8 research outputs found
Quantum dynamics in strong fluctuating fields
A large number of multifaceted quantum transport processes in molecular
systems and physical nanosystems can be treated in terms of quantum relaxation
processes which couple to one or several fluctuating environments. A thermal
equilibrium environment can conveniently be modelled by a thermal bath of
harmonic oscillators. An archetype situation provides a two-state dissipative
quantum dynamics, commonly known under the label of a spin-boson dynamics. An
interesting and nontrivial physical situation emerges, however, when the
quantum dynamics evolves far away from thermal equilibrium. This occurs, for
example, when a charge transferring medium possesses nonequilibrium degrees of
freedom, or when a strong time-dependent control field is applied externally.
Accordingly, certain parameters of underlying quantum subsystem acquire
stochastic character. Herein, we review the general theoretical framework which
is based on the method of projector operators, yielding the quantum master
equations for systems that are exposed to strong external fields. This allows
one to investigate on a common basis the influence of nonequilibrium
fluctuations and periodic electrical fields on quantum transport processes.
Most importantly, such strong fluctuating fields induce a whole variety of
nonlinear and nonequilibrium phenomena. A characteristic feature of such
dynamics is the absence of thermal (quantum) detailed balance.Comment: review article, Advances in Physics (2005), in pres
Holographic interferometry as a method to study conformational changes in macromolecules
This paper concerns with our measurements of reaction center (RC) volume changes in the course of photoactivation using the method of holographic interferometry. As a principal value, we studied changes of a solution refraction index (Δn) influenced by the sample volume expansion due to temperature changes (ΔnT), light absorption (Δnabs) and changes in the volume of photoactive molecules (DnV). Using the scheme of temperature compensation we could reduce the task to the case ΔnT <<Δnabs, ΔnV. At RC concentrations close to 10¹⁵ cm-³, our experimental setup enabled to register the shift of an interference pattern up to 0.1 of the bandwidth. Our estimations for the case of a protein solution yields in relative changes in the molecular volume within 10-³...10-²
Semi-quantitative model of the gating of KcsA ion channel. 2. Dynamic self-organization model of the gating
The aim of this series of papers is to develop the semi-quantitative theory of the gating of KcsA channel. Methods. For this purpose available structural and electrophysiological data and the results of molecular dynamics simulations were used in the context of the concept of dynamical self-organization. In the second paper we describe the principles of dynamic self-organization and develop the theory of KcsA channel gating based on this concept. Conclusions. Present work is the first successful attempt of combining the structure and dynamics of real protein and the general concept of dynamic self-organizatio