bluuebunny/crossref_metadata_2025 huggingface dataset:
Metallocene Sulfoxides as Precursors of Metallocenes with Planar Chirality
Authors: Ferber Benoit , Kagan Henri B.
Published: March 2007

The preparation of metallocene sulfoxides and their ortho‐diastereoselective functionalization are described. The applications of enantiopure 1,2‐ and 1,3‐disubstituted metallocenes are reviewed, with special emphasis on the preparation of ligands for asymmetric catalysis. The sulfoxide functionality is a useful, traceless, chiral diastereoselective ortho‐directing group, as explained in the article. It allows one to synthesize a wide range of enantiopure metallocenes with planar chirality and predictible configuration. Most of the examples are related to the ferrocene area.
Distaler Ladungstransport in Peptiden
Authors: Schlag Edward W. , Sheu Sheh‐Yi , Yang Dah‐Yen , Selzle Heinrich L. , Lin Sheng Hsien
Published: March 2007

Biologische Systeme transportieren Ladungen und reaktive Prozesse häufig über beträchtliche Entfernungen. Traditionelle Modelle der chemischen Kinetik können solche extremen distalen Prozesse gewöhnlich nicht beschreiben. In diesem Aufsatz betrachten wir ein atomares Modell für eine distale Informationsübertragung, das speziell für Peptide entwickelt wurde. Dabei wird die chemische Reaktivität als Ergebnis distaler Wirkungen betrachtet, die auf einer difunktionalen Zwei‐Stufen‐Kinetik, verbunden mit Bewegungen von Peptiden auf der Sub‐Pikosekundenskala beruht. Das difunktionale Modell ergibt einen hocheffizienten Transport von Ladung und Reaktivität über eine beträchtliche Entfernung in einem isolierten Peptid; in einer wässrigen Umgebung wird dagegen eine sehr niedrige Effizienz gefunden. Dem Modell zufolge findet in einer Peptidumgebung eine ultraschnelle Übertragung von Ladung und Reaktivität über eine beträchtliche Entfernung statt. In einem Protein können viele solcher Domänen aktiv sein.
Distal Charge Transport in Peptides
Authors: Schlag Edward W. , Sheu Sheh‐Yi , Yang Dah‐Yen , Selzle Heinrich L. , Lin Sheng Hsien
Published: March 2007

Biological systems often transport charges and reactive processes over substantial distances. Traditional models of chemical kinetics generally do not describe such extreme distal processes. In this Review, an atomistic model for a distal transport of information, which was specifically developed for peptides, is considered. Chemical reactivity is taken as the result of distal effects based on two‐step bifunctional kinetics involving unique, very rapid motional properties of peptides in the subpicosecond regime. The bifunctional model suggests highly efficient transport of charge and reactivity in an isolated peptide over a substantial distance; conversely, a very low efficiency in a water environment was found. The model suggests ultrafast transport of charge and reactivity over substantial molecular distances in a peptide environment. Many such domains can be active in a protein.
The Algorithmically Structured Systematic Exploration of Subject's State of Mind: II Reliability and Construct Validity
Authors: Le Mer Marie‐Noëlle , Stoléru Serge
Published: March 2007

Objective: To investigate the reliability and validity of a newly developed semistructured interview, the Algorithmically Structured Systematic Exploration of Subject's State of Mind (Assess_Mind). Method: Twelve scales have been developed and used to rate 86 Assess_Mind interviews conducted with patients undergoing in vitro fertilization treatment. For each rating scale, we assessed interrater reliability, interviewer effect, and construct validity. In addition, a factor analysis of scales was performed. To study the validity of scales and of the factors yielded by factor analysis, patients were assessed with a psychopathological battery including the Child Project Questionnaire, the State‐Trait Anxiety Inventory, the Perceived Stress Scale, and the Ways of Coping Checklist. Results: For 11 of the 12 scales, interrater reliability was fair to excellent. There was no significant interviewer effect affecting any of the scales. In addition, the validity of nine of these 11 scales was demonstrated by their correlations with questionnaires measuring similar constructs. Conclusion: Nine of the Assess_Mind scales appear to have adequate psychometric properties. Copyright © 2007 John Wiley & Sons, Ltd.
The making of a social insect: developmental architectures of social design
Authors: Page Robert E. , Amdam Gro V.
Published: March 2007

We marvel at the social complexity of insects, marked by anatomically and behaviorally distinguishable castes, division of labor and specialization—but how do such systems evolve? Insect societies are composed of individuals, each undergoing its own developmental process and each containing its own genetic information and experiencing its own developmental and experiential environment. Yet societies appear to function as if the colonies themselves are individuals with novel “social genes” and novel social developmental processes. We propose an alternative hypothesis. The origins of complex social behavior, from which insect societies emerge, are derived from ancestral developmental programs. These programs originated in ancient solitary insects and required little evolutionary remodeling. We present evidence from behavioral assays, selective breeding, genetic mapping, functional genomics and endocrinology, and comparative anatomy and physiology. These insights explain how complex social behavior can evolve from heterochronic changes in reproductive signaling systems that govern ubiquitous and ancient relationships between behavior and ovarian development. BioEssays 29:334–343, 2007. © 2007 Wiley Periodicals, Inc.
Cell mechanics and stress: from molecular details to the ‘universal cell reaction’ and hormesis
Authors: Agutter Paul S.
Published: March 2007

The ‘universal cell reaction’ (UCR), a coordinated biphasic response to external (noxious and other) stimuli observed in all living cells, was described by Nasonov and his colleagues in the mid‐20th century. This work has received no attention from cell biologists in the West, but the UCR merits serious consideration. Although it is non‐specific, it is likely to be underpinned by precise mechanisms and, if these mechanisms were characterized and their relationship to the UCR elucidated, then our understanding of the integration of cellular function could be improved. As a step towards identifying such mechanisms, I review some recent advances in understanding cell mechanics and the stress response and I suggest potentially testable hypotheses. There is a particular need for time‐course studies of cellular responses to different stimulus doses or intensities. I also suggest a correspondence with hormesis; re‐investigation of the UCR using modern biophysical and molecular‐biological techniques might throw light on this much‐discussed phenomenon. BioEssays 29:324–333, 2007. © 2007 Wiley Periodicals, Inc.
Nucleomorph genomes: structure, function, origin and evolution
Authors: Archibald John M.
Published: March 2007

The cryptomonads and chlorarachniophytes are two unicellular algal lineages with complex cellular structures and fascinating evolutionary histories. Both groups acquired their photosynthetic abilities through the assimilation of eukaryotic endosymbionts. As a result, they possess two distinct cytosolic compartments and four genomes—two nuclear genomes, an endosymbiont‐derived plastid genome and a mitochondrial genome derived from the host cell. Like mitochondrial and plastid genomes, the genome of the endosymbiont nucleus, or ‘nucleomorph’, of cryptomonad and chlorarachniophyte cells has been greatly reduced through the combined effects of gene loss and intracellular gene transfer. This article focuses on the structure, function, origin and evolution of cryptomonad and chlorarachniophyte nucleomorph genomes in light of recent comparisons of genome sequence data from both groups. It is now possible to speculate on the reasons that nucleomorphs persist in cryptomonads and chlorarachniophytes but have been lost in all other algae with plastids of secondary endosymbiotic origin. BioEssays 29:392–402, 2007. © 2007 Wiley Periodicals, Inc.
Size assessment and growth control: how adult size is determined in insects
Authors: Mirth Christen Kerry , Riddiford Lynn M.
Published: March 2007

Size control depends on both the regulation of growth rate and the control over when to stop growing. Studies of Drosophila melanogaster have shown that insulin and Target of Rapamycin (TOR) pathways play principal roles in controlling nutrition‐dependent growth rates. A TOR‐mediated nutrient sensor in the fat body detects nutrient availability, and regulates insulin signaling in peripheral tissues, which in turn controls larval growth rates. After larvae initiate metamorphosis, growth stops. For growth to stop at the correct time, larvae need to surpass a critical weight. Recently, it was found that the insulin‐dependent growth of the prothoracic gland is involved in assessing when critical weight has been reached. Furthermore, mutations in DHR4, a repressor of ecdysone signaling, reduce critical weight and adult size. Thus, the mechanisms that control growth rates converge on those assessing size to ensure that the larvae attain the appropriate size at metamorphosis. BioEssays 29:344–355, 2007. © 2007 Wiley Periodicals, Inc.
What a difference copy number variation makes
Authors: Kehrer‐Sawatzki Hildegard
Published: March 2007

DNA copy number variation (CNV) represents a considerable source of human genetic diversity. Recently,1 a global map of copy number variation in the human genome has been drawn up which reveals not only the ubiquity but also the complexity of this type of variation. Thus, two human genomes may differ by more than 20 Mb and it is likely that the full extent of CNV still remains to be discovered. Nearly 3000 genes are associated with CNV. This high degree of variability with regard to gene copy number between two individuals challenges definitions of normality. Many CNVs are located in regions of complex genomic structure and this currently limits the extent to which these variants can be genotyped by using tagging SNPs. However, some CNVs are already amenable to genome‐wide association studies so that their influence on human phenotypic diversity and disease susceptibility may soon be determined. BioEssays 29:311–313, 2007. © 2007 Wiley Periodicals, Inc.
GTP‐binding proteins of the Rho/Rac family: regulation, effectors and functions in vivo
Authors: Bustelo Xosé R. , Sauzeau Vincent , Berenjeno Inmaculada M.
Published: March 2007

Rho/Rac proteins constitute a subgroup of the Ras superfamily of GTP hydrolases. Although originally implicated in the control of cytoskeletal events, it is currently known that these GTPases coordinate diverse cellular functions, including cell polarity, vesicular trafficking, the cell cycle and transcriptomal dynamics. In this review, we will provide an overview on the recent advances in this field regarding the mechanism of regulation and signaling, and the roles in vivo of this important GTPase family. BioEssays 29:356–370, 2007. © 2007 Wiley Periodicals, Inc.
A unifying new model of cytokinesis for the dividing plant and animal cells
Authors: Dhonukshe Pankaj , Šamaj Jozef , Baluška František , Friml Jiří
Published: March 2007

Cytokinesis ensures proper partitioning of the nucleocytoplasmic contents into two daughter cells. It has generally been thought that cytokinesis is accomplished differently in animals and plants because of the differences in the preparatory phases, into the centrosomal or acentrosomal nature of the process, the presence or absence of rigid cell walls, and on the basis of ‘outside‐in’ or ‘inside‐out’ mechanism. However, this long‐standing paradigm needs further reevaluation based on new findings. Recent advances reveal that plant cells, similarly to animal cells, possess astral microtubules that regulate the cell division plane. Furthermore, endocytosis has been found to be important for cytokinesis in animal and plant cells: vesicles containing endocytosed cargo provide material for the cell plate formation in plants and for closure of the midbody channel in animals. Thus, although the preparatory phases of the cell division process differ between plant and animal cells, the later phases show similarities. We unify these findings in a model that suggests a conserved mode of cytokinesis. BioEssays 29:371–381, 2007. © 2007 Wiley Periodicals, Inc.
Ultrasensitive peroxynitrite‐based luminescence with L‐012 as a screening system for antioxidative/antinitrating substances, e.g. Tylenol® (acetaminophen), 4‐OH tempol, quercetin and carboxy‐PTIO
Authors: Dyke Knox Van , Ghareeb Erica , Dyke Mark Van , Thiel David H. Van
Published: March 2007

Previously our group developed a water‐soluble antioxidant screening system using the luminescence of the reaction of peroxynitrite and luminol. In the present study we replaced luminol with the luminol‐like compound L‐012. This increases the production of luminescence approximately 100‐fold and therefore, with a higher signal:noise ratio, this new system can detect antioxidation and antinitration effects at lower doses of the inhibitor. We studied acetaminophen (Tylenol®) and its metabolite 3‐nitroacetaminophen, tyrosine and nitrotyrosine and all these substances were inhibitory in a dose‐responsive manner and below micromolar amounts. In addition quercetin, a polyphenol, was highly active (below micromolar amounts) as an antioxidant and antinitrating compound. 4‐OH tempol, the stable free radical, superoxide dismutase (SOD) mimetic, was inhibitory in a dose‐responsive manner and below micromolar amounts. Carboxy‐PTIO was inhibitory at 10 times micromolar amount but not below that dose, which may be related to colour quenching, since the drug is deeply blue, or possibly it is an inhibitor with a slow kinetic profile. Finally, the amino acid tyrosine has been found to be inhibitory in micromolar amounts, similar to acetaminophen. This indicates that tyrosine can act as an antioxidant and antinitration target alone or conjugated in protein, e.g. insulin. Copyright © 2007 John Wiley & Sons, Ltd.
Determination of ibuprofen in pharmaceutical formulations using time‐resolved terbium‐sensitized luminescence
Authors: Al‐Kindy Salma M. Z. , Suliman Fakhr Eldin O.
Published: March 2007

A sensitive and specific luminescence method for the determination of ibuprofen (IB) in pharmaceutical formulations in aqueous solution is described. The method is based on the luminescence sensitization of terbium (Tb3+) by formation of ternary complex with IB in the presence of tri‐n‐octylphosphine oxide (TOPO) and Tween‐20 as surfactant. The luminescence signal for Tb–IB–TOPO is monitored at λex = 229 nm and λem = 545 nm. Optimum conditions for the formation of the complex in aqueous system, were 16 mmol/L TRIS buffer, pH 5.7, TOPO 200 µmol/L and 15 µmol/L of Tb3+, which allows for the determination of 9.7 × 10−7 – 9.7 × 10−6 mol/L IB with a detection limit of 1.2 × 10−7 mol/L. The relative standard deviations of the method were <1.4%, indicating excellent reproducibility. The proposed method was successfully applied for the assays of IB in pharmaceutical formulations with average recoveries of 100.3–102.5%. Copyright © 2007 John Wiley & Sons, Ltd.
Heterologous expression and characterization of recombinant glycerol dehydratase from Klebsiella pneumoniae in Escherichia coli
Authors: Wang Fenghuan , Qu Huijin , Tian Pingfang , Tan Tianwei
Published: March 2007

Glycerol dehydratase (EC 4.2.1.30), as one of the key enzymes in converting glycerol to the valuable intermediate 1,3‐propanediol, is important for biochemical industry. The dhaB genes encoding coenzyme B12‐dependent glycerol dehydratase in Klebsiella pneumoniae were cloned and expressed in Escherichia coli. An effective co‐expression system of multiple subunits protein was constructed. Heterologous expression vectors were constructed using the splicing by overlap extension‐PCR technique to co‐express the three subunits of the glycerol dehydratase. After induction by isopropyl‐β‐D‐thiogalactopyranoside, SDS‐PAGE analysis revealed that: (i) only the α subunit of glycerol dehydratase was expressed in direct expression system, (ii) the three subunits of glycerol dehydratase with predicted molecular massess of 64 (agr;), 22 (β), and 16 kDa (γ) were expressed simultaneously in co‐expression system, and (iii) the fusion expression system expressed the fusion protein of 99 kDa. Enzyme assay showed that the activities of three heterologous expression products were 27.4, 2.3, and 0.2 U/mg. The highest enzyme activity was almost 17 times of that in K. pneumoniae. The recombinant enzyme was purified and biochemically characterized. The apparent Km values of the enzyme for coenzyme B12 and 1, 2‐propanediol were 8.5 nM and 1.2 mM, respectively. The enzyme showed maximum activity at pH 8.5 and 37°C.
Application of cellulose‐based self‐assembled tri‐enzyme system in a pseudo‐reagent‐less biosensor for biogenic catecholamine detection
Authors: Rabinovich Mikhail L. , Vasil'chenko Liliya G. , Karapetyan Karen N. , Shumakovich Galina P. , Yershevich Olga P. , Ludwig Roland , Haltrich Dietmar , Hadar Yitzhak , Kozlov Yuri P. , Yaropolov Alexander I.
Published: March 2007

Amorphous cellulose was used as a specific carrier for the deposition of self‐assembled multienzyme complexes capable of catalyzing coupled reactions. Naturally glycosylated fungal cellobiohydrolases (CBHs) of glycosyl hydrolase families 6 and 7 were specifically deposited onto the cellulose surface through their family I cellulose‐binding modules (CBM). Naturally glycosylated fungal laccase was then deposited onto the preformed glycoprotein layer pretreated by ConA, through the interaction of mannosyl moieties of fungal glycoproteins with the multivalent lectin. The formation of a cellulase‐ConA‐laccase composite was proven by direct and indirect determination of activity of immobilized laccase. In the absence of cellulases and ConA, no laccase deposition onto the cellulose surface was observed. Finally, basidiomycetous cellobiose dehydrogenase (CDH) was deposited onto the cellulose surface through the specific interaction of its FAD domain with cellulose. The obtained paste was applied onto the surface of a Clark‐type oxygen electrode and covered with a dialysis membrane. In the presence of traces of catechol or dopamine as mediators, the obtained immobilized multienzyme composite was capable of the coupled oxidation of cellulose by dissolved oxygen, thus providing the basis for a sensitive assay of the mediator. Swollen amorphous cellulose plays three different roles in the obtained biosensor as: (i) a gelforming matrix that captures the analyte and its oxidized intermediate, (ii) a specific carrier for protein self‐assembly, and (iii) a source of excess substrate for a pseudo‐reagent‐less assay with signal amplification. The detection limit of such a tri‐enzyme biosensor is 50‐100 nM dopamine.
Comprehensive survey of p94/calpain 3 substrates by comparative proteomics – Possible regulation of protein synthesis by p94
Authors: Ono Yasuko , Hayashi Chikako , Doi Naoko , Kitamura Fujiko , Shindo Mayumi , Kudo Kenichi , Tsubata Takuichi , Yanagida Mitsuaki , Sorimachi Hiroyuki
Published: March 2007

Calpain represents a family of Ca2+‐dependent cytosolic cysteine proteases found in almost all eukaryotes and some bacteria, and is involved in a variety of biological phenomena, including brain function. Several substrates of calpain are aggressively proteolyzed under pathological conditions, e.g., in neurodegenerating processes, fodrin is proteolyzed by calpain. Because very small amounts of substrate are proteolyzed by calpain under normal biological conditions, the molecular identities of calpain substrates are largely unknown. In this study, an extensive survey of the substrates of p94/calpain 3 in COS7 cells was executed using iTRAQTM labeling and 2‐D LC‐MALDI analysis. p94 was used because: (i) several p94 splicing variants are expressed in brain tissue even though p94 itself is a skeletal‐muscle‐specific calpain, and (ii) it exhibits Ca2+‐independent activity in COS cells, which makes it useful for evaluating the effects of p94 protease activity on proteins without perturbing the cells. Our approach revealed several novel protein substrates for p94, including the substrates of conventional calpains, components of the protein synthesis system, and enzymes of the glycolytic pathway. The results demonstrate the usefulness and sensitivity of this approach for mining calpain substrates. A combination of this method with other analytical methods would contribute to elucidation of the biological relevance of the calpain family.
Bio‐electrosprays: A novel electrified jetting methodology for the safe handling and deployment of primary living organisms
Authors: Odenwälder Patrick K. , Irvine Scott , McEwan Jean R. , Jayasinghe Suwan N.
Published: March 2007

Electrohydrodynamic jetting (EHDJ) which is also known as electrosprays (ES) has recently been elucidated as a unique electrified biotechnique for the safe handling and deployment of living organisms. This high intensity electric field driven jetting methodology is now referred to as “bioelectrosprays” (BES). Previously these charged jets have only been shown to jet‐process immortalized cells which have undergone expected cellular behavior when compared with control cells. In this paper we demonstrate the ability to jet process primary living organisms in the stable conejetting mode. Finally the viability of the bio‐electrosprayed living organisms has been assessed employing a flow cytometry approach which forms the discussion in this paper. Our findings further establish BES as a competing biotechnique, which could be employed for the deposition of primary living organisms according to a predetermined active cellular architecture. One day this could be used for the fabrication of viable tissues and organs for repair or replacement. These advanced studies carried out on BES have direct widespread applications ranging from developmental biology to regenerative and therapeutic medicine, which are a few amongst several other areas of study within the life sciences.
Scavenging effects of phenolic compounds on reactive oxygen species
Authors: Aboul‐Enein Hassan Y. , Kruk Irena , Kładna Aleksandra , Lichszteld Krzysztof , Michalska Teresa
Published: March 2007

Phenolic compounds are widely present in plants and they have received considerable attention due to their antioxidant property. In this article we report the results of a study of the reactivity of 10 selected phenolics (sesamol, three phenolic acids, three flavonols, one flavone, and two flavanones) with superoxide anion radical (O), hydroxyl radical (HO•) and singlet oxygen (1O2). The following generators of reactive oxygen species were used: 18‐crown‐6/KO2/dimethylsulfoxide (DMSO) or hypoxanthine/xanthine oxidase as sources of O, the Fenton reaction carried out in a sodium trifluoroacetate (pH 6.15) for HO•, and a mixture of alkaline aqueous H2O2 and cobalt ions for 1O2. We have employed chemiluminescence, electron spin resonance spin trapping, and spectrophotometry techniques to examine an antioxidative property. All tested compounds acted as scavengers of various reactive oxygen species. The reactivity indexes (β) for the reaction of the phenolic compounds with HO• were calculated. © 2007 Wiley Periodicals, Inc. Biopolymers 86: 222–230, 2007.

This 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
Electrocyclic Ring Opening of cis‐Bicyclo[m.n.0]alkenes: The Anti‐Woodward–Hoffmann Quest
Authors: Silva López Carlos , Nieto Faza Olalla , de Lera Ángel R.
Published: March 2007

The dubbed anti‐Woodward–Hoffmann ring‐opening reaction of cis‐bicyclo[4.2.0]oct‐7‐ene to yield cis,cis‐cycloocta‐1,3‐diene has been intensively studied with robust, high‐level computational methods. This reaction has been found to proceed through a conrotatory allowed pathway to afford cis,trans‐cycloocta‐1,3‐diene followed by E to Z isomerization, instead of a disrotatory forbidden pathway, as suggested. Computational calculations of kinetic isotope effects are consistent with this interpretation and the experimental values. The study of lower bicyclic homologues with [3.2.0], [2.2.0] and [2.1.0] skeletons indicates the feasibility of a mechanistic change towards the anti‐Woodward–Hoffmann disrotatory path. This is clearly favored for the ring opening of the highly strained cis‐bicyclo[2.1.0]pent‐2‐ene and is highly competitive with the conrotatory path for cis‐bicyclo[2.2.0]hex‐2‐ene. Therefore, the rearrangement of the smallest bicyclic cyclobutene is predicted computationally to be an anti‐Woodward–Hoffmann disrotatory electrocyclic ring‐opening reaction.
A Comparative Relativistic DFT and Ab Initio Study on the Structure and Thermodynamics of the Oxofluorides of Uranium(IV), (V) and (VI)
Authors: Shamov Grigory A. , Schreckenbach Georg , Vo Thach N.
Published: March 2007

All the possible uranium(VI, V, IV) oxides, fluorides and oxofluorides were studied theoretically by using density functional theory (DFT) in the generalised gradient approximation (GGA), and three different relativistic methods (all‐electron scalar four component Dyall RESC method (AE), relativistic small‐core ECPs, and zeroth order regular approximation ZORA). In order to test different correlation methods, for the two former relativistic methods hybrid DFT, and, for the AE method, MP2 molecular orbital calculations were performed as well. Single‐point AE‐CCSD(T) energies were calculated on MP2 geometries as well. Energies of the uranium(VI) and (V) oxofluorides dissociation, uranium(VI) fluoride hydrolysis and oxofluoride disproportionation were calculated and compared against the available experimental thermochemical data. AE‐CCSD(T) energies were the closest to the experiment. For GGA DFT methods, all the relativistic methods used yield similar results. For thermochemistry, the best quantitative agreement with the experimental and CCSD(T) values for both UO and UF bond strengths was obtained with hybrid DFT methods, provided that a reliable basis set was used. Both the GGA DFT and MP2 MO methods show overbinding of these bonds; moreover, this overbinding was found to be not uniform but strongly dependent on the coordination environment of the uranium atom in each case. UO vibrational frequencies given by hybrid DFT, however, are systematically overestimated, and are better reproduced by GGA DFT; MP2 values usually fall in‐between. Reaction enthalpies, UO frequencies and complex geometries given by the PBE, MPBE, BPBE, BLYP and OLYP GGA functionals are quite similar, with OLYP performing slightly better than the others but still not as good as hybrid DFT. The geometries of the molecules are found to be influenced by the following factors: the inverse transinfluence (ITI) of the oxygen ligand and, for UV, and UIV, the Jahn–Teller distortion.
Synthesis, Structure, and Characterization of Three Series of 3d–4f Metal‐Organic Frameworks Based on Rod‐Shaped and (6,3)‐Sheet Metal Carboxylate Substructures
Authors: Luo Feng , Batten Stuart R. , Che Yunxia , Zheng Ji‐Min
Published: March 2007

Three series of porous lanthanide metal‐organic coordination polymers, namely [Cu(bpy)Ln3(ip)5(Hip)(H2O)] [Ln = Er (1 a), Y (1 b), Eu (1 c); bpy = 2,2′‐bipyridine, H2ip=isophthalic acid], [Cu3(bpy)2Ln2(ip)6(H2O)5] [Ln = Yb (2 a), Gd (2 b), Tb (2 c)], and [Cu3Ln2(ip)6] [Ln = Eu (3 a), Gd (3 b)] have been synthesized hydrothermally by the reaction of the combination of 3d–4f metal centers and N‐/O‐donor ligands. X‐ray diffraction analyses reveal that polymers 1 a–c and 2 a–c, as well as 3 a, b are isomorphous in structure. Polymers 1 a–c consist of 3D α‐Po networks based on a inorganic rod‐shaped secondary building units (SBUs) of {Er6Cu2(bipy)2(O2C)11} which are 27.03 Å in length. Polymers 2 a–c also contain 3D α‐Po networks, constructed from shorter (14.79 Å) but similarly rod‐shaped SBUs of {Yb2Cu3(bpy)2(O2C)12}. The structure also contains hydrogen‐bonded (H2O)6 chains which can be reversibly dehydrated/rehydrated. Polymers 3 a, b contain metal carboxylate substructures which have 2D (6,3) topologies; these layers are bridged by the ip2− ligands to give an overall 3D network which contains two sorts of cavities. This series of Ln–Cu coordination polymers are further characterized by antiferromagnetic behavior.
Icosahedral and Ring‐Shaped Allotropes of Phosphorus
Authors: Karttunen Antti J. , Linnolahti Mikko , Pakkanen Tapani A.
Published: March 2007

The existence of two new allotropic forms of phosphorus, icosahedral cages and ring‐shaped chains, is predicted. The cages and rings are nanostructural modifications of the black and the red phosphorus, respectively. The icosahedral and ring‐shaped allotropes are compared with the experimentally known allotropic forms of phosphorus by quantum chemical methods. Both the cages and the rings are thermodynamically favored over the white phosphorus, the rings being comparable to the Hittorf's violet phosphorus and to the recently discovered fibrous red phosphorus. The stabilities of the icosahedral cages increase as a function of their size, having structural resemblance with the rhombohedral black phosphorus. The high thermodynamic stability of the phosphorus nanostructures suggests their experimental synthesis to be viable.
Specific Recognition of Human Telomeric G‐Quadruplex DNA with Small Molecules and the Conformational Analysis by ESI Mass Spectrometry and Circular Dichroism Spectropolarimetry
Authors: Zhou Jiang , Yuan Gu
Published: March 2007

Electrospray ionization mass spectrometry (ESI‐MS) was utilized to investigate the binding affinity and stoichiometry of small molecules with human telomeric G‐quadruplex DNA. The binding‐affinity order obtained for the (AGGGTT)4 quadruplex was: Tel01>ImImImβDp≫PyPyPyγImImImβDp. The specific binding of Tel01 and PyPyPyγImImImβDp in one system consisting of human telomeric G‐quadruplex and duplex DNA was observed directly for the first time. This revealed that PyPyPyγImImImβDp has a binding specificity for the duplex DNA, whereas Tel01 selectively recognizes the G‐quadruplex DNA. Moreover, both ESI‐MS and circular dichroism (CD) spectra indicated that Tel01 favored the formation and stabilization of the antiparallel G‐quadruplex, and a structural transition of the (AGGGTT)4 sequence from a coexistence of parallel and antiparallel G‐quadruplexes to a parallel G‐quadruplex induced by annealing.
Intramolecular Reactions in Pseudo‐Geminally Substituted [2.2]Paracyclophanes
Authors: Bondarenko Lidija , Hentschel Silke , Greiving Helmut , Grunenberg Jörg , Hopf Henning , Dix Ina , Jones Peter G. , Ernst Ludger
Published: March 2007

A selection of pseudo‐geminally substituted [2.2]paracyclophanes, the alkynes 6, 7, 10, 11 a, and 11 b and the alkenes 8 and 9 were prepared for the study of intraannular reactions between functional groups in direct juxtaposition. Whereas 9 and 10 provide the corresponding cyclobutane and cyclobutene derivatives on irradiation (12 and 13, respectively), the bis‐alkynes 7 and 11 b do not lead to a cyclobutadiene intermediate. In the latter case the “half‐closed” butadiene derivative 17 was isolated. A Paterno–Büchi reaction took place on irradiation of 8 and 6, although the oxetene intermediate 21 produced in the second example did not survive the reaction conditions (ring‐opening to 22). Bromine addition to 9, 10, and 7 occurred with high stereoselectivity (formation of the dibromides 27, 30, and 33, respectively), and is rationalized by postulating the formation of the cationic intermediates 26, 29, and 32, respectively. To study the interaction of a carbocation with a facing triple bond, the alcohol 34 was prepared from 6. On acid treatment ring closure to the triply‐bridged phane 38 took place, accompanied by the hydration of the triple bond to the ketoalcohol 37. In an interesting intraannular [2+3]cycloaddition reaction the bis‐acetylene 11 a, on treatment with n‐butyl lithium, provided the cyclopentadiene derivative 42. That the two triple bonds of a pseudo‐geminal diacetylene can engage in a cyclization reaction leading to the cyclopentadienone complex 44 was also shown by treating 11 b with iron pentacarbonyl.
Conformation‐Dependent Racemization of Aspartyl Residues in Peptides
Authors: Kuge Katsunori , Brack André , Fujii Noriko
Published: March 2007

Biologically uncommon D‐aspartyl (D‐Asp) residues have been detected in proteins of various tissues of elderly humans. The presence of D‐Asp has been explained as a result of the racemization of L‐Asp (denoted as Asp) in the protein of inert tissues. We have previously suggested that the racemization of Asp may depend on the conformation of the peptide chain. However, the nature of the peptide conformation that affects the D‐Asp formation has not yet been examined. Here we report the kinetics of Asp racemization in two model peptides, (Asp‐Leu)15 and (Leu‐Asp‐Asp‐Leu)8‐Asp, which form β‐sheet structures and α‐helical structures, respectively. For the β‐sheet structures, the activation energy of racemization of Asp residues was 27.3 kcal mol−1, the racemization rate constant at 37 °C was 2.14×10−2 per year and the time required to reach a D/L ratio of 0.99 at 37 °C was 122.6 years as estimated from the Arrhenius equation. For the α‐helical structures, the activation energy of racemization was 18.4 kcal mol−1, the racemization rate constant 20.02×10−2 per year and the time 13.1 year. These results suggest that Asp residues inserted in α‐helical peptides are more sensitive to racemization than Asp residues inserted in peptides adopting β‐sheet structures. The results clearly indicate that the racemization rate of Asp residues in peptides depends on the secondary structure of the host peptide.
Cyanation: Providing a Three‐in‐One Advantage for the Design of n‐Type Organic Field‐Effect Transistors
Authors: Kuo Ming‐Yu , Chen Hsing‐Yin , Chao Ito
Published: March 2007

The theoretical work presented here demonstrates that, when substitution takes place at appropriate positions, cyanation could be a useful tool for reducing the internal reorganization energy of molecules. A molecular‐orbital‐based explanation is given for this fundamentally important phenomenon. Some of the cyanated pentacene derivatives (nCN‐PENT‐n) not only have internal reorganization energies for electron transfer (λ−) smaller than that of pentacene, but the λ− values are even of the same magnitude as the internal reorganization energy for hole transfer (λ+) of pentacene, a small value that few organic compounds have surpassed. In addition, cyanation raises the electron affinity of the parent compound and may afford good electronic couplings between neighboring molecules, because of its ability in promoting π‐stacking. For the design of high performance n‐Type Organic field‐effect transistors, high electron affinities, large intermolecular electronic couplings, and small reorganization energies are necessary. Cyanation may help in all three aspects. Two cyanated trialkylsilylethynyl pentacene derivatives with known π‐stacking structures are predicted to provide reasonably small internal reorganization energies, large electronic couplings, and high electron affinities. They have the potential to outperform N‐fluoroalkylated dicyanoperylene‐3,4:9,10‐bis(dicarboximides) (PDI‐FCN2) in terms of electron mobility.
Towards the Design of Neutral Molecular Tweezers for Anion Recognition
Authors: Hermida‐Ramón Jose M. , Estévez Carlos M.
Published: March 2007

Molecular tweezers are simple molecular receptors that can be characterized by the presence of two flat pincers separated by a more or less rigid tether. They have the ability to form complexes with a substrate molecule by gripping the substrate between the tips of the tweezers in a similar manner to that of mechanical tweezers. Klärner et al. synthesized one of the structurally simplest molecular tweezers, which is reported to bind electrodeficient aromatic and aliphatic substrates as well as organic cations. Complexes between these molecular tweezers and electron‐rich aromatic, aliphatic, or anionic substrates have not been observed. Inspired by several recent reports that describe the interaction of hexafluorobenzene with electron‐rich sites of molecules, we conducted a theoretical study to show the possibility of building molecular tweezers, based on those synthesized by Klärner, which were able to bind to anions and thus increase their potential as molecular receptors. We characterized complexes formed between several fluorinated derivatives of simple tweezers and an iodine anion, and analyzed the nature of the intermolecular interactions as well as the energetics for the process of complexation. The stabilization trend reflected by the energetic results when fluorine substituents were added to benzene rings confirms our hypothesis about the possibility of obtaining neutral tweezers composed of aromatic rings that can bind anions.
Intramolecular Carbolithiation of 2,6‐Dilithio‐1,6‐heptadienes: An Experimental and Theoretical Study
Authors: Sanz Roberto , Ignacio José M. , Rodríguez Miguel A. , Fañanás Francisco J. , Barluenga José
Published: March 2007

2,6‐Dilithio‐1,6‐heptadienes 3 undergo intramolecular carbolithiation in Et2O/N,N,N′,N′‐tetramethylethylenediamine (TMEDA) at the lithiated double bonds to afford 1,2‐bis(lithiomethyl)cyclopentenes 5. Reaction of these dianions with electrophiles affords a number of 1,2‐difunctionalized cyclopentene derivatives 7–10. The ease of carbolithiation of 2,6‐dilithio‐1,6‐heptadiene (3 a) compared to that of 2‐lithio‐1,6‐heptadiene (14) has been studied experimentally. A series of ab initio molecular‐orbital calculations on the course of the reaction were carried out and the results were compared to those for the corresponding intramolecular carbolithiation of an isolated double bond. The LiC interactions found in the transition state by this theoretical study support a carbolithiation pathway for the cyclization of 2,6‐dilithio‐1,6‐heptadienes.
Rapid and Simple Solid‐Phase Esterification of Sialic Acid Residues for Quantitative Glycomics by Mass Spectrometry
Authors: Miura Yoshiaki , Shinohara Yasuro , Furukawa Jun‐ichi , Nagahori Noriko , Nishimura Shin‐Ichiro
Published: March 2007

A rapid and quantitative method for solid‐phase methyl esterification of carboxy groups of various sialylated oligosaccharides has been established. The method employed a triazene derivative, 3‐methyl‐1‐p‐tolyltriazene, for facile derivatization of oligosaccharides immobilized onto general solid supports such as Affi‐Gel Hz and gold colloidal nanoparticles in a multiwell plate. The workflow protocol was optimized for the solid‐phase processing of captured sialylated/unsialylated oligosaccharides separated from crude sample mixtures by chemical ligation. From tryptic and/or PNGase F‐digest mixtures of glycoproteins, purification by chemoselective immobilization, esterification and recovery were achieved in the same well of the filter plate within three hours when used in conjunction with “glycoblotting technology” (S.‐I. Nishimura, K. Niikura, M. Kurogochi, T. Matsushita, M. Fumoto, H. Hinou, R. Kamitani, H. Nakagawa, K. Deguchi, N. Miura, K. Monde, H. Kondo, High‐throughput protein glycomics: Combined use of chemoselective glycoblotting and MALDI‐TOF/TOF mass spectrometry: Angew. Chem. 2005, 117, 93–98; Angew. Chem. Int. Ed. 2005, 44, 91–96). The recovered materials were directly applicable to subsequent characterization by mass spectrometric techniques such as MALDI‐TOF for large‐scale glycomics of both neutral and sialylated oligosaccharides. On‐bead/on‐gold nanoparticle derivatization of glycans containing sialic acids allowed rapid and quantitative glycoform profiling by MALDI‐TOF MS with reflector and positive ion mode. In addition to its simplicity and speed, the method eliminates the use of unfavorable halogenated solvents such as chloroform and dichloromethane or volatile solvents such as diethyl ether and hexane, resulting in a practical and green chemical method for automated robotic adaptation.
Ovarian cancer screening with annual transvaginal sonography
Authors: van Nagell John R. , DePriest Paul D. , Ueland Frederick R. , DeSimone Christopher P. , Cooper Amy L. , McDonald J. Matt , Pavlik Edward J. , Kryscio Richard J.
Published: March 2007

BACKGROUND

Ovarian cancer has the highest mortality rate of all gynecologic malignancies, and most women present with advanced‐stage disease. The current investigation was performed to determine the efficacy of annual transvaginal sonography (TVS) as a screening method for ovarian cancer.

METHODS

Annual TVS screening was performed on 25,327 women from 1987 to 2005. Asymptomatic women aged ≥50 years and women aged ≥25 years who had a family history of ovarian cancer were eligible for participation in this trial.

RESULTS

Among 364 patients (1.4%) with a persisting ovarian tumor on TVS who underwent exploratory laparoscopy or laparotomy with tumor removal, 35 primary invasive ovarian cancers, 9 serous ovarian tumors of low malignant potential, and 7 cancers metastatic to the ovary were detected. Stage distribution was as follows: 28 patients had stage I disease, 8 patients had stage II disease, and 8 patients had stage III disease. Four patients died of disease, 2 patients died of other causes, and 38 patients were alive and well from 0.5 years to 15.8 years after diagnosis (mean, 5.3 years). Nine women developed ovarian cancer within 12 months of a negative screen (false‐negative results), and 3 of these patients died of disease. TVS screening had a sensitivity of 85.0%, specificity of 98.7%, positive predictive value of 14.01%, and negative predictive value of 99.9%. After 107,276 screening years, there have been 7 ovarian cancer deaths in the annually screened population and 3 ovarian cancer deaths among women who were noncompliant. Excluding patients with nonepithelial or borderline ovarian malignancies, the survival of patients with ovarian cancer in the annually screened population was 89.9% ± 10.1% at 2 years and 77.2% ± 22.8% at 5 years.

CONCLUSIONS

TVS screening, when it was performed annually, was associated with a decrease in disease stage at detection and with case‐specific ovarian cancer mortality, but it was not effective in detecting ovarian cancers in women who had normal ovarian volume. Cancer 2007; © 2007 American Cancer Society.
Btk and phospholipase Cγ2 can function independently during B cell development
Authors: Halcomb Kristina E. , Contreras Cristina M. , Hinman Rochelle M. , Coursey Terry G. , Wright Heather L. , Satterthwaite Anne B.
Published: March 2007

The pre‐BCR and the BCR regulate B cell development via a signalosome nucleated by the adaptor protein B cell linker protein (BLNK). Formation of this complex facilitates activation of phospholipase C (PLC) γ2 by Bruton's tyrosine kinase (Btk). To determine whether Btk and PLCγ2 also have separate functions, we generated Btk–/–PLCγ2–/– mice. They demonstrated a block in development at the pre‐B stage and increased pre‐BCR surface expression. This phenotype was more severe than that of Btk–/– or PLCγ2–/– mice. Although both Btk and PLCγ2 were required for proliferation of splenic B cells in response to BCR cross‐linking, they contributed differently to anti‐IgM‐induced phosphorylation of ERK. Btk–/– and PLCγ2–/– mice each had a reduced frequency of Igλ‐expressing B cells and impaired migration of pre‐B cells towards stromal cell‐derived factor 1. However, the increase in pre‐B cell malignancy that occurs in BLNK–/– mice in the absence of Btk was not observed in the absence of PLCγ2. Thus, Btk and PLCγ2 act both in concert and independently throughout B cell development.
Redox‐Induced μ‐Acetato and μ‐Oxo Core Interconversions in Dinuclear Manganese Tris(2‐methylpyridyl)amine (tpa) Complexes: Isolation and Characterization of [Mn2III(μ‐O)(μ‐O2CCH3)(tpa)2]3+
Authors: Collomb Marie‐Noëlle , Mantel Claire , Romain Sophie , Duboc Carole , Leprêtre Jean‐Claude , Pécaut Jacques , Deronzier Alain
Published: March 2007

The electrochemical properties of the bis(μ‐acetato) complex [Mn2II(O2CCH3)2(tpa)2]2+ (12+) [tpa = tris(2‐methylpyridyl)amine] in an organic medium (CH3CN) have been studied. Two successive controlled potential oxidations of a solution of 12+ at 0.7 and 1.1 V vs. Ag/Ag+ (10 mM) allow the selective and nearly quantitative formation of the mono‐(μ‐oxo) mono‐(μ‐acetato) complex [Mn2III(O)(O2CCH3)(tpa)2]3+ (23+) and the bis(μ‐oxo) complex [Mn2IV(O)2(tpa)2]4+ (34+), respectively. These results show that each substitution of an acetate group by an oxo group is caused by an overall two‐electron oxidation of the corresponding dimanganese complex. The associated electrochemical back transformations were also investigated. Complex 23+, which possesses a rare mono‐(μ‐oxo) mono‐(μ‐acetato) motif, has been isolated and characterized by X‐ray crystallography. This complex crystallizes in the monoclinic system, space group P21/n with a = 11.9899(17), b = 35.050(5), c = 12.3952(18) Å, β = 101.218(6)°, Z = 4. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)
Unusual T4(1) Water Chain Stabilized in the One‐Dimensional Chains of a Copper(II) Coordination Polymer
Authors: Jin Yi , Che Yunxia , Batten Stuart R. , Chen Pangkuan , Zheng Jimin
Published: March 2007

A novel T4(1) water chain in a new CuII coordination polymer, {[Cu(C4H6N2)2(C4H2O4)] (H2O)3}n (1, where C4H6N2 = 2‐methylimidazole, C4H2O4 = maleate), has been synthesized and structurally characterized by single‐crystal X‐ray diffraction. Thermogravimetry, infrared spectroscopy, elemental analysis, and magnetic analysis have also been used to characterize 1. Complex 1 crystallizes in the trigonal space group P3221, and the 1‐D chains composed of cyclic water tetramers play an important role in stabilizing the overall polymeric structure. Furthermore, this 1‐D water chain presents an unusual association mode of water molecules.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)
Hydrothermal Synthesis of Single Crystalline (K,Na)NbO3 Powders
Authors: Sun Ce , Xing Xianran , Chen Jun , Deng Jinxia , Li Lu , Yu Ranbo , Qiao Lijie , Liu Guirong
Published: March 2007

(K1–xNax)NbO3 (x = 0.01, 0.24, 0.89, 0.91, 0.99) single crystalline powders with perovskite structure were synthesized by a hydrothermal method with Nb2O5 in a mixed solution of KOH and NaOH at 220 °C for 24 h. XRD investigations showed that the structure of the synthesized (K1–xNax)NbO3 ceramics changed from a KNbO3‐type orthorhombic phase (space group Bmm2) to a NaNbO3‐type monoclinic phase (space group Pm) with the increase of Na content. The present results confirmed that (K1–xNax)NbO3 exhibited a morphotropic phase boundary (MPB) at around 50 %K separating the orthorhombic phase and monoclinic phase. FE‐SEM images showed that the morphological structures of niobates were cubes and nanofingers. The TEM image and the selected area electron diffraction pattern of (K0.01Na0.99)NbO3 showed the as‐synthesized powder was single crystalline and indexed to be monoclinic. The phase evolution of the products in the hydrothermal route revealed that the hydrothermal synthesis of (K1–xNax)NbO3 underwent two steps, where an intermediate product (K8–8xNa8x)Nb6O19·n H2O was found in the early stage and then pure (K1–xNax)NbO3 was obtained after another 30 min of hydrothermal treatment.(© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007)