405 research outputs found
First-Passage Time Distribution and Non-Markovian Diffusion Dynamics of Protein Folding
We study the kinetics of protein folding via statistical energy landscape
theory. We concentrate on the local-connectivity case, where the
configurational changes can only occur among neighboring states, with the
folding progress described in terms of an order parameter given by the fraction
of native conformations. The non-Markovian diffusion dynamics is analyzed in
detail and an expression for the mean first-passage time (MFPT) from non-native
unfolded states to native folded state is obtained. It was found that the MFPT
has a V-shaped dependence on the temperature. We also find that the MFPT is
shortened as one increases the gap between the energy of the native and average
non-native folded states relative to the fluctuations of the energy landscape.
The second- and higher-order moments are studied to infer the first-passage
time (FPT) distribution. At high temperature, the distribution becomes close to
a Poisson distribution, while at low temperatures the distribution becomes a
L\'evy-like distribution with power-law tails, indicating a non-self-averaging
intermittent behavior of folding dynamics. We note the likely relevance of this
result to single-molecule dynamics experiments, where a power law (L\'evy)
distribution of the relaxation time of the underlined protein energy landscape
is observed.Comment: 26 pages, 10 figure
Diffusion Dynamics, Moments, and Distribution of First Passage Time on the Protein-Folding Energy Landscape, with Applications to Single Molecules
We study the dynamics of protein folding via statistical energy-landscape
theory. In particular, we concentrate on the local-connectivity case with the
folding progress described by the fraction of native conformations. We obtain
information for the first passage-time (FPT) distribution and its moments. The
results show a dynamic transition temperature below which the FPT distribution
develops a power-law tail, a signature of the intermittency phenomena of the
folding dynamics. We also discuss the possible application of the results to
single-molecule dynamics experiments
Studies on electrostatic interactions of colloidal particles under two-dimensional confinement
We study the effective electrostatic interactions between a pair of charged
colloidal particles without salt ions while the system is confined in two
dimensions. In particular we use a simplified model to elucidate the effects of
rotational fluctuations in counterion distribution. The results exhibit
effective colloidal attractions under appropriate conditions. Meanwhile,
long-range repulsions persist over most of our studied cases. The repulsive
forces arise from the fact that in two dimensions the charged colloids cannot
be perfectly screened by counterions, as the residual quadrupole moments
contribute to the repulsions at longer range. And by applying multiple
expansions we find that the attractive forces observed at short range are
mainly contributed from electrostatic interactions among higher-order electric
moments. We argue that the scenario for attractive interactions discussed in
this work is applicable to systems of charged nanoparticles or colloidal
solutions with macroions.Comment: 23 pages, 11 figures, 1 tabl
SCOZA for Monolayer Films
We show the way in which the self-consistent Ornstein-Zernike approach
(SCOZA) to obtaining structure factors and thermodynamics for Hamiltonian
models can best be applied to two-dimensional systems such as thin films. We
use the nearest-neighbor lattice gas on a square lattice as an illustrative
example.Comment: 10 pages, 5 figure
Effects of overexpression of IL-10, IL-12, TGF-β and IL-4 on allergen induced change in bronchial responsiveness
BACKGROUND: An increasing prevalence of allergic diseases, such as atopic dermatitis, allergic rhinitis and bronchial asthma, has been noted worldwide. Allergic asthma strongly correlates with airway inflammation caused by the unregulated production of cytokines secreted by allergen-specific type-2 T helper (Th2) cells. This study aims to explore the therapeutic effect of the airway gene transfer of IL-12, IL-10 and TGF-β on airway inflammation in a mouse model of allergic asthma. METHODS: BALB/c mice were sensitized to ovalbumin (OVA) by intraperitoneal injections with OVA and challenged by nebulized OVA. Different cytokine gene plasmids or non-coding vector plasmids were instilled daily into the trachea up to one day before the inhalatory OVA challenge phase. RESULTS: Intratracheal administration of IL-10, IL-12 or TGF-β can efficiently inhibit antigen-induced airway hyper-responsiveness and is able to largely significantly lower the number of eosinophils and neutrophils in bronchoalveolar lavage fluid of ovalbumin (OVA) sensitized and challenged mice during the effector phase. Furthermore, the effect of IL-10 plasmids is more remarkable than any other cytokine gene plasmid. On the other hand, local administration of IL-4 gene plasmids before antigen challenge can induce severe airway hyper-responsiveness (AHR) and airway eosinophilia. CONCLUSION: Our data demonstrated that anti- inflammatory cytokines, particularly IL-10, have the therapeutic potential for the alleviation of airway inflammation in murine model of asthma
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