bluuebunny/crossref_metadata_2025_split huggingface dataset:
Gap junctional intercellular communication capacity by gap‐FRAP technique: A comparative study
Authors: Abbaci Muriel , Barberi‐Heyob Muriel , Stines Jean‐René , Blondel Walter , Dumas Dominique , Guillemin François , Didelon Jacques 
Published: January 2007

AbstractGap junctions play an important role in vital functions, including the regulation of cell growth and cell differentiation. Connexins 43 (Cx43) are the most widely expressed gap junction proteins. Cellular localization of phosphorylated Cx43 has been implicated in the capacity of gap junctional intercellular communication (GJIC). To follow the functionality of GJIC of different cell types, in monolayer cultures, characterized by different patterns of phosphorylated Cx43, we used a fluorescence recovery after photobleaching (FRAP) technique, and compared two tracers, 5(6)‐carboxyfluorescein diacetate (CFDA) and calcein acetoxymethylester (AM). The GJIC capacity was quantified by estimating fluorescence redistribution parameters. The functionality of GJIC was in relation with the staining localization of phosphorylated Cx43 to the cell–cell contact areas, corresponding to gap junctions between contacting cells. GJIC involvement in fluorescence restitution after photobleaching was checked by a gap junction channel inhibition assay. We demonstrated that the choice of the dye did not significantly influence the fluorescence recovery percentages despite a cell line‐dependent CFDA release, whereas it had an important impact on fluorescence kinetic profiles. This study reinforces the interest of the gap‐FRAP approach to quantify modifications in the functionality of gap junctions and, above all, argues about the limits of CFDA for 3‐D future approaches.
Self‐Assembly of Semifluorinated Minidendrons Attached to Electron‐Acceptor Groups into Pyramidal Columns
Authors: Percec Virgil , Aqad Emad , Peterca Mihai , Imam Mohammad R. , Glodde Martin , Bera Tusha K. , Miura Yoshiko , Balagurusamy Venkatachalapathy S. K. , Ewbank Paul C. , Würthner Frank , Heiney Paul A. 
Published: January 2007

AbstractThe synthesis and self‐assembly of twelve semifluorinated first‐generation dendrons or minidendrons attached to electron‐acceptor (n‐type) groups generated from various combinations of eight acceptors and three dendrons are reported. Dendrons attached to small electron‐acceptor molecules mediate their self‐assembly into π‐stacks located in the center of a supramolecular helical pyramidal column with the long axis of the acceptor perpendicular to the long axis of the column. Dendrons attached to large electron‐acceptor molecules, such as perylene bisimide, mediate the assembly of their acceptors in an unprecedented arrangement of π‐stacks that have the long axis of the acceptors parallel to the long axis of the supramolecular pyramidal column. All supramolecular columns self‐organize into various periodic columnar arrays that exhibit liquid‐crystalline phases, crystalline phases, or a liquid‐crystalline phase with enhanced intracolumnar order. The present study demonstrates the simplicity and the versatility of the concept of assembly of n‐type electroactive groups mediated by semifluorinated dendrons and assesses the scope and limitations of this supramolecular strategy.
First‐Principles Molecular Dynamics Evaluation of Thermal Effects on the NMR 1JLi,C Spin–Spin Coupling
Authors: de la Lande Aurélien , Fressigné Catherine , Gérard Hélène , Maddaluno Jacques , Parisel Olivier 
Published: January 2007

AbstractCar–Parrinello (CP) molecular dynamics were applied to sample conformations of various models of organolithium aggregates which are chosen to estimate 1JLi,C NMR coupling constants. The results show that the deviations from the values computed using static (optimized) geometries are small provided no large‐amplitude motions occur within the timescale of the simulations. In the case of the vinyllithium dimer, for which rotation of the vinyl chain is observed, this approach allows analysis of the various contributions to the experimentally measured constants. For the trisolvated methyllithium monomer, partial decoordination of solvating dimethyl ether is observed and results in a significant shift of 1JLi,C. All these results highlight that a varied physicochemical machinery is hidden behind general empirical formulas, such as the Bauer–Winchester–Schleyer rule used experimentally.
The Supramolecular Helical Architecture of 8‐Oxoinosine and 8‐Oxoguanosine Derivatives
Authors: Lena Stefano , Cremonini Mauro A. , Federiconi Francesco , Gottarelli Giovanni , Graziano Carla , Laghi Luca , Mariani Paolo , Masiero Stefano , Pieraccini Silvia , Spada Gian Piero 
Published: January 2007

AbstractThe 8‐oxoguanosine derivative 1 and the 8‐oxoinosine derivative 2 b, with appropriate substituents on their ribose moieties, form hexagonal lyotropic mesophases in hydrocarbon solvents. Small‐angle X‐ray scattering analysis of a film of 1 and of the mesophase of 2 b, and NMR and CD spectra of isotropic solutions of 2 b, indicate that in both cases the supramolecular structures adopted are continuous helices formed by a hydrogen‐bond network between the heterocyclic bases. Notably, while derivative 2 b, which bears large substituents on its ribose moiety, undergoes self‐assembly and mesophase formation, oxoinosine 2 a, with only decanoyl groups on its ribose moiety, does not. This may be ascribed to the reduced amphiphilic properties of the latter and the absence of aromatic groups.
The First Pure ΛHT Rotamer of a Complex with a cis‐[Metal(nucleotide)2] Unit: A cis‐[Pt(amine)2(nucleotide)2] ΛHT Rotamer with Unique Molecular Structural Features
Authors: Benedetti Michele , Tamasi Gabriella , Cini Renzo , Marzilli Luigi G. , Natile Giovanni 
Published: January 2007

Abstractcis‐[PtA2(nucleotide)2] complexes (A2 stands for two amines or a diamine) have been extensively investigated as model compounds for key cisplatin–DNA adducts. All cis‐[metal(nucleotide/nucleoside)2] complexes with guanine and related purines characterized in the solid state thus far have the ΔHT conformation (head‐to‐tail orientation of the two bases and right‐handed chirality). In sharp contrast, the ΛHT conformation (left‐handed chirality) dominates in acidic and neutral aqueous solutions of cis‐[PtA2(5′‐GMP)2] complexes. Molecular models and solution experiments indicate that the ΛHT conformer is stabilized by 5′‐phosphate/N1H hydrogen‐bond interactions between cis nucleotides with the normal anti conformation. However, this evidence, while compelling, is indirect. At last, conditions have been defined to allow crystallization of this elusive conformer. The structure obtained reveals three unique features not present in all other cis‐[PtA2(nucleotide)2] solid‐state structures: a ΛHT conformation, very strong hydrogen‐bond interactions between the phosphate and N1H of cis nucleotides, and a very small dihedral angle between the planes of the two guanines lying nearly perpendicular to the coordination plane. These new results indicate that, because there are no local base–base repulsions precluding the ΛHT conformer, global forces rather than local interactions account for the predominance of the ΔHT conformer over the ΛHT conformer in the solid state and in both inter‐ and intrastrand HT crosslinks of oligonucleotides and DNA.
Analysis of Intramolecular Dynamic Processes in Enantiomeric Diaryl Atropisomers and Related Derivatives by 2H NMR Spectroscopy in Polypeptide Liquid Crystals
Authors: Lafon Olivier , Lesot Philippe , Fan Chun‐An , Kagan Henri B. 
Published: January 2007

AbstractWe demonstrate the analytical potential of 2H‐{1H} NMR spectroscopy in weakly ordering, chiral lyotropic liquid crystals made of poly(γ‐benzyl‐L‐glutamate) (PBLG) dissolved in chloroform or dichloromethane for investigating the intramolecular dynamic processes of four deuterated diaryls (derivatives of 1‐(4′‐methylphenyl)naphthalene). When the rotation of the aryl groups about the sp2sp2 bond is sufficiently slow relative to the NMR timescale, the method allows the spectral discrimination of enantiomeric atropisomers or enantiotopic directions in the prochiral derivatives. The effect of the position of substituents on the phenyl group on the conformational dynamics of these compounds has been examined as well as the nature of the organic co‐solvent. When coalescence phenomena are observed, simulation of the experimental 2H‐{1H} lineshapes using a formalism tailored for two deuterons undergoing mutual exchange allows the rate constants and the activation parameters for the internal rotation processes to be calculated. Experimental values of ΔH≠ have been compared with data evaluated by molecular modelling calculations and the activation parameters are discussed for the various compounds. It is shown that these polypeptide mesophases have no significant impact on the interconversion dynamics of these compounds. In contrast with the nematic thermotropic phases, Haller's equation cannot be used to predict the evolution of the quadrupolar splittings (ΔνQ values), and hence the order parameters, versus T in the PBLG mesophases. For these particular lyotropic systems, it is shown that an exponential function of the form ΔνQ[Hz]=C×exp (−E/RT[K]) provides excellent agreement between the experimental and expected ΔνQ values. Analysis of the results reported in this work suggests that orientation and chiral discrimination phenomena in these lyotropic solvents could be treated separately because they would involve different interaction mechanisms.
Synthesis and Structures of Cross‐Conjugated Bis‐dehydroannulenes with a Y‐Enediyne Motif and Different π Topologies
Authors: Bandyopadhyay Arkasish , Varghese Babu , Hopf Henning , Sankararaman Sethuraman 
Published: January 2007

AbstractA synthesis of cross‐conjugated bis‐dehydroannulenes with different topologies of the π electrons by CuII‐mediated oxidative coupling of the corresponding terminal acetylenic precursors is reported. In general, of the two possible modes of cyclization, which would yield either a [13]annulene or an [18]annulene, the precursors yielded exclusively the bis‐dehydro[13]annulenes. However, one example of the formation of a bis‐dehydro[18]annulene is also reported. The mode of cyclization to form either the [13]annulene or the [18]annulene is explained on the basis of the conformational preference of the core unit bearing the Y‐enediyne moieties. The structures of the two types of bis‐annulenes have been unequivocally established by means of single‐crystal X‐ray crystallographic analysis.
One‐Pot Solid‐Phase Glycoblotting and Probing by Transoximization for High‐Throughput Glycomics and Glycoproteomics
Authors: Shimaoka Hideyuki , Kuramoto Hiromitsu , Furukawa Jun‐ichi , Miura Yoshiaki , Kurogochi Masaki , Kita Yoko , Hinou Hiroshi , Shinohara Yasuro , Nishimura Shin‐Ichiro 
Published: January 2007

AbstractThe development of rapid and efficient methods for high‐throughput protein glycomics is of growing importance because the glycoform‐focused reverse proteomics/genomics strategy will greatly contribute to the discovery of novel biomarkers closely related to cellular development, differentiation, growth, and aging as well as a variety of diseases such as cancers and viral infection. Recently, we communicated that rapid and efficient purification of carbohydrates can be achieved by employing sugar‐specific chemical ligation with aminooxy‐functionalized polymers, which we termed “glycoblotting” (see S.‐I. Nishimura et al., Angew. Chem. 2005, 117, 93–98; Angew. Chem. Int. Ed. 2005, 44, 91–96). The chemoselective blotting of oligosaccharides present in crude biological materials onto synthetic polymers relies on the unique oxime‐bond formation between aminooxy group displayed on the supporting materials and aldehyde/ketone group at the reducing terminal of all oligosaccharides, thus enabling highly selective and rapid oligosaccharide purification. Aiming to improve the detection sensitivity of the released oligosaccharides, we introduce here a novel strategy for one‐pot solid‐phase glycoblotting and probing by transoximization. We found that oligosaccharides captured by the polymer supports via the oxime bond can be released in the presence of excess O‐substituted aminooxy derivatives in a weakly acidic condition. The released oligosaccharides could be recovered as newly formed oxime derivatives of the O‐substituted aminooxy compound added, thus demonstrating the simultaneous releasing and probing. In addition, we synthesized a novel aminooxy‐functionalized monomer, N‐[2‐[2‐(2‐tert‐butoxycarbonylaminooxyacetylamino‐ethoxy)ethoxy]ethyl]‐2‐methacrylamide, which allows for the large‐scale preparation of a versatile polymer characterized by its high stability, high blotting capacity, and easy use. The one‐pot protocol allowed to profile 23 kinds of N‐glycan chains of human serum glycoproteins. This concept was further applied for the glycopeptides analysis in a crude mixture followed by galactose oxidase treatment to generate free aldehyde group at the non‐reducing terminal of oligosaccharide moiety of glycopeptides. Our technique may be implemented in existing biochemistry and molecular diagnostics laboratories because enriched oligosaccharides and glycopeptides by solid‐phase transoximization with high‐sensitive labeling reagents are widely applicable in a variety of common analytical methods using two‐dimensional HPLC, LC/MS, and capillary electrophoresis as well as modern mass spectrometry.
Total Synthesis, Molecular Editing and Evaluation of a Tripyrrolic Natural Product: The Case of “Butylcycloheptylprodigiosin”
Authors: Fürstner Alois , Radkowski Karin , Peters Hartwig , Seidel Günter , Wirtz Conny , Mynott Richard , Lehmann Christian W. 
Published: January 2007

AbstractConflicting reports are found in the literature on whether the ortho‐pyrrolophane derivative 6, which has been named “butylcycloheptylprodigiosin” even though it is a cyclononane derivative, is a natural product or merely a mis‐assigned structure. This dispute has now been resolved by an unambiguous total synthesis of this complex alkaloid which confirms the initial structure assignment. The chosen approach is largely catalysis‐based, featuring the first application of a “Narasaka–Heck” reaction in natural product chemistry. This palladium‐catalyzed transformation allows the unsaturated oxime ester 26 to be converted into the bicyclic dihydropyrrole 27. Other notable reactions of the reported approach to 6 are a regioselective Tsuji–Trost reaction of the doubly allylic acetate 21 with methyl acetoacetate, a base‐induced aromatization of 27 to the corresponding pyrrole 28, a chemoselective oxidation of the benzylic methyl group in 33 with cerium ammonium nitrate in a biphasic reaction medium that does not affect the labile pyrrole nucleus, and a Suzuki cross‐coupling for the completion of the heterocyclic domain. Diversification in the latter step leads to a set of analogues that differ from the natural product in the terminal (hetero)arene ring. This structural modification results in complete loss of the very pronounced ability of the parent compound 6 to induce oxidative cleavage in double stranded DNA in the presence of CuII. Several cyclononane‐, cyclononene‐ and cyclononadiene derivatives prepared en route to 6 have been characterized by crystal structure analysis, allowing the conformational behavior of nine‐membered carbocycles to be studied.
Molecular dynamics study of the conformational dynamics and energetics of some large‐ring cyclodextrins (CDn, n = 24, 25, 26, 27, 28, 29)
Authors: Gotsev Martin G. , Ivanov Petko M. , Jaime Carlos 
Published: January 2007

AbstractMolecular dynamics simulations in water solution were performed on six large‐ring cyclodextrins (LR‐CDs) with a degree of polymerization 24, 25, 26, 27, 28, and 29. The AMBER parm99 force field and explicit water molecules (TIP3P) were used in the simulations. The present research was aimed at further extending our knowledge on the structural dynamics and the energetics of this new class of compounds that may eventually provide chiral cavities suitable for formation of inclusion complexes with small molecules, and, accordingly, to serve as host structures for chiral recognition. The study focused on several representatives flanking CD26—the largest LR‐CD for which X‐ray data is available. Both the monitoring of the structural variations during the simulations as well as the analyses of energy balances are indicative for high flexibility of the macrorings. Slight differences of the overall preferred shapes were detected with diminishing the size of the macromolecules from CD29 to CD24. An elongated cavity (CD28) or a double parallel strand in different specific representations are the dominating motifs in the LR‐CDs studied: with loops at the two ends (CD25, CD28, CD29), with a loop at one end (CD25), twisted (CD26, CD27) or twisted with an open portion in the middle (CD24), helical (CD24, CD25), or linking two loops from one of their sides (CD27). Two loops connected by an arc (CD28, CD29) and a cavity with the shape of an extended rectangular (CD24, CD28) appear preferentially during the conformational interconversions of the two larger CDs, whereas helical motifs are present in the smaller macrorings: an extended helix with ends linked by an arc (CD24), helical turn and helical portion (CD26, CD27). A triple propeller conformation or three symmetrical loops of almost equal size were also detected for CD26 and CD29, respectively. The present results further support the hypothesis for the existence of more than one cavity in large‐ring cyclodextrins and suggest preferred conformations in water solution for the LR‐CDs with degree of polymerization from 24 to 29. Chirality, 2007. © 2007 Wiley‐Liss, Inc.
Evidence for multiple signaling pathways in single squid olfactory receptor neurons
Authors: Mobley Arie Sitthichai , Mahendra Gandham , Lucero Mary T. 
Published: January 2007

AbstractAt least two different G‐protein‐mediated transduction cascades, the adenylate cyclase and phospholipase C (PLC) pathway, process chemosensory stimuli for various species. In squid olfactory receptor neurons (ORNs), physiological studies indicate that both pathways may be present; however, confirmation of the transduction molecules at the protein level is absent. Here we provide evidence that the G‐proteins involved in both adenylate cyclase and PLC pathways are present in squid ORNs (Lolliguncula brevis). We used immunoblotting to show that Gαolf, Gαq, and a downstream effector, enzyme PLC140, are present in the squid olfactory epithelium (OE). To localize these proteins to one or more of the five morphological cell types described for squid OE, paraformaldehyde‐fixed olfactory organs were cryosectioned (10 μm), double‐labeled for Gαolf, Gαq, or PLC140, and imaged. Analysis of serial sections from entire olfactory organs for epithelial area and patterns of immunofluorescence revealed a region of highest immunoreactivity at the anterior half of the organ. At the cellular level, type 1 cells could not be distinguished morphologically and were not included in the analysis. The three labeling patterns observed in type 2 cells were Gαq alone, PLC140 alone, and colocalization of Gαq and PLC140. Subsets of cell types 3, 4, and 5 showed colocalization of Gαolf with Gαq but not with PLC140. These data suggest that the PLC pathway predominates in type 2 cells; however, coexpression of Gαolf with Gαq in cell types 3, 4, and 5 suggests that both pathways may participate in olfactory transduction in non‐type 2 squid ORNs. J. Comp. Neurol. 501:231–242, 2007. © 2007 Wiley‐Liss, Inc.
Behavior of Ni‐Doped MgMoO4 Single‐Phase Catalysts for Synthesis of Multiwalled Carbon Nanotube Bundles
Authors: Li Y. , Zhang X. , Geise H. J. , van Tendeloo G. 
Published: January 2007

AbstractA significant effect is found when various ratios of CH4/H2 and CH4/N2 are used for the synthesis of multiwalled carbon nanotube (MWNT) bundles on nickel‐doped MgMoO4 (Ni/Mo/MgO) as a catalyst. The absorption of hydrogen makes the nickel–molybdenum nanoparticles highly dispersed on the porous MgO, and the synergism of nickel–molybdenum has the effect that sufficient carbon atoms are rapidly dissolved in the molten nickel‐molybdenum nanoparticles, leading to a high yield of MWNTs. The phase transformations of the catalysts and the formation mechanism of the MWNT bundles on Ni/Mo/MgO catalyst are also presented.
CVD‐Fabricated Aluminum Oxide Coatings from Aluminum tri‐iso‐propoxide: Correlation Between Processing Conditions and Composition
Authors: Gleizes A. N. , Vahlas C. , Sovar M.‐M. , Samélor D. , Lafont M.‐C. 
Published: January 2007

AbstractThis paper presents results on aluminum oxide thin films processed using metal–organic (MO) CVD from aluminum tri‐iso‐propoxide (ATI) without any additional oxygen source, in the temperature range 623–973 K. The films do not diffract X‐rays, except when grown at 973 K or annealed at 1073 K. Their composition was investigated using several techniques; electron probe micro analysis (EPMA), energy dispersive X‐ray spectroscopy (EDX), elastic recoil detection analysis (ERDA), and Rutherford back‐scattering spectroscopy (RBS). It corresponds to the formula AlO(OH) for those grown at 623 K. The composition of films prepared above 688 K corresponds to the formula Al2O3. Between 623 K and 688 K, partly hydroxylated films are obtained. This is confirmed by Fourier transform infrared (FTIR) transmission spectroscopy (no OH absorption band in the 3500 cm–1 region for films prepared above 688 K), and by thermogravimetric analysis (TGA, DTG) (no significant mass loss for films prepared above 688 K). Observations using the transmission electron microscopy (TEM) showed that films prepared at 623 K are amorphous, while those prepared at 973 K are nanocrystalline. In both cases, γ‐Al2O3 crystals are formed and progressively grow on exposure to the TEM electron beam. Knowing the correlation between processing conditions and the composition of such films should help optimize the process with regards to any aimed property of use.
Thermomechanical Properties of Parylene X, A Room‐Temperature Chemical Vapor Depositable Crosslinkable Polymer
Authors: Senkevich J. J. , Woods B. W. , McMahon J. J. , Wang P.‐I 
Published: January 2007

AbstractPoly(p‐xylylene) has existed commercially for many years but has never gained widespread acceptance due to its poor thermal and optical properties. Parylene X, a new chemical vapor depositable polymer on the same process platform as poly(p‐xylylene), is a copolymer of poly(ethynyl‐p‐xylylene) and poly(p‐xylylene). It exhibits thermal stability to at least 420 °C, has a low coefficient of thermal expansion of 55 ppm after it is crosslinked, and exhibits low stress. It possesses a glass transition temperature of 73 °C and starts to crosslink at ∼160 °C with a peak isotherm at 250 °C. The ethynyl functional groups crosslink to form the very stable phenyl moiety.