Adsorption of His-tagged peptide to Ni, Cu and Au (100) surfaces: Molecular dynamics simulation

Molecular dynamics (MD) simulations are performed to study the interaction of His-tagged peptide with three different metal surfaces in explicit water. The equilibrium properties are analyzed by using pair correlation functions (PCF) to give an insight into the behavior of the peptide adsorption to metal surfaces in water solvent. The intermolecular interactions between peptide residues and the metal surfaces are evaluated. By pulling the peptide away from the peptide in the presence of solvent water, peeling forces are obtained and reveal the binding strength of peptide adsorption on nickel, copper and gold. From the analysis of the dynamics properties of the peptide interaction with the metal surfaces, it is shown that the affinity of peptide to Ni surface is the strongest, while on Cu and An the affinity is a little weaker. In MD simulations including metals, the His-tagged region interacts with the substrate to an extent greater than the other regions. The work presented here reveals various interactions between His-tagged peptide and Ni/Cu/Au surfaces. The interesting affinities and dynamical properties of the peptide are also derived. The results give predictions for the structure of His-tagged peptide adsorbing on three different metal surfaces and show the different affinities between them, which assist the understanding of how peptides behave on metal surfaces and of how designers select amino sequences in molecule devices design. (c) 2007 Elsevier Ltd. All rights reserved.

Computer simulation on the collision-sticking dynamics of two colloidal particles in an optical trap

Collisions of a particle pair induced by optical tweezers have been employed to study colloidal stability. In order to deepen insights regarding the collision-sticking dynamics of a particle pair in the optical trap that were observed in experimental approaches at the particle level, the authors carry out a Brownian dynamics simulation. In the simulation, various contributing factors, including the Derjaguin-Landau-Verwey-Overbeek interaction of particles, hydrodynamic interactions, optical trapping forces on the two particles, and the Brownian motion, were all taken into account. The simulation reproduces the tendencies of the accumulated sticking probability during the trapping duration for the trapped particle pair described in our previous study and provides an explanation for why the two entangled particles in the trap experience two different statuses. (c) 2007 American Institute of Physics.

Fiscal imbalances, inflation and sovereign default dynamics

Resumen: La cuestión central que este artículo busca responder es como la política monetaria puede afectar el comportamiento de equilibrio de primas por riesgo soberano y cesación de pagos. El artículo se basa en el modelo de “una-tasa-interés”. La deuda pública se hace riesgosa a causa de una política fiscal activa, como en Uribe (2006), reflejando la habilidad limitada de la autoridad fiscal para controlar el superávit primario. El problema de insolvencia es debido a una oleada de mala suerte (shocks negativos que afectan el superávit primario). Pero en contraste a los resultados de Uribe, a medida que aumenta el costo de la deuda soberana (que resulta de un excedente primario débil), la cesación de pagos se anticipa y es reflejada por una creciente prima de riesgo en el país y una probabilidad de cesación de pagos. La cesación de pagos se define como un incumplimiento de un acuerdo contractual y por ende la decisión es tomada por la autoridad fiscal. Mientras tanto, objetivos conflictivos entre la autoridad monetaria y fiscal juegan un rol importante en llevar a la autoridad fiscal a la cesación de pagos sobre sus pasivos. La característica de la política del gobierno necesaria para restaurar el equilibrio después de la cesación de pagos también es analizada.