bluuebunny/crossref_metadata_2025_split huggingface dataset:
Multimodal Interventional Molecular Imaging of Tumor Margins and Distant Metastases by Targeting αvβ3 Integrin
Authors: Bunschoten Anton , Buckle Tessa , Visser Nils L. , Kuil Joeri , Yuan Hushan , Josephson Lee , Vahrmeijer Alexander L. , van Leeuwen Fijs W. B. 
Published: April 2012

Abstractαvβ3 Integrin is involved in (tumor‐induced) angiogenesis and is a promising candidate for the specific visualization of both primary tumors and of their distant metastases. Combination of radioactive and fluorescent imaging labels in a single multimodal, or rather hybrid, RGD‐based imaging agent enables integration of pre‐, intra‐, and postoperative angiogenesis imaging. A hybrid imaging agent targeting the αvβ3 integrin—111In‐MSAP‐RGD (MSAP=multifunctional single‐attachment‐point reagent), which contains a targeting moiety, a pentetic acid (DTPA) chelate, and a cyanine dye—was evaluated for its potential value in combined lesion detection and interventional molecular imaging in a 4T1 mouse breast cancer model. SPECT/CT and fluorescence imaging were used to visualize the tumor in vivo. Tracer distribution was evaluated ex vivo down to the microscopic level. The properties of 111In‐MSAP‐RGD were compared with those of 111In‐DTPA‐RGD. Biodistribution studies revealed a prolonged retention and increased tumor accumulation of 111In‐MSAP‐RGD relative to 111In‐DTPA‐RGD. With 111In‐MSAP‐RGD, identical features could be visualized preoperatively (SPECT/CT) and intraoperatively (fluorescence imaging). As well as the primary tumor, 111In‐MSAP‐RGD also enabled detection and accurate excision of distant metastases in the head and neck region of the mice. Therefore, the hybrid RGD derivative 111In‐MSAP‐RGD shows potential in preoperative planning and fluorescence‐based surgical intervention.
Key Amino Acid Residues for Reversed or Improved Enantiospecificity of an ω‐Transaminase
Authors: Humble Maria Svedendahl , Cassimjee Karim Engelmark , Abedi Vahak , Federsel Hans‐Jürgen , Berglund Per 
Published: April 2012

AbstractTransaminases inherently possess high enantiospecificity and are valuable tools for stereoselective synthesis of chiral amines in high yield from a ketone and a simple amino donor such as 2‐propylamine. Most known ω‐transaminases are (S)‐selective and there is, therefore, a need of (R)‐selective enzymes. We report the successful rational design of an (S)‐selective ω‐transaminase for reversed and improved enantioselectivity. Previously, engineering performed on this enzyme group was mainly based on directed evolution, with few exceptions. One reason for this is the current lack of 3D structures. We have explored the ω‐transaminase from Chromobacterium violaceum and have used a homology modeling/rational design approach to create enzyme variants for which the activity was increased and the enantioselectivity reversed. This work led to the identification of key amino acid residues that control the activity and enantiomeric preference. To increase the enantiospecificity of the C. violaceum ω‐transaminase, a possible single point mutation (W60C) in the active site was identified by homology modeling. By site‐directed mutagenesis this enzyme variant was created and it displayed an E value improved up to 15‐fold. In addition, to reverse the enantiomeric preference of the enzyme, two other point mutations (F88A/A231F) were identified. This double mutation created an enzyme variant, which displayed substrate dependent reversed enantiomeric preference with an E value shifted from 3.9 (S) to 63 (R) for 2‐aminotetralin.
Highly Concentrated Aqueous Dispersions of Graphene Exfoliated by Sodium Taurodeoxycholate: Dispersion Behavior and Potential Application as a Catalyst Support for the Oxygen‐Reduction Reaction
Authors: Sun Zhenyu , Masa Justus , Liu Zhimin , Schuhmann Wolfgang , Muhler Martin 
Published: April 2012

AbstractA high‐yielding exfoliation of graphene at high concentrations in aqueous solutions is critical for both fundamental study and future applications. Herein, we demonstrate the formation of stable aqueous dispersions of pristine graphene by using the surfactant sodium taurodeoxycholate under tip sonication at concentrations of up to 7.1 mg mL−1. TEM showed that about 8 % of the graphene flakes consisted of monolayers and 82 % of the flakes consisted of less than five layers. The dispersions were stable regardless of freezing (−20 °C) or heat treatment (80 °C) for 24 h. The concentration could be significantly improved to about 12 mg mL−1 by vacuum‐evaporation of the dispersions at ambient temperature. The as‐prepared graphene dispersions were readily cast into conductive films and were also processed to prepare Pt/graphene nanocomposites that were used as highly active electrocatalysts for the oxygen‐reduction reaction.
Scaffold‐Inspired Enantioselective Synthesis of Biologically Important Spiro[pyrrolidin‐3,2′‐oxindoles] with Structural Diversity through Catalytic Isatin‐Derived 1,3‐Dipolar Cycloadditions
Authors: Shi Feng , Tao Zhong‐Lin , Luo Shi‐Wei , Tu Shu‐Jiang , Gong Liu‐Zhu 
Published: April 2012

AbstractCatalytic asymmetric construction of the biologically important spiro[pyrrolidin‐3,2′‐oxindole] scaffold with contiguous quaternary stereogenic centers in excellent stereoselectivities (up to >99:1 d.r., 98 % ee) has been established by using an organocatalytic 1,3‐dipolar cycloaddition of isatin‐based azomethine ylides. This protocol represents the first example of catalytic asymmetric 1,3‐dipolar cycloadditions involving azomethine ylides generated in situ from unsymmetrical cyclic ketones. In addition, theoretical calculations were performed on the transition state of the reaction to understand the stereochemistry. Preliminary bioassays with these spiro[pyrrolidin‐3,2′‐oxindole] revealed that several compounds showed moderate cytotoxicity to SW116 cells.
Synthesis, Anti‐HIV Activity Studies, and in silico Rationalization of Cyclobutane‐Fused Nucleosides
Authors: Figueras Antoni , Miralles‐Llumà Rosa , Flores Ramon , Rustullet Albert , Busqué Félix , Figueredo Marta , Font Josep , Alibés Ramon , Maréchal Jean‐Didier 
Published: April 2012

AbstractThe present work describes some recent approaches to novel 3‐oxabicyclo[3.2.0]heptane‐type nucleosides structurally similar to the potent anti‐HIV agent stavudine (d4T). To gain knowledge at the molecular level relevant for further synthetic designs, the lack of activity of these compounds was investigated by computational approaches accounting for three main physiological requirements of anti‐HIV nucleosides: their drug‐likeness, their activation process, and their subsequent interaction with HIV reverse transcriptase (HIV‐RT). Our results show that the inclusion of the fused cyclobutane at the 2′‐ and 3′‐positions of the sugar portion provides drug‐like compounds. Nonetheless, the presence of this cyclobutane moiety prevents binding orientations consistent with the catalytic activation for at least one of the enzymes known to activate d4T. To the best of our knowledge, this is the first study to explicitly consider the simulation of the entire activation process to rationalize anti‐HIV activities.
Small‐strain heterogeneous elastoplasticity revisited
Authors: Francfort Gilles A. , Giacomini Alessandro 
Published: April 2012

AbstractThe elastoplastic quasi‐static evolution of a multiphase material—a material with a pointwise varying yield surface and elasticity tensor, together with interfaces between the phases—is revisited in the context of conservative globally minimizing movements. Existence is shown, and classical evolutions are recovered under natural constraints on the plastic dissipation potential. Special attention is paid to the interfaces where the correct dissipation has to be enforced on the interfaces. Further, the evolution is shown to be a limit of that obtained for a model with linear isotropic hardening as the hardening becomes vanishingly small. The duality between plastic strains and admissible stresses is also revisited for Lipschitz boundaries, and its role in deriving a classical evolution is circumscribed. © 2012 Wiley Periodicals, Inc.
Photoinduced Electron Transfer in a Ferrocene–Distyryl BODIPY Dyad and a Ferrocene–Distyryl BODIPY–C60 Triad
Authors: Liu Jian‐Yong , El‐Khouly Mohamed E. , Fukuzumi Shunichi , Ng Dennis K. P. 
Published: April 2012

AbstractA ferrocene–distyryl BODIPY dyad and a ferrocene–distyryl BODIPY–C60 triad are synthesized and characterized. Upon photoexcitation at the distyryl BODIPY unit, these arrays undergo photoinduced electron transfer to form the corresponding charge‐separated species. Based on their redox potentials, determined by cyclic voltammetry, the direction of the charge separation and the energies of these states are revealed. Femtosecond transient spectroscopic studies reveal that a fast charge separation (kCS=1.0×1010 s−1) occurs for both the ferrocene–distyryl BODIPY dyad and the ferrocene–distyryl BODIPY–C60 triad, but that a relatively slow charge recombination is observed only for the triad. The lifetime of the charge‐separated state is 500 ps. Charge recombination of the dyad and triad leads to population of the triplet excited sate of ferrocene and the ground state, respectively.
Opportunistic channel allocation decision making in cognitive radio communications
Authors: Shatila Hazem , Khedr Mohamed , Reed Jeffrey H. 
Published: April 2012

SUMMARYThe global spread of wireless devices with mobile Internet access and the increasing demand of multimedia‐based applications are fueling the need for wireless broadband networks. IEEE 802.16 and 802.20 are standards for a broadband wireless access with promising cognitive radio features to support mobile Internet access. However, because of the fast changing radio environment and the demand for dynamic spectrum allocation mechanisms, these standards must continuously readjust different radio parameters. The cognitive radio makes decisions based on its built‐in inference engine, which also in time can adapt itself to different situations through the process of learning from experience. In this paper we present an automated opportunistic decision making and learning process for cognitive radio based on uncertainty reasoning algorithms. This novel approach is well suited in fast changing wireless environments with vague, incomplete, and heterogeneous information. Theory and simulations prove that decision making and learning of the cognitive radio based on the proposed approach cope with the changes in the radio environment. In this work we use fuzzy logic for the learning and decision making of the cognitive radio. Simulation also show that our approach provides accurate and precise decisions on allocating spectrum to mobile Internet users even in fast varying radio conditions. Copyright © 2012 John Wiley & Sons, Ltd.
Host plant defense signaling in response to a coevolved herbivore combats introduced herbivore attack
Authors: Woodard Anastasia M. , Ervin Gary N. , Marsico Travis D. 
Published: April 2012

AbstractDefense‐free space resulting from coevolutionarily naïve host plants recently has been implicated as a factor facilitating invasion success of some insect species. Host plants, however, may not be entirely defenseless against novel herbivore threats. Volatile chemical‐mediated defense signaling, which allows plants to mount specific, rapid, and intense responses, may play a role in systems experiencing novel threats. Here we investigate defense responses of host plants to a native and exotic herbivore and show that (1) host plants defend more effectively against the coevolved herbivore, (2) plants can be induced to defend against a newly‐associated herbivore when in proximity to plants actively defending against the coevolved species, and (3) these defenses affect larval performance. These findings highlight the importance of coevolved herbivore‐specific defenses and suggest that naïveté or defense limitations can be overcome via defense signaling. Determining how these findings apply across various host–herbivore systems is critical to understand mechanisms of successful herbivore invasion.
Phylogenetic analysis of cryptic speciation in the polychaete Pygospio elegans
Authors: Kesäniemi J. E. , Rawson P. D. , Lindsay S. M. , Knott K. E. 
Published: April 2012

AbstractDevelopment in marine invertebrate species can take place through a variety of modes and larval forms, but within a species, developmental mode is typically uniform. Poecilogony refers to the presence of more than one mode of development within a single species. True poecilogony is rare, however, and in some cases, apparent poecilogony is actually the result of variation in development mode among recently diverged cryptic species. We used a phylogenetic approach to examine whether poecilogony in the marine polychaete worm, Pygospio elegans, is the result of cryptic speciation. Populations of worms identified as P. elegans express a variety of developmental modes including planktonic, brooded, and intermediate larvae; these modes are found both within and among populations. We examined sequence variation among partial mitochondrial cytochrome c oxidase subunit I sequences obtained for 279 individual worms sampled across broad geographic and environmental scales. Despite a large number of unique haplotypes (121 haplotypes from 279 individuals), sequence divergence among European samples was low (1.7%) with most of the sequence variation observed within populations, relative to the variation among regions. More importantly, we observed common haplotypes that were widespread among the populations we sampled, and the two most common haplotypes were shared between populations differing in developmental mode. Thus, our results support an earlier conclusion of poecilogony in P elegans. In addition, predominantly planktonic populations had a larger number of population‐specific low‐frequency haplotypes. This finding is largely consistent with interspecies comparisons showing high diversity for species with planktonic developmental modes in contrast to low diversity in species with brooded developmental modes.
A comparison of four methods for detecting weak genetic structure from marker data
Authors: Jones Owen R. , Wang Jinliang 
Published: April 2012

AbstractGenetic structure is ubiquitous in wild populations and is the result of the processes of natural selection, genetic drift, mutation, and gene flow. Genetic drift and divergent selection promotes the generation of genetic structure, while gene flow homogenizes the subpopulations. The ability to detect genetic structure from marker data diminishes rapidly with a decreasing level of differentiation among subpopulations. Weak genetic structure may be unimportant over evolutionary time scales but could have important implications in ecology and conservation biology. In this paper we examine methods for detecting and quantifying weak genetic structures using simulated data. We simulated populations consisting of two putative subpopulations evolving for up to 50 generations with varying degrees of gene flow (migration), and varying amounts of information (allelic diversity). There are a number of techniques available to detect and quantify genetic structure but here we concentrate on four methods: FST, population assignment, relatedness, and sibship assignment. Under the simple mating system simulated here, the four methods produce qualitatively similar results. However, the assignment method performed relatively poorly when genetic structure was weak and we therefore caution against using this method when the analytical aim is to detect fine‐scale patterns. Further work should examine situations with different mating systems, for example where a few individuals dominate reproductive output of the population. This study will help workers to design their experiments (e.g., sample sizes of markers and individuals), and to decide which methods are likely to be most appropriate for their particular data.
Structural and DFT Studies of Dibromine and Diiodine Adducts of a Sulfur‐Rich Thiocarbonyl Donor
Authors: Mancini Annalisa , Pala Luca , Aragoni M. Carla , Arca Massimiliano , Devillanova Francesco A. , Hursthouse Michael B. , Light Mark E. , Skabara Peter J. , Bricklebank Neil 
Published: April 2012

Abstract4,5‐Bis(benzoylthio)‐1,3‐dithiole‐2‐thione (1) forms molecular adducts with dibromine (2) and diiodine (3), which display a range of complementary primary X–X and S–X and secondary S···X and X···X bonding interactions. Compounds 2 and 3 were characterised by X‐ray diffraction analysis and FT‐Raman spectroscopy. Compound 2, which is derived from the additive dibromine oxidation of 1, features a near linear Br–S–Br moiety that is coplanar with the dithiole‐2‐thione heterocycle. The S–Br bonds in 2 are asymmetric; the asymmetry arises mainly through a combination of intramolecular S···Br bonds between the Br atoms and the thioether S atoms of the donor, and an intermolecular S···Br contact between one of the bromine atoms and the hypervalent S atom of an adjacent molecule. DFT calculations carried out on 2 with different functionals agree and show that the geometry featuring the SBr2 moiety coplanar with the heterocycle is more stable by about 9 kcal mol–1 than that with the SBr2 unit perpendicular to the plane of the heterocycle. DFT calculations indicate that the formation of 2 can be explained based on the charge distribution on the hypothetical cationic intermediate [1–Br]+. Diiodine complex 3 is a molecular charge‐transfer species, with an almost linear S–I–I moiety. The unit cell contains two molecules of donor 1, related by a centre of inversion, which form a dimer pair held together by two intermolecular S···S and two S···O contacts. The packing of the dimers generates various cavities that are able to accommodate I2 molecules as “guests”, in one case the guest diiodine molecule bonds with the sulfur atoms of the benzoylthio‐groups and acts as a bridge between adjacent dimers, in another the diiodine is disordered along the channel‐like cavity. The terminal iodine atom of each S–I–I fragment interacts with two additional I2 molecules leading to infinite chains in the [01–1] direction.
Catalysis of C–C Cross‐Coupling Reactions in Aqueous Solvent by Bis‐ and Tris(ferrocenyltriazolylmethyl)arene–β‐Cyclodextrin‐Stabilized Pd0 Nanoparticles
Authors: Liang Liyuan , Diallo Abdou K. , Salmon Lionel , Ruiz Jaime , Astruc Didier 
Published: April 2012

AbstractMono‐, bis‐, and tris(4‐ferrocenyl‐1,2,3‐triazolylmethyl)arene–β‐cyclodextrin adducts have been used to prepare new Pd0 nanoparticle (PdNP) catalysts for C–C cross‐coupling reactions in EtOH/H2O. The results show that these catalysts work well in Miyaura–Suzuki and Heck reactions with iodoarenes at 25 and 80 °C, respectively, with turnover numbers (TONs) of up to 31000 for standard Miyaura–Suzuki reactions of PhI when 10 ppm of the Pd catalyst (5 nm PdNPs) were used. The results show the benefit for PdNP catalysis of encapsulating hydrophobic catalytic systems between peripheral water‐solubilizing cyclodextrins as bolamphiphile‐like materials because the open monoferrocenyltriazolylmethylbenzene system shows a considerably reduced catalytic efficiency compared with bis‐ and tris(4‐ferrocenyl‐1,2,3‐triazolylmethyl)arene–β‐cyclodextrin adducts.
Copper(I)‐Dioxygen Reactivity in a Sterically Demanding Tripodal Tetradentate tren Ligand: Formation and Reactivity of a Mononuclear Copper(II) End‐On Superoxo Complex
Authors: Kobayashi Yuki , Ohkubo Kei , Nomura Takashi , Kubo Minoru , Fujieda Nobutaka , Sugimoto Hideki , Fukuzumi Shunichi , Goto Kei , Ogura Takashi , Itoh Shinobu 
Published: April 2012

AbstractReaction of a copper(I) complex supported by a sterically demanding tripodal tetradentate ligand, HIPT3tren, and O2 gave a mononuclear copper(II) end‐on superoxo complex. Spectroscopic (UV/Vis, resonance Raman, ESR, and 1H‐NMR) and DFT studies have been performed. The O2‐binding process as well as the reaction toward external substrates have been investigated kinetically to demonstrate the unique behavior of the copper(II) end‐on superoxo complex, which may occur as a result of the existence of the hydrophobic core around the copper coordination sphere created by the HIPT3tren ligand.
Stormwater input of pyrethroid insecticides to an urban river
Authors: Weston Donald P. , Lydy Michael J. 
Published: April 2012

Abstract
The American River flows for nearly 50 km through highly urbanized lands surrounding Sacramento, California, USA. Twenty-three streams, drainage canals, or pumping stations discharge urban runoff to the river, with the cumulative effect of nearly doubling the river's flow during rain events. During winter storms, the water column in the most downstream 13-km reach of the river exhibited toxicity to the standard testing species, Hyalella azteca, in 52% of samples, likely because of the pyrethroid insecticide bifenthrin. The compound is heavily used by professional pest controllers, either as a liquid perimeter treatment around homes or as granules broadcast over landscaped areas. It was found in 11 of 12 runoff sources examined, at concentrations averaging five times the H. azteca 96-h EC50. Quantified inputs of bifenthrin should have been sufficient to attain peak concentrations in the river twice those actually observed, suggesting loss by sedimentation of particulates and pesticide adsorption to the substrate and/or vegetation. Nevertheless, observed bifenthrin concentrations in the river were sufficient to cause water column toxicity, demonstrated during six storms studied over three successive winters. Toxicity and bifenthrin concentrations were greatest when river flow was low (&lt;23 m3/s) but persisted even at atypically high flows (585 m3/s). Environ. Toxicol. Chem. 2012; 31: 1579–1586. © 2012 SETAC
Revisiting concepts of visceral nociception in irritable bowel syndrome
Authors: Keszthelyi D. , Troost F.J. , Simrén M. , Ludidi S. , Kruimel J.W. , Conchillo J.M. , Masclee A.A. 
Published: April 2012

AbstractBackground and ObjectiveIrritable bowel syndrome (IBS) is a common disorder characterized by abdominal pain related to defecation with a change in bowel habit. Patients with IBS often exhibit increased visceral sensitivity, which can be tested clinically by rectal balloon distension procedures. This paper aims to give an overview of mechanisms involved in visceral hypersensitivity in IBS by reviewing recent literature.Databases and Data TreatmentA literature search in the electronic databases Pubmed and MEDLINE was executed using the search terms ‘visceral pain’ or ‘visceral nociception’ or ‘visceral hypersensitivity’ and ‘irritable bowel syndrome.’ Both original articles and review articles were considered for data extraction.ResultsRecent advances in molecular neurophysiology provide knowledge to better understand the underlying mechanism in pain generation in the human gut, in particular, in IBS patients. Sensitization of peripheral nociceptive afferents, more specifically high‐threshold afferents, has been proposed as one of the principle mechanism in the development of visceral hypersensitivity. On the other hand, central mechanisms also play an important role. In terms of clinical testing of visceral perception, considerable discrepancies remain, however, across different centres.ConclusionAlterations in the modulatory balance of pro‐ and antinociceptive central processing of noxious peripheral input may serve as in integrative hypothesis for explaining visceral hypersensitivity in IBS. Nevertheless, it remains troublesome to estimate the contribution of central and peripheral factors in visceral hypersensitivity, posing a challenge in determining effective therapeutic entities.