Ionizing radiation is responsible for production of double strand breaks (DSB) in a DNA structure. In contrast to sparsely ionizing radiation, densely ionizing radiation produces DSBs that are randomly distributed along the DNA molecule and can form clusters of various size. The paper discusses minimalistic models that describe observable pattern of distribution of fragment lengths in DNA segments irradiated with heavy ions and applies the formalism to interpret the recent experimental data collected by use of the atomic force microscope (AFM).
The non-selective voltage activated cation channel from the human red cells, which is activated at depolarizing potentials, has been shown to exhibit counter-clockwise gating hysteresis. We have analyzed the phenomenon with the simplest possible phenomenological models by assuming 2×2 discrete states, i.e. two normal open/closed states with two different states of "gate tension." Rates of transitions between the two branches of the hysteresis curve have been modeled with single-barrier kinetics by introducing a real-valued "reaction coordinate" parameterizing the protein's conformational change. When described in terms of the effective potential with cyclic variations of the control parameter (an activating voltage), this model exhibits typical "resonant effects": synchronization, resonant activation and stochastic resonance. Occurrence of the phenomena is investigated by running the stochastic dynamics of the model and analyzing statistical properties of gating trajectories.
The constructive role of non-Gaussian random fluctuations is studied in the context of the passage over the dichotomously switching potential barrier. Our attention focuses on the interplay of the effects of independent sources of fluctuations: an additive stable noise representing non-equilibrium external random force acting on the system and a fluctuating barrier. In particular, the influence of the structure of stable noises on the mean escape time and on the phenomenon of resonant activation (RA) is investigated. By use of the numerical Monte Carlo method it is documented that the suitable choice of the barrier switching rate and random external fields may produce resonant phenomenon leading to the enhancement of the kinetics and the shortest, most efficient reaction time.
Conference Committee Involvement (1)
Noise and Fluctuation in Biological, Biophysical, and Biomedical Systems