Search results for "Physics::Biological Physics"
showing 10 items of 78 documents
Silicatein conjugation inside nanoconfined geometries through immobilized NTA–Ni(ii) chelates
2013
The chemical modification and bioconjugation processes inside confined geometries by His-tagged silicatein promote sensitive changes in the polarity and surface charge density that mainly contribute to the ionic current rectification properties of the single conical nanopores.
Sugar-induced stabilization of the monoolein Pn3m bicontinuous cubic phase during dehydration
2001
To explore the molecular mechanism of the protective function of sugars on cubic lipidic systems, the mesomorphic properties of the monoolein-water system, dehydrated in the presence of a series of sugars, have been studied by osmotic stress experiments. Two bicontinuous inverse cubic structures $(Pn3m$ and $\mathrm{Ia}3d)$ and a lamellar ${L}_{\ensuremath{\alpha}}$ phase form under dehydration in pure water. In sugar solutions, the $\mathrm{Pn}3m$ phase shows an extraordinary stability: as a function of sugar concentration, the lattice parameter decreases to very low values, but no phase transitions occur. Instead, the $\mathrm{Pn}3m$ to $\mathrm{Ia}3d$ phase transition is obtained by equi…
Electronic Excitation Energy Transfer between Two Single Molecules Embedded in a Polymer Host
2007
Unidirectional electronic excitation energy transfer from a photoexcited donor chromophore to a ground state acceptor chromophore - both linked by a rigid bridge - has been investigated by low temperature high-resolution single molecule spectroscopy. Our approach allows for accurately accessing static disorder in the donor and acceptor electronic transitions and to calculate the spectral overlap for each couple. By plotting the experimentally determined transfer rates against the spectral overlap, we can distinguish and quantify Förster- and non-Förster-type contributions to the energy transfer.
Red Spectral Forms of Chlorophylls in Green Plant PSI - A Site-Selective and High-Pressure Spectroscopy Study
2003
One of the special spectroscopic characteristics of photosystem I (PSI) complexes is that they possess absorption and emission bands at lower energy than those of the reaction center. In this paper, the red pigment pools of PSI-200, PSI-core, and LHCI complex from Arabidopsis thaliana have been characterized at low temperatures by means of spectrally selective (hole-burning and fluorescence line-narrowing) and high-pressure spectroscopic techniques. It was shown that the green plant PSI-200 complex has at least three red pigment pools, from which two are located in the PSI-core and one, in the peripheral light-harvesting complex I (LHCI). All of the red pigment pools are characterized by st…
STATISTICAL MECHANICS OF NONCLASSIC SOLITONIC STRUCTURES-BEARING DNA SYSTEM
2011
We theoretically investigate the thermodynamic properties of modified oscillator chain proposed by Peyrard and Bishop. This model obtained by adding the quartic anharmonicity term to the coupling in the Peyrard–Bishop model is useful to model the coexistence of various phases of the molecule during the denaturation phenomenon. Within the model, the negative anharmonicity is responsible for the sharpness of calculated melting curves. We perform the transfer integral calculations to demonstrate that the model leads to a good agreement with known experimental results for DNA.
EnCurv: Simple Technique of Maintaining Global Membrane Curvature in Molecular Dynamics Simulations.
2021
The EnCurv method for maintaining membrane curvature in molecular dynamics simulations is introduced. The method allows maintaining any desired curvature in a sector of lipid membrane bent in a single plane without adding any unphysical interactions into the system and without restrictions on lateral and transversal lipid diffusion and distribution. The current implementation is limited to the membranes curved in a single plane but generalization to arbitrary curvature and membrane topology is possible. The method is simple, easy to implement, and scales linearly with the system size. EnCurv is agnostic to the force field, simulation parameters, and membrane composition. The proof of princi…
Magnetic dipole with a flexible tail as a self-propelling microdevice.
2012
By numerical simulations, it is illustrated that a magnetic dipole with a flexible tail behaves as a swimmer in AC magnetic fields. The behavior of the swimmer on long time scales is analyzed and it is shown that due to the flexibility of the tail two kinds of torques arise, the first is responsible for the orientation of the swimmer perpendicularly to the AC field and the second drags the filament in the direction of the rotating field. Due to this, circular trajectories of the swimmer are possible; however, these are unstable. The self-propulsion velocity of this swimmer is higher than the velocities of other magnetic microdevices for comparable values of the magnetoelastic number.
Controlling stability and transport of magnetic microswimmers by an external field
2019
We investigate the hydrodynamic stability and transport of magnetic microswimmers in an external field using a kinetic theory framework. Combining linear stability analysis and nonlinear 3D continuum simulations, we show that for sufficiently large activity and magnetic field strengths, a homogeneous polar steady state is unstable for both puller and pusher swimmers. This instability is caused by the amplification of anisotropic hydrodynamic interactions due to the external alignment and leads to a partial depolarization and a reduction of the average transport speed of the swimmers in the field direction. Notably, at higher field strengths a reentrant hydrodynamic stability emerges where t…
Ballistic phonon transport in dielectric membranes
2006
We have calculated the ballistic phononic heat transport in dielectric membranes as a function of radiator temperature and membrane thickness. The phonon modes of such membranes are known as Lamb-modes from elasticity theory. The striking result is that, for a fixed temperature, the radiated power first decreases with decreasing membrane thickness, but then develops a minimum when the transition to two dimensionality is reached. Further decrease of the membrane thickness in the 2D limit leads to increasing radiated power.
Excitation Transport in Helical Proteins
1994
Recent results for excitation dynamics in and IR-absorption spectrum of helical polypeptides are briefly reviewed.