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Different Complexes (different + complex)
Selected AbstractsSocial learning and mother's behavior in manipulative tasks in infant marmosetsAMERICAN JOURNAL OF PRIMATOLOGY, Issue 6 2009Vera Dell'Mour Abstract High levels of social tolerance are considered to promote social learning, as they allow direct observation of a manipulating conspecific and facilitate scrounging. Owing to tolerance toward infants, infancy is thought to be especially suited for learning socially transmitted behaviors. Despite this, few studies have investigated social learning of infants, particularly in manipulative tasks where observation might be most helpful. Here, we investigated (1) the influence of social learning on task acquisition in infant marmosets, and (2) whether the mother augments her behavior in a way that may enhance social learning by her infants. We tested infant and juvenile marmosets in four different complex foraging-related tasks, featuring large living insects (two tasks) or artificially embedded prey (two tasks). Each individual observed the mother solving two of the tasks and served as a control in the other two tasks. Observers manipulated more and succeeded sooner than control animals, suggesting that observing the mother promoted learning either directly or by decreasing neophobia. Moreover, the data suggest that learning in 11,15 week-old infants might be promoted actively by the mother. She solved the tasks, consumed less food, and consumed it later than when foraging with older offspring or alone. Furthermore, the results indicate the possible importance of the third and fourth month of infancy as the crucial ontogenetic period for social learning in marmosets, corroborating recent observations of free-living common marmosets. Am. J. Primatol. 71:503,509, 2009. © 2009 Wiley-Liss, Inc. [source] Capillary electrophoresis as a probe of enantiospecific interactions between photoactive transition metal complexes and DNAELECTROPHORESIS, Issue 15 2003James P. Schaeper Abstract Recently, we have demonstrated the capacity to separate chiral transition metal (TM) complexes of the type [M(diimine)3]n+ using CE buffers containing chiral tartrate salts. In separate work, several chromium(III)- tris -diimine complexes in particular have been shown to bind enantioselectively with calf-thymus (CT) DNA, and a qualitative assessment of the relative strength and enantiospecificity of this interaction is of significant interest in the characterization of these complexes as potential DNA photocleavage agents. Here, we describe two convenient approaches to investigate such binding behavior using chiral CE. For complexes with lower DNA affinities exhibiting primarily surface binding, DNA itself is used as the chiral resolving agent in the electrophoretic buffer. In this approach, resolution of the TM complexes into their , and , isomers is achieved with the isomer eluting later exhibiting superior binding affinity toward DNA. For more strongly bound TM complexes containing ligands known to intercalate with DNA, the [Cr(diimine)3]3+ complexes are preincubated with oligonucleotide and subsequently enantiomerically resolved in a dibenzoyl- L -tartrate buffer system that facilitates analysis of the unbound TM species only. Differences in isomer binding affinity are distinguished by the relative peak areas of the ,- and ,-isomers, and relative binding strengths of different complexes can be inferred from comparison of the total amount of unbound complex at equivalent DNA/TM ratios. [source] Magnetic, 57Fe Mössbauer, and IR Monitoring of the Thermal Spin Transition in a New Family of Iron(II) Spin-Transition ComplexesEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 12 2003Arno F. Stassen Abstract A new family of iron(II) tetrafluoroborate and perchlorate spin-crossover compounds has been synthesised and is discussed. The iron(II) ion is surrounded by six 1-ethyltetrazole ligands, which are halogen-substituted on the C2 atom of the ethyl group. The spin-crossover temperatures T1/2 are high compared to the unsubstituted (1-alkyltetrazole)iron(II) complexes. The shape of the spin-transition curve (i.e. ,HS vs. T) varies largely over the different complexes and appears to be influenced neither by the crystal packing, nor by the electronic effects. The temperature-dependent spin-transition behaviour has been studied by magnetic susceptibility and by 57Fe-Mössbauer spectroscopy. These data have been supported by temperature-dependent mid-range infrared spectroscopy: the thermally induced spin transition has been observed by direct monitoring of the aromatic C,H stretching frequency. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003) [source] Comparison of Cyclodextrin-Dipeptide Inclusion Complexes in the Absence and Presence of Urea by Means of Capillary Electrophoresis, Nuclear Magnetic Resonance and Molecular ModelingEUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 18 2007Benjamin Waibel Abstract The use of capillary electrophoresis (CE) modified with cyclodextrin (CD) for the separation of stereoisomers of peptides is well established. To increase the solubility of ,-CD, urea is often added to the buffer which may influence the complexation of a CD with a guest molecule. The aim of the present study was to investigate the influence of urea on the complexation between dipeptides and ,-CD using Ala-Phe and Ala-Tyr as model compounds. For this purpose three different analytical methods were employed: capillary electrophoresis (CE), 1H-NMR spectroscopy and molecular dynamics simulations (MD). Electropherograms of the peptide enantiomers were different in the presence and absence of urea. For example, at pH,2.5 in the absence of urea the enantiomers of Ala-Tyr are not separated in contrast to the use of buffers containing urea. Applying "complexation-induced chemical shift (CICS)" in NMR spectroscopy and rotating frame Overhauser enhancement spectroscopy (ROESY) revealed differences in the complexation of the peptide enantiomers by ,-CD in the absence and presence of urea suggesting the stabilization of the complex through the phenolic hydroxyl group of tyrosine. MD simulations for different complexes were carried out with consideration of both water and urea molecules in solution. Simulations were performed for 1 ns. In conclusion, NMR spectroscopy and MD methods help to understand the structure of peptide-CD complexes and the separation and migration behavior in CE. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2007) [source] Insights into the design of a hybrid system between Anabaena ferredoxin-NADP+ reductase and bovine adrenodoxinFEBS JOURNAL, Issue 4 2003Merche Faro The opportunity to design enzymatic systems is becoming more feasible due to detailed knowledge of the structure of many proteins. As a first step, investigations have aimed to redesign already existing systems, so that they can perform a function different from the one for which they were synthesized. We have investigated the interaction of electron transfer proteins from different systems in order to check the possibility of heterologous reconstitution among members of different chains. Here, it is shown that ferredoxin-NADP+ reductase from Anabaena and adrenodoxin from bovine adrenal glands are able to form optimal complexes for thermodynamically favoured electron transfer reactions. Thus, electron transfer from ferredoxin-NADP+ reductase to adrenodoxin seems to proceed through the formation of at least two different complexes, whereas electron transfer from adrenodoxin to ferredoxin-NADP+ reductase does not take place due because it is a thermodynamically nonfavoured process. Moreover, by using a truncated adrenodoxin form (with decreased reduction potential as compared with the wild-type) ferredoxin-NADP+ reductase is reduced. Finally, these reactions have also been studied using several ferredoxin-NADP+ reductase mutants at positions crucial for interaction with its physiological partner, ferredoxin. The effects observed in their reactions with adrenodoxin do not correlate with those reported for their reactions with ferredoxin. In summary, our data indicate that although electron transfer can be achieved in this hybrid system, the electron transfer processes observed are much slower than within the physiological partners, pointing to a low specificity in the interaction surfaces of the proteins in the hybrid complexes. [source] McLafferty rearrangement of the radical cations of butanal and 3-fluorobutanal: A theoretical investigation of the concerted and stepwise mechanismsJOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 3 2008Daniel Norberg Abstract The stepwise and concerted pathways for the McLafferty rearrangement of the radical cations of butanal (Bu+) and 3-fluorobutanal (3F-Bu+) are investigated with density functional theory (DFT) and ab initio methods in conjunction with the 6-311+G(d,p) basis set. A concerted transition structure (TS) for Bu+, (H), is located with a Gibbs barrier height of 37.7 kcal/mol as computed with CCSD(T)//BHandHLYP. Three pathways for the stepwise rearrangement of Bu+ have been located, which are all found to involve different complexes. The barrier height for the H, transfer is found to be 2.2 kcal/mol, while the two most favorable TSs for the C,,C, cleavage are located 8.9 and 9.2 kcal/mol higher. The energies of the 3F-Bu+ system have been calculated with the promising hybrid meta-GGA MPWKCIS1K functional of DFT. Interestingly, the fluorine substitution yields a barrier height of only 20.5 kcal/mol for the concerted TS, (3F-H). A smaller computed dipole moment, 12.1 D, for (3F-H) compared with 103.2 D for (H) might explain the stabilization of the substituted TS. The H, transfer, with a barrier height of 4.9 kcal/mol, is found to be rate-determining for the stepwise McLafferty rearrangement of 3F-Bu+, in contrast to the unsubstituted case. By inspection of the spin and charge distributions of the stationary points, it is noted that the bond cleavages in the concerted rearrangements are mainly of heterolytic nature, while those in the stepwise channels are found to be homolytic. © 2007 Wiley Periodicals, Inc. J Comput Chem, 2008 [source] Surface Plasmon Resonance Spectroscopy as a Tool to Study Polyplex-Glycoaminoglycan InteractionsMACROMOLECULAR RAPID COMMUNICATIONS, Issue 12 2005Peter Dubruel Abstract Summary: This article reports the application of surface plasmon resonance (SPR) to monitor the interaction between polymer-DNA complexes and glycoaminoglycans (GAG). The GAG selected was hyaluronic acid (HA). First a HA derivative containing a disulfide linkage was synthesized, enabling chemisorption onto a gold surface. Next, the interaction between different complexes (prepared using PEI or PDMAEMA) and HA was studied using SPR. This study clearly indicates that GAG-polyplex interactions depend on the type of polymer selected and on the charge ratio of the polyplexes prepared. The derivative developed opens up new perspectives in the field of nonviral gene delivery. [source] Electrospray mass spectrometric studies of the complexational behavior of maleonitrile thiacrown ethers with various metalsRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 5 2006Ines Starke Electrospray ionization was employed to study the mass spectrometric behavior of the maleonitrile tetrathiacrown ethers mn12S4 (1) and mn13S4 (2) and maleonitrile pentathiacrown ether mn15S5 (3) and of their complexes with various metal salts (MX2, M,=,Pd, Pt, Ni, Co, Fe; X,=,Cl, CrCl3, Ni(BF4)2, TlPF6 or Cd(NO3)2) and Cu(SO3CF3)2. Both singly charged, [MXL]+ and [MXL2]+, and doubly charged complexes, [MLn]2+ (n,=,2,5), were observed. The formation of the different complexes consisting of the transition metal ion, the counterion and the various crown ethers and their subsequent dissociation was also studied by collision-induced dissociation measurements which were also used to evaluate the relative stabilities of the complexes. It was found that the collisional voltages for the dissociation of the complexes were generally greater in the [MXL]+ complexes than in the corresponding [MXL2]+ complexes. Copyright © 2006 John Wiley & Sons, Ltd. [source] Oxidative addition of different electrophiles with rhodium(I) carbonyl complexes of unsymmetrical phosphine,phosphine monoselenide ligandsAPPLIED ORGANOMETALLIC CHEMISTRY, Issue 8 2006Pratap Chutia Abstract Dimeric chlorobridge complex [Rh(CO)2Cl]2 reacts with two equivalents of a series of unsymmetrical phosphine,phosphine monoselenide ligands, Ph2P(CH2)nP(Se)Ph2 {n = 1(a), 2(b), 3(c), 4(d)}to form chelate complex [Rh(CO)Cl(P,Se)] (1a) {P,Se = ,2 -(P,Se) coordinated} and non-chelate complexes [Rh(CO)2Cl(P,Se)] (1b,d) {P,Se = ,1 -(P) coordinated}. The complexes 1 undergo oxidative addition reactions with different electrophiles such as CH3I, C2H5I, C6H5CH2Cl and I2 to produce Rh(III) complexes of the type [Rh(COR)ClX(P,Se)] {where R = C2H5 (2a), X = I; R = CH2C6H5 (3a), X = Cl}, [Rh(CO)ClI2(P,Se)] (4a), [Rh(CO)(COCH3)ClI(P,Se)] (5b,d), [Rh(CO)(COH5)ClI-(P,Se)] (6b,d), [Rh(CO)(COCH2C6H5)Cl2(P,Se)] (7b,d) and [Rh(CO)ClI2(P,Se)] (8b,d). The kinetic study of the oxidative addition (OA) reactions of the complexes 1 with CH3I and C2H5I reveals a single stage kinetics. The rate of OA of the complexes varies with the length of the ligand backbone and follows the order 1a > 1b > 1c > 1d. The CH3I reacts with the different complexes at a rate 10,100 times faster than the C2H5I. The catalytic activity of complexes 1b,d for carbonylation of methanol is evaluated and a higher turnover number (TON) is obtained compared with that of the well-known commercial species [Rh(CO)2I2],. Copyright © 2006 John Wiley & Sons, Ltd. [source] Triphenylantimony(v) Catecholates and o -Amidophenolates: Reversible Binding of Molecular OxygenCHEMISTRY - A EUROPEAN JOURNAL, Issue 14 2006Vladimir K. Cherkasov Prof. Dr. Abstract Novel neutral antimony(V) complexes were isolated as crystalline materials and characterized by IR and NMR spectroscopy: o -amidophenolate complexes [4,6-di- tert -butyl- N -(2,6-dimethylphenyl)- o -amidophenolato]triphenylantimony(V) (Ph3Sb[AP-Me], 1) and [4,6-di- tert -butyl- N -(2,6-diisopropylphenyl)- o -amidophenolato]triphenylantimony(v) (Ph3Sb[AP- iPr], 2); catecholate complexes (3,6-di- tert -butyl-4-methoxycatecholato)triphenylantimony(V) (Ph3Sb[(MeO)Cat], 3), its methanol solvate 3,CH3OH (4); (3,6-di- tert -butyl-4,5-di-methoxycatecholato)triphenylantimony(V) (Ph3Sb[(MeO)2Cat], 5) and its acetonitrile solvate 5,CH3CN (6). Complexes 1,7 were synthesized by oxidative addition of the corresponding o -iminobenzoquinones or o -benzoquinones to Ph3Sb. In the case of the phenanthrene-9,10-diolate (PhenCat) ligand, two different complexes were isolated: Ph3Sb[PhenCat] (7) and [Ph4Sb]+[Ph2Sb(PhenCat)2], (8). Complexes 7 and 8 were found to be in equilibrium in solution. Molecular structures of 2, 4, 6, and 8 were determined by X-ray crystallography. Complexes 1,7 reversibly bind molecular oxygen to yield Ph3Sb[L-Me]O2 (9), Ph3Sb[L- iPr]O2 (10), Ph3Sb[(MeO)L,]O2 (11), Ph3Sb[(MeO)2L,]O2 (12) and Ph3Sb[PhenL,]O2 (13), which contain five-membered trioxastibolane species (where L is the O,O,,N-coordinated derivative of a 1-hydroperoxy-6-(N -aryl)-iminocyclohexa-2,4-dienol, and L, the O,O,,O,,-coordinated derivative of 6-hydroperoxy-6-hydroxycyclohexa-2,4-dienone). Complexes 9,13 were characterized by IR and 1H NMR spectroscopy and X-ray crystallography. [source] Synthesis and Characterization of Three Diverse Coordination Frameworks under Co-ligand InterventionCHINESE JOURNAL OF CHEMISTRY, Issue 2 2009Ping LIU Abstract The chelating organic ligands of 2,2,-bipyridine (2,2,-bipy), di(pyrid-2-yl)amine (dpa) and 2,6-di(pyrid-2-ylamino)pyridine (dpap) were respectively applied to react with H2fum (fumaric acid) and copper salts, affording three different complexes [Cu2(fum)(2,2,-bipy)4]·2ClO4 (1), [Cu2(µ-OH)2(fum)(dpa)2]·2H2O (2) and [Cu(SO4)(H2O)(dpap)]·H2O (3). These complexes were determined by single-crystal X-ray diffraction. Each penta-coordinated Cu(II) ion exhibits a distorted trigonal bipyramidal geometry in 1. The fum ligand links copper ions to form a dinuclear copper unit. While in 2, the fum ligands connect [Cu2(µ-OH)2(dpa)2] unit to construct a 1D zigzag chain. Unexpectedly, when dpap instead of dpa was used under the same conditions, only one mononuclear complex 3 was formed. Crystal packings show that 1,3 form 3D supramolecular architectures through non-covalent interactions (multiple hydrogen bonds and C,H··· ,/,-, interactions). In addition, the study of the magnetic property reveals dominating ferromagnetic interactions between Cu(II) atoms in 1. [source] | |||||||||||||