bluuebunny/crossref_metadata_2025_split huggingface dataset:
Role of RANK ligand in normal and pathologic bone remodeling and the therapeutic potential of novel inhibitory molecules in musculoskeletal diseases
Authors: Cohen Stanley 
Published: February 2006

AbstractThis is the first article in a new series entitled “Clinical Aspects of Molecular Research in Rheumatology,” which will appear regularly in Arthritis Care & Research. As with all health care professionals, our readership is increasingly faced with the reality that in medicine today there is simply “too much to know.” This is particularly true for those confronted by the challenges of interpreting the remarkable advances occurring in the fields of cellular and molecular biology as applied to research in rheumatology. This series will present concise reviews written by leaders in the field that are tailored to nonlaboratory‐based readers. It is hoped that these articles will provide both an overview of cutting edge science in an interpretable format, and provide direction for those desiring to learn more about the precise topics. We welcome reader feedback and ideas for future topics.Leonard H. Calabrese, DOSection Editor
Effect of membrane mimicking environment on the conformation of a pore‐forming (xSxG)6peptide
Authors: Thundimadathil Jyothi , Roeske Roger W. , Guo Lili 
Published: February 2006

AbstractThe mechanism of membrane interaction by β‐sheet peptides is important to understand fundamental principles of folding of β‐barrel proteins and various β‐amyloid proteins. Here, we examined the conformational characteristics of a porin‐like channel forming (xSxG)6peptide in solution and membrane‐mimicking environments (CD and ATR–IR) to understand the structural changes of the peptide during membrane association and channel formation. A comparison of the peptide conformations in different microenvironments showed that β‐sheet formation is enhanced in membrane‐mimicking liposomes and SDS‐micelles. The lipid‐induced β‐sheet formation was confirmed by the formation of a characteristic β‐sheet structure on mixing a methanolic solution of the peptide (partially folded) with preformed liposomes. The amphipathicity of the peptide; increased hydrogen bonding, hydrophilicity, and reduction in dimensionality of the membrane surface; membrane–peptide interaction–forces; and presence of flexible glycines might facilitate β‐sheet formation in membranes. Though the CD spectra of both the peptide‐bound and peptide‐incorporated lipids are reminiscent of a β‐sheet structure, a significant variation in the peak positions of the two β‐sheet structures was noticed. The channel characteristics of (xSxG)6in the presence of low ionic strength solutions of NEt3BzCl and glucosammonium chloride are comparable to those reported under high ionic strength solutions. Altogether the data suggest that the channel formation by (xSxG)6proceeds via β‐sheet aggregate formation at the membrane surface, β‐sheet insertion, and rearrangement into a β‐barrel–like structure. The β‐barrel–like channel formation most likely arises from a sequence similarity to β‐barrel porins whereas the lipid‐induced β‐sheet formation is governed by the above‐mentioned factors. © 2006 Wiley Periodicals, Inc. Biopolymers (Pept Sci) 84: 317–328, 2006This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com
Orientational order of Australian spider silks as determined by solid‐state NMR
Authors: Bonev B. , Grieve S. , Herberstein M. E. , Kishore A. I. , Watts A. , Separovic F. 
Published: February 2006

AbstractA simple solid‐state NMR method was used to study the structure of 13C‐ and 15N‐enriched silk from two Australian orb‐web spider species, Nephila edulis and Argiope keyserlingi. Carbon‐13 and 15N spectra from alanine‐ or glycine‐labeled oriented dragline silks were acquired with the fiber axis aligned parallel or perpendicular to the magnetic field. The fraction of oriented component was determined from each amino acid, alanine and glycine, using each nucleus independently, and attributed to the ordered crystalline domains in the silk. The relative fraction of ordered alanine was found to be higher than the fraction of ordered glycine, akin to the observation of alanine‐rich domains in silk‐worm (Bombyx mori) silk. A higher degree of crystallinity was observed in the dragline silk of N. edulis compared with A. keyserlingi, which correlates with the superior mechanical properties of the former © 2006 Wiley Periodicals, Inc. Biopolymers 82:134–143, 2006This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com
X‐ray photoelectron spectroscopic and Raman analysis of silk fibroin–Cu(II) films
Authors: Zhou Li , Chen Xin , Dai Weilin , Shao Zhengzhong 
Published: February 2006

AbstractThere is evidence to suggest that Cu(II) is involved in the natural spinning process of a silkworm helping to convert the concentrated silk fibroin (SF) solution (or dope) into tough insoluble threads. To investigate the interaction between SF and Cu(II), a series of regenerated SF (RSF) films with different mass ratios of Cu(II) to SF were prepared. X‐ray photoelectron spectroscopy (XPS) was employed to study the chemical interaction between Cu(II) and SF in these Cu(II)–RSF films. A significant change in the binding energy of Cu 2p3/2 demonstrated that the chemical state of Cu(II) in the Cu(II)–RSF films was affected by the interaction between Cu(II) and SF. Moreover, chemical shifts of N 1s and O 1s of SF were also detected, implying that Cu(II) may coordinate with both N and O atoms in the SF. In addition, Raman spectra of the same series of Cu(II)–RSF films recorded the conformation transition of SF that may occur by the coordination of Cu(II) and SF macromolecular chains. © 2006 Wiley Periodicals, Inc. Biopolymers 82: 144–151, 2006This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com
Staging of chronic myeloid leukemia in the imatinib era
Authors: Cortes Jorge E. , Talpaz Moshe , O'Brien Susan , Faderl Stefan , Garcia‐Manero Guillermo , Ferrajoli Alessandra , Verstovsek Srdan , Rios Mary B. , Shan Jenny , Kantarjian Hagop M. 
Published: February 2006

AbstractBACKGROUNDSeveral staging classification systems, all of which were designed in the preimatinib era, are used for chronic myeloid leukemia (CML). The World Health Organization (WHO) recently proposed a new classification system that has not been validated clinically. The authors investigated the significance of the WHO classification system and compared it with the classification systems used to date in imatinib trials (“standard definition”) to determine its impact in establishing the outcome of patients after therapy with imatinib.METHODSIn total, 809 patients who received imatinib for CML were classified into chronic phase (CP), accelerated phase (AP), and blast phase (BP) based on standard definitions and then were reclassified according to the new WHO classification system. Their outcomes with imatinib therapy were compared, and the value of individual components of these classification systems was determined.RESULTSWith the WHO classification, 78 patients (10%) were reclassified: 45 patients (6%) were reclassified from CP to AP, 14 patients (2%) were reclassified from AP to CP, and 19 patients (2%) were reclassified from AP to BP. The rates of complete cytogenetic response for patients in CP, AP, and BP according to the standard definition were 72%, 45%, and 8%, respectively. After these patients were reclassified according to WHO criteria, the response rates were 77% (P = 0.07), 39% (P = 0.28), and 11% (P = 0.61), respectively. The 3‐year survival rates were 91%, 65%, and 10%, respectively, according to the standard classification and 95% (P = 0.05), 63% (P = 0.76), and 16% (P = 0.18), respectively, according to the WHO classification. Patients who had a blast percentage of 20–29%, which is considered CML‐BP according to the WHO classification, had a significantly better response rate (21% vs. 8%; P = 0.11) and 3‐year survival rate (42% vs. 10%; P = 0.0001) compared with patients who had blasts ≥ 30%.CONCLUSIONSDifferent classification systems had an impact on the outcome of patients, and some prognostic features had different prognostic implications in the imatinib era. The authors believe that a new, uniform staging system for CML is warranted, and they propose such a system. Cancer 2006. © 2006 American Cancer Society.
Homolysis of N‐alkoxyamines: A Computational Study
Authors: Gaudel‐Siri Anouk , Siri Didier , Tordo Paul 
Published: February 2006

AbstractDuring nitroxide‐mediated polymerization (NMP) in the presence of a nitroxide R2(R1)NO., the reversible formation of N‐alkoxyamines [PON(R1)R2] reduces significantly the concentration of polymer radicals (P.) and their involvement in termination reactions. The control of the livingness and polydispersity of the resulting polymer depends strongly on the magnitude of the bond dissociation energy (BDE) of the CON(R1)R2bond. In this study, theoretical BDEs of a large series of model N‐alkoxyamines are calculated with the PM3 method. In order to provide a predictive tool, correlations between the calculated BDEs and the cleavage temperature (Tc ), and the dissociation rate constant (kd ), of the N‐alkoxyamines are established. The homolytic cleavage of the NOC bond is also investigated at the B3P86/6‐311++G(d,p)//B3LYP/6‐31G(d), level. Furthermore, a natural bond orbital analysis is carried out for some N‐alkoxyamines with a OCON(R1)R2fragment, and the strengthening of their CON(R1)R2bond is interpreted in terms of stabilizing anomeric interactions.
A Theoretical Study of the Structure and Bonding of UOX4(X=F, Cl, Br, I) Molecules: The Importance of InverseTransInfluence
Authors: Kovács Attila , Konings Rudy J. M. 
Published: February 2006

AbstractThe structural and bonding properties of the uranium(VI) oxyhalides UOX4(X=F, Cl, Br, I) have been investigated by quantum chemical calculations at three different levels of theory: quasi‐relativistic density functional theory (DFT) in conjunction with a triple‐zeta all‐electron basis set, as well as MP2 and the Becke3–Perdew–Wang91 exchange‐correlation functional in conjunction with relativistic effective core potentials. The computations located four stationary points on the potential energy surface: a tetragonal pyramid with the O atom in the apical position (C4v ), a trigonal bipyramid with the O atom in the equatorial position (C2v ), a trigonal bipyramid with the O atom in the axial position (C3v ) and aCsstructure derived fromC3vby opening the XeqUXeqangle to near 180°. TheCsminimum, however, seems to be an artefact of the Becke–Perdew functional on the flat potential energy surface. In theC3vstructure, the linear XaxUO moieties show clearly the geometrical consequences of the inversetransinfluence (ITI) effect. This interaction can stabilise these sterically less favoured geometries. Two important trends are revealed by our computations: 1) UOX4with the small X=F prefers theC3vstructure, whereas with increasing halogen size the sterically less crowdedC2vstructure is more important; and 2) MP2 theory accounts to a lesser extent for the ITI effect with respect to DFT, which results in different structural preferences (MP2 forC2v , DFT forC3v ) in the heavier halides. In addition, an important bonding property of the UOX4molecules is the clear triple‐bond character of the formally double UO bonds.
Computational Studies on the Cyclization of Polycyclic Aromatic Hydrocarbons in the Synthesis of Curved Aromatic Derivatives
Authors: Buñuel Elena , Marco‐Martínez Juan , Díaz‐Tendero Sergio , Martín Fernando , Alcamí Manuel , Cárdenas Diego J. 
Published: February 2006

AbstractComputational studies on the cyclization reactions of some polycyclic aromatic hydrocarbons (PAHs) were performed at the DFT level. Compounds C26H14 and C24H14, which show the connectivity of C60 fullerene fragments, were chosen as suitable models to study the formation of curved derivatives by six‐ or five‐membered ring formation, upon oxidation to their radical cations. Four possible pathways for the cyclization process were considered: a) initial CC bond formation to afford a curved derivative, followed by dehydrogenation; b) homolytic CH cleavage prior to cyclization; c) initial concerted H2 elimination and subsequent cyclization; and d) deprotonation of the radical cations prior to cyclization. Computed reaction and activation energies for these reactions show that direct cyclization from radical cations (pathway a) is the lowest‐energy mechanism. The formation of five‐membered rings is somewhat more favourable than benzannulation. After new cycle formation, homolytic CH dissociation to afford the corresponding cations is the most favourable process. These cations react with H. without barrier to give H2. Intermediate deprotonations are strongly disfavoured. The relatively low activation energies compared with carbon cage rearrangements suggest that ionization of PAHs can be used for the tailored preparation of nonplanar derivatives from suitable precursors.
A Kinetic Study of the Reaction between N,N‐Dimethyl‐p‐toluidine and its Electrogenerated Radical Cation in a Room Temperature Ionic Liquid
Authors: Evans Russell G. , Compton Richard G. 
Published: February 2006

AbstractThe reaction between N,N‐dimethyl‐p‐toluidine (DMT) and the radical cation generated through its one‐electron oxidation has been studied electrochemically in the room temperature ionic liquid N‐methyl‐N‐butylpyrrolidinium bis(trifluoromethylsulfonyl)imide, [Py14][NTf2]. Kinetic information obtained as linear sweep and cyclic voltammetry collected at 5 μm, 10 μm and 0.3 mm diameter platinum disk electrodes over a range of initial substrate concentrations and scan rates spanning five orders of magnitude was complemented by chronoamperometric measurements designed to probe the rate of diffusion. At the fastest scan rates the homogeneous reactions following the initial electron transfer were effectively out‐run, facilitating an assessment of the electrode kinetics using DIGISIM®and a validated Nicholson′s method. Through digital simulation the voltammetry was then shown to be consistent with a mechanism established for the same reaction in acetonitrile, involving dimerisation of the DMT radicals following an initial and rate‐determining proton transfer step. After careful consideration of all parameters, a bimolecular rate constant of (3.4±1.1)×102dm3 mol−1s−1was deduced by fitting the data. This was compared to the equivalent value for acetonitrile and, in light of this, the implications on the viability of ionic liquids for use as alternative mainstream solvents briefly assessed.
Resonant X‐ray Scattering: A Tool for Structure Elucidation in Liquid Crystals
Authors: Gleeson Helen F. , Hirst Linda S. 
Published: February 2006

AbstractThe use of resonant X‐ray scattering to determine structures in liquid crystal systems is surveyed. This powerful experimental technique utilises “forbidden reflections” to determine the subtle differences in interlayer orientation that differentiate several smectic systems. The technique relies on the materials containing an atom to which the X‐ray energy can be tuned, usually sulphur or selenium. Experiments are often carried out on free‐standing films that provide a highly monodomain structure that allows high‐resolution measurements to be made, and, hence, structural details to be determined. Alternatively, resonant scattering has been demonstrated for materials contained in glass devices that permit the application of electric fields to the system, in a manner analogous to that used in liquid crystal devices. The resonant scattering technique provides unequivocal descriptions of the packing in smectic systems, and the way in which the packing is distorted in electric fields. This Minireview describes the principles behind resonant X‐ray scattering, its application to liquid crystals and some of the potential for the future.
Exploring Two‐State Reaction Pathways in the Photodimerization of Cyclohexadiene
Authors: Domingo Luis R. , Pérez‐Prieto Julia 
Published: February 2006

AbstractThe ground‐ (S0 ) and lowest triplet‐state (T1 ) pathways associated with dimerization of cyclohexadiene to give [2+2] and [4+2] cycloadducts have been theoretically studied at the UBLYP and UB3LYP levels of theory with the 6‐31G* basis set. The DFT energies were validated by CCSD(T) single‐point energy calculations. These cycloaddition reactions follow stepwise mechanisms with formation of bis‐allylic biradical (BB) intermediates. In the S0 ground state, the interaction between two cyclohexadiene molecules with formation of BB intermediate IN(S0 ) has a large activation enthalpy of 32.0 kcal mol−1. On the other hand, CC bond‐formation in the lowest triplet state (T1 ) leading to BB intermediate IN(T1 ) has a low activation enthalpy of 5.0 kcal mol−1, but the subsequent ring closure involves a very large activation enthalpy of 43.4 kcal mol−1. Triplet‐to‐singlet intersystem crossing from IN(T1 ) to IN(S0 ) favors cyclization to give the corresponding [2+2] and [4+2] cycloadducts.
Microwave Synthesis of Nanoporous Materials
Authors: Tompsett Geoffrey A. , Conner William Curtis , Yngvesson K. Sigfrid 
Published: February 2006

AbstractStudies in the last decade suggest that microwave energy may have a unique ability to influence chemical processes. These include chemical and materials syntheses as well as separations. Specifically, recent studies have documented a significantly reduced time for fabricating zeolites, mixed oxide and mesoporous molecular sieves by employing microwave energy. In many cases, microwave syntheses have proven to synthesize new nanoporous structures. By reducing the times by over an order of magnitude, continuous production would be possible to replace batch synthesis. This lowering of the cost would make more nanoporous materials readily available for many chemical, environmental, and biological applications. Further, microwave syntheses have often proven to create more uniform (defect‐free) products than from conventional hydrothermal synthesis. However, the mechanism and engineering for the enhanced rates of syntheses are unknown. We review the many studies that have demonstrated the enhanced syntheses of nanoporous oxides and analyze the proposals to explain differences in microwave reactions. Finally, the microwave reactor engineering is discussed, as it explains the discrepancies between many microwave studies.
Femtosecond Relaxation Dynamics of Solvated Electrons in Liquid Ammonia
Authors: Lindner Jörg , Unterreiner Andreas‐N. , Vöhringer Peter 
Published: February 2006

AbstractThe ultrafast relaxation dynamics of the well‐known solvated electron in liquid ammonia solutions are investigated with femtosecond near‐infrared pump–probe absorption spectroscopy. Immediately after photoexcitation, the dynamic absorption spectrum of the electron is substantially red‐shifted with respect to its stationary spectrum. A subsequent dynamic blue shift of the pump–probe spectrum occurs on a timescale of 150 fs. The data are understood in terms of ground‐state “cooling” and can be quantitatively simulated by an intuitive temperature‐jump model employing a dynamically evolving Kubo line shape for the electronic resonance. A simple estimate implies that, on average, the electron in the liquid is coordinated to six nearest‐neighbor ammonia molecules. An equivalent analysis of the data based on a bubble‐formation/cavity‐contraction mechanism is briefly outlined.
Theoretical Study on the Structures and Electronic Spectra of TCNE2−
Authors: Cuesta Inmaculada García , Sánchez‐Marín José , Sánchez de Merás Alfredo M. J. 
Published: February 2006

AbstractInvestigations into the charge‐separated states and electron‐transfer transitions in tetracyanoethylene (TCNE) complexes have recently generated much interest. In this work we present theoretical calculations showing that the most stable structure of the dianion TCNE2−has D2dsymmetry in vacuum as well as in the solvents dichloromethane and acetonitrile. By means of the coupled cluster linear response, we compute the vertical electronic spectrum in both the gas phase and solution. The theoretical results are compared to the experimental data and good agreement is achieved.
Enantiodiscrimination between an N‐Acetyl‐L‐cysteine SAM and Proline: An In Situ Spectroscopic and Computational Study
Authors: Bieri Marco , Bürgi Thomas 
Published: February 2006

AbstractA combination of attenuated total reflection infrared (ATR‐IR) and modulation excitation spectroscopy (MES) is used to study the enantiodiscriminating interactions between proline and a chiral, self‐assembled monolayer (SAM) of N‐acetyl‐L‐cysteine on gold. The N‐acetyl‐L‐cysteine SAM consists of a mixture of protonated and deprotonated molecules. Whereas both species are influenced by adsorbed proline, only the deprotonated molecules are involved in enantiodiscrimination. Density functional theory (DFT) calculations reveal that electrostatics dominates the interaction between the two molecules. By modulating the absolute configuration of proline over the chiral SAM, and a subsequent phase‐sensitive detection of the periodically varying signals in the ATR‐IR spectra, the small spectral differences between the diastereomeric complexes are spotted. The resulting difference spectrum is in qualitative agreement with the spectrum predicted by the DFT calculations.
Defining and maximizing PPT—a novel performance parameter for IEEE 802.11 DCF
Authors: Li Yun , Long Ke‐Ping , Zhao Wei‐Liang 
Published: February 2006

AbstractMuch research has been conducted on saturation throughput of IEEE802.11 DCF, and has led to some improvement. But increasing the successful transmission probability of packet is also important for saving stations' battery energy and decreasing the packet delay. In this paper, we define a new performance parameter, named Product of successful transmission Probability and saturation Throughput (PPT), for 802.11 DCF, which binds successful transmission probability and saturation throughput together. An analysis is given to maximize PPT. An expression of optimal minimum contention windows (CWmin) is obtained analytically for maximizing PPT. For simplicity, we give a name DCF‐PPT to the 802.11 DCF that sets its CWminaccording to this expression. The performance of DCF‐PPT is simulated with different stations in terms of saturation throughput, successful transmission probability and PPT. The simulation results indicate that, compared to 802.11 DCF, DCF‐PPT can significantly increase the PPT and successful transmission probability (about 0.95) on condition that the saturation throughput is not decreased. Copyright © 2006 John Wiley & Sons, Ltd.