H-D exchange on graphite-potassium intercalation compounds

Potassium graphite intercalation compounds are able to activate C-H bonds of hydrocarbons at room temperature. In this paper, the hydrogen-deuterium exchange of CHD(3) in the presence of C(8)K, C(24)K and C(36)K is described.     

Eigenvalues of the Dirac Operator on Fibrations over S1

We consider the Dirac operator on fibrations overS ¹ which have up to holonomy a warped product metric. Wegive lower bounds for the eigenvalues on M and if the Diracoperator on the typical fibre F has a kernel, we calculatethe corresponding part of the spectrum on M explicitly.Moreover, we discuss the dependence of the spectrum of theholonomy and obtain bounds for the multiplicity of the eigenvalues.     

Properties and adsorptive capacity of amino acids modified chitosans for copper ion removal

This work presents the results of the modification of lateral groups of chitosan (2-amino-2-desoxy-β-D-glucose) by the reaction with different amino acids (glycine, L-lysine, -glutamic acid and L-isoleucine) under acid catalysis. The Cu²⁺ adsorption capacity of pure chitosan and of the chemically modified chitosans were also evaluated. The modification reaction favored the amide formation of the C-2 carbon of the glycoside ring under the adopted reaction conditions: reaction time and temperature and using sulfuric acid as a catalyst. The Cu²⁺ adsorption kinetics and equilibrium response using pure chitosan and the chemically modified chitosans as adsorbents showes that the adsorption capacity of equilibrium depended on the initial ion concentration. The response of each adsorbent gave good correlation with Langmuir's isotherm model. The following maximum adsorption capacity constants were obtained: 172.4 mg/g for chitosan and 69.9, 34.4, and 26.7 mg/g for modified chitosan with glycine, L-glutamic acid, and L-lysine, respectively. The adsorptive capacity seems to be dependent on the length and complexity of the added group.     

Structure and Ordering Principles of Ultrathin Organic Molecular Films on Surfaces of Layered Semiconductors Organic-on-Inorganic MBE

Epitaxially ordered thin films of large planar organic molecules can be obtained on layered inorganic semiconductors by organic molecular beam deposition in UHV. Analysis by low energy electron diffraction (LEED) and thermal desorption spectroscopy (TDS) yields structural parameters and binding energies. The conditions necessary for order formation are analyzed. Epitaxial data are given for hexabenzocoronene (HBC) and naphthalene-tetracarboxylic-dianhydride (NTCDA) on graphite, MoS₂ and GeS.     

Expanded Conformations of Monomeric Tau Initiate Its Amyloidogenesis**

Understanding early amyloidogenesis is key to rationally develop therapeutic strategies. Tau protein forms well-characterized pathological deposits but its aggregation mechanism is still poorly understood. Using single-molecule force spectroscopy based on a mechanical protection strategy, we studied the conformational landscape of the monomeric tau repeat domain (tau-RD_244-368). We found two sets of conformational states, whose frequency is influenced by mutations and the chemical context. While pathological mutations Δ280K and P301L and a pro-amyloidogenic milieu favored expanded conformations and destabilized local structures, an anti-amyloidogenic environment promoted a compact ensemble, including a conformer whose topology might mask two amyloidogenic segments. Our results reveal that to initiate aggregation, monomeric tau-RD_244-368 decreases its polymorphism adopting expanded conformations. This could account for the distinct structures found in vitro and across tauopathies.