bluuebunny/crossref_metadata_2025_split huggingface dataset:
Cancer in Noonan, Costello, cardiofaciocutaneous and LEOPARD syndromes
Authors: Kratz Christian P. , Rapisuwon Suthee , Reed Helen , Hasle Henrik , Rosenberg Philip S. 
Published: April 2011

AbstractNoonan syndrome (NS), Costello syndrome (CS), cardiofaciocutaneous syndrome (CFCS), and LEOPARD syndrome (now also referred to as Noonan syndrome with multiple lentigines or NSML) are clinically overlapping dominant disorders that are caused by mutations in RAS signaling pathway genes. The spectrum of cancer susceptibility in this group of disorders has not been studied in detail. We identified more than 1900 cases of NS, CS, CFCS, or NSML reported in the literature between 1937 and 2010; 88 cancers were reported. The most common cancers reported in 1051 NS subjects were neuroblastoma (n = 8), acute lymphoblastic leukemia (n = 8), low grade glioma (n = 6), and rhabdomyosarcoma (n = 6). These associations are biologically plausible, given that somatic RAS pathway mutations are known to occur in these specific cancers. In addition, 40 childhood cases of myeloproliferative disease were described in individuals with NS, several of whom experienced a benign course of this hematologic condition. We confirmed the previously described association between CS and cancer in 268 reported individuals: 19 had rhabdomyosarcoma, 4 had bladder cancer, and 5 had neuroblastoma. By age 20, the cumulative incidence of cancer was approximately 4% for NS and 15% for CS; both syndromes had a cancer incidence peak in childhood. The cancers described in CFCS and NSML overlapped with those reported in NS and CS. Future epidemiologic studies will be required to confirm the described cancer spectrum and to estimate precise cancer risks. Published 2011 Wiley‐Liss, Inc.
Stability of genetic regulatory networks with interval time‐varying delays and stochastic perturbation
Authors: He Yong , Fu Ling‐Yun , Zeng Jin , Wu Min 
Published: April 2011

AbstractThis paper studies the delay‐dependent stability for genetic regulatory networks with both interval time‐varying delays and stochastic perturbation. By considering the relationship among the time‐varying delays, its upper bound and their difference, and introducing an improved‐free‐weighting matrix (IFWM) approach, some less conservative stability criteria are proposed without ignoring any useful terms in the weak infinitesimal operator of the Lyapunov‐Krasovskii functional. Two numerical examples are given to illustrate the effectiveness and the reduced conservativeness of the obtained results.© 2011 John Wiley and Sons Asia Pte Ltd and Chinese Automatic Control Society
Fifty hertz magnetic fields individually affect chromatin conformation in human lymphocytes: Dependence on amplitude, temperature, and initial chromatin state
Authors: Sarimov Ruslan , Alipov Eugene D. , Belyaev Igor Y. 
Published: April 2011

AbstractEffects of magnetic field (MF) at 50 Hz on chromatin conformation were studied by the method of anomalous viscosity time dependence (AVTD) in human lymphocytes from two healthy donors. MF within the peak amplitude range of 5–20 µT affected chromatin conformation. These MF effects differed significantly between studied donors, and depended on magnetic flux density and initial condensation of chromatin. While the initial state of chromatin was rather stable in one donor during one calendar year of measurements, the initial condensation varied significantly in cells from another donor. Both this variation and the MF effect depended on temperature during exposure. Despite these variations, the general rule was that MF condensed the relaxed chromatin and relaxed the condensed chromatin. Thus, in this study we show that individual effects of 50 Hz MF exposure at peak amplitudes within the range of 5–20 µT may be observed in human lymphocytes in dependence on the initial state of chromatin and temperature. Bioelectromagnetics 32:570–579, 2011. © 2011 Wiley‐Liss, Inc.
Cleavage of Phosphodiesters and of DNA by a Bis(guanidinium)naphthol Acting as a Metal‐Free Anion Receptor
Authors: Ullrich Stefan , Nazir Zarghun , Büsing Arne , Scheffer Ute , Wirth Daniela , Bats Jan W. , Dürner Gerd , Göbel Michael W. 
Published: April 2011

AbstractPhosphoric acid diesters form anions at neutral pH. As a result of charge repulsion they are notoriously resistant to hydrolysis. Nucleophilic attack, however, can be promoted by different types of electrophilic catalysts that bind to the anions and reduce their negative charge density. Although in most cases phosphodiester‐cleaving enzymes and synthetic catalysts rely on Lewis acidic metal ions, some exploit the guanidinium residues of arginine as metal‐free electrophiles. Here we report that a combination of two guanidines and a hydroxy group yields highly reactive receptor molecules that can attack a broad range of phosphodiester substrates by nucleophilic displacement at phosphorus in a single‐turnover mode. Some stable O‐phosphates were isolated and characterized further by NMR spectroscopy. The bis(guanidinium)naphthols also cleave plasmid DNA, presumably by a transphosphorylation mechanism.
Model choice and squared prediction errors in PLS regression
Authors: Ergon Rolf , Halstensen Maths , Esbensen Kim H. 
Published: April 2011

AbstractSquared prediction errors (SPE) in are discussed in relation to the conventional PLSR versus bidiagonalization model and algorithm issue concerning residual and prediction consistency, with focus on process monitoring and fault detection. Our analysis leads to the conclusion that conventional PLSR based on the NIPALS algorithm is ambiguous in SPE values caused by process faults. The basic reason for this is that the sample residuals are not found as projections onto the orthogonal complement of the space where the scores and regression solution are located, and where also the statistical limit is defined. The alternative non‐orthogonalized PLSR and bidiagonalization (Bidiag2) algorithms, as well as a simple re‐formulation of the NIPALS algorithm (RE‐PLSR), give unambiguous SPE values, and the last two of these also retain orthogonal score vectors. While prediction results from all of these methods in theory are identical, our conclusion is that methods where the and SPE values for process faults are uncorrelated should be preferred. Tests with added errors on real data do not indicate that this conclusion should be altered because of such errors. Copyright © 2011 John Wiley & Sons, Ltd.
High‐Temperature Experimental and Theoretical Study of Magnetic Interactions in Diamond and Pseudo‐Diamond Frameworks Built up from Hexanuclear Tantalum Clusters
Authors: Perić Berislav , Cordier Stéphane , Cuny Jérôme , Gautier Régis , Guizouarn Thierry , Planinić Pavica 
Published: April 2011

AbstractMagnetic interactions in solid‐state tantalum cluster compounds have been evidenced by using magnetic susceptibility measurements and corroborated by broken‐symmetry DFT calculations. The three selected compounds are based on [Ta6X12(H2O)6]3+ (X=Cl or/and Br) units with edge‐bridged Ta6 octahedral clusters. Although two of them crystallise in the tetragonal space group I41/a, all compounds exhibit a similar arrangement of paramagnetic clusters related to the diamond structural framework (Fdm space group). Magnetic parameters were fitted by using the [5,4] Padé approximant of high‐temperature series expansion of susceptibility for the Heisenberg model (S=1/2) in the diamond framework, assuming only nearest‐neighbouring interactions. Such a model appropriately describes magnetic‐susceptibility measurements at temperatures T>0.7|J|/k. The magnetic interaction parameter J between two [Ta6Cl12(H2O)6]3+ clusters is estimated to be −64.28(7) cm−1; it has been enhanced by replacing several chlorine inner ligands with bromine ones (J=−123(3) cm−1 for two [Ta6Br7.7(1)Cl4.3(1) (H2O)6]3+ clusters) and is strongest between two bromine [Ta6Br12(H2O)6]3+ clusters with a value of −155(1) cm−1. Broken‐symmetry DFT calculations within spin–dimer analysis confirmed this trend. Those interactions can be explained on the basis of the overlap between singly occupied a2u orbitals localised on neighbouring clusters.
Enantioselective Conjugate Addition of Nitro Compounds to α,β‐Unsaturated Ketones: An Experimental and Computational Study
Authors: Manzano Rubén , Andrés José M. , Álvarez Rosana , Muruzábal María D. , de Lera Ángel R. , Pedrosa Rafael 
Published: April 2011

AbstractA series of chiral thioureas derived from easily available diamines, prepared from α‐amino acids, have been tested as catalysts in the enantioselective Michael additions of nitroalkanes to α,β‐unsaturated ketones. The best results are obtained with the bifunctional catalyst prepared from L‐valine. This thiourea promotes the reaction with high enantioselectivities and chemical yields for aryl/vinyl ketones, but the enantiomeric ratio for alkyl/vinyl derivatives is very modest. The addition of substituted nitromethanes led to the corresponding adducts with excellent enantioselectivity but very poor diastereoselectivity. Evidence for the isomerization of the addition products has been obtained from the reaction of chalcone with [D3]nitromethane, which shows that the final addition products epimerize under the reaction conditions. The epimerization explains the low diastereoselectivity observed in the formation of adducts with two adjacent tertiary stereocenters. Density functional studies of the transition structures corresponding to two alternative activation modes of the nitroalkanes and α,β‐unsaturated ketones by the bifunctional organocatalyst have been carried out at the B3LYP/3‐21G* level. The computations are consistent with a reaction model involving the Michael addition of the thiourea‐activated nitronate to the ketone activated by the protonated amine of the organocatalyst. The enantioselectivities predicted by the computations are consistent with the experimental values obtained for aryl‐ and alkyl‐substituted α,β‐unsaturated ketones.
Exploration on asymmetric synthesis of flavanone catalyzed by (S)‐pyrrolidinyl tetrazole
Authors: Zhou Shubao , Zhou Yuqiang , Xing Yalan , Wang Naixing , Cao Linghua 
Published: April 2011

AbstractAn improved method of the synthesis of flavanones catalyzed by pyrrolidine and BF3·Et2O has been developed and a lot of flavanones could be easily synthesized via this method. The asymmetric synthesis of flavanone from benzaldehyde and 5‐fluoro‐2‐hydroxyacetophenone has been studied and flavanone with moderate enantioselectivity was obtained in one step. Chirality, 2011. © 2011 Wiley‐Liss, Inc.
Practical access to the proline analogs (S,S,S)‐ and (R,R,R)‐2‐methyloctahydroindole‐2‐carboxylic acids by HPLC enantioseparation
Authors: Sayago Francisco J. , Pueyo María J. , Calaza M. Isabel , Jiménez Ana I. , Cativiela Carlos 
Published: April 2011

AbstractAn efficient methodology for the preparation of the α‐tetrasubstituted proline analog (S,S,S)‐2‐methyloctahydroindole‐2‐carboxylic acid, (S,S,S)‐(αMe)Oic, and its enantiomer, (R,R,R)‐(αMe)Oic, has been developed. Starting from easily available substrates and through simple transformations, a racemic precursor has been synthesized in excellent yield and further subjected to HPLC resolution using a cellulose‐derived chiral stationary phase. Specifically, a semipreparative (250 mm × 20 mm ID) Chiralpak® IC column has allowed the efficient resolution of more than 4 g of racemate using a mixture of n‐hexane/tert‐butyl methyl ether/2‐propanol as the eluent. Multigram quantities of the target amino acids have been isolated in enantiomerically pure form and suitably protected for incorporation into peptides. Chirality, 2011. © 2011 Wiley‐Liss, Inc.
Chirality responsive helical poly(phenylacetylene) bearing L‐proline pendants
Authors: Kawamura Hiroaki , Takeyama Yoshihisa , Yamamoto Miho , Kurihara Hiroyuki , Morino Kazuhide , Yashima Eiji 
Published: April 2011

AbstractA novel, optically active, cis‐transoidal poly(phenylacetylene) bearing an L‐proline residue as the pendant group (poly‐1) was prepared by the polymerization of the corresponding monomer using a rhodium catalyst in water, and its chiroptical property was investigated using circular dichroism spectroscopy. poly‐1 showed intense Cotton effects in the UV–visible region of the polymer backbone in water, resulting from the prevailing one‐handed helical conformation induced by the covalent‐bonded chiral L‐proline pendants and exhibited a unique helix‐sense inversion in response to external, achiral, and chiral stimuli, such as the solvent and interactions with chiral small molecules. We found that poly‐1 could enantioselectively trap 1,1′‐2‐binaphthol within its hydrophobic helical cavity inside the polymer in aqueous media and underwent an inversion of its helical sense in the presence of one of the enantiomers. The effect of the optical purity of 1,1′‐2‐binaphthol on the chiroptical properties of poly‐1 was also investigated. Chirality 23:35–42, 2011 © 2011 Wiley Periodicals, Inc.
A DV‐Xα study on the electronic structures of cubane‐like iron‐sulfur cluster compounds
Authors: Tang Huang , Liu Chun‐Wan 
Published: April 2011

AbstractThe electronic structures of six cubane‐like cluster compounds of the type [Fe4S4L4]n (L = SH, OH, and Cl, n=‐2 and −3; L=NO, n = 0 and −1) have been calculated by using DV‐Xα method, and the bonding properties are discussed with emphasis on the ligand effect on cluster bonding. The comparisons of MO energies and cluster charge distributions with the experimental data are made, and the differences between the early studies and the present one are also briefly commented.
Quantum‐chemical investigation on hydrogen bonding interaction of hydrogen fluoride dimer at various mutual orientations
Authors: Ji‐Min (J. M. Yan) Yan , Williams D. E. 
Published: April 2011

AbstractHydrogen bonding interaction in hydrogen fluoride dimer has been investigated by quantum‐chemical calculation with 6‐311G** basis set at various mutual orientations. Atomic charges and charge transfer have been calculated by means of potential‐derived method, and decomposition of hydrogen bonding interaction has been executed. The calculation results show that there is a variation range for the energy‐stable orientations, the charge transfer in the range presents maximum value, and the charge transfer interaction plays a decisive role in the hydrogen bonding.
The ion transfer of the basic dye rhodamine B across the liquid‐liquid interface of two immiscible solvents
Authors: Sun Zhi‐Sheng , Wang Er‐Kang 
Published: April 2011

AbstractThe ion transfer of the basic dye rhodamine B at the interface between water and nitrobenzene, water and 1, 2‐dichloroethane, as well as water and nitrobenzene ‐ chlorobenzene mixtures has been studied by cyclic voltammetry and chronopotentiometry with linear current scanning. A transfer mechanism of rhodamine B is proposed in terms of its electrochemical behavior, dissociation and distribution equilibria, and is ascribed as diffusion‐controlled reversible process of rhodamine B. The experimental data obtained for the relationship between interracial half‐wave potential ΔWoφ° and pH are in agreement with the theoretical equation based on the mechanism, and the standard interfacial potential differences ΔWoφ° and standard Gibbs energies ΔWoG° are calculated by extrapolation. The effect of the nature of solvent on the transfer behavior and the stability of the interface have been discussed.
The synthesis and structural studies of mixed ligand complex, tris(1‐phenyl‐3‐methyl‐4‐trifluoroacetyl‐pyrazol‐5‐one)mono(1‐phenyl‐3‐methyl‐pyrazol‐5‐one)neodymium(III) monohydrate
Authors: Huang Chun‐Hui , Zhang Shi‐Wei , Deng An‐Ping , Tang Hui‐Tong , Xu Guang‐Xian 
Published: April 2011

AbstractA mixed ligand neodymium complex containing 1‐phenyl‐3‐methyl‐4‐trifluoroacetyl‐pyrazol‐5‐one (HPMTFP) and 1‐phenyl‐3‐methyl‐pyrazol‐5‐one (PMP), with molecular formula Nd (PMTFP)3·PMP·H2O was synthesized. Its crystal and molecular structure has been determined by single crystal X‐ray diffraction method. The complex crystallizes in monoclinic system with space group C52‐P21/n. There are four formula units in a cell of dimensions a = 12.837(3), b = 23.763(5), c = 16.810(4) Å, β = 109.58(2)°. The structure has been refined by full‐matrix least‐squares techniques to a final R value of 0.0487 and Rw value of 0.432. The neodymium atom is coordinated to eight oxygen atoms with the average Nd—O bond length 2.439Å. Its thermostability, and mass spectrum have been discussed.
Crystal and molecular structure of guanidinium hexatungsto‐bis(p‐aminophenylarsonate) tetrahydrate,[C(NH2)3]4[p‐NH3C6H4As)2W6O25]·4H2O
Authors: Liu Ben‐Yao , Ku (Gu Yi‐Dong) Yih‐Tong , Gu Yi‐Dong , Wang Xin 
Published: April 2011

AbstractThe crystal structure of a new type arylarsonic polytungstate [C(NH2)3]4[p‐NH3C6H4As)2W6O25]·4H2O was determined by single‐crystal X‐ray diffraction analysis. It belongs to triclinic, space group \documentclass{article}\pagestyle{empty}\begin{document} \[ P\bar 1 \] \end{document}, with cell dimensions a = 12.863(3), b = 18.912(3), c = 21.383(4) Å α = 91.14(2)°, β = 93.65(3)°, γ = 92.25(3)°, V = 5185.9 Å3, Z = 4, Dc = 2.753 g/cm3. The intensity data were collected on an Enraf‐Nonius CAD4 diffractometer with Mo Kα radiation. The positions of all tungsten and arsenic atoms were determined by direct method. The other non‐hydrogen atoms were revealed by difference Fourier synthesis. The structure was refined by fullmatrix least‐squares procedure to a final R value of 0.070. The crystal structure contains two similar but nonidentical molecules. Two similar anions consist of a ring of six WO6 octahedra, which are connected with one face‐sharing, two corner‐sharings and three edge‐sharings, and two p‐aminophenylarsonic tetrahedra capped above and below the ring. In each WO6 ring, four tungsten atoms, which are joined with edge‐sharing oxygen atoms, are almost coplanar, while the two others, which are joined with face‐sharing oxygen atoms, protrude out of the ring towards the same side. The two arsenic atoms in each anion are not equivalent in their bonding manner. In each anion, all non‐hydrogen atoms of each organic group are in the same plane. Each molecule contains one anion, four C(NH2)3+ cations and four water molecules. There are many hydrogen bonds between cations and anions throughout the whole crystal. The amino groups can accept protons, so that the charge of the resulting anion decreases and [(RAs)2W6O25]4‐ type complexes are formed.
The improvement of Cα atom positions of trichosanthin—–An application of phase filtering procedure to three‐dimensional structure determination of protein
Authors: Xia Zong‐Xiang , Zhang Zhi‐Ming 
Published: April 2011

AbstractWang's phase filtering procedure has been applied to the structure study of trichosanthin crystals belonging to space group C2. The MIR phases at 3Å resolution have been improved with the accumulative phase shift of 31.8° and the figure of merit has been improved from 0.54 to 0.84. The resulted electron density map at 3Å resolution has been much improved with a higher ratio of the electron density of the protein to the noise in the solvent region. The minimap has been interpreted more reasonably than the previous maps, giving the overall course of the polypeptide chain substantially the same as previously reported except for containing more secondary structure and a few short segments traced differently. The first 85 Cα atoms of the polypeptide chain are located in about the same positions as determined previously with an exception of a short segment but the amino acid residues after that shift along the chain with a maximum shift of about 15 residues. The electron density of side chains agrees better with the primary structure. The conformation and the three‐dimensional structure as well as the major heavy‐atom binding sites for the two molecules in an asymmetric unit are substantially the same. The structure of trichosanthin shows more similarity to ricin A chain than that reported previously.
Photochemical properties of hypocrellin A, B and their oxides
Authors: Zhao Kai‐Hong , Jiang Li‐Jin 
Published: April 2011

AbstractHypocrellin A and B in methanol were autosensitized and photooxygenated to 1, 4, 6, 7 and 2, 5, 8, 9 respectively. 1 in methanol was photooxygenated to 6 and 7 under the sensitization by HB. 1 in methanol was photooxygenated to 7 under the sensitization by Rose bengal. 1 in benzene irradiated with medium‐pressure‐mercury lamp was photolyzed to 3 in the presence of iodine.
Intramolecular energy transfer between chromophores separated by a rigid steroid bridge: II. Energy transfer as a probe to determine the ratio of two epimers
Authors: Tong Zhen‐He , Yang Guo‐Qiang , Wu Shi‐Kang 
Published: April 2011

AbstractThe singlet‐singlet intramolecular energy transfer between naphthalene moiety and dansy! group held apart by a rigid steroid bridge was investigated for two molecules: β‐(1‐naphthyl) acetoxy‐17α‐dansyl‐Δ5androstene (3a) and 3β‐(1‐naphthyl)acetoxy‐17 β‐dansyl‐Δ5androstene (3b). The rates of energy transfer for 3a and 3b in cyclohexane are 6.9 × 106 and 1.1 × 108 s−1 respectively. The difference in energy transfer rate between 3a and 3b is attributed to the different donor‐acceptor separation and orientation. The ratio of the two epimers in the synthesized product mixture was obtained from the fluorescence decay measurements.
Studies on sulfinato‐dehalogenation: XII. Sodium dithionite‐initiated addition of N, N‐diethyliododifluoroacetamide to multiple bonds
Authors: Huang Wei‐Yuan , Lü Long , Zhang Yuan‐Fa 
Published: April 2011

AbstractN, N‐deithyl‐iododifluoroacetamide 1 reacted with alkenes, alkynes in aqueous acetonitrile solutions of sodium dithionite and sodium hydrogen carbonate at room temperature to give the corresponding adducts, thus constituting a new method for introducing the CF2 group into organic molecules. Compound 1 reacted with conjugated olefins 2b, c to afford the iodine‐free adducts 7b, c. The adducts 3d—f, from addition of 1 to alkenes 2d—f, could be converted into α,α‐difluoro‐γ‐lactones 5d—f by treatment with silica gel. Compound 1 reacted with ethyl vinyl ether 2i to give aldehyde 8, and perfluoroalkyl or polyfluoroalkyl iodides reacted similarly. A radical mechanism was proposed for the addition reaction. Under the same condition, N,N‐diethyl‐bromodifluoroacetamide produced only the corresponding sulfinate Et2NC(O)CF2SO2Na.
Total synthesis of cis‐shisool
Authors: Wang Zhi‐Qin , Lai Chun‐Qiu 
Published: April 2011

AbstractThis paper describes the total synthesis of cis‐shisool through intermediate 3, which was derived from the Diels‐Alder adduct 4 (or 5). The structure of the isomers produced by the Diels‐Alder reaction of cyclohexadiene and crotonate has been elucidated by means of GC and NMR. Methylenation of 12 with Zn‐CH2Br2‐TiCl4 or Ph3P=CH2 retains the stereochemistry of the carbon atom adjacent to the carbonyl group.
Asymmetric epoxidation of gibberellates by the modified Sharpless reagent
Authors: Wang Zhi‐Min , Zhou Wei‐Shan 
Published: April 2011

AbstractAsymmetric epoxidation of methyl gibberellate by the modified Sharpless reagent at various temperature is described. Compound 8 and 9 can be used as the key intermediates for the syntheses of the polyhydroxygibberellins.
Organic reactions in chiral micelles: 7. The structural effects on the asymmetric oxidation of prochiral sulfides in chiral micelles
Authors: Zhang Yong‐Min , Fu Chun‐Ling , Fan Wei‐Qiang 
Published: April 2011

AbstractA variety of phenyl alkyl sulfides were oxidized enantioselectively with NaIO4 in chiral micellar systems formed from eight chiral surfactants, to give optical active sulfoxides. The enantiomer excesses ranged from 1.6 to 15.0%. To understand the mechanistic detail of this asymmetric oxidation in chiral micelle, the effects of structure both in substrates and surfactants on the optical yield of the oxidation were studied and discussed. Generally, increasing the alkyl chain length both in surfactants and in substrates enhances the optical yield, also the surfactant with hydroxy group at its appropriate position gives better enantioselectivity, suggesting the enzymic characteristics of the chiral micelle.