An efficient algorithm for calculating the electronic matrix element T» for electron-transfer reactions between a donor D and acceptor A in biological systems is presented. The tight-binding Hamiltonian and the Green s-function formalism are used to obtain T» via the renormalizedperturbation expansion. This procedure permits taking into account the detailed structure of the array provided by the specific protein that assists the electron transfer. As an application, results are presented for the calculation of some of these matrix elements in metal-labeled myoglobin, and comparison with experimental data is made. By analyzing the self-energies at each site of the array, these results can be understood as a small-denominator effect.

We study the thermodynamics of a two-dimensional polydisperse ideal gas model of different species of aggregates. We show that if these aggregates are distinguished not only by their sizes but also by their ability to display shape fluctuations, the system presents dominance of one or other species, depending on the temperature region. This result, which emerges solely from the statistics of the model in total absence of interaggregate interactions, describes well the observed temperature dependence of light scattering in dispersions of dimyristoyl phosphatidylglycerol, a negatively charged lipid.

We consider the dynamics of cargo driven by a collection of interacting molecular motors in the context of an asymmetric simple exclusion processes (ASEP). The model is formulated to account for i) excluded volume interactions, ii) the observed asymmetry of the stochastic movement of individual motors and iii) interactions between motors and cargo. Items (i) and(ii) form the basis of ASEP models and have already been considered in the literature to study the behavior of motor density profile [4]. Item (iii) is new. It is introduced here as an attempt to describe explicitly the dependence of cargo movement on the dynamics of motors. The steady-state solutions of the model indicate that the system undergoes a phase transition of condensation type as the motor density varies. We study the consequences of this transition to the properties of cargo velocity.

Pores in bilayer membranes of amphiphilic molecules: Coarse-grained molecular dynamics simulations compared with simple mesoscopic models