bluuebunny/crossref_metadata_2025_split huggingface dataset:
trans–cis Photoisomerization of the Styrylpyridine Ligand in [Re(CO)3(2,2′‐bipyridine)(t‐4‐styrylpyridine)]+: Role of the Metal‐to‐Ligand Charge‐Transfer Excited States
Authors: Bossert Julien , Daniel Chantal 
Published: April 2006

AbstractThe trans‐cis isomerization of the styrylpyridine carbon–carbon double bond induced by visible light irradiation in fac‐[Re(CO)3(bpy)(stpy)]+ (bpy = 2,2′‐bipyridine; stpy = t‐4‐styrylpyridine) has been investigated by means of quantum‐chemical methods. The structures of the various cis and trans conformers of [Re(CO)3(bpy)(stpy)]+ have been optimized at the density functional theory (DFT) level. Three rotational conformers for the most stable trans isomer lie within 2.3 kJ mol−1 each other. The energy difference between the cis and trans isomers is 27.0 kJ mol−1. The electronic spectroscopy of the most stable conformers has been investigated by time‐dependent DFT (TD‐DFT) and complete active space self‐consistent field/CAS second order perturbation theory (CASSCF/CASPT2) calculations. The lowest absorption bands are dominated by metal‐to‐ligand charge‐transfer (MLCT, dRe→π*bpy) transitions calculated at about 25 000 cm−1 and by a strong intraligand 1IL (πstpy→π*stpy) transition in the near UV region. On the basis of CASSCF potential energy curves (PECs) calculated as a function of the torsion angle of the CC bond of the styrylpyridine ligand, it is shown that the role of the low‐lying MLCT states is important in the photoisomerization mechanism. In contrast to the free organic ligand, in which the singlet mechanism is operational via the 1IL (S1) and electronic ground (S0) states, coordination to the rhenium steers the isomerization to the triplet PEC corresponding to the 3IL state. From the 3ILt (t = trans) the system evolves to the perpendicular intermediate 3ILp (p = perpendicular) following a 90° rotation around the styrylpyridine CC bond. The metal center acts as a photosensitizer because of the presence of photoactive MLCT states under visible irradiation. The position of the crossing between the 3IL and electronic ground state PEC determines the quantum yield of the isomerization process.
High‐Spin‐ and Low‐Spin‐State Structures of [Fe(chloroethyltetrazole)6](ClO4)2 from Synchrotron Powder Diffraction Data
Authors: Dova Eva , Peschar René , Sakata Makoto , Kato Kenichi , Schenk Henk 
Published: April 2006

AbstractThe spin‐crossover complex [Fe(teec)6](ClO4)2 (teec = chloroethyltetrazole) exhibits a 50 % incomplete spin crossover in the temperature range 300–30 K. Time‐resolved synchrotron powder diffraction experiments have been carried out to elucidate its structural behavior. We report crystal structure models of this material at 300 K (high spin) and 90 K (low spin), as solved from synchrotron powder diffraction data by using Genetic Algorithm and Parallel Tempering techniques and refined with Rietveld refinement. During short synchrotron powder diffraction experiments (five minutes duration) two distinguishable lattices were observed the quantities of which vary with temperature. The implication of this phenomenon, that is interpreted as a structural phase transition associated with the high‐to‐low spin crossover, and the structural characteristics of the high‐spin and low‐spin models are discussed in relation to other compounds showing a similar type of spin‐crossover behavior.
Exploring the Hydration of Pb2+: Ab Initio Studies and First‐Principles Molecular Dynamics
Authors: Gourlaouen Christophe , Gérard Hélène , Parisel Olivier 
Published: April 2006

AbstractEven though lead is a well‐known toxicant widely scattered throughout the world since antiquity, its chemistry is poorly documented at the molecular level. Here we investigate the hydration of the Pb2+ ion by means of first‐principles molecular dynamics (Car–Parrinello molecular dynamics, CPMD). We found that the hydrated cation is heptacoordinated in a dynamically holodirected arrangement roughly corresponding to a fluxional distorted pentagonal bipyramid. The time‐averaged PbO bond length is especially large and amounts to 2.70 Å with an associated root‐mean‐square deviation of 0.26 Å. This results from a dynamic exchange between short (<2.6 Å), intermediate (2.6–3.0 Å) and long (>3.0 Å) PbO bonds. The latter very long PbO distance implies that the determination of the coordination number nc from experimental work may not necessarily yield values directly comparable to the theoretical value of nc=7, since not all experimental techniques would recognize such a long distance as a bond to the metal cation. Pronounced disorders are evidenced in the second shell, characteristic of a chaotropic cation, and exchanges between the first and second shells cannot be excluded on a timescale of a few tens of picoseconds.
A DNA‐Binding Copper(I) Metallosupramolecular Cylinder that Acts as an Artificial Nuclease
Authors: Childs Laura J. , Malina Jaroslav , Rolfsnes Britt Elin , Pascu Mirela , Prieto Maria J. , Broome Mark J. , Rodger P. Mark , Sletten Einar , Moreno Virtudes , Rodger Alison , Hannon Michael J. 
Published: April 2006

AbstractThe DNA binding of a dicationic pyridylimine‐based dicopper(I) metallosupramolecular cylinder is reported together with its ability to act as an artificial nuclease. The cylinder binds strongly to DNA; more strongly than the spherical dication [Ru(phen)3]2+(phen=1,10‐phenanthroline), but more weakly than the corresponding tetracationic cylinders. DNA coiling effects are not observed with this dication, in contrast to the situation with the previously reported tetracationic cylinder involving a similar ligand. Linear dichroism (LD) data suggests that the dicopper cylinder binds in a different orientation from that of the tetracationic iron cylinder. Furthermore, the dicopper cylinder shows DNA‐cleavage activity in the presence of peroxide. Of particular note is that the cylinder displays a marked and unusual ability to cleave both DNA strands at the same site, probably reflecting its dinuclear nature and possibly its mode of binding to the DNA.
Anticancer Cyclometalated [AuIIIm(C∧N∧C)mL]n+ Compounds: Synthesis and Cytotoxic Properties
Authors: Li Carrie Ka‐Lei , Sun Raymond Wai‐Yin , Kui Steven Chi‐Fai , Zhu Nianyong , Che Chi‐Ming 
Published: April 2006

AbstractA series of cyclometalated gold(III) compounds [Aum(C∧N∧C)mL]n+ (m=1–3; n=0–3; HC∧N∧CH=2,6‐diphenylpyridine) was prepared by ligand substitution reaction of L with N‐donor or phosphine ligands. The [Aum(C∧N∧C)mL]n+ compounds are stable in solution in the presence of glutathione. Crystal structures of the gold(III) compounds containing bridging bi‐ and tridentate phosphino ligands reveal the presence of weak intramolecular π⋅⋅⋅π stacking between the [Au(C∧N∧C)]+ units. Results of MTT assays demonstrated that the [Aum(C∧N∧C)mL]n+ compounds containing nontoxic N‐donor auxiliary ligands (2) exert anticancer potency comparable to that of cisplatin, with IC50 values ranging from 1.5 to 84 μM. The use of [Au(C∧N∧C)(1‐methylimidazole)]+ (2 a) as a model compound revealed that the gold(III)‐induced cytotoxicity occurs through an apoptotic cell‐death pathway. The cell‐free interaction of 2 a with double‐stranded DNA was also examined. Absorption titration showed that 2 a binds to calf‐thymus DNA (ctDNA) with a binding constant of 4.5×105 dm3 mol−1 at 298 K. Evidence from gel‐mobility‐shift assays and viscosity measurements supports an intercalating binding mode for the 2 a–DNA interaction. Cell‐cycle analysis revealed that 2 a causes S‐phase cell arrest after incubation for 24 and 48 hours. The cytotoxicity of 3 b–g toward cancer cells (IC50=0.04–4.3 μM) correlates to that of the metal‐free phosphine ligands (IC50=0.1–38.0 μM), with [Au2(C∧N∧C)2(μ‐dppp)]2+ (3 d) and dppp (dppp=1,2‐bis(diphenylphosphino)propane) being the most cytotoxic gold(III) and metal‐free compounds, respectively. Compound 3 d shows a cytotoxicity at least ten‐fold higher than the other gold(III) analogues; in vitro cellular‐uptake experiments reveal similar absorptions for all the gold(III) compounds into nasopharyngeal carcinoma cells (SUNE1) (1.18–3.81 ng/cell; c.f., 3 d=2.04 ng/cell), suggesting the presence of non‐gold‐mediated cytotoxicity. Unlike 2 a, both gold(III) compounds [Au(C∧N∧C)(PPh3)]+ (3 a) (PPh3=triphenylphosphine) and [Au2(C∧N∧C)2(μ‐dppp)]2+ (3 d) interact only weakly with ctDNA and do not arrest the cell cycle.
Lewis Base Stabilized Phosphanylborane
Authors: Schwan Karl‐Christian , Timoskin Alexey Y. , Zabel Manfred , Scheer Manfred 
Published: April 2006

AbstractThe abstraction of the Lewis acid from [W(CO)5(PH2BH2⋅NMe3)] (1) by an excess of P(OMe3)3 leads to the quantitative formation of the first Lewis base stabilized monomeric parent compound of phosphanylborane [H2PBH2⋅NMe3] 2. Density functional theory (DFT) calculations have shown a low energetic difference between the crystallographically determined antiperiplanar arrangement of the lone pair and the trimethylamine group relative to the PB core and the synperiplanar conformation. Subsequent reactions with the main‐group Lewis acid BH3 as well as with an [Fe(CO)4] unit as a transition‐metal Lewis acid led to the formation of [(BH3)PH2BH2⋅NMe3] (3), containing a central H3BPH2BH2 unit, and [Fe(CO)4(PH2BH2⋅NMe3)] (4), respectively. In oxidation processes with O2, Me3NO, elemental sulfur, and selenium, the boranylphosphine chalcogenides [H2P(Q)BH2⋅NMe3] (Q = S 5 b; Se 5 c) as well as the novel boranyl phosphonic acid [(HO)2P(O)BH2⋅NMe3] (6 a) are formed. All products have been characterized by spectroscopic as well as by single‐crystal X‐ray structure analysis.
Neutral Helium Compounds: Theoretical Evidence for a Large Class of Polynuclear Complexes
Authors: Borocci Stefano , Bronzolino Nicoletta , Grandinetti Felice 
Published: April 2006

AbstractAb initio calculations at the MP2 and CCSD(T) levels of theory disclose the conceivable existence of neutral complexes containing up to four helium atoms. These species are formally obtained by replacing the hydrogen atoms of parent molecules such as CH4, SiH4, NH3, PH3, H2O, H2S, C2H2, C2H4, and C6H6with NBeHe moieties, which behave as monovalent functional groups containing helium. The geometries and vibrational frequencies of these M(NBeHe)n(n>1; M=central moiety) polyhelium complexes have been investigated at the MP2(full)/6‐31G(d) level of theory, and their stability with respect to the loss of helium atom(s) has been evaluated by means of single‐point calculations at the CCSD(T)/6‐311G(d,p) level of theory. Molecules such as HnC(NBeHe)4−nand HnSi(NBeHe)4−n(n=0–3), C2(NBeHe)2, andortho‐,meta‐, andpara‐C6H4(NBeHe)2were invariably characterized as energy minima, and were found to be stable with respect to the loss of helium atom(s) by approximately 4–5 kcal mol−1. On the other hand, species such as C2(NBeHe)4and C6(NBeHe)6were characterized as high‐order saddle points on the potential‐energy surface, and were unstable with respect to helium atom(s) loss owing to the bending motion of the NBeHe groups. The molecules containing N, P, O, or S as the central atom also showed a variable topology and include second‐order saddle points such as S(NBeHe)2, third‐order saddle points such as HN(NBeHe)2, but also minimum‐energy structures such as O(NBeHe)2and HP(NBeHe)2, which are also stable by approximately 5 kcal mol−1with respect to the helium atom(s) loss. These results suggest the conceivable existence of an, in principle, very large class of M(NBeHe)n(n>1) polyhelium complexes, whose stability may be substantially affected by the nature and the size of the central moiety M. Atoms‐in‐Molecules (AIM) calculations on selected species invariably suggest that, in our investigated M(NBeHe)n(n>1) compounds, the beryllium–helium interaction is essentially electrostatic.
Nonlinear recursive method to solid deformable structure dynamic problems
Authors: Hwang Yunn‐Lin 
Published: April 2006

AbstractThe recursive projection schemes used in most existing recursive methods for solid deformable structure dynamic problems lead to dense coefficient matrices in the acceleration equations and consequently there is a strong dynamic coupling between the joint and elastic coordinates. When the number of elastic degrees of freedom increases, the size of the coefficient matrix in the acceleration equations becomes large and consequently the use of these recursive methods for solving for the joint and elastic accelerations becomes less efficient. This paper discusses the problems associated with the recursive projection schemes used in the existing recursive methods, and it is shown that decoupling the joint and elastic accelerations using the nonlinear recursive method requires the factorization of nonlinear matrices whose dimensions are independent of the number of elastic degrees of freedom of the open‐loop and closed‐loop system. An amalgamated formulation that can be used to decouple the elastic and joint accelerations is then proposed. The use of the nonlinear recursive method developed in this paper is demonstrated using an open‐loop free‐falling deformable double pendulum system and a closed‐loop four‐bar mechanism. Copyright © 2006 John Wiley & Sons, Ltd.
Numerical determination of the solvent diffusion coefficient in a concentrated polymer solution
Authors: Kojić Nikola , Kojić Aleksandar , Kojić Milos̆ 
Published: April 2006

AbstractIn chemical engineering applications involving solvent removal from a concentrated polymer solution where diffusion is the governing process (e.g. dry spinning of synthetic silk‐like fibres), the determination of the concentration‐dependent diffusion coefficient is essential. Diffusion of solvent through such a polymer solution can be described by Fick's law. We propose a numerical procedure to obtain the dependence of the diffusion coefficient on solvent concentration. The procedure employs the finite element method to model a pan weighing experiment, in which a small amount of the polymer solution is placed in a pan and allowed to evaporate into air. In the computational model, the changing depth of the polymer solution is taken into account and the varying diffusion coefficient is determined so as to match the experimentally recorded mass loss. Copyright © 2006 John Wiley & Sons, Ltd.
Flow cytometry analysis of gap junction‐mediated cell–cell communication: Advantages and pitfalls
Authors: Fonseca Paula Candida , Nihei Oscar Kenji , Savino Wilson , Spray David C. , Alves Luiz Anastacio 
Published: April 2006

AbstractBackground:Since the first morphological description of the gap junctions use electron microscopy, a considerable number of techniques has been introduced to evaluate gap junction channel functionality, many of which use dye transfer techniques, such as dye injection and fluorescent dye transfer, analyzed by flow cytometry.Methods:To analyze dye transfer, generally one population of cells is incubated with calcein‐AM (0.5 μM) for 30 min at 37°C, and the other population was incubated with the lipophilic dye DiIC18 (3) (10 μM) for 1 h at 37°C; after incubation, these cells were washed five times with PBS and cocultured for different times, and then the dye transfer was analyzed by flow cytometry.Results:In this short overview, we focus on some advantages and disadvantages of flow cytometry as a technique to investigate gap junction‐mediated intercellular communication (GJIC). In addition, we point out some technical pitfalls that we have encountered when applying this technique to study gap junctions in immune system cells.Conclusions:Analysis of fluorescent dye transfer by flow cytometry is a useful tool to investigate GJIC. However, some points must be taken into consideration before using this methodology, which are discussed herein. © 2006 International Society for Analytical Cytology
Automated fluorescent in situ hybridization (FISH) analysis of t(9;22)(q34;q11) in interphase nuclei
Authors: Kajtár Béla , Méhes Gábor , Lörch Thomas , Deák Linda , Kneifné Marika , Alpár Donát , Pajor László 
Published: April 2006

AbstractBackground:For chronic myeloid leukemia, the FISH detection of t(9;22)(q34;q11) in interphase nuclei of peripheral leukocytes is an alternative method to bone marrow karyotyping for monitoring treatment. With automation, several drawbacks of manual analysis may be circumvented. In this article, the capabilities of a commercially available automated image acquisition and analysis system were determined by detecting t(9;22)(q34;q11) in interphase nuclei of peripheral leukocytes.Methods:Three peripheral blood samples of normal adults, 21 samples of CML patients, and one sample of a t(9;22)(q34;q11) positive cell‐line were used.Results:Single nuclei with correctly detected signals amounted to 99.6% of nuclei analyzed after exclusion of overlapping nuclei and nuclei with incorrect signal detection. A cut‐off value of 0.84 μm was defined to discriminate between translocation positive and negative nuclei based on the shortest distance between signals. Using this value, the false positive rate of the automated analysis for negative samples was 7.0%, whereas that of the manual analysis was 5.8%. Automated and manual results showed strong correlation (R2 = 0.985), the mean difference of results was only 3.7%.Conclusions:A reliable and objective automated analysis of large numbers of cells is possible, avoiding interobserver variability and producing statistically more accurate results than manual evaluation. © 2006 International Society for Analytical Cytology
Unconventional detection methods for microfluidic devices
Authors: Viskari Pertti J. , Landers James P. 
Published: April 2006

AbstractThe direction of modern analytical techniques is to push for lower detection limits, improved selectivity and sensitivity, faster analysis time, higher throughput, and more inexpensive analysis systems with ever‐decreasing sample volumes. These very ambitious goals are exacerbated by the need to reduce the overall size of the device and the instrumentation – the quest for functional micrototal analysis systems epitomizes this. Microfluidic devices fabricated in glass, and more recently, in a variety of polymers, brings us a step closer to being able to achieve these stringent goals and to realize the economical fabrication of sophisticated instrumentation. However, this places a significant burden on the detection systems associated with microchip‐based analysis systems. There is a need for a universal detector that can efficiently detect sample analytes in real time and with minimal sample manipulation steps, such as lengthy labeling protocols. This review highlights the advances in uncommon or less frequently used detection methods associated with microfluidic devices. As a result, the three most common methods – LIF, electrochemical, and mass spectrometric techniques – are omitted in order to focus on the more esoteric detection methods reported in the literature over the last 2 years.
Functionalized magnetic micro‐ and nanoparticles: Optimization and application to μ‐chip tryptic digestion
Authors: Bílková Zuzana , Slováková Marcela , Minc Nicolas , Fütterer Claus , Cecal Roxana , Horák Daniel , Beneš Milan , le Potier Isabelle , Křenková Jana , Przybylski Michael , Viovy Jean‐Louis 
Published: April 2006

AbstractThe preparation of an easily replaceable protease microreactor for μ‐chip application is described. Magnetic particles coated with poly(N‐isopropylacrylamide), polystyrene, poly(2‐hydroxyethyl methacrylate‐co‐ethylene dimethacrylate), poly(glycidyl methacrylate), [(2‐amino‐ethyl)hydroxymethylen]biphosphonic acid, or alginic acid with immobilized trypsin were utilized for heterogeneous digestion. The properties were optimized, with the constraint of allowing immobilization in a microchannel by a magnetic field gradient. To obtain the highest digestion efficiency, sub‐micrometer spheres were organized by an inhomogeneous external magnetic field perpendicularly to the direction of the channel. Kinetic parameters of the enzyme reactor immobilized in μ‐chip capillary (μ‐chip immobilized magnetic enzyme reactor (IMER)) were determined. The capability of the proteolytic reactor was demonstrated by five model (glyco)proteins ranging in molecular mass from 4.3 to 150 kDa. Digestion efficiency of proteins in various conformations was investigated using SDS‐PAGE, HPCE, RP‐HPLC, and MS. The compatibility of the μ‐chip IMER system with total and limited proteolysis of high‐molecular‐weight (glyco)proteins was confirmed. It opens the route to automated, high‐throughput proteomic μ‐chip devices.
Analysis of arsenic compounds by capillary electrophoresis using indirect UV and mass spectrometric detections
Authors: Kitagawa Fumihiko , Shiomi Kazutaka , Otsuka Koji 
Published: April 2006

AbstractCE with indirect UV and mass‐spectrometric detection was used for the simultaneous determination of arsenic acid (As(V)), arsenous acid (As(III)), monomethylarsonic acid (MMA), dimethylarsinic acid (DMA), trimethylarsine oxide (TMAO), tetramethylarsonium ion (TMA+), arsenobetaine (AB), and arsenocholine (AC). In the CE‐indirect UV analysis, a baseline separation of arsenic species was successfully achieved by using a basic background solution (BGS) for anions and an acidic BGS for cations, respectively. The LOD values in CE‐indirect UV for the individual analytes were 7.8, 12.5, 7.8, 12.5, 62.5, 125, 250, and 62.5 ppm, respectively. To achieve sensitive and selective analysis, CE coupled with ESI‐MS was applied to the determination of arsenic compounds. The organic arsenic species were successfully separated with a higher sensitivity by CE‐MS using the acidic BGS. The LODs in CE‐MS for MMA, DMA, TMAO, TMA+, AB, and AC were 1.0, 0.1, 0.01, 0.1, 0.01, and 0.01 ppm, respectively. In contrast, the analysis of inorganic arsenic species (As(V) and As(III)) resulted in a lower detectability in CE‐MS compared to that obtained with the CE‐indirect UV analysis. However, the speciation of eight arsenics by CE‐MS was successfully achieved in a single run by switching the ESI polarity during MS detection.
Rapid detection of Staphylococcus aureus by a combination of monoclonal antibody‐coated latex and capillary electrophoresis
Authors: Gao Peng , Xu Guowang , Shi Xianzhe , Yuan Kailong , Tian Jing 
Published: April 2006

AbstractThe rapid detection of pathogenic bacteria is extremely important in biotechnology and clinical diagnosis. CE has been utilized in the field of bacterial analysis for many years, but to some extent, simultaneous separation and identification of certain microbes from complex samples by CE coupled with UV detector is still a challenge. In this paper, we propose a new strategy for rapid separation and identification of Staphylococcus aureus (S. aureus) in bacterial mixtures by means of specific mAb‐coated latex coupled with CZE. An appropriate set of conditions that selectively isolated S. aureus from the microorganisms Escherichia coli, Pseudomonas aeruginosa, and Klebsiella pneumoniae were established. S. aureus could be differentiated from the others by unique peaks in the electropherograms. The validity was also confirmed by LIF with antibodies specific to both the latex and the microbial cells. The LOD is as low as 9.0×105 colony forming unit/mL. We have also utilized this technology to identify S. aureus in a stool sample coming from a healthy volunteer spiked successfully with S. aureus. This CZE‐UV technique can be applied to rapid diagnosis of enteritis caused by S. aureus or other bacterial control‐related fields needing rapid identification of target pathogens from microbial mixtures. In theory, this method is suitable for the detection of any bacterium as long as corresponding bacterium‐specific antibody‐coated latex is available.