Volume 119, Issue 23, 15 December 2003
Index of content:
Exploring the Opsin shift with ab initio methods: Geometry and counterion effects on the electronic spectrum of retinal119(2003); http://dx.doi.org/10.1063/1.1632898View Description Hide Description
To study the effect of the charged chromophore environment on the absorptionspectrum of rhodopsin, we have calculated excited state energies of chromophore models using multi-configurational second-order perturbation theory. Taking advantage of the recently solved crystal structures of rhodopsin we have considered different chromophore geometries and their interaction with the Glu113 counterion, water and Glu181 in different protonation states. We observe a strongly blueshifted state upon inclusion of Glu113/water to the wave function; the effect of the additional carboxyl group appears to be overbalanced by the complex counterion.
119(2003); http://dx.doi.org/10.1063/1.1632902View Description Hide Description
We examine the effective force between two nanometer scale solutes in water by Molecular Dynamics simulations. Macroscopic considerations predict a strong reduction of the hydrophobic attraction between solutes when the latter are charged. This is confirmed by the simulations which point to a surprising constancy of the effective force between oppositely charged solutes at contact, while like charged solutes lead to significantly different behavior between positive and negative pairs. The latter exhibit the phenomenon of “like-charge attraction” previously observed in some colloidal dispersions.
119(2003); http://dx.doi.org/10.1063/1.1633751View Description Hide Description
We report on a combined high resolution electron energy loss spectroscopy and x-rays photoelectron spectroscopy investigation of the interaction at room temperature of with thin and ultra-thin MgO films grown on Ag(100). We find a strongly enhanced dissociation probability in the monolayer and sub-monolayer regime, indicative of an active role of the Ag substrate in the dissociation process. The active sites are suggested to be oxygen atoms with low coordination at the border of monolayer MgO islands.