bluuebunny/crossref_metadata_2025_split huggingface dataset:
Transcriptional Profiling of Bipotential Embryonic Liver Cells to Identify Liver Progenitor Cell Surface Markers
Authors: Ochsner Scott A. , Strick-Marchand Hélène , Qiu Qiong , Venable Susan , Dean Adam , Wilde Margaret , Weiss Mary C. , Darlington Gretchen J. 
Published: July 2007

AbstractThe ability to purify to homogeneity a population of hepatic progenitor cells from adult liver is critical for their characterization prior to any therapeutic application. As a step in this direction, we have used a bipotential liver cell line from 14 days postcoitum mouse embryonic liver to compile a list of cell surface markers expressed specifically by liver progenitor cells. These cells, known as bipotential mouse embryonic liver (BMEL) cells, proliferate in an undifferentiated state and are capable of differentiating into hepatocyte-like and cholangiocyte-like cells in vitro. Upon transplantation, BMEL cells are capable of differentiating into hepatocytes and cholangiocytes in vivo. Microarray and Gene Ontology (GO) analysis of gene expression in the 9A1 and 14B3 BMEL cell lines grown under proliferating and differentiating conditions was used to identify cell surface markers preferentially expressed in the bipotential undifferentiated state. This analysis revealed that proliferating BMEL cells express many genes involved in cell cycle regulation, whereas differentiation of BMEL cells by cell aggregation causes a switch in gene expression to functions characteristic of mature hepatocytes. In addition, microarray data and protein analysis indicated that the Notch signaling pathway could be involved in maintaining BMEL cells in an undifferentiated stem cell state. Using GO annotation, a list of cell surface markers preferentially expressed on undifferentiated BMEL cells was generated. One marker, Cd24a, is specifically expressed on progenitor oval cells in livers of diethyl 1,4-dihydro-2,4,6-trimethyl-3,5-pyridinedicarboxylate-treated animals. We therefore consider Cd24a expression a candidate molecule for purification of hepatic progenitor cells.Disclosure of potential conflicts of interest is found at the end of this article.
Selective Targeting of Adenoviral Vectors to Neural Precursor Cells in the Hippocampus of Adult Mice: New Prospects for In Situ Gene Therapy
Authors: Schmidt Anke , Haas Stefan J.-P. , Hildebrandt Steve , Scheibe Johanna , Eckhoff Birthe , Racek Tomáš , Kempermann Gerd , Wree Andreas , Pützer Brigitte M. 
Published: July 2007

Abstract
The adult brain contains neural precursor cells (NPC) that are attracted to brain lesions, such as areas of neurodegeneration, ischemia, and cancer. This suggests that NPC engineered to promote lineage-specific differentiation or to express therapeutic genes might become a valuable tool for restorative cell therapy and for targeting therapeutic genes to diseased brain regions. Here we report the identification of NPC-specific ligands from phage display peptide libraries and show their potential to selectively direct adenovirus-mediated gene transfer to NPC in adult mice. Identified peptides mediated specific virus binding and internalization to cultured neurospheres. Importantly, peptide-mediated adenoviral vector infection was restricted to precursor cells in the hippocampal dentate gyrus of pNestin-green fluorescent protein transgenic or C57BL/6 mice. Our approach represents a novel method for specific manipulation of NPC in the adult brain and may have major implications for the use of precursor cells as therapeutic delivery vehicles in the central nervous system.
Disclosure of potential conflicts of interest is found at the end of this article.
Synthesis and association properties in water solution of random copolymers of 2‐acrylamido‐2‐methyl‐1‐propane sulfonic acid and isodecyl methacrylate—potential application as surfactants in micellar‐enhanced ultrafiltration processes
Authors: Peinado Carmen , Catalina Fernando , San Miguel Verónica 
Published: July 2007

AbstractHydrophobically modified water‐soluble polymers have been prepared by copolymerization of 2‐acrylamido‐2‐methylpropane sulfonic acid (AMPS) and isodecyl methacrylate (iDMA) in N,N‐dimethylformamide under nitrogen atmosphere, varying the composition feed. Fluorescence spectroscopy was used to further confirm the copolymers self‐aggregate in water. Critical concentration of the self‐aggregate formation (CAC) decreased by increasing the molar fraction of iDMA in the AMPSco copolymers and varied between 1.20 and 0.04 g/L depending on the degree of hydrophobic modification. Hence, copolymer composition and charge density allowed tuning the pseudomicellar characteristics of these new amphiphilic copolymers. The addition of a salt or a low‐molecular‐weight surfactant was studied. Binding of CTAB to the AMPSco copolymers leads to a high decrease of CAC, i.e., 0.006 g/L. Effect of the composition in the viscosimetric behavior of the hydrophobically modified copolymers AMPSco was investigated. The removal of single metal ions, Cu2+, and m‐cresol from aqueous solutions by ultrafiltration with the help of the copolymers was investigated. Equilibrium dialysis experiments demonstrate that the formation of hydrophobic microdomains can be used to control the sequestration of foulants, and thus these novel copolymers have potential application as polymeric surfactants in micellar‐enhanced ultrafiltration processes for water purification. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007
Studies of Allylic Substitution Catalysed by a Palladium Complex of a C2‐Symmetric Bis(aziridine): Preparation and NMR Spectroscopic Investigation of a Chiral π‐Allyl Species
Authors: Andersson Pher G. , Harden Adrian , Tanner David , Norrby Per‐Ola 
Published: July 2007

AbstractThe chiral palladium π‐allyl intermediate for the catalytic asymmetric synthesis shown in Scheme 1 has been isolated as the PF salt. MM 2 calculations have been performed and the structure of the palladium complex in solution has also been investigated by means of NMR spectroscopy. Both the computational and spectroscopic results suggest that in the complex the bidentate bis(aziridine) ligand adopts a conformation that forces the π‐allyl moiety out of the normally preferred square‐planar geometry. This nicely explains the very high enantioselectivity observed in the title reaction.
The Design of Selective Chelating Agents: 1,3,5‐Trideoxy‐1,3,5‐tris‐(dimethylamino)‐cis‐inositol, a Powerful Ligand for Hard and Highly Charged Metal Ions
Authors: Hegetschweiler Kaspar , Kradolfer Thomas , Gramlich Volker , Hancock Robert D. 
Published: July 2007

AbstractA series of compounds containing the mononuclear complexes [M(tdci)2]3+ (tdci = 1,3,5‐trideoxy‐1,3,5‐tris(dimethylamino)‐cis‐inositol, M = Al, Fe, Ga, In) and [M(tdci)2]4+ (M = Ti, Ge, Sn) was prepared and characterized by elemental analysis, NMR spectroscopy, and FAB mass spectrometry. Characteristic fragmentation reactions in the mass spectra were elucidated. X‐ray analysis of the AlIII, FeIII, GaIII, and InIII complexes revealed that two neutral, zwitterionic tdci ligands coordinate to the metal cation exclusively through deprotonated alkoxo groups. The six coordinated oxygen donors and the six NH protons form a hydrophilic pocket, whereas the two cyclohexane rings and the twelve methyl groups form two hydrophobic shells. The hydrophilic pocket is filled with twelve water molecules, which are arranged as a second and a third coordination sphere around the metal cation. The reactivity in aqueous solution was investigated by potentiometric measurements. The bis complexes proved to be stable at pH 7. The evaluated formation constants show an increase of stability in the order AlIII<InIII<GaIII<FeIII. The measurements established that tdci is one of the most effective tridentate ligands for small (r ⩽ 0.8Å) and highly charged cations. The different chelating properties of tdci and of the unmethylated 1,3,5‐triamino‐ 1,3,5‐trideoxy‐cis‐inositol are discussed in terms of different steric requirements and different types of solvation of the corresponding complexes in aqueous solution.
Synthesis of a Methyl Heptaglucoside with Phytoalexin Elicitor Activity Based on Oxidative Coupling of Glucals
Authors: Timmers Cornelis M. , van der Marel Gijsbert A. , van Boom Jacques H. 
Published: July 2007

AbstractSeveral suitable building blocks for the construction of the phytoalexin elicitor α‐methyl‐32, 34‐di‐β‐D‐glucopyranosylgentiopentaoside (2) were readily accessible by oxidative coupling of glucals. Block coupling of trimeric phenylseleno‐ and ethylthioglucosyl donors 17 and 18 with tetrasaccharide 16 in the presence of the thiophilic promoter N‐iodosuccinimide and catalytic trifluoromethanesulfonic acid furnished the desired heptaglucan 2 in high overall yield.
Supramolecular Structure, Physical Properties, and Langmuir‐Blodgett Film Formation of an Optically Active Liquid‐Crystalline Phthalocyanine
Authors: van Nostrum Cornelus F. , Bosman Anton W. , Gelinck Gerwin H. , Schouten Pieter G. , Warman John M. , Kentgens Arno P. M. , Devillers Marinus A. C. , Meijerink Andries , Picken Stephen J. , Sohling Ulrich , Schouten Arend‐Jan , Nolte Roeland J. M. 
Published: July 2007

AbstractThe structure and physical properties of optically active, metal‐free 2,3,9,10,16,17,23,24‐octa (S‐3,7‐dimethyloctoxy)phthalocyanine ((S)‐Pc(8,2)) are reported and compared with those of the phthalocyanine with (R,S) side chains (mixture of 43 stereoisomers). Unlike the latter compound, (S)‐Pc(8,2) lacks a crystalline phase. A freshly prepared sample is in a distorted mesophase and reorganizes irreversibly to a more ordered phase above 65 °C. X‐ray diffraction and circular dichroism studies indicate that the molecules are stacked in columns which have a hexagonal arrangement and a left‐handed helical superstructure, that is, a novel chiral Dh* mesophase. Solid state NMR measurements reveal that the phthalocyanine units in the columns begin to vibrate laterally when the temperature is increased. At 111 °C (Dh* → Dr transition) they start to rotate around their columnar axes and at the same time the side chains become liquidlike. Energy migration is very efficient in the chiral Dh* phase and also in the frozen mesophase below 3 °C, as follows from luminescence spectroscopy. Intracolumnar charge transport, studied by the time‐resolved microwave conductivity technique, turns out to be slower in the helically distorted columns than in linear columns. (S)‐Pc(8,2) forms a very stable bilayer at the air‐water interface, which can be transferred to give a high quality Langmuir‐Blodgett film. The fact that this phthalocyanine is mesogenic at room temperature is thought to be responsible for this behavior.
Neutral Cobalt Carbonyl Catalysts for the Equilibration Between CO and P(OPh)3 Ligands in Carbonylcobaltates
Authors: Ciuffarin Ennio , Fachinetti Giuseppe , Funaioli Tiziana , Isola Mauro 
Published: July 2007

AbstractThe substitution reaction of [Co(CO)4]− by P(OPh)3 was investigated in THF. Under a CO atmosphere, the reaction consists of an equilibrium, which, in order to be established, needs [Co2(CO)6(P(OPh)3)2]. The catalysis by this neutral carbonyl is formally related to a previously reported case, where either [Co2(CO)8] or [Co4(CO)12] was found to be necessary for the 13CO scrambling in [Co(CO)4]−. The kinetic analysis reported in this paper indicates, however, that the two CO labilizations differ in their mechanism‐the substitution by P(OPh)3 is ascribed to a disproportionation‐synproportionation of [Co2(CO)6(P(OPh)3)2].
Light‐Triggered Molecular Devices: Photochemical Switching Of optical and Electrochemical Properties in Molecular Wire Type Diarylethene Species
Authors: Gilat Sylvain L. , Kawai Stephen H. , Lehn Jean‐Marie 
Published: July 2007

AbstractOrganic photochromic systems represent a starting point for the elaboration of light‐triggered molecular switching devices. The novel bispyridinium and bispyridine compounds 12+ and 6 were synthesized as their uncyclized isomers from 3,5‐dibromo‐2‐methylthiophene in overall yields of 43 and 44%, respectively. The diarylethene photochromes 2 and 10–13, substituted with electron donors and acceptors, were prepared from 5‐methylthiophene‐2‐carboxaldehyde in 21–32% overall yield. All of the compounds were found to exhibit pronounced photochromic properties. Irradiation with UV light resulted in essentially complete photocyclization of the open forms to the intensely coloured closed isomers which could, in turn, be reconverted back to the open state with visible light of γ>600 nm. The absorption maxima of the described compounds in their closed forms are shifted far towards, and even into, the near‐IR region. Whereas no thermochromic properties were observed for the open isomers, the rates of thermal decolouration of the cyclized forms was found to be highly dependent on the nature of the substituents on the thiophene rings. It was demonstrated that reversible photochemical interconversion between the two photochromic states could be used to effectively switch a number of physical properties. Thus, the molecules 12+ and 12 represent two kinds of redox switches, the former in reduction and the latter in oxidation, in which electron conduction is switched on in the closed state and off in the open state. Compound 12 may also be considered to be a photoswitchable analogue of tetrathiafulvalene type substances. On the other hand, compound 2 displays a marked increase in nonlinear optical activity on conversion from the open to the closed form. Such systems are prototypes of photoswitchable molecular wires where electron conduction and push‐pull interaction can be reversibly modulated by an external stimulus, namely, irradiation by light.
Synthesis, Structure, and Reactivity of Chiral Rhenium N‐Pyrrolyl Complexes Regiochemistry of Electrophilic Addition and Unprecedented Rearrangements to Carbon‐Ligated Species
Authors: Johnson Todd J. , Alvey Luke J. , Brady Monika , Mayne Charles L. , Arif Atta M. , Gladysz J. A. 
Published: July 2007

AbstractReaction of [{Re}(OTf)] (1; {Re} — (η5‐C5H5)Re(NO)(PPh3) and potassium pyrrolide gives the N‐pyrrolyl complex magnified image2, 88%). Reactions of 2 with (CF3CO)2O/N(C2H5)3 and CH3O2CC=CCO2CH3 give 3‐ and 2‐substituted pyrrolyl complexes magnified image respectively (3, R/R′ = H/COCF3, 77%; 5, R/R′ = C(CO2CH3)=CHCO2CH3/H, 69–87%). Free pyrrole is much less reactive towards these reagents. Reactions of 2 and TfOH or HBF4·OEt2 give the 2H‐pyrrole adducts magnified image+X− (7+X−; 89–83%). At 0–25°C in CH2Cl2, these rearrange to the carbon‐ligated tautomers magnified image+X−(8+X−) and then magnified image+X−; (9+X−; 72–96 h, 90–96%). Reaction of 1 and pyrrole in refluxing toluene gives 8+TfO− and then 9−TfO− (92%). However, 1 and pyrrole react too slowly in CH2Cl2 to be intermediates in the conversion of 7+TfO− to 9+TfO−. Reaction of 9+ TfO− and KH gives the C‐pyrrolyl complex magnified image (68%), which adds TfOH to give 9+TfO−. Mechanistic aspects of the preceding reactions are discussed. The crystal structures of 2 and 9+TfO− are determined, and the NC4Hx ligand conformations analyzed with extended Hückel MO calculations.
Stereoselective Homologation–Amination of Aldehydes by Addition of Their Nitrones to C‐2 Metalated Thiazoles—A General Entry to α‐Amino Aldehydes and Amino Sugars
Authors: Dondoni Alessandro , Franco Santiago , Junquera Federico , Merchán Francisco L. , Merino Pedro , Tejero Tomás , Bertolasi Valerio 
Published: July 2007

AbstractA general method for the homologation of aldehydes to α‐amino aldehydes (aminohomologation) has been developed, which employs nitrones as iminium derivatives of the aldehydes. Key operations include a) the addition of a thiazole metalated at C‐2 to the N‐benzylnitrone derived from the aldehyde, b) the reductive dehydroxylation of the resultant thiazolyl N‐benzylhydroxylamine, and c) the unmasking of the formyl group from the thiazole ring. The homologation sequence was studied by employing nitrones derived from various chiral polyalkoxy aldehydes and dialdoses. The addition of 2‐lithiothiazole to these nitrones was syn‐selective, whereas the reaction with the same nitrones precomplexed with Lewis acids was anti‐selective. Hence, from each nitrone a pair of diastereoisomeric hydroxylamines was obtained. These compounds were then converted by the above sequence into α‐epimeric α‐amino aldehydes. Model elaborations of some of these products afforded the amino sugars D‐glucosamine, D‐mannosamine, D‐nojirimycin, and advanced intermediates for the synthesis of destomic acid and lincosamine.
Ligand Design for Securing Ferromagnetic Exchange Coupling in Multimetallic Complexes
Authors: Gordon‐Wylie Scott W. , Bominaar Emile L. , Collins Terrence J. , Workman José M. , Claus Brian L. , Patterson Robert E. , Williams Stacy A. , Conklin Brenda J. , Yee Gordon T. , Weintraub Susan T. 
Published: July 2007

AbstractAn approach is suggested for using ligands to control exchange coupling in multinuclear ions. The idea arose from structural, EPR, and magnetic studies of [PPh4]3 (Scheme 1). Ferromagnetic coupling has been found between the CoII and each CoIII in 3 with J = −22 ± 5 cm−1 (JS1 · S2). It is suggested that dominant antiferromagnetic superexchange is absent because of the strong σ‐donor capacity of the tetradentate ligand [k4‐PAC*]4− (Fig. 1). The ligand interacts at CoIII primarily with a single d orbital; it is thus best able to participate in superexchange. The interaction makes the unique d orbital strongly σ‐antibonding and empty for each d6, S = 1, CoIII ion in 3, that is, unavailable for antiferromagnetic coupling, but available for ferromagnetic pathways by a Goodenough‐Kanamori mechanism. By corollary, when any [k4‐PAC*]4−‐type ligand with any magnetic ion Ma in the tetradentate site binds any magnetic ion Mb in the bidentate site, ferromagnetic coupling should be favored provided Ma is not a d9 ion.
Synthesis, Conformational Analysis and Comparative Protein Binding of a Galabioside and Its Thioglycoside Analogues
Authors: Nilsson Ulf , Johansson Roger , Magnusson Göran 
Published: July 2007

AbstractThe two thio analogues (2 and 3) of TMSEt galabioside [2‐(trimethylsilyl)ethyl 4‐O‐(α‐D‐galactopyranosyl)‐β‐D‐galactopyranoside, 1], having anomeric sulfur instead of anomeric oxygen atoms, were synthesized and their conformations investigated by NMR and computational (MM 3) methods. A spacer galabioside was covalently coupled to aminated microtiter plates, and binding of a bacterial pilus adhesin (PapG) to the plates was inhibited by the soluble ligands 1, 2 and 3. The ligand 2, which has an intersaccharidic sulfur linkage, was a much less efficient inhibitor than 1, which has the natural oxygen linkage. The inhibitory power of ligand 3 was only slightly less than that of 1. An NMR experiment with 1 and 2, in which hydroxyl‐group hydrogens had been partially (50%) substituted by deuterium, demonstrated the presence (in 1) and absence (in 2) of an intramolecular (HO 2′ – HO 6) hydrogen bond. This result indicates that the conformations of 1 and 2 are different and that the difference is sufficient to cause the observed (≈ 30 times) reduction of the saccharide‐protein binding strength.
An Ab Initio Study of Structures and Energetics of Copper Sulfide Clusters
Authors: Dehnen Stefanie , Schäfer Ansgar , Ahlrichs Reinhart , Fenske Dieter 
Published: July 2007

AbstractThe results of ab initio calculations for the sulfur‐bridged copper clusters [Cu2nSn(PR3)m] (n = 1–4, 6; m = 0, 2, 4, 6, 8; RH, CH3) were compared with those of theoretical investigations of the selenium‐containing analogues that have been recently reported. The theoretical work was carried out in order to find a possible explanation for the experimentally observed–different–properties of both cluster types. The structural principles turned out to be independent of the chalcogen, except the necessary shortening of the copper–chalcogen atomic distance that results from the formal substitution of sulfur for selenium. Comparison of the energetics of the sulfur‐ and selenium‐containing compounds showed that it is necessary to discuss the influence of the tertiary phosphine ligands that protect the existing clusters from reaction to give the solids Cu2S and Cu2Se. However the results of the calculations suggest that the different thermodynamic data of the cluster core and the CuP bonds–at least if PH3 or PMe3 are taken into account–cannot be the only cause for the differences in the experimental behaviour. The responsibility rests rather with kinetic effects, such as the steric demand of the actual ligands or the activation energy of decomposition of the ligand shell during the cluster‐forming reaction.
Solution Phase and Single Crystal Diffraction X‐ray Analyses of Diprotonated Porphyrin Isomers—Etioporphyrin, Etioporphycene, and Etiocorrphycene Bishydroperchlorate Salts
Authors: Sessler Jonathan L. , Brucker Eric A. , Lynch Vincent , Choe Michael , Sorey Steven , Vogel Emanuel 
Published: July 2007

AbstractThe diprotonated, bishydroperchlorate forms of three isomeric β‐octaalkyl‐substituted tetrapyrrolic macro‐cycles, namely, etioporphyrin II (1), etio porphycene (2), and etiocorrphycene (3), have been characterized both in chloroform solution, by UV/visible spectroscopy and 1H and proton‐correlated 2D 15N NMR methods, and in the solid state, by single‐crystal X‐ray diffraction analyses. In the solid state, in marked contradistinction to what is observed for the corresponding free‐base forms, the macrocyclic portion of these salts were found to be distorted significantly from planarity with the two perchlorate counteranions being held above and below the average N4 plane by N–H … O hydrogen bonds in all three cases. In solution, 1H and proton‐correlated 2D 15N NMR experiments reveal molecular ions of relatively high symmetry (D2h, D2h, and C2v in the case of 1·(HClO4)2, 2·(HClO4)2, and 3·(HClO4)2, respectively) as would be anticipated on the basis of the solid‐state results. These same NMR analyses, while revealing slight differences between the three salts in the NH and meso 1H NMR spectral regions, also serve to confirm the generalized congeneric nature of 1·(HClO4)2, 2·(HClO4)2, and 3·(HClO4)2 and support the assignment of the latter two species as being porphyrin‐like salts. UV/vis analyses further support this conclusion; in all three instances, strong Soret‐ and Q‐like transitions are observed in dichloromethane that are both distinct from each other (λmax=404, 549, 570, 593; 388, 409, 599, 666; and 419, 559, 604 for 1·(HClO4)2, 2·(HClO4)2, and 3·(HClO4)2, respectively) and from those of the corresponding free‐base forms (λmax=396, 496, 530, 565, 619; 382, 570, 617, 657; and 410, 509, 539, 574, 628 for 1, 2, and 3 respectively). Protonation experiments were carried out by exposing dichloromethane solutions of the isomers to aqueous perchlorate/perchloric acid solutions of differing pH. These studies reveal that while porphycene 2 adds two protons readily and concurrently, becoming 50% diprotonated when exposed to perchlorate/perchloric solutions with a pH of around 3.6, porphyrin 1 and corrphycene 3 are protonated in a stepwise manner; they become 50% monoprotonated when exposed to perchlorate/perchloric solutions of pH≈︁3.7 and 3.9, respectively, and diprotonated at pH≤0.8 and 1.3, respectively.