Nuclear quantum effect on the hydrogen-bonded structure of guanine�Ccytosine pair

The structure of Watson?CCrick type guanine?Ccytosine (G?CC) base pair has been studied by classical hybrid Monte Carlo (HMC) and quantum path integral hybrid Monte Carlo (PIHMC) simulations on the semiempirical PM6 potential energy surface. For the three NH?X hydrogen-bonded moieties, the intramolecular NH bonds are found systematically longer while the H?X distance shorter in the PIHMC simulation than in the HMC simulation. We found that the hydrogen bonded length N?X correlates with the H?X distance, but not with the NH distance. A correlation is also between the neighboring hydrogen bonds in the G?CC base pair.     

Projective structures with discrete holonomy representations

Let denote the set of projective structures on a compact Riemann surface whose holonomy representations are discrete. We will show that each component of the interior of is holomorphically equivalent to a complex submanifold of the product of Teichmüller spaces and the holonomy representation of every projective structure in the interior of is a quasifuchsian group.

     

Acid-catalyzed transformation of rubrene to indenonaphthacene and its paired interacting orbital (PIO) analysis

Treatment of rubrene (5,6,11,12-tetraphenylnaphthacene) with trifluoroacetic acid in dichloromethane gives 4b,9,10-triphenyl-4b,9-dihydroindeno[1,2,3-fg]naphthacene (1) as the sole isolable product. Paired interacting orbital (PIO) analysis indicates that the reaction is initiated by preferential attack of H⁺ at C(11) position of rubrene.     

Electron transport with mobility above 10–3 cm2/Vs in amorphous film of co‐planar bipyridyl‐substituted oxadiazole

We demonstrate that a bipyridyl substituted oxadiazole (Bpy‐OXD) shows high electron mobility that reached above 10^–3 cm²/Vs. We believe that the high mobility results from both the hybrid molecular structure of the two electron‐accepting units: bipyridyl and oxadiazole, and the planar molecular structure based on its lack of sterically hindered bulky substituent. The computational analysis elucidates that the amorphous nature of Bpy‐OXD in thin‐film state probably results from the polymorphic effect in isolated state and the volume effect in solid state. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Isothermal differential scanning calorimetry on an exothermic phenomenon during thermal decomposition of hydromagnesite 4 MgCO3 · Mg(OH)2 · 4 H2O

An exothermic phenomenon and a simultaneous rapid evolution of a small amount of carbon dioxide at ?500°C during thermal decomposition of hydromagnesite 4 MgCO₃ · Mg(OH)₂ · 4 H₂O was studied by isothermal DSCTG in a carbon dioxide atmosphere. It was quantitatively confirmed that the exothermic phenomenon was due to crystallization of MgCO₃ from the amorphous phase and that the evolution of carbon dioxide was due to decomposition of the MgCO₃ by the heat of crystallization (?3.4 kcal mole^?1.     

Synthesis of hexagonal nickel hydroxide nanosheets by exfoliation of layered nickel hydroxide intercalated with dodecyl sulfate ions

One-nanometer-thick nickel hydroxide nanosheets were prepared by exfoliation of layered nickel hydroxides intercalated with dodecyl sulfate (DS) ions. The shape of the nanosheets was hexagonal, as was that of the layered nickel hydroxides intercalated with DS ions. The nickel hydroxide nanosheets exhibited charge-discharge properties in strong alkaline electrolyte. The morphology of the nanosheet changed during the electrochemical reaction.     

Quantum proton transfer in hydrated sulfuric acid clusters: a perspective from semiempirical path integral simulations

We have carried out path-integral molecular dynamics simulations for hydrated sulfuric acid clusters to understand acid-dissociation and hydrogen-bonded structural rearrangement processes in these clusters from a quantum mechanical viewpoint. The simulations were performed using the PM6 semiempirical electronic structure level whose parameters were modified on the basis of the specific reaction parameters strategy so that relative energies of optimized structures, as well as water binding energies reproduce ab initio and density-functional theory calculations. We have found that the acid dissociation processes, first and second deprotonation, effectively occur in a hydrated cluster with a specific cluster size. The mechanisms of the proton-transfer processes were analyzed in detail and it was found that the distance between O in sulfuric acid and O in the proton-accepting water is playing an important role. We also found that the water coordination number of the poton-accepting water is important in the proton-transfer processes.