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A series of density functional calculations were performed on several substituted fullerenes to determine the relationship among curvature, patch type, and reactivity of the C-C site. It was found that the binding energy between the Pt(PH3)2 unit and fullerene is almost independent of the size of the cage and of the number of metals coordinated on the fulerene surface.

The observation of new heterofullerenes with metal atoms incorporated into the fullerene network through the replacement of two carbon atoms by a single metal atom is reported. Experimental evidence for the ability of [C59M](super +1) and [C55M](super -1) to bind to olefins is presented.

The structural, energetic, spectroscopic, electronic and bonding properties of [[[Mo.sub.3]Cu[S.sub.4][(dmpe).sub.3][Cl.sub.4]].sup.+] and [Mo.sub.3]Ni[Si.sub.4][(dmpe).sub.3][Cl.sub.4] with 16 metal clusters, where dmpe = 1,2-bis(dimethylphosphino)ethane, are analyzed. The electronic delocalization present in these cluster complexes are attributed to the metal formal oxidation states.

The stabilities of highly hydrogenated and fluorinated [80]fullerenes, both empty and containing the Sc3N molecule are calculated using the density functional method. Addition of 44 atoms to i-Sc3NC80 was found to be most favorable due to the formation of six octahedrally located benzenoid rings, while addition of up to 52 atoms gives a structure stabilized by the presence of four benzenoid rings.

The synthesis of three [60]fullerence adducts with 15-membered-ring orifices on the fullerence cage are studied. The existence of many different functional groups on the rim of the orifice is very promising for further regioselective functionalization and enlargement of the orifice size.

To examine the bonding between the scandium atoms and the fullerene cage, density functional calculations were performed on Sc(sub 3)N@C(sub 80) and Sc(sub 3)@N(sub 78). Geometric optimization of the structure of Sc(sub 3)N@C(sub 78) indicates that the carbon cage expands to accommodate the Sc(sub 3)N unit within the cage.

A combined experimental and computational investigation on the Ag-catalysed decarboxylation of benzoic acids is reported herein. The present study demonstrates that a substituent at the ortho position exerts dual effects in the decarboxylation event. On one hand, ortho-substituted benzoic acids are inherently destabilised starting materials compared to their meta- and para-substituted counterparts. On the other hand, the presence of an ortho-electron-withdrawing group results in an additional stabilisation of the transition state. The combination of both effects results in an overall reduction of the activation energy barrier associated with the decarboxylation event. Furthermore, the Fujita-Nishioka linear free energy relationship model indicates that steric bulk of the substituent can also exert a negative effect by destabilising the transition state of decarboxylation. [ABSTRACT FROM AUTHOR]

This article explores the quintessential “person–environment” relationship that forms the core of the subdiscipline of social geography within the context of a national accountability shift from state to society in England. Two Audit Commission datasets are mined to establish homogeneous clusters of residential socioeconomic status and quality of life status before being cross-tabulated to detect genuine issues that affect each characteristic locality. In three of the four cross-tabulations, significant differences on economic well-being, life-long learning, and health distinguish correspondences, whereas in the other, less tangible, case, such factors as the use of cultural facilities, community cohesion, and people’s access to work seem to matter. The implications for research, policy, and practice are duly considered. [ABSTRACT FROM PUBLISHER]

Protein kinases play critical roles in cellular activation and differentiation, and are involved in numerous pathophysiological processes. As a critical component of the regulatory circuitry of the cell, the kinase domain has the ability to integrate multiple signals, yielding a predetermined output. In PKC and other protein kinases of the AGC family, several phosphorylation sites control the activity, but these are in turn influenced by the presence of ligands in the binding pocket, which promotes phosphorylation. Here, we take PKC-theta as a prototypical member of the family and use molecular dynamics simulations to investigate the cross-talk that exists between regulatory and functional sites. We first show how the apo-unphosphorylated form of the kinase is populating a conformational space in which access to the ATP binding site and to the activation loop (AL) are simultaneously hindered. This could explain why the inactive state is not only catalytically incompetent but also resistant to activation. AL phosphorylation induces ATP binding site opening, which can then readily accept the cofactor. But the signal transmission mechanism works both ways, and if ligand binding to the unphosphorylated form occurs first, the AL is de-protected and becomes exposed to phosphorylation, thus providing an explanation for the paradoxical activation of PKCs by their inhibitors. Proteins 2012; © 2011 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

Recent experiments with amyloid-beta (Aβ) peptides indicate that the formation of toxic oligomers may be an important contribution to the onset of Alzheimer's disease. The toxicity of Aβ oligomers depend on their structure, which is governed by assembly dynamics. However, a detailed knowledge of the structure of at the atomic level has not been achieved yet due to limitations of current experimental techniques. In this study, replica exchange molecular dynamics simulations are used to identify the expected diversity of dimer conformations of Aβ10-35 monomers. The most representative dimer conformation has been used to track the dimer formation process between both monomers. The process has been characterized by means of the evolution of the decomposition of the binding free energy, which provides an energetic profile of the interaction. Dimers undergo a process of reorganization driven basically by inter-chain hydrophobic and hydrophilic interactions and also solvation/desolvation processes. [ABSTRACT FROM AUTHOR]

Fullerenes containing a trimetallic nitride template (TNT) within the cage are a particularly interesting class of endohedral metallofullerenes. Recently two exohedral derivatives of the Sc3N@C80 fullerene have been synthesized: a Diels-Alder and a fulleropyrrolidine cycloadduct. The successful isolation, purification, and structural elucidation of these metallofullerenes derivatives have encouraged us to understand how the chemical reactivity is affected by TNT encapsulation. First of all, we predicted the most reactive exohedral sites, taking into account the double bond character and the pyramidalization angle of the C-C bonds. For this purpose, a full characterization of all different types of C-C bonds of the following fullerenes was carried out: Ih-C60:1, D3-C68:6140, D3-Sc3N@C68, D5h-C70:1, D3h′-C78:5, D3h-Sc3N@C78, Ih-C80:7 and several isomers of Sc3N@C80. Finally the exohedral reactivity of these TNT endohedral metallofullerenes, via [4 + 2] cycloaddition reactions of 1,3-butadiene, was corroborated by means of DFT calculations. [ABSTRACT FROM AUTHOR]

We report here for the first time a full comparison of the exohedral reactivity of a given fullerene and its parent trinitride template endohedral metallofullerene. In particular, we study the thermodynamics and kinetics for the Diels-Alder [4 + 2] cycloaddition between 1,3-butadiene and free D3h′-C78 fullerene and between butadiene and the corresponding endohedral D3h-Sc3N@C78 derivative. The reaction is studied for all nonequivalent bonds, in both the free and the endohedral fullerenes, at the BP86/TZP//BP86/DZP level. The change in exohedral reactivity and regioselectivity when a metal cluster is encapsulated inside the cage is profound. Consequently, the Diels-Alder reaction over the free fullerene and the endohedral derivative leads to totally different cycloadducts. This is caused by the metal nitride situated inside the fullerene cage that reduces the reactivity of the free fullerene and favors the reaction over different bonds. [ABSTRACT FROM AUTHOR]

A systematic search of the regioisomers of the heterofullerenes, C57Pt2 and C56Pt2, has been carried out by means of density functional calculations to find the most stable structures. Both heterofullerenes incorporate two metal atoms into the fullerene surface. In the case of C57Pt2, one platinum atom substitutes one carbon atom of C60 and the other platinum atom replaces a C--C bond, whereas in C56Pt2 each platinum atom replaces one C--C bond. Several geometric factors were studied, three of which have particularly important effects on the relative stabilities of the regioisomers: the Pt--Pt separation, the number of C--C bonds remaining after substitution, and the type of C--C bond that is substituted. All these factors indicate that the deformation of the carbon framework is a general factor that governs the relative stabilities of the regioisomers. Because a high number of factors affect the stability of the heterofullerenes we also used chemometric techniques in this study. Partial least-squares (PLS) regression was used to establish the structure-energy relationships of C57Pt2 and C56Pt2 heterofullerenes. The understanding gained of the factors that affect the relative isomers stabilities has allowed us to predict the stabilities of larger disubstituted carbon cages, for example, C81Pt2 heterofullerene.