Mechanisms of membrane toxicity of hydrocarbons.

One of Feynman's early applications of path integrals was to superfluid $^{4}\mathrm{He}$. He showed that the thermodynamic properties of Bose systems are exactly equivalent to those of a peculiar type of interacting classical "ring polymer." Using this mapping, one can generalize Monte Carlo simulation techniques commonly used for classical systems to simulate boson systems. In this review, the author introduces this picture of a boson superfluid and shows how superfluidity and Bose condensation manifest themselves. He shows the excellent agreement between simulations and experimental measurements on liquid and solid helium for such quantities as pair correlations, the superfluid density, the energy, and the momentum distribution. Major aspects of computational techniques developed for a boson superfluid are discussed: the construction of more accurate approximate density matrices to reduce the number of points on the path integral, sampling techniques to move through the space of exchanges and paths quickly, and the construction of estimators for various properties such as the energy, the momentum distribution, the superfluid density, and the exchange frequency in a quantum crystal. Finally the path-integral Monte Carlo method is compared to other quantum Monte Carlo methods.

Path integrals in the theory of condensed helium

The motivation for this review arises from the conviction that, as a result of the mass of experimental data and observations collected in recent years, the study of the physical properties of membranes is now entering a new stage of development. More and more, experiments are being designed to answer specific, detailed questions about membranes which will lead to a quantitative understanding of the way in which the physical properties of membranes are related to and influence their biological function.

https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S0033583500003735

Physical properties of the fluid lipid-bilayer component of cell membranes: a perspective.

When high-amplitude, short-duration pulsed electric fields are applied to cells and tissues, the permeability of the cell membranes and tissue is increased. This increase in permeability is currently explained by the temporary appearance of aqueous pores within the cell membrane, a phenomenon termed electroporation. During the past four decades, advances in fundamental and experimental electroporation research have allowed for the translation of electroporation-based technologies to the clinic. In this review, we describe the theory and current applications of electroporation in medicine and then discuss current challenges in electroporation research and barriers to a more extensive spread of these clinical applications.

/pdf/electroporation-based-technologies-for-medicine-principles-2dek202ypv.pdf

Electroporation-Based Technologies for Medicine: Principles, Applications, and Challenges

http://www.phys.ttu.edu/~huang24/Umbrella.pdf

A Microscopic Interaction Model of Maximum Solubility of Cholesterol in Lipid Bilayers

Passive ion permeability of lipid membranes modelled via lipid-domain interfacial area

The need for a mechanism for energy transfer in proteins, such as the Davydov model, is emphasized Here we concentrate on the finite-temperature properties of the Davydov model in three regimes: the quantum regime, in which both the excitation and the lattice are treated quantum mechanically; the mixed quantum-classical regime, in which the excitation is treated quantum mechanically but the lattice is considered classical; and the classical regime, in which both the excitation and the lattice are treated classically The equilibrium behavior can be determined exactly in the three regimes and thus provides a way to evaluate the validity of the latter two regimes as well as a reference point for the nonequilibrium studies Our results indicate that while at low temperature both the classical and the semiclassical regimes differ from the full quantum Davydov system, at biological temperatures the mixed quantum-classical regime leads to the same equilibrium behavior as the full quantum Davydov system The nonequilibrium properties in the mixed quantum-classical regime are studied with a different set of equations of motion for finite temperature, which are derived in great detail in Sec VI At biological temperatures, these equations predict that the Davydov soliton is unstable However, the states populated at biological temperatures preserve one of the features of the Davydov soliton, namely, the localization of the amide I excitation The nonequilibrium equations in Sec VI lead to a Brownian-like motion of the amide I excitation from the active site to other regions of the protein This stochastic mechanism for energy transfer may constitute a first step in many biological processes

Davydov model: The quantum, mixed quantum-classical, and full classical systems

Intrinsic molecules in lipid membranes change the lipid-domain interfacial area: cholesterol at domain interfaces.

Davydov has proposed a mechanism for energy transfer in proteins, according to which the energy liberated in an enzymatic reaction can be stored and transported in the form of a soliton. In recent years a debate has been going on concerning the thermal stability of the Davydov soliton. Here it is shown, first, that the two-quantum state is visibly more stable than the one-quantum state, and, second, that the usual Langevin dynamics, whereby the thermal lifetime of the Davydov soliton is estimated, must be viewed as underestimating, possibly very strongly, the soliton lifetime.

Two reasons why the Davydov soliton may be thermally stable after all.

We investigate the motion of a self-localized quasiparticle in a discrete lattice taking into account the interaction of the quasiparticle with the vibrations of the lattice. Using an original method to control the velocity of solitonlike excitations in a discrete system, the dependence of their velocity, momentum, and energy on the carrying wave vector is analyzed. The velocity of the solitonlike excitations is found to saturate at wave vectors below those predicted by continuum models. This is as found in experimental observations. Also, the properties of the Peierls-Nabarro relief, caused by the lattice discreteness, and pinning of a soliton by this barrier, are studied. The influence of the initial condition on the Peierls-Nabarro barrier and soliton motion is investigated. For low-width solitons, a critical value of the wave vector is needed to overcome the Peierls-Nabarro barrier.

L. Cruzeiro-Hansson

Papers

Passive ion permeability of lipid membranes modelled via lipid-domain interfacial area

Davydov model: The quantum, mixed quantum-classical, and full classical systems

Intrinsic molecules in lipid membranes change the lipid-domain interfacial area: cholesterol at domain interfaces.

Two reasons why the Davydov soliton may be thermally stable after all.

Soliton dynamics and Peierls-Nabarro barrier in a discrete molecular chain