共查询到10条相似文献,搜索用时 8 毫秒
1.
A recently introduced DNA nanodevice can be used to
selectively bind or release the protein thrombin triggered by DNA
effector strands. The release process is not well described by
simple first or second order reaction kinetics. Here, fluorescence
resonance energy transfer and fluorescence correlation
spectroscopy experiments are used to explore the kinetics of the
release process in detail. To this end the influence of
concentration variations and also of temperature is determined.
The relevant kinetic parameters are extracted from these
experiments and the kinetic behavior of the system is simulated
numerically using a set of rate equations. The hydrodynamic radii
of the aptamer device alone and bound to thrombin are determined
as well as the dissociation constant for the aptamer
device-thrombin complex. The results from the experiments and a
numerical simulation support the view that the DNA effector strand
first binds to the aptamer device followed by the displacement of
the protein. 相似文献
2.
B. Coluzzi E. Yeramian 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,56(4):349-365
We study numerically the effect of sequence heterogeneity on the
thermodynamic properties of a Poland-Scheraga model for DNA denaturation
taking into account self-avoidance, i.e. with exponent cp = 2.15
for the loop length probability distribution. In complement to previous
on-lattice Monte Carlo like studies, we consider here off-lattice numerical
calculations for large sequence lengths, relying on efficient algorithmic
methods. We investigate finite size effects with the definition of an
appropriate intrinsic length scale x, depending on the parameters of
the model. Based on the occurrence of large enough rare regions, for a
given sequence length N, this study provides a qualitative picture for the
finite size behavior, suggesting that the effect of disorder could be sensed
only with sequence lengths diverging exponentially with x. We further look
in detail at average quantities for the particular case x = 1.3, ensuring
through this parameter choice the correspondence between the off-lattice and
the on-lattice studies. Taken together, the various results can be cast in a
coherent picture with a crossover between a nearly pure system like
behavior for small sizes
, as observed in the on-lattice
simulations, and the apparent asymptotic behavior indicative of disorder
relevance, with an (average) correlation length exponent
νr ≥2/d (=2). 相似文献
3.
We present a theoretical model for the evolution of mixture concentrations in a micro-pervaporation device, similar to those
recently presented experimentally. The described device makes use of the pervaporation of water through a thin PDMS membrane
to build up a solute concentration profile inside a long microfluidic channel. We simplify the evolution of this profile in
binary mixtures to a one-dimensional model which comprises two concentration-dependent coefficients. The model then provides
a link between directly accessible experimental observations, such as the widths of dense phases or their growth velocity,
and the underlying chemical potentials and phenomenological coefficients. It shall thus be useful for quantifying the thermodynamic
and dynamic properties of dilute and dense binary mixtures. 相似文献
4.
J. de Vries R. Hoekstra R. Morgenstern T. Schlathölter 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2003,24(1-3):161-164
Ionization and fragmentation of the DNA base thymine upon
interaction with keV Cq+ ions
(q
= 1 -
6) has been studied. By means of time-of-flight
spectrometry of two or more thymine fragments in coincidence
with an ejected electron we could investigate particular
dissociation channels by means of their associated
kinetic-energy-release. The fragmentation dynamics are strongly
influenced by the Cq+ charge state:
for low q values mainly
fragmentation due to direct collisions is observed. With
increasing q, electron capture
becomes more important. For larger q we could identify several Coulomb
explosion channels, leading to very energetic fragments. 相似文献
5.
G. Adjanor M. Athènes F. Calvo 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,53(1):47-60
We introduce a path-sampling scheme that allows equilibrium
state-ensemble averages to be computed by means of a biased
distribution of non-equilibrium paths. This non-equilibrium method is
applied to the case of the 38-atom Lennard-Jones atomic cluster, which
has a double-funnel energy landscape. We calculate the free energy
profile along the Q4 bond orientational order parameter. At high or
moderate temperature the results obtained using the non-equilibrium
approach are consistent with those obtained using conventional
equilibrium methods, including parallel tempering and Wang-Landau
Monte Carlo simulations. At lower temperatures, the non-equilibrium
approach becomes more efficient in exploring the relevant inherent
structures. In particular, the free energy agrees with the
predictions of the harmonic superposition approximation. 相似文献
6.
We consider an ideal chain whose ends are fixed without fluctuation at different points, possibly by optical tweezers. We
derive a two-point probability distribution of a corresponding random walk and explicitly calculate the scattering function.
We find that the contour plot of the resulting function shows a kind of normal butterfly pattern, contaminated by wavy texture.
These results are compared with some representative previous models. 相似文献
7.
Gene delivery process in a single animal cell after femtosecond laser microinjection 总被引:1,自引:0,他引:1
Yoichiroh Hosokawa Seriya Iguchi Yuji Hiraki Chisa Shukunami 《Applied Surface Science》2009,255(24):9880-9884
Microinjection of extracellular molecules into a single animal cell was performed by an amplified femtosecond laser irradiation. When a single-shot laser pulse was focused on the plasma membrane of a single fibroblast from the mouse cell line NIH3T3 with a high-numerical aperture objective lens, a transient hole with a diameter of 1 μm was formed. The delivery process of extracellular molecules immediately after the hole formation was monitored by a fluorescence staining with fluoresceinisothiocyanate-dextran (FITC-dextran). Then the gene expression was confirmed using a DNA plasmid of an enhanced green fluorescent protein (EGFP). The gene expression was observed when the laser pulse was focused first on the cellular membrane and then on the nuclear membrane, while the gene was not expressed when the laser was focused only on the cellular membrane. On the basis of these results, the efficiency of gene delivery by the femtosecond laser microinjection and the subsequent gene expression were clarified. 相似文献
8.
W. Chin M. Mons I. Dimicoli F. Piuzzi B. Tardivel M. Elhanine 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,20(3):347-355
By using depopulation laser techniques, like IR-UV population labeling coupled to mass-selected R2PI detection, we confirm
that four tautomers are responsible for the near UV spectroscopy (310-280 nm) of guanine: two enol and two keto forms, each
pair having a 7NH and a 9NH form. Besides the UV spectroscopy of each tautomer, additional information on the excited state
nature and dynamics is obtained from fluorescence studies. In particular, the quenching of fluorescence beyond 285 nm, the
existence of a background absorption, as well as the existence of a strongly red-shifted component in the fluorescence emission
provides evidence for a strong electronic mixing in the excited state together with an efficient non-radiative process. The
details of these features are found to be tautomer-dependent. Comparison of the present results with literature data on other
purine molecules, like adenine or 9-substituted guanines, enables us to propose a new insight on the spectroscopy and dynamics
of the purine molecules. First, a large variability of the tautomer distribution in the gas phase is found within the purine
family, in particular a molecular change, as simple as a 9-methylation on guanine, can reduce the tautomer distribution to
a single species (enol form). Since the absorption spectrum is tautomer-dependent as well as substituent-dependent, it turns
out that the tautomer population is one of the major parameters that control the overall shape of the UV spectrum. Second,
the excited state model, often evoked in the literature, which involves electronic coupling between excited states of different
natures, namely ππ* and nπ* states, might account for the present fluorescence measurements on guanine, providing an extensive excited state electronic
mixing is assumed for these systems.
Received 24 June 2002 Published online 13 September 2002 相似文献
9.
N.V. Brilliantov V.V. Malinin R.R. Netz 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,18(3):339-345
A continuous liquid flow in a vacuum (a liquid beam) of an aqueous solution of adenine salt containing hydrochloric acid or
sodium hydroxide was irradiated with an intense pulsed IR laser at 3 μm, which is resonant to a vibrational mode related to
the OH stretch vibration of H2O. Neutral species isolated into the vacuum were ionized by a pulsed UV laser at 270 nm, and the product ions were mass-analyzed
by a time-of-flight mass spectrometer. It is found that AH 2
2 + . 2Cl- and [A-iH] i - .
iNa+ (i = 1-3) are isolated in the vacuum from the aqueous acidic and alkaline solutions, respectively, under irradiation of the
IR laser, and undergo four-photon ionization involving decomposition and proton transfer of the intermediate species under
irradiation of the UV laser.
Received 1st May 2002 Published online 13 September 2002 相似文献
10.
P.G. de Gennes 《The European physical journal. E, Soft matter》2002,7(1):31-34
When a glassy polymer film is formed by evaporation, the region near the free surface is polymer rich and becomes glassy first,
as noticed long ago by Scriven et al. We discuss the thickness of this “crust” and the time interval where it is present --before freezing of the whole film. We
argue that the crust is under mechanical tension, and should form some cracks. This may be the source of the roughness observed
on the final, dry films, when the solvent vapor pressure is high (and leads to thin crusts).
Received 13 November 2001 相似文献