [bppH]+ cations and a I3– anion chain. The clusters 1–3 obtained from the reaction between polyiodide complexes and an organic ligand suggest that this simple synthetic approach is likely to be applicable to the construction of polymeric clusters. The third‐order NLO effects of 1 were studied by Z‐scan techniques. The polymeric cluster exhibits good nonlinearities and the effective third‐order NLO refractive index (n2) value is 2.56 × 10–12 esu which is comparable to those of most cluster monomers and polymers. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
Hydrogen Bonding and Proton Transfer to the Trihydride Complex [Cp*MoH3(dppe)]: IR, NMR, and Theoretical Investigations
Authors: Belkova Natalia V. , Revin Pavel O. , Besora Maria , Baya Miguel , Epstein Lina M. , Lledós Agustí , Poli Rinaldo , Shubina Elena S. , Vorontsov Evgenii V. 
Published: March 2006

AbstractThe interaction between [Cp*MoH3(dppe)] (dppe = Ph2PCH2CH2PPh2) and a variety of proton donors hasbeen investigated by a combination of experiments andDFT calculations. Weak proton donors [2‐monofluoroethanol (MFE) and trifluoroethanol (TFE)] allow the determination of basicity factor (Ej = 1.42 ± 0.02) and thermodynamicparameters for the hydrogen bond formation (ΔHHB =–4.9 ± 0.2 and –6.1 ± 0.3 kcal mol–1; ΔSHB = –15.7 ± 0.7 and–20.4 ± 1 cal mol–1 K–1 for MFE and TFE, respectively). For TFE, a stable low‐temperature proton‐transfer equilibrium (220–240 K) with the cationic classical tetrahydrido derivative [Cp*MoH4(dppe)]+ could be investigated independently by UV/Vis (ΔH°PT = –2.8 ± 0.4 kcal mol–1 and ΔS°PT =–15 ± 2 cal mol–1 K–1) and 1H NMR (ΔH°PT = –2.7 ± 0.5kcal mol–1 and ΔS°PT = –11 ± 2 cal mol–1 K–1) spectroscopy. Upon warming, however, the tetrahydride evolves by dihydrogen loss and formation of a hydride‐free diamagnetic product. Stronger proton donors [hexafluoroisopropanol (HFIP), p‐nitrophenol (PNP), perfluoro‐tert‐butyl alcohol (PFTB), and HBF4·OEt2] lead to more extensive proton transfer at lower donor/Mo ratios. A 1:1 proton‐transfer stoichiometry is indicated independently by a titration experiment with UV/Vis monitoring for the [Cp*MoH3(dppe)]–PNP reaction, and by a stopped‐flow kinetics investigation for the [Cp*MoH3(dppe)]–HFIP reaction. For all proton‐transfer processes investigated, the classical tetrahydrido cation forms directly, without the observation of a nonclassical intermediate. DFT calculations have been carried out on the interaction between TFE and HFIP and the model compound [CpMoH3(dpe)] (dpe = H2PCH2CH2PH2) both in the gas phase and in CH2Cl2 solvent with the polarizable continuum model and, to a more limited extent, on the full [Cp*MoH3(dppe)] system. A detailed comparison of the observed and calculated frequency shifts for the M–H vibrations is presented. The calculations have explored therelative energy and geometry of various configurations involving either a hydride ligand or the metal as the principal proton‐accepting site. They have also probed two principal proton‐transfer pathways, leading to the unobserved nonclassical intermediate and to the observed classical product. From these studies, it appears that a nonclassical intermediate may be obtained by a kinetically controlled proton transfer to a hydride site, followed by an intramolecular rearrangement through a very low energy barrier. However, a competitive low‐energy pathway for direct proton transfer at the metal site is also revealed by the calculations. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
Basicity of Amines in the Gas Phase – Analysis of the Base‐Strengthening Effect of an N‐Trityl Group by Use of a Triadic Formula
Authors: Vianello Robert , Maskill Howard , Maksić Zvonimir B. 
Published: March 2006

AbstractAn ab initio theoretical method based on a triadic formula has been employed to calculate changes in proton affinities (PAs) after sequential substitution of C–H by C–phenyl in methylamine and in the N‐methyl component of N‐methylacetamide. The overall objective was to investigate the cause of the recently reported unexpected basicity‐enhancing effect of the N‐trityl group in several amines and in acetamide. The triadic method indicates that the increase in PA from NH3 to CH3NH2 is principally due to destabilisation of the lone pair, compensated to some degree by a smaller bond energy term. The increasing PAs along the series CH3NH2, PhCH2NH2, Ph2CHNH2 and Ph3CNH2 are mainly due to an increasing relaxation energy effect following increasing phenyl substitution, supported by increasing bond energy terms. Introduction of para‐methoxy substituents in tritylamine would be calculated to result in small incremental increases in PA, in agreement with experimental findings. The PA of tricyclohexylmethylamine (233.6 kcal·mol–1) is calculated to be similar to that of trimethoxytritylamine (233.5 kcal·mol–1), a consequence of the destabilisation of the lone pair on nitrogen by the three bulky cyclohexyl groups. Results for acetamide indicate that protonation on oxygen is more favourable than on nitrogen, which supports the intuitive argument that conventional π‐electron resonance stabilisation of the O‐protonated cation should be appreciably greater than hyperconjugative stabilisation of the N‐protonated isomer. The increase in PA along the series MeCONHCH3, MeCONHCH2Ph, MeCONHCHPh2 and MeCONHCPh3 parallels the increase from CH3NH2 to Ph3CNH2 and is again principally a consequence of the increasing relaxation energies, which dominate the negative bond energy term contributions. Prior to protonation, the nitrogen atom of MeNHAc is perfectly planar, consistently with resonance delocalisation of the nitrogen lone pair into the carbonyl group. In contrast, there is a 6.5 % degree of pyramidalisation at the nitrogen in TrNHAc [calculated at the B3LYP/6‐31G(d) level], indicating a reduced resonance interaction due to steric crowding, in support of a previous suggestion. Finally, the computed PAs and predicted first adiabatic ionisation energies are in satisfactory agreement with experimental results where these are available.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
Synthesis of Pyrazoles by Treatment of 3‐Benzylchromones, 3‐Benzylflavones and Their 4‐Thio Analogues with Hydrazine
Authors: Lévai Albert , Silva Artur M. S. , Cavaleiro José A. S. , Alkorta Ibon , Elguero José , Jekő József 
Published: March 2006

AbstractThe synthesis of pyrazoles 13–24 has been accomplished by treatment of 3‐benzylchromones 1–5, 3‐benzylflavones 6–12 and their 4‐thio analogues 25–29 with hydrazine hydrate in hot pyridine. A plausible reaction mechanism for the formation of pyrazoles 13–24 is discussed. A 1H NMR study in [D6]DMSO allowed the presence of both pyrazole annular tautomers to be observed, due to the presence of intramolecular hydrogen bonds in each tautomer (OH‐‐N and NH‐‐O). GIAO/B3LYP/6‐311++G** calculations were carried out on some model pyrazoles to provide a theoretical basis for the NMR experimental observations.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
Access to Variously Substituted 5,6,7,8‐Tetrahydro‐3H‐quinazolin‐4‐ones via Diels–Alder Adducts of Phenyl Vinyl Sulfone to Cyclobutene‐Annelated Pyrimidinones
Authors: Dalai Suryakanta , Belov Vladimir N. , Nizamov Shamil , Rauch Karsten , Finsinger Dirk , de Meijere Armin 
Published: March 2006

AbstractUnder basic conditions (Et3N, dioxane), the aromatic amidines 4 and also S‐methylisothiourea 4g cleanly undergo Michael addition to methyl 2‐chloro‐2‐cyclopropylideneacetate (5), followed by intramolecular nucleophilic substitution, cyclopropyl to cyclobutyl ring enlargement, deprotonation and cyclization with elimination of methanol to afford the cyclobutene‐annelated pyrimidinones 6 in 43–83 % yield (7 examples). Thermal cyclobutene‐ring opening of the latter at 175 °C followed by regioselective Diels–Alder cycloaddition with phenyl vinyl sulfone gives the 2‐aryl‐6‐(phenylsulfonyl)‐5,6,7,8‐tetrahydroquinazolinone derivatives 12 in 39–83 % yield (7 examples). Base‐induced elimination of benzenesulfinic acid and subsequent catalytic hydrogenation leads to the 2‐aryltetrahydroquinazolinone derivatives 14 in excellent yields (6 examples). Deprotonation at the sulfonyl‐substituted center, alkylation and subsequent elimination of benzenesulfinic acid followed by catalytic hydrogenation gives the 2,6‐disubstituted tetrahydroquinazolinones 17a‐R. Nucleophilic substitution of the methylthio group in 12g by secondary amines yields the 2‐(dialkylamino)tetrahydroquinazolinones 14i–k.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
Star‐Shaped Push‐Pull Compounds Having 1,3,5‐Triazine Cores
Authors: Meier Herbert , Karpuk Elena , Christof Holst Hans 
Published: March 2006

AbstractThe 1,3,5‐triazines 9–11 having OPV chains in the 2‐, 4‐ and 6‐position represent star‐shaped compounds which exhibit strong push‐pull effects. Their long‐wavelength absorption S0 → S1 is characterized by an intramolecular charge transfer (ICT) from the dialkylamino group as electron donor D via the conjugated chain to the 1,3,5‐triazine core as electron acceptor A. Protonation of the dialkylamino group removes the donor capability, whereas protonation of the 1,3,5‐triazine ring enhances the acceptor strength. Thus, the prevailing protonation site has a crucial influence on the push‐pull effect and the ICT. The transition energies ΔE (S0 → S1) pass through a minimum for the second generation 10 in the electroneutral series 9–11; on the contrary they pass through a maximum for 10b in the protonated series 9a, 10b, 11b. These unexpected results are explained by the superposition of different effects, namely the extension of the conjugation from 9 to 11, the decreasing ICT for growing distances of D and A, the aggregation, and the positions of the protonation in the presence of increasing amounts of CF3COOH. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
Enantiodifferentiation of Aliphatic Ethers by the Dirhodium Method
Authors: Díaz Gómez Edison , Albert Dieter , Duddeck Helmut , Kozhushkov Sergei I. , de Meijere Armin 
Published: March 2006

AbstractThe enantiomers of chiral aliphatic ethers can easily bedifferentiated by the dirhodium method, i.e. by 1H and13C NMR spectroscopy in the presence of the chiral auxiliary Rh2[(+)‐MTPA]4. This is the first direct chiral recognitionby spectroscopic methods in this class of ligand compounds. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
Intermolecular [4+2] Cycloadditions of a Reactive Cyclopentadienone
Authors: Harmata Michael , Gomes Maria G. 
Published: March 2006

AbstractA reactive cyclopentadienone gives Diels–Alder cycloadducts with a variety of dienes in high yield and often with extremely high levels of regio‐ and stereoselectivity. The high degree of generality of this reaction suggests it will be of use in organic synthesis. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)
Transformation of tertiary butyl mercaptan in aerobic environments
Authors: Kalainesan S. , Erickson L.E. , Hutchinson S.L.L. , Urban J.E. , Karthikeyan R. 
Published: March 2006

AbstractTertiary butyl mercaptan (TBM) is a malodorant that is added to natural gas in small quantities to aid in its detection. The objective of this study was to investigate the degradation of TBM under aerobic conditions.A bacterial culture was found that grew well on TBM in liquid minimal media under aerobic conditions. The doubling time was about 98 h at 30° C. In cultures where iron fillings were added, the growth rate increased and the doubling time was 44 h. In studies with manganese dioxide and potassium permanganate, TBM was oxidized chemically at rates that were rapid compared to those in the microbiological studies.Soil microcosms containing soil, water, and TBM were set up using two different soils and their headspace was sampled during a 62‐day period of study. In the first set, there was significantly greater reduction in TBM and production of carbon dioxide in the treatments compared to that of the sterilized controls. An intermediate product di‐tertiary‐butyl disulfide (DTBD) was identified. The experimental results show that TBM appears to be biodegradable in soil–water systems under aerobic conditions. © 2006 American Institute of Chemical Engineers Environ Prog, 2006
Motivation and synthesis of the FIAC experiment: Reproducibility of fMRI results across expert analyses
Authors: Poline Jean‐Baptiste , Strother Stephen C. , Dehaene‐Lambertz Ghislaine , Egan Gary F. , Lancaster Jack L. 
Published: March 2006

AbstractThe Functional Imaging Analysis Contest (FIAC) culminated in the FIAC Workshop held at the 11th Annual Meeting of the Organization for Human Brain Mapping in Toronto in 2005. This special issue summarizes various analyses used by contestants with a single functional magnetic resonance imaging (fMRI) study, a cortical‐language study using sentence repetition. The results from the cognitive neuroscientists who developed the test‐base language study, and report their data analysis, are complemented by expert analyses of the same test‐base data by most of the major groups actively developing fMRI software packages. Analyses include many variants of the general linear model (GLM), cutting‐edge spatial‐ and temporal‐wavelets, permutation‐based, and ICA approaches. A number of authors also include surface‐based approaches. Several articles describe the important emerging areas of diagnostics for GLM analysis, multivariate predictive modeling, and functional connectivity analysis. While the FIAC did not achieve all of its goals, it helped identify new activation regions in the test‐base data, and more important, through this special issue it illustrates the significant methods‐driven variability that potentially exists in the literature. Variable results from different methods reported here should provide a cautionary note and motivate the Human Brain Mapping community to explore more thoroughly the methodologies they use for analyzing fMRI data. Hum Brain Mapp 27:351–359, 2006. © 2006 Wiley‐Liss, Inc.
Phosphorylation of the neural cell adhesion molecule on serine or threonine residues is induced by adhesion or nerve growth factor
Authors: Matthias Stephanie , Horstkorte Rüdiger 
Published: March 2006

AbstractThe neural cell adhesion molecule (NCAM) is a member of the immunoglobulin superfamily and plays a crucial role during development and regeneration. It is expressed in three major isoforms; two of them with intracellular domains of different length and one without any intracellular domain. NCAM is known to be phosphorylated and contains up to 49 serine or threonine residues, which could be phosphorylated. However, the impact of NCAM phosphorylation is still unclear. Here we describe NCAM being phosphorylated during neuronal differentiation of PC12 cells. We provide evidence that protein kinase C is involved in the phosphorylation of NCAM. In agreement with our earlier observation that the protein phosphatase 1 is associated with NCAM, we additionally found that NCAM is a substrate for the protein phosphatase 1 but not for the protein phosphatase 2A. © 2006 Wiley‐Liss, Inc.
Functional expression of A glutamine transporter responsive to down‐regulation by lipopolysaccharide through reduced promoter activity in cultured rat neocortical astrocytes
Authors: Ogura Masato , Nakamichi Noritaka , Takano Katsura , Oikawa Hirotaka , Kambe Yuki , Ohno Yu , Taniura Hideo , Yoneda Yukio 
Published: March 2006

AbstractThe prevailing view is that the glutamine (Gln) transporter (GlnT/ATA1/SAT1/SNAT1) is a member of the system A transporter superfamily with the ability to fuel the glutamate/Gln cycle at nerve terminals in glutamatergic neurons. Semiquantitative reverse transcription‐polymerase chain reaction revealed similarly high expression of mRNA for GlnT by rat brain neocortical astrocytes as well as neurons, with progressively lower expression by cerebellar astrocytes, hippocampal astrocytes, and whole‐brain microglia in culture. [3H]Gln was accumulated in a temperature‐dependent manner with a saturable profile in both cultured neocortical neurons and astrocytes, whereas biochemical and pharmacological analyses on [3H]Gln accumulation revealed the expression of both system A and system L transporters by cultured neocortical neurons and astrocytes. Exposure to lipopolysaccharide (LPS) for 24 hr resulted in a significant decrease in both GlnT mRNA expression and [3H]Gln accumulation, with a concomitant drastic increase in nitrite formation in cultured neocortical astrocytes. Moreover, LPS significantly inhibited the promoter activity of GlnT in the astrocytic cell line C6 glioma cells as well as primary rat neocortical astrocytes in culture. These results suggest that activation by LPS would lead to down‐regulation of the expression of GlnT responsible for the incorporation of extracellular Gln into intracellular spaces across plasma membranes through the inhibition of its promoter activity in cultured rat neocortical astrocytes. © 2006 Wiley‐Liss, Inc.
Genetically modified bone morphogenetic protein signalling Alters traumatic brain injury‐induced gene expression responses in the adult mouse
Authors: Israelsson Charlotte , Lewén Anders , Kylberg Annika , Usoskin Dmitry , Althini Susanna , Lindeberg Jonas , Deng Chu‐Xia , Fukuda Tomokazu , Wang Yun , Kaartinen Vesa , Mishina Yuji , Hillered Lars , Ebendal Ted 
Published: March 2006

AbstractThree genetic mouse models were examined to define effects of bone morphogenetic protein (BMP) signalling on gene expression in normal and injured adult brain. CaMKII‐Cre eliminated the BMP receptor Acvr1 (Alk2) and the common TGFβ superfamily signal mediator Smad4 or activated a constitutively active Acvr1 in postnatal forebrain neurons. All mutants followed mendelian ratios, with no overt phenotypic changes. In situ hybridization demonstrated normal patterns of the dendritic marker MAP2 (Mtap2) throughout cortex despite neuron‐specific losses of Acvr1 or Smad4. However, strong up‐regulation of Mtap2 transcript in these mice was found by quantitative RT‐PCR (qRT‐PCR), indicating that Mtap2 is normally suppressed by BMP. Traumatic brain injury (TBI) resulted in increases of histone‐associated DNA fragments in both control and Smad4‐deficient cortex. Several cell‐type‐specific transcripts known to be involved in injury‐related responses were measured by qRT‐PCR. Gfap mRNA was strongly up‐regulated in controls as well as in the loss‐of‐BMP‐signalling mutants. Notably, activated Acvr1 signalling gave significantly lower TBI‐induced up‐regulations of Gfap and Phox2a mRNA levels, indicating reductions in astroglial and neuronal reactions to injury. Strong impairment in injury‐induced Timp1 transcript up‐regulation was also seen in these mice. In contrast, osteopontin (Spp1) transcript levels in activated microglia were not reduced by Acvr1 signalling. Altogether, the data suggest that BMP signalling is dispensable in adult cortical neurons but that augmented BMP signalling affects molecular changes associated with neuronal lesions. © 2006 Wiley‐Liss, Inc.
Hyaluronic acid attenuates osteoarthritis development in the anterior cruciate ligament‐transected knee: Association with excitatory amino acid release in the joint dialysate
Authors: Jean Yen‐Hsuan , Wen Zhi‐Hong , Chang Yi‐Chen , Lee Herng‐Sheng , Hsieh Shih‐Peng , Wu Ching‐Tang , Yeh Chun‐Chang , Wong Chih‐Shung 
Published: March 2006

AbstractWe previously reported increased release of the excitatory amino acid (EAA) neurotransmitters, glutamate and aspartate, during the early stage of experimental osteoarthritis (OA). Our present objective was to study the effect of intraarticular injection of hyaluronic acid (HA) on OA development, and to analyze concomitant changes in EAA levels in dialysates of anterior cruciate ligament‐transected (ACLT) knee joints. OA was induced in Wistar rats by ACLT of one hindlimb; the knee of the other hindlimb was used as the sham‐operated control. HA group (n = 12) were injected intraarticularly in the ACLT knee with 1 mg of HA once a week for 5 consecutive weeks, starting at 8 weeks after surgery. Saline group (n = 12) were injected as above with normal saline. The sham‐operated group, underwent arthrotomy, but not ACLT, and received no treatment (n = 14). Twenty weeks after surgery, knee joint dialysates were collected by microdialysis and EAA levels assayed by high‐performance liquid chromatography, and gross morphological examination and histopathological evaluation were performed on the medial femoral condyles and synovia. Rats receiving intraarticular HA injections showed a significantly lower degree of cartilage degeneration on the medial femoral condyle at both the macroscopic level and on the Mankin grading scale than rats receiving saline injections. Intraarticular HA treatment also suppressed synovitis. Moreover, glutamate and aspartate levels were significantly reduced in the HA group compared to the saline group. Intraarticular injection of HA limits articular cartilage and synovium damage and OA formation, and, in parallel, reduces EAA levels in ACLT joint dialysates. This study suggests that the underlying mechanism of the anti‐inflammatory effect of HA is to inhibit glutamate and aspartate release in ACLT knee joints, which attenuates the early development of OA. © 2006 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res
Chondrocyte gene expression in osteoarthritis: Correlation with disease severity
Authors: Eid Karim , Thornhill Thomas S. , Glowacki Julie 
Published: March 2006

AbstractOsteoarthritis is characterized by a progressive degradation of cartilage structure and function. This study tests the hypothesis that disease severity is characterized by alterations in expression of cartilage‐specific genes for aggrecan and collagen type II. Cartilage, discarded from six subjects undergoing knee replacement, was subdivided into homogeneous portions by the surgeon according to the Outerbridge classification. For four subjects, it was possible to separate the tissue into two or three fractions with different disease severity. Portions of each sample were prepared either for histological analysis and ranking according to the Mankin system or for RNA extraction. Quantitative, competitive RT‐PCR assays were used for measurement of mRNA for aggrecan, collagen type II, and glyceraldehyde‐3‐phosphate dehydrogenase. Clinical grading was correlated with histological score (Spearman r = 0.60, p = 0.043). There was a striking decrease in expression of aggrecan and collagen II that was correlated with increase in the grade in regions of cartilage within an individual subject. In the series of 12 samples, there was an inverse correlation between aggrecan expression and osteoarthritis grade (Spearman r = −0.59, p = 0.042). In conclusion, there was an inverse relationship between regional disease severity in osteoarthritis and expression of aggrecan. Use of quantitative, competitive RT‐PCR is practical for assessment of chondrocyte gene signatures. © 2006 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res