232 research outputs found
A length-dynamic Tonks gas theory of histone isotherms
We find exact solutions to a new one-dimensional (1D) interacting particle
theory and apply the results to the adsorption and wrapping of polymers (such
as DNA) around protein particles (such as histones). Each adsorbed protein is
represented by a Tonks gas particle. The length of each particle is a degree of
freedom that represents the degree of DNA wrapping around each histone.
Thermodynamic quantities are computed as functions of wrapping energy, adsorbed
histone density, and bulk histone concentration (or chemical potential); their
experimental signatures are also discussed. Histone density is found to undergo
a two-stage adsorption process as a function of chemical potential, while the
mean coverage by high affinity proteins exhibits a maximum as a function of the
chemical potential. However, {\it fluctuations} in the coverage are
concurrently maximal. Histone-histone correlation functions are also computed
and exhibit rich two length scale behavior.Comment: 5 pp, 3 fig
Decoration of MoSI Nanowires with Platinum Nanoparticles and Transformation into Molybdenum-nanowire Nased Networks
In this communication, we present solution-based coating procedure of MoSI nanowires (NW) with
platinum nanoparticles. The average particle diameter was found to be around 2.82 nm, showing a narrow
size distribution. This single-step in situ reduction method at room temperature in water solution can
easily be applied for large-scale applications. We also prepared two-dimensional networks of MoSI NW
bundles by deposition via spraying from a purified stable dispersion in acetonitrile onto NaCl crystals and
nonconductive silicon wafer with pre-assembled molybdenum electrodes. The formation of a conductive
molybdenum network was achieved by annealing in hydrogen due to coalescence of the templates MoSI
bundles during transformation. Stable water dispersion of molybdenum NW network was prepared by
simply dissolving the NaCl substrate with molybdenum network on the surface.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3516
Decoration of MoSI Nanowires with Platinum Nanoparticles and Transformation into Molybdenum-nanowire Nased Networks
In this communication, we present solution-based coating procedure of MoSI nanowires (NW) with
platinum nanoparticles. The average particle diameter was found to be around 2.82 nm, showing a narrow
size distribution. This single-step in situ reduction method at room temperature in water solution can
easily be applied for large-scale applications. We also prepared two-dimensional networks of MoSI NW
bundles by deposition via spraying from a purified stable dispersion in acetonitrile onto NaCl crystals and
nonconductive silicon wafer with pre-assembled molybdenum electrodes. The formation of a conductive
molybdenum network was achieved by annealing in hydrogen due to coalescence of the templates MoSI
bundles during transformation. Stable water dispersion of molybdenum NW network was prepared by
simply dissolving the NaCl substrate with molybdenum network on the surface.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3516
Relaxation kinetics of biological dimer adsorption models
We discuss the relaxation kinetics of a one-dimensional dimer adsorption
model as recently proposed for the binding of biological dimers like kinesin on
microtubules. The non-equilibrium dynamics shows several regimes: irreversible
adsorption on short time scales, an intermediate plateau followed by a
power-law regime and finally exponential relaxation towards equilibrium. In all
four regimes we give analytical solutions. The algebraic decay and the scaling
behaviour can be explained by mapping onto a simple reaction-diffusion model.
We show that there are several possibilities to define the autocorrelation
function and that they all asymptotically show exponential decay, however with
different time constants. Our findings remain valid if there is an attractive
interaction between bound dimers.Comment: REVTeX, 6 pages, 5 figures; to appear in Europhys. Letters; a Java
applet showing the simulation is accessible at
http://www.ph.tum.de/~avilfan/rela
Magnetic versus nonmagnetic doping effects on the magnetic ordering in the Haldane chain compound PbNi2V2O8
A study of an impurity driven phase-transition into a magnetically ordered
state in the spin-liquid Haldane chain compound PbNi2V2O8 is presented. Both,
macroscopic magnetization as well as 51V nuclear magnetic resonance (NMR)
measurements reveal that the spin nature of dopants has a crucial role in
determining the stability of the induced long-range magnetic order. In the case
of nonmagnetic (Mg2+) doping on Ni2+ spin sites (S=1) a metamagnetic transition
is observed in relatively low magnetic fields. On the other hand, the magnetic
order in magnetically (Co2+) doped compounds survives at much higher magnetic
fields and temperatures, which is attributed to a significant anisotropic
impurity-host magnetic interaction. The NMR measurements confirm the predicted
staggered nature of impurity-liberated spin degrees of freedom, which are
responsible for the magnetic ordering. In addition, differences in the
broadening of the NMR spectra and the increase of nuclear spin-lattice
relaxation in doped samples, indicate a diverse nature of electron spin
correlations in magnetically and nonmagnetically doped samples, which begin
developing at rather high temperatures with respect to the antiferromagnetic
phase transition.Comment: 10 pages, 7 figure
Generic flow profiles induced by a beating cilium
We describe a multipole expansion for the low Reynolds number fluid flows
generated by a localized source embedded in a plane with a no-slip boundary
condition. It contains 3 independent terms that fall quadratically with the
distance and 6 terms that fall with the third power. Within this framework we
discuss the flows induced by a beating cilium described in different ways: a
small particle circling on an elliptical trajectory, a thin rod and a general
ciliary beating pattern. We identify the flow modes present based on the
symmetry properties of the ciliary beat.Comment: 12 pages, 6 figures, to appear in EPJ
Hydrodynamic flow patterns and synchronization of beating cilia
We calculate the hydrodynamic flow field generated far from a cilium which is
attached to a surface and beats periodically. In the case of two beating cilia,
hydrodynamic interactions can lead to synchronization of the cilia, which are
nonlinear oscillators. We present a state diagram where synchronized states
occur as a function of distance of cilia and the relative orientation of their
beat. Synchronized states occur with different relative phases. In addition,
asynchronous solutions exist. Our work could be relevant for the synchronized
motion of cilia generating hydrodynamic flows on the surface of cells.Comment: 5 pages, 4 figures, v2: minor correction
Force-Velocity Relations of a Two-State Crossbridge Model for Molecular Motors
We discuss the force-velocity relations obtained in a two-state crossbridge
model for molecular motors. They can be calculated analytically in two limiting
cases: for a large number and for one pair of motors. The effect of the
strain-dependent detachment rate on the motor characteristics is studied. It
can lead to linear, myosin-like, kinesin-like and anomalous curves. In
particular, we specify the conditions under which oscillatory behavior may be
found.Comment: 5 pages, 4 figures, REVTeX; thoroughly revised version; also
available at http://www.physik.tu-muenchen.de/~frey
A Master equation approach to modeling an artificial protein motor
Linear bio-molecular motors move unidirectionally along a track by
coordinating several different processes, such as fuel (ATP) capture,
hydrolysis, conformational changes, binding and unbinding from a track, and
center-of-mass diffusion. A better understanding of the interdependencies
between these processes, which take place over a wide range of different time
scales, would help elucidate the general operational principles of molecular
motors. Artificial molecular motors present a unique opportunity for such a
study because motor structure and function are a priori known. Here we describe
use of a Master equation approach, integrated with input from Langevin and
molecular dynamics modeling, to stochastically model a molecular motor across
many time scales. We apply this approach to a specific concept for an
artificial protein motor, the Tumbleweed.Comment: Submitted to Chemical Physics; 9 pages, 7 figure
Molecular dynamics in tilted bilayer smectic phases: a proton nuclear magnetic resonance relaxometry study
A proton nuclear magnetic resonance (NMR) relaxation study of molecular dynamics in the liquid crystal 4-octylphenyl 2-chloro-4-(4-cyanobenzoyloxy)benzoate (DB8Cl) is presented. DB8Cl molecules possess a strong polar terminal group and form, in addition to the nematic phase, three different smectic phases: bilayer smectic A, bilayer smectic C, and anticliniclike smectic C phase. The proton spin-lattice relaxation times were measured in all mesophases over a broad frequency range of six decades by applying conventional and fast field-cycling NMR techniques. The parameters obtained in the analysis of the experimental data give quantitative information on molecular motions, particularly for the tilted smectic phases of DB8Cl. In contrast to former conjectures, we found that the low-frequency relaxation in the bilayer smectic C phases results from director fluctuations about the layer normal, which occur without distortion of the layers, and from layer undulations, similar to those in the smectic A phase. In the low-temperature bilayer smectic C phase, a considerable slowing-down of molecular translational diffusion is observed. It confirms indirectly the anticlinic character of this mesophase. Measurements of angular dependence of the relaxation times at 60 MHz support the conclusions obtained from the frequency dispersion data.info:eu-repo/semantics/publishedVersio
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