Entity

Time filter

Source Type


Xiao-Feng P.,University of Electronic Science and Technology of China | Xiao-Feng P.,CAS Shenyang International Center for Materials Physics
Progress in Biophysics and Molecular Biology | Year: 2012

A new theory of bio-energy transport along protein molecules in living systems, where the energy is released by hydrolysis of adenosine triphosphate (ATP), is proposed based on some physical and biological reasons. In the new theory, the Davydov's Hamiltonian and wave function of the systems are simultaneously modified and extended. A new interaction has been added into Davydov's Hamiltonian. The wave function of the excitation state of single particles for the excitons in the Davydov model is replaced by a new wave function of two-quanta quasicoherent state. In such a case, the bio-energy is transported by the new soliton, which differs from the Davydov's soliton. The soliton is formed through self- trapping of two excitons interacting amino acid residues. The exciton is generated by vibrations of amide-I (CO stretching) arising from the energy of hydrolysis of ATP. The properties of the new soliton are extensively studied by analytical method and its lifetime is calculated using the nonlinear quantum perturbation theory and a wide ranges of parameter values relevant to protein molecules. The lifetime of the new soliton at the biological temperature 300K is enough large and belongs to the order of 10-10s, or τ/τ0≥700, in which the soliton can transports over several hundreds amino acid residues. These studied results show clearly that the new soliton is thermally stable and has so larger lifetime that it can play an important role in biological processes. Thus the new model is a candidate of the bio-energy transport mechanism in protein molecules. In the meanwhile, the influences of structure nonuniformity in protein molecules and temperature of the systems on the states and properties of the soliton transport of bio-energy are numerically simulated and studied by the fourth-order Runge-Kutta method. The structure nonuniformity arises from the disorder distributions of masses of amino acid residues, side groups and impurities, which results also in the fluctuations of the spring constant of protein molecules, dipole-dipole interaction between the neighboring amides, exciton-phonon (vibration of amino acids)interaction, chain-chain interaction among the three channels and ground state energy of the systems. We investigated the behaviors and states of the new solitons in a single protein molecular chain and α-Helix protein molecules with three channels under influences of the structure nonuniformity. We prove first that the bio-energy is transported by a soliton, which can move without dispersion, retaining its shape, velocity and energy in a uniform and periodic protein molecule. When the structure nonuniformity exists, although the fluctuations of the spring constant, dipole-dipole interaction constant, exciton-phonon coupling constant and ground state energy and the nonuniformity distributions of masses of amino acid residues can change the states and properties of motion of new soliton, they are still quite stable and very robust against these structure nonuniformities, i.e., even there are a larger structure nonuniformity in the protein molecules, the new solitons cannot be still dispersed. If the effects of thermal perturbation of medium on the soliton in nonuniform proteins is considered again, the new soliton can transport also over a larger spacing of 400 amino acids and has a longer time period of 300ps, it is still thermally stable up to 320K under the influence of the above structure nonuniformities. However, the new soliton disperses in the case of a higher temperature of 325K and in more large structure nonuniformity. Thus, we determine that the new soliton's lifetime and critical temperature are 300ps and 320K, respectively. These results are also consistent with analytical data obtained via quantum perturbed theory. For α-Helix protein molecules with three channels, the results obtained show that the structure nonuniformity and quantum fluctuation can change the states and features of the new solitons, for example, the amplitudes, energies and velocities of the new soliton are decreased, but the solitons have been not destroyed, they can still transport steadily along the molecular chains retaining energy and momentum. When the quantum fluctuations are larger, such as, structure disorders and quantum fluctuations of 0.67<αK<2, ΔW=±8%W-, ΔJ=±1%J-, Δ(χ1+χ2)=±3%(χ-1+χ-2) and ΔL=±1%L- and Δe{open}0=e{open}|βn|, e{open}=0.1meV, |βn|<0.5, the new soliton is still stable. Therefore, the new solitons are quite robust against these nonuniform effects. However, they will be dispersed or disrupted in cases of very large structure nonuniformity. When the influence of temperature on solitons is considered, we find that the new solitons can transport steadily over 333 amino acid residues in the case of a long time period of 120ps, in which the soliton can retain its shape and energy to travel forward along protein molecules after their mutual collision at the biological temperature of 300K. However, the soliton disperses in cases of higher temperatures 325K under action of a larger structure disorder. Thus, its critical temperature is about 320K. When the effects of structure nonuniformity andtemperature are considered simultaneously, then the new soliton has still high thermal stability andcan transport also along the protein molecular chains retaining its amplitude, energy and velocity, they will disperses in the larger fluctuations, for example, 0.67M-


Pang X.-F.,University of Electronic Science and Technology of China | Pang X.-F.,CAS Shenyang International Center for Materials Physics
Physics of Life Reviews | Year: 2011

The bio-energy transport is a basic problem in life science and related to many biological processes. Therefore to establish the mechanism of bio-energy transport and its theory have an important significance. Based on different properties of structure of α-helical protein molecules some theories of bio-energy transport along the molecular chains have been proposed and established, where the energy is released by hydrolysis of adenosine triphosphate (ATP). A brief survey of past researches on different models and theories of bio-energy, including Davydov's, Takeno's, Yomosa's, Brown et al.'s, Schweitzer's, Cruzeiro-Hansson's, Forner's and Pang's models were first stated in this paper. Subsequently we studied and reviewed mainly and systematically the properties, thermal stability and lifetimes of the carriers (solitons) transporting the bio-energy at physiological temperature 300 K in Pang's and Davydov's theories. From these investigations we know that the carrier (soliton) of bio-energy transport in the α-helical protein molecules in Pang's model has a higher binding energy, higher thermal stability and larger lifetime at 300 K relative to those of Davydov's model, in which the lifetime of the new soliton at 300 K is enough large and belongs to the order of 10-10 s or τ/τ0≥700. Thus we can conclude that the soliton in Pang's model is exactly the carrier of the bio-energy transport, Pang's theory is appropriate to α-helical protein molecules. © 2011 Elsevier B.V.


Zhu X.,Harbin Institute of Technology | Lu Z.,Harbin Institute of Technology | Wei B.,Harbin Institute of Technology | Huang X.,Harbin Institute of Technology | And 3 more authors.
Journal of Power Sources | Year: 2011

In this study, a simple and cost-effective dry-pressing method has been used to fabricate a symmetrical solid oxide fuel cell (SOFC) where the dense yttria-stabilized zirconia (YSZ) electrolyte film is sandwiched between two symmetrical porous YSZ layers in which La0.75Sr0.25Cr 0.5Mn0.5O3-δ (LSCM) based anode and cathode are incorporated using wet impregnation techniques. The maximum power densities (Pmax) of a single cell with 32 wt.% LSCM impregnated YSZ anode and cathode reach 333 and 265 mW cm-2 at 900 °C in dry H2 and CH4, respectively. The cell performance is further improved with additional impregnation of a small amount of Sm-doped CeO 2 (SDC) or Ni. When 6 wt.% Ni as catalyst is added to both the anode and cathode, Pmax values of 559 and 547 mW cm-2 can be achieved, which are better than with SDC. The effect of Ni on the cathode performance is also investigated by impedance spectra analysis. © 2010 Elsevier B.V.


Shi X.,Liaoning University of Petroleum and Chemical Technology | Wei G.,Northeastern University China | Wei G.,CAS Shenyang International Center for Materials Physics
Physica Scripta | Year: 2014

It has been well established that the spin-1 Blume-Capel (BC) model in a time-dependent oscillating external field and a crystal field interaction exhibits a rich variety of topology in nonequilibrium dynamic phase diagrams. Some interesting dynamic behaviors, quite different from the standard Ising model, have been observed. However, there are some disagreements among these theoretical studies. Here we use the effective-field theory (EFT) and the Monte Carlo method (MC) to show that the dissimilarity among the mean-field theory and EFT results is due to the neglect of thermal fluctuations. The effects of thermal fluctuations on the dynamic phase boundary and the dynamic tricritical point are investigated. The MC method is then carried out to confirm if the reentrant phenomenon obtained by the EFT is correct or not. The dynamic phase diagram of the kinetic BC model given by the MC method is also plotted. © 2014 The Royal Swedish Academy of Sciences.


Shi X.,Liaoning University of Petroleum and Chemical Technology | Shi X.,Northeastern University China | Wei G.,Northeastern University China | Wei G.,CAS Shenyang International Center for Materials Physics
Physica A: Statistical Mechanics and its Applications | Year: 2012

The effective-field theory (EFT) is used to study the dynamical response of the kinetic spin-1 BlumeCapel model in the presence of a sinusoidal oscillating magnetic field. The effective-field dynamic equations are given for the honeycomb lattice (Z=3). The dynamic order parameter, the dynamic quadruple moment, the hysteresis loop area and the dynamic correlation are calculated. We have found that the behavior of the system strongly depends on the crystal interaction D. The dynamic phase boundaries separating the paramagnetic phase and the ferromagnetic phase are obtained. There is the region of the phase space where both a paramagnetic phase and a ferromagnetic phase coexist. The dynamic transition from one region to the other can be of first or second order depending on the frequency of the magnetic field. There is no dynamic tricritical point on the dynamic phase transition line. The results are also compared with those obtained from the mean-field theory (MFT). © 2011 Elsevier B.V. All rights reserved.

Discover hidden collaborations