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61.
Recent experiments on unzipping of RNA helix-loop structures by force have shown that ≈40-base molecules can undergo kinetic
transitions between two well-defined “open” and “closed” states, on a timescale ≈1 sec [Liphardt et al., Science 297, 733-737 (2001)]. Using a simple dynamical model, we show that these phenomena result from the slow kinetics
of crossing large free energy barriers which separate the open and closed conformations. The dependence of barriers on sequence
along the helix, and on the size of the loop(s) is analyzed. Some DNA and RNA sequences that could show dynamics on different
time scales, or three(or more)-state unzipping, are proposed. Our dynamical model is also applied to the unzipping of long
(kilo-basepair) DNA molecules at constant force.
Received 29 July 2002 / Received in final form 5 February 2003 Published online: 16 April 2003
RID="a"
ID="a"e-mail: cocco@ldfc.u-strasbg.fr
RID="b"
ID="b"e-mail: jmarko@uic.edu
RID="c"
ID="c"e-mail: monasson@lpt.ens.fr 相似文献
62.
We report measurements of the dynamics of force relaxation in single mitotic chromosomes, following step strains applied with micropipettes of force constant approximately 1 nN/microm. The force relaxes exponentially after an elongation (l/l(0)) to less than 3x native length, with a relaxation time approximately 2 sec. This relaxation time corresponds to an effective viscosity approximately 10(5) times that of water. We experimentally rule out solvent flow into the chromosome as the mechanism for the relaxation time. Instead, the relaxation can be explained in terms of the disentanglement dynamics of approximately 80 kb chromatin loop domains. 相似文献
63.
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67.
In this paper, we present an existence result for weak efficient solution for the vector optimization problem. The result is stated for invex strongly compactly Lipschitz functions. 相似文献
68.
Martin Sahlberg Premysl Beran Thomas Kollin Nielsen Yngve Cerenius Krisztina Kads Marko P.J. Punkkinen Levente Vitos Olle Eriksson Torben R. Jensen Yvonne Andersson 《Journal of solid state chemistry》2009,182(11):3113-3117
A novel aluminium rich alloy for hydrogen storage has been discovered, ScAl0.8Mg0.2, which has very promising properties regarding hydrogen storage capacity, kinetics and stability towards air oxidation in comparison to hydrogen absorption in state-of-the-art intermetallic compounds. The absorption of hydrogen was found to be very fast, even without adding any catalyst, and reversible. The discovered alloy crystallizes in a CsCl-type structure, but decomposes to ScH2 and Al(Mg) during hydrogen absorption. Detailed analysis of the hydrogen absorption in ScAl0.8Mg0.2 has been performed using in situ synchrotron radiation powder X-ray diffraction, neutron powder diffraction and quantum mechanical calculations. The results from theory and experiments are in good agreement with each other. 相似文献
69.
Heinz Falk Helmut Marko Norbert Müller Wolfgang Schmitzberger Hugo Stumpe 《Monatshefte für Chemie / Chemical Monthly》1990,121(11):893-901
Summary Apomyoglobin was reconstituted with bile pigments of the verdinoid, 2,3-dihydroverdinoid, pterobilinoid, and violinoid type. Absorption and circular dichroism data as well as formation constants of the complexes were measured. From these results it was concluded that chromophore binding and induced chirality of these pigments are mainly governed by a lipophilic region opposite to the propionic side chain(s) and the asymmetric position of the hydrogen bonding acceptors of the propionic acid side chain(s) at the entrance of the protein pocket.Dedicated to Prof. Dr. A. Eschenmoser on occasion of his 65th birthday 相似文献
70.
Mirjana M. Radanović Marko V. Rodić Stevan Armaković Sanja J. Armaković Ljiljana S. Vojinović-Ješić Vukadin M. Leovac 《Journal of Coordination Chemistry》2017,70(16):2870-2887
Two nitrate salts of the well-known, and due to its significant biological activity very important, compound pyridoxylidene aminoguanidine (PLAG) were obtained in the form of single crystals. Thus this ligand is structurally characterized for the first time. In addition, the first data on the structure of a Schiff base of aminoguanidine with the active form of vitamin B6, i.e. pyridoxal-phosphate, of the formula PLPAG·HCl·2H2O, are presented. Two new square-pyramidal Cu(II) complexes of PLAG were synthesized and their physicochemical and structural properties analyzed. In these complexes, PLAG is coordinated as a zwitter-ion, in a tridentate ONN manner, via the oxygen atom of the deprotonated phenolic OH-group and nitrogen atoms of the azomethine and imino group of the aminoguanidine moiety. For the first time it was possible to make a comparative analysis of the structural properties of ligand salts and the coordinated ligand, so the effects of coordination could be unequivocally pointed out. Common fragments encountered in ligand structures were compared by half-normal probability plots. Density functional theory calculations have been conducted in order to gain insight into reactive properties of the investigated molecules. Molecular electrostatic potential, average local ionization energy surfaces, and Fukui functions have been calculated in order to obtain further information on the reactive properties. 相似文献