Biomedical subjects

Nikos Theodorakopoulos

Publications and source records attributed to Nikos Theodorakopoulos.

3 recordsLinked to original sources

PubMed2004

Nonlinear structures and thermodynamic instabilities in a one-dimensional lattice system.

The equilibrium states of the discrete Peyrard-Bishop Hamiltonian with one end fixed are computed exactly from the two-dimensional nonlinear Morse map. These exact nonlinear structures are interpreted as domain walls, interpolating between bound and unbound segments of the chain. Their free energy is calculated to leading order beyond the Gaussian approximation. Thermodynamic instabilities (e.g., DNA unzipping and/or thermal denaturation) can be understood in terms of domain wall formation.

Computer Simulation↗

PubMed2003

Thermal denaturation of a helicoidal DNA model.

We study the static and dynamical properties of DNA in the vicinity of its melting transition, i.e., the separation of the two strands upon heating. The investigation is based on a simple mechanical model which includes the helicoidal geometry of the molecule and allows an exact numerical evaluation of its thermodynamical properties. Dynamical simulations of long-enough molecular segments allow the study of the structure factors and of the properties of the denaturated regions. Simulations of finite chains display the hallmarks of a first order transition for sufficiently long-ranged stacking forces although a study of the model's "universality class" strongly suggests the presence of an "underlying" continuous transition.

Biophysical Phenomena↗

PubMed2003

Thermodynamic instabilities in one-dimensional particle lattices: a finite-size scaling approach.

One-dimensional thermodynamic instabilities are phase transitions, not prohibited by Landau's argument because the energy of the domain wall which separates the two phases is infinite. Whether they actually occur in a given system of particles must be demonstrated on a case-by-case basis by examining the properties of the corresponding singular transfer integral (TI) equation. The present work deals with the generic Peyrard-Bishop model of DNA denaturation. In the absence of exact statements about the spectrum of the singular TI equation, I use Gauss-Hermite quadratures to achieve a single-parameter-controlled approach to rounding effects; this allows me to employ finite-size scaling concepts in order to demonstrate that a phase transition occurs and to derive the critical exponents.

Journal Article↗