bluuebunny/crossref_metadata_2025_split huggingface dataset:
Role of aromatic residues in stabilizing the secondary and tertiary structure of avian pancreatic polypeptide
Authors: Palermo Nicholas Y. , Csontos József , Murphy Richard F. , Lovas Sándor 
Published: October 2007

AbstractAvian pancreatic polypeptide (aPP) is a 36 residue protein that exhibits a tertiary fold. Results of previous experimental and computational studies indicate that the structure of aPP is stabilized more by nonbonded interactions than by the hydrophobic effect. Aromatic residues are known to participate in a variety of long‐range nonbonded interactions, with both backbone atoms and the atoms of other side‐chains, which could be responsible, in part, for the stability of both the local secondary structure and the tertiary fold. The effect of these aromatic interactions on the stability of aPP was calculated using BHandHLYP/cc‐pVTZ. Aromatic residues were shown to participate in multiple hydrogen bonded and weakly polar interactions in the secondary structure. The energies of the weakly polar interactions are comparable with those of hydrogen bonds. Aromatic residues were also shown to participate in multiple weakly polar interactions across the tertiary fold, again with energies similar to those of hydrogen bonds. © 2007 Wiley Periodicals, Inc. Int J Quantum Chem, 2008
Mass fingerprinting of toxic fractions from the venom of the Indian red scorpion,Mesobuthus tamulus: biotope‐specific variation in the expression of venom peptides
Authors: Newton Kirsti A. , Clench Malcolm R. , Deshmukh Ranjana , Jeyaseelan Kandiah , Strong Peter N. 
Published: October 2007

AbstractThe red scorpion,Mesobuthus tamulus, is found in two distinct biotopes within the Indian state of Maharastra—a tropical, sea‐level biotope and a semi‐arid biotope, up to 600 m. Scorpions from these two geographical areas show marked differences in toxicity. Using mass spectrometry, we have shown biotope‐specific variation in the expression of peptides from scorpions collected from these two distinct areas. Matrix‐assisted laser desorption/ionisation time‐of‐flight mass spectrometry (MALDI‐TOFMS) and reversed‐phase liquid chromatography/electrospray ionisation mass spectrometry (LC/ESI‐MS) were assessed as techniques for obtaining mass fingerprint data. On line LC/ESI‐MS was judged to be the method of choice and unique biotope‐specific mass fingerprints, with key diagnostic markers, were obtained. Copyright © 2007 John Wiley & Sons, Ltd.
Direct visualisation of peptide hormones in cultured pancreatic islet alpha‐ and beta‐cells by intact‐cell mass spectrometry
Authors: Buchanan Christina M. , Malik Arpita S. , Cooper Garth J. S. 
Published: October 2007

AbstractThe application of intact‐cell mass spectrometry (ICM) by matrix‐assisted laser desorption/ionisation time‐of‐flight (MALDI‐TOF) mass spectrometry to achieve direct protein‐profiling of bacterial species is now well established. However, this methodology has not to our knowledge been applied to the analysis of mammalian cells in routine culture. Here, we describe a novel application of ICM by which we have identified proteins in intact cells from two lines representative of pancreatic islet α‐ and β‐cells. Adherent αTC1 clone 9 and βTC6 F7 cells were harvested into phosphate‐buffered saline (PBS) using enzyme‐free dissociation buffer before 1 µL of cell suspension was spotted onto MALDI plates. Cells were overlaid with sinapinic acid then washed with pure water before application of a final coat of sinapinic acid. Data in the 2000–20 000 m/z range were acquired in linear mode on a Voyager DE‐Pro mass spectrometer. The proteins which ionised were composed in large part of peptide hormones (e.g. insulin and glucagon) known to be packaged into the secretory granules of the β‐ and α‐cells respectively. However, in addition to visualising the peptides expected to be associated with these cells, a mass consistent with oxyntomodulin was identified in the cultured α‐cells, a finding not previously reported to our knowledge. In summary, this paper describes, for the first time, a rapid and direct method useful for identifying secretory products in intact endocrine cells. Copyright © 2007 John Wiley & Sons, Ltd.
State feedback controller design of networked control systems with interval time‐varying delay and nonlinearity
Authors: Peng Chen , Tian Yu‐Chu , Tadé Moses O. 
Published: October 2007

AbstractThis paper proposes a method for robust state feedback controller design of networked control systems with interval time‐varying delay and nonlinearity. The key steps in the method are to construct an improved interval‐delay‐dependent Lyapunov functional and to introduce an extended Jessen's inequality. Neither free weighting nor model transformation is employed in the derivation of system stability criteria. It is shown that the maximum allowable bound on the nonlinearity could be computed through solving a constrained convex optimization problem; and the maximum allowable delay bound and the feedback gain of a memoryless controller could be derived by solving a set of linear matrix inequalities. Numerical examples are given to demonstrate the effectiveness of the proposed method. Copyright © 2007 John Wiley & Sons, Ltd.
Mimetic entry and bandwagon effect: the rise and decline of international equity joint venture in China
Authors: Xia Jun , Tan Justin , Tan David 
Published: October 2007

AbstractThe rise and decline of foreign entry strategies in transition economies is an important yet largely overlooked issue in the literature. This study is a step toward filling this gap by examining how mimetic entry within reference groups and the emergence of a competing strategy affect the bandwagon phenomenon of a dominant strategy in the context of China, where international equity joint ventures (EJVs) used to be a dominant entry strategy among foreign firms in the 1990s. Findings from a sample of 1,123 EJVs formed in China's non‐restricted industries from 1990 to 2003 show that the impact of home and host‐country industry effects are not symmetric between the EJV rise and decline periods. Cross‐border merger and acquisition (M&A) as a competing strategy has an important impact during the EJV decline period but not the rise period. The interactive effects between EJV and M&A strategies occur only in the host‐country industries. We discuss such results and offer suggestions for future research. Copyright © 2007 John Wiley & Sons, Ltd.
Elementary teachers' epistemological and ontological understanding of teaching for conceptual learning
Authors: Kang Nam‐Hwa 
Published: October 2007

AbstractThe purpose of this study was to examine the ways in which elementary teachers applied their understanding of conceptual learning and teaching to their instructional practices as they became knowledgeable about conceptual change pedagogy. Teachers' various ways to interpret and utilize students' prior ideas were analyzed in both epistemological and ontological dimensions of learning. A total of 14 in‐service elementary teachers conducted an 8‐week‐long inquiry into students' conceptual learning as a professional development course project. Major data sources included the teachers' reports on their students' prior ideas, lesson plans with justifications, student performance artifacts, video‐recorded teaching episodes, and final reports on their analyses of student learning. The findings demonstrated three epistemologically distinct ways the teachers interpreted and utilized students' prior ideas. These supported Kinchin's epistemological categories of perspectives on teaching including positivist, misconceptions, and systems views. On the basis of Chi's and Thagard's theories of conceptual change, the teachers' ontological understanding of conceptual learning was differentiated in two ways. Some teachers taught a unit to change the ontological nature of student ideas, whereas the others taught a unit within the same ontological categories of student ideas. The findings about teachers' various ways of utilizing students' prior ideas in their instructional practices suggested a number of topics to be addressed in science teacher education such as methods of utilizing students' cognitive resources, strategies for purposeful use of counter‐evidence, and understanding of ontological demands of learning. Future research questions were suggested. © 2007 Wiley Periodicals, Inc. J Res Sci Teach 44: 1292–1317, 2007
Identification and characterization of a novel yeast ω3‐fatty acid desaturase acting on long‐chain n‐6 fatty acid substrates from Pichia pastoris
Authors: Zhang Xinxin , Li Mingchun , Wei Dongsheng , Xing Laijun 
Published: October 2007

AbstractA cDNA sequence putatively encoding a ω3‐fatty acid desaturase gene was isolated from methylotrophic yeast Pichia pastoris GS115. The deduced amino acid sequence of this cloned cDNA showed high identity to known fungal ω3‐fatty acid desaturases. Functional identification of this gene heterologously in Saccharomyces cerevisiae strain INVScl indicated that the deduced amino acid sequence exhibited ω3‐fatty acid desaturase activity. The newly identified ω3‐fatty acid desaturase, named Pp‐FAD3, is novel because it showed broad n‐6 fatty acid substrate specificity by its ability to convert all the 18‐carbon and 20‐carbon n‐6 substrates examined to the corresponding n‐3 fatty acids, with an approximately equivalent high conversion rate. Pp‐FAD3 is the first known yeast ω3‐fatty acid desaturase to act on long‐chain n‐6 fatty acid substrates. Heterologous expression of the newly identified ω3 desaturase in different hosts will be an alternative method to increase the flow of n‐6 fatty acid intermediates into their n‐3 derivatives. Pp‐fad3 has been assigned GenBank Accession No. EF116884. Copyright © 2007 John Wiley & Sons, Ltd.
Genome‐wide analysis of coding DNA and amino acid variation in Saccharomyces cerevisiae
Authors: Tan Haidong , Wang Jinxia , Yang Fan , Zhao Zongbao K. 
Published: October 2007

AbstractThe possible causes of variation on amino acid composition in the yeast Saccharomyces cerevisiae were investigated genome‐wide. The results indicated that: (a) the base composition of coding DNA and amino acid composition was similar among all the chromosomes, which was in sharp contrast with the great varies of the composition of the individual's coding DNA and amino acid; (b) some amino acids (e.g. Cys and Trp) were not present in all the proteins; and (c) amino acid bias was associated with a base bias (in terms of A‐, G‐, C‐ and T‐rich codons). Based on the third rule and a proposed universal trend of amino acid gain and loss in protein evolution, the changing pattern of coding DNA was predicted to be T‐ and C‐accruing, whereas A and G were consistently reducing. All these results held the potential to reveal precisely how DNA ongoing change has a major effect on the composition of proteins. Copyright © 2007 John Wiley & Sons, Ltd.
The transcriptional inhibitor thiolutin blocks mRNA degradation in yeast
Authors: Pelechano Vicent , Pérez‐Ortín José E. 
Published: October 2007

AbstractThiolutin is commonly used as a general inhibitor of transcription in yeast. It has been used to calculate mRNA decay rates by stopping the transcription and then determining the relative abundance of individual mRNAs at different times after inhibition. We report here that thiolutin is also an inhibitor of mRNA degradation, and thus its use can lead to miscalculations of mRNA half‐lives. The inhibition of mRNA decay seems to affect the mRNA degradation pathway without impeding poly(A) shortening, given that the decay rate of total poly(A) amount is not reduced by thiolutin. Moreover, the thiolutin‐dependent inhibition of mRNA degradation has variable effects on different functional groups of genes, suggesting that they use various degradation pathways for their mRNAs. Copyright © 2007 John Wiley & Sons, Ltd.
Membrane topology and post‐translational modification of the Saccharomyces cerevisiae essential protein Rot1
Authors: Angeles Juanes M. , Carlos Igual J. , Carmen Bañó M. 
Published: October 2007

AbstractROT1 is an essential gene that has been related to cell wall biosynthesis, the actin cytoskeleton and protein folding. In order to help to understand its molecular function, we carried out a characterization of the Rot1 protein. It is primarily located at the endoplasmic reticulum–nuclear membrane facing the lumen. Rot1 migrates more slowly than expected, which might suggest post‐translational modification. Our results indicate that Rot1 is a protein that is neither GPI‐anchored nor O‐glycosylated. In contrast, it is N‐glycosylated. By a directed mutagenesis of several Asn residues, we identified that the protein is simultaneously glycosylated at N103, N107 and N139. Although the mutation of these three N sites is not lethal, cellular growth is impaired. Sequence analysis predicts a transmembrane domain at the C‐terminus. This fragment affects neither the targeting of the Rot1 protein to the ER nor its N‐glycosylation, although it is important for the anchoring of the protein to the membrane and for its functionality. The existence of a signal sequence at the N‐terminus has been suggested. However, deletion of this fragment impedes neither translocation to the ER nor N‐glycosylation, but it is required for cell viability. Finally, we found that Rot1 is translocated to the ER by an SRP‐independent post‐translational mechanism which depends on Sec62. Copyright © 2007 John Wiley & Sons, Ltd.
Expression of glycerol 3‐phosphate dehydrogenase gene (CvGPD1) in salt‐tolerant yeast Candida versatilis is stimulated by high concentrations of NaCl
Authors: Watanabe Yasuo , Nagayama Kisako , Tamai Youichi 
Published: October 2007

AbstractWe cloned the glycerol 3‐phosphate dehydrogenase (GPDH) gene (CvGPD1) from salt‐tolerant yeast Candida versatilis. When CvGPD1 was expressed in glycerol synthesis‐deficient Saccharomyces cerevisiae cells, the salt tolerance of the recombinant strain was enhanced, and NADP+‐dependent GPDH (EC 1.1.1.94), Cvgpd1p synthesis and recovery of glycerol synthesis were confirmed. The transcription of CvGPD1 in C. versatilis cells was stimulated by high concentrations of NaCl. The relationship between expression of CvGPD1 and growth of C. versatilis cells in the mash of Japanese seasonings (miso‐ and shoyu‐moromi) is also discussed. The Accession No. for the sequenced DNA fragment is AB296385. Copyright © 2007 John Wiley & Sons, Ltd.
Reaktionen von MeInCl2 mit Lithiumalkoholaten
Authors: Chamazi Navabeh Nami , Heravi Majid M. , Neumüller Bernhard 
Published: October 2007

AbstractReactions of MeInCl2 with Lithium AlcoholatesMeInCl2 was treated with two equivalents of LiOR (R = iPr, tBu) in boiling toluene to give the In‐O cage compounds [(InMe)4(InCl)3(Cl)5(OiPr)5(O)2] (1) and [Li(InMe)5(InCl)(Cl)2(OtBu)8(O)] (2). 1 and 2 were characterized by NMR and IR techniques as well as by X‐ray structure determinations. According to them 1 can be divided formally into the two complex fragments [(InMe)(MeInCl)(InCl)(OiPr)3(O)] and [(InMe)(MeInCl)(InCl2)(OiPr)2(O)] which coordinate one unit of InCl3. In 2 the complex fragments [Li(InMe)2(OtBu)4] and [(InMe)(MeInCl)2(InCl)(OtBu)4(O)] coordinate a Cl– ion.
Synthesis, Crystal Structures and Properties of the Trimetaphosphimates Na2M(PO2NH)3 · 2H2O with M = K, Tl
Authors: Sedlmaier Stefan J. , Johrendt Dirk , Oeckler Oliver , Schnick Wolfgang 
Published: October 2007

AbstractThe double salt disodium thallium(I) tri‐μ‐imidocyclotriphosphate dihydrate, Na2Tl(PO2NH)3 · 2H2O, was obtained by evaporation of combined, equimolar, aqueous solutions of Na3(PO2NH)3 · 4H2O and TlOOCCH3. The structure determination of the pseudo‐merohedrally twinned crystals of Na2Tl(PO2NH)3 · 2H2O was performed by single‐crystal X‐ray methods ($P{\bar 1}$, no. 2, a = 799.1(2), b = 799.3(2), c = 864.6(2) pm, α = 76.83(3)°, β = 83.81(3)°, γ = 77.57(3)°, Z = 2). In the crystal structure the trimetaphosphimate ring shows a chair conformation and two cyclic anions are connected to each other by six N‐H···O hydrogen bonds. The [(PO2NH)3]3− pairs are interconnected in a three‐dimensional network building strands along [1–10] by coordination to the sodium ions, with several coordinating bonds to the thallium ions and further hydrogen bonds. According to an ELF‐calculation, there is no stereochemical influence of the 6s2‐electron pair at the thallium(I) ion in Na2Tl(PO2NH)3 · 2H2O. This finding is corroborated by a comparison with the analogous potassium compound, Na2K(PO2NH)3 · 2H2O, which was found to be isotypic to Na2Tl(PO2NH)3 · 2H2O.
Synthesis, Structure and Dynamics of a C2‐symmetrical Bis(oxazolinylmethylene)pyrrolinato‐Zinc Complex
Authors: Capacchione Carmine , Wadepohl Hubert , Gade Lutz H. 
Published: October 2007

AbstractReaction of 2,5‐bis(cyanomethyl)pyrrole with L‐valinol in presence of zinc trifluoromethansulfonate and subsequent work‐up with aqueous NaCl gave the corresponding zinc complex 2, in which the double bonds of the pyrrole ring isomerize to give rise to a conjugated chromophore. Its molecular structure displays tetrahedral distortion from planarity, as was established by a single crystal structure analysis. The non‐planarity of 2 gives rise to a dynamic behaviour in solution with the chlorido‐ligand swinging through the plane spanned by the three N‐donor functions.
Centered Indium Cubes as Structural Motifs in SrRh2In8 and SrIrIn4
Authors: Muts Ihor R. , Zaremba Vasyl I. , Pöttgen Rainer 
Published: October 2007

AbstractThe indium‐rich intermetallic compounds SrRh2In8 and SrIrIn4 were synthesised from the elements in sealed tantalum ampoules in a high‐frequency furnace. Both samples were investigated by X‐ray powder and single crystal diffraction: CaCo2Al8 type, Pbam, a = 1617.0(3), b = 1387.4(3), c = 438.26(9) pm, wR2 = 0.0495, 1971 F2 values, 70 variables for SrRh2In8 and LaCoAl4 type, Pmma, a = 867.8(2), b = 432.33(9), c = 765.4(2) pm, wR2 = 0.0516, 692 F2 values, 24 variables for SrIrIn4. In both structures, the indium atoms build up two‐dimensional networks of distorted triangles, squares, and pentagons in an AA stacking sequence. The resulting trigonal and square prismatic voids are filled by the transition metal and indium atoms, respectively. In SrIrIn4 the pentagonal prisms are occupied by strontium, while the latter are alternatingly occupied by strontium and indium in SrRh2In8. Together the transition metal and indium atoms build up complex three‐dimensional [IrIn4] (261–288 pm Ir–In and 310–335 pm In–In) and [Rh2In8] (261–292 pm Rh–In and 290–348 pm In–In) networks in which the strontium atoms are located in distorted pentagonal tubes.
Pt4S4 Clusters with Functionalized Thiosemicarbazones derived from 5‐Acetylbarbituric Acid
Authors: Bermejo Elena , Castiñeiras Alfonso , García‐Santos Isabel , Gómez‐Rodriguez Lourdes , Sevillano Paloma 
Published: October 2007

AbstractReaction of K2[PtCl4] with thiosemicarbazones derived from 5‐acetylbarbituric acid led to the isolation of the tetranuclear species [Pt(AcbM)]4 · 2/2DMSO · 2DMSO · 5H2O (1) and [Pt(AcbE)]4 · 4DMSO · 2H2O (2) (H2AcbM = 5‐acetylbarbituric‐4N‐methyl thiosemicarbazone and H2AcbE = 5‐acetylbarbituric‐4N‐ethyl thiosemicarbazone). Both of these compounds feature a Pt4S4 cluster in which some of the Pt–Pt distances suggest the existence of weak metal‐metal interactions. Crystals of these tetranuclear species are stabilized by intermolecular π‐π stacking interactions. The two compounds have almost equivalent molecular structures, differing only in the orientation of the substituent on the amine nitrogen atom of the thiosemicarbazone. The two tetranuclear complexes contain the thiosemicarbazone bonded as a terdentate ligand to the platinum atom through the thiolate sulfur atom, the azomethine nitrogen atom and the alcoholate oxygen atom of the 5‐acetylbarbiturate function.
Synthese und Charakterisierung neuer intramolekular phosphorstabilisierter Aluminium‐, Gallium‐ und Indiumorganyle
Authors: Schumann Herbert , Girgsdies Frank , Heymer Bernd , Kaufmann Jens , Marschall Christian , Wassermann Wilfried 
Published: October 2007

AbstractSynthesis and Characterization of New Intramolecularly Phosphorus stabilized Aluminium, Gallium, and Indium OrganylsThe intramolecularly phosphorus stabilized element‐13 organyls Me2M(CH2)3P(t‐Bu)2 (M = Al (1), Ga (2), In (3)) and Cl2M(CH2)3P(t‐Bu)2 (M = Al (5), Ga (6)) are formed by reacting Me2MCl and MCl3 with t‐Bu2P(CH2)3MgCl and t‐Bu2P(CH2)3Li (4), respectively. The reaction of Et2PCH2C6H4Br‐2 (7) with BuLi and Me2InCl produces Me2InC6H4CH2PEt2‐2 (8). [Me2InCH2PMe2]2 (9) results from the reaction of Me2PCH2Li with Me2InCl. The successive addition of BuLi, Cl(CH2)3Br, and Me2AlCl to t‐BuPH2 does not lead to the expected Me2Al(CH2)3PH(t‐Bu) (10), but affords [{cyclo‐P(t‐Bu)(CH2)3}CO2](AlMe2Cl)2 (12) formed during work‐up in the presence of CO2. The new compounds were characterized by elemental analyses, 1H, 13C, and 31P NMR spectroscopy, as well as mass spectrometry. Additionally, the structures of 2 and 12 were determined by single crystal X‐ray diffraction.
Zur Bildung einer Zinn‐Zinn‐Bindung in Bis(hexamethyldisilazyl)‐Zinn(II) unter C‐H Bindungsbruch
Authors: Veith Michael , Gasthauer Matthias , Zimmer Michael , Huch Volker 
Published: October 2007

AbstractFormation of a Tin‐Tin‐Bond from Bis(hexamethyldisilazyl)‐Tin(II) under Fission of a C‐H BondBis(hexamethyldisilazyl)tin(II) in excess reacts with the molecular alumosiloxane (Ph2SiO)8(AlO(OH))4 to yield the well known tin(II) derivative (Ph2SiO)8(AlO2)4Sn2 and the novel bicyclic [(Me3Si)2N]Sn[N(SiMe3)SiMe2CH2]2Sn[N(SiMe3)2] containing a tin‐tin bond, which is formally related to the starting molecule by a missing hydrogen atom. From X‐ray diffraction studies on single crystals it follows that the new compound has almost C2 point symmetry (the twofold axis intersecting the tin‐tin bond) and that this tin‐tin bond is the fusion edge of anellated fivefold Sn‐Sn‐N‐Si‐C rings. The bond connecting the almost tetrahedrally coordinated tin atoms (2.737(2) Å) is astonishingly very short. This feature is also reflected in the spectroscopic data (1H, 13C, 29Si, 119Sn‐NMR) of the compound with a coupling constant 1J (117Sn/119Sn) of 9529 Hz.
On the Mechanism of CO2 Insertion into the Mg‐N Bond of Molecular Mono‐ and Dinuclear Magnesium Compounds: A Quantum Chemical Study
Authors: Himmel Hans‐Jörg 
Published: October 2007

AbstractHerein the mechanism for CO2 fixation by alkylmagnesium amides and magnesium bisamides is analyzed on the basis of DFT (density functional theory) calculations relying on the functionals BP86 and B3LYP in combination with a TZVPP basis set. Monomeric as well as dimeric compounds were considered, and prior to the CO2 reactions the thermodynamics of several equilibria (monomer‐dimer, disproportionation) is analyzed. Additional calculations were performed to study the mechanism for CO2 fixation in the presence of a chelating donor molecule, namely ethylene diamine, which preferentially complexes the monomeric alkylmagnesium amide. On the basis of the calculations it is suggested that (i) for monomeric magnesium compounds CO2 insertion into the Mg‐N bonds proceeds without a barrier to an intermediate featuring a four‐membered MgOCN ring and then with a relatively small barrier to the carbamate, (ii) for dinuclear magnesium compounds CO2 insertion is opposed by a significant barrier, and (iii) the addition of donor ligands which coordinate to the monomeric species shifts the monomer‐dimer equilibrium to the monomer side, and in addition leads to direct carbamate formation without any intermediate stage and with no reaction barrier. The studies might be of interest for a better understanding of enzymatic reactivity.