391 research outputs found
The necessity of cell banks
Current progress in cell biology is connected with the development of somatic cell reprogramming technology. As a result of this technology, it is possible to produce induced pluripotent stem cells (iPSCs) from human somatic cells, for instance, from skin cells. As well as embryonic stem cells, these iPSCs possess pluripotency. Production of iPSCs opened new horizons for patient-specific cell therapy. Many researchers consider iPSCs a real basis for future regenerative medicine. Production of a patient’s iPSCs, their differentiation into somatic cells, and subsequent transplantation to a patient would allow them to avoid immunological rejection. In addition, a recently developed technology of directed genome modification, CRISPR/Cas, allows correction of genetic mutations in iPSCs. Thus, genetic mutations could be corrected in vitro, and after differentiation into a desired cell type, these cells could be transplanted to a patient. In addition, CRISPR/Cas could be used to introduce practically any mutations into iPSCs for the creation of disease-specific model cell lines that would facilitate disease mechanism studies and pharmaceutical drug testing. It is possible to turn off any gene or genes as well as to insert a genetic construct into a selected genomic region to temporarily turn on and off genes and remove chromosomal regions. Cell banks that are open to general use are necessary for efficient usage of iPSCs in biomedical research. Currently, there are no pluripotent stem cell lines in Russian Federation cell banks. Moreover, it is essential to develop standardized practice of culture and storage of that cell type. This mini-review focuses on the necessity of the creation of a pluripotent stem cell bank in the Russian Federation, a detailed description, and a recommended protocol for cell line deposition and usage
Creation of transgenic mice susceptible to coronaviruses: a platform for studying viral pathogenesis and testing vaccines
Over the past 20 years, coronaviruses have caused three epidemics: SARS-CoV, MERS-CoV, and SARS-CoV2, with the first two having a very high lethality of about 10 and 26 %, respectively. The last outbreak of coronavirus infection caused by SARS-CoV2 in 2019 in China has swept the entire planet and is still spreading. The source of these viruses in humans are animals: bats, Himalayan civets, and camels. The genomes of MERS-CoV, SARS-CoV and SARS-CoV2 are highly similar. It has been established that coronavirus infection (SARS-CoV and SARS-CoV2) occurs through the viral protein S interaction with the lung epithelium – angiotensin-converting enzyme receptor 2 (ACE2) – due to which the virus enters the cells. The most attractive model for studying the development of these diseases is a laboratory mouse, which, however, is resistant to coronavirus infection. The resistance is explained by the difference in the amino acid composition of mouse Ace2 and human ACE2 proteins. Therefore, to create mice susceptible to SARS-CoV and SARS-CoV2 coronaviruses, the human ACE2 gene is transferred into their genome. The exogenous DNA of the constructs is inserted into the recipient genome randomly and with a varying number of copies. Based on this technology, lines of transgenic mice susceptible to intranasal coronavirus infection have been created. In addition, the use of the technology of targeted genome modification using CRISPR/Cas9 made it possible to create lines of transgenic animals with the insertion of the human ACE2 gene under the control of the endogenous murine Ace2 gene promoter. This “humanization” of the Ace2 gene makes it possible to obtain animals susceptible to infection with coronaviruses. Thus, transgenic animals that simulate coronavirus infections and are potential platforms for testing vaccines have now been created
adiabatic versus nonadiabatic dressed-state dynamics
We discuss how a recent pump-probe study [Kelkensberg et al., Phys. Rev. Lett.
103, 123005 (2009)] of the dissociative ionization of H2, under the combined
effect of a single extreme ultraviolet attosecond pulse and an intense near-
infrared pulse, actually represents a transition-state spectroscopy of the
strong-field dissociation step, i.e., of the (probe-pulse-)dressed H2+
molecular ion. The way the dissociation dynamics is influenced by the duration
of the near-infrared probe pulse, and by the time delay between the two
pulses, is discussed in terms of adiabatic versus nonadiabatic preparation and
transport of time-parametrized Floquet resonances associated with the
dissociating molecular ion. Under a long probe pulse, the field-free
vibrational states of the initial wave packet are transported, in a one-to-one
manner, onto the Floquet resonances defined by the field intensity of the
probe pulse and propagated adiabatically under the pulse. As the probe pulse
duration shortens, nonadiabatic transitions between the Floquet resonances
become important and manifest themselves in two respects: first, as a
vibrational shake-up effect occurring near the peak of the short pulse, and
second, through strong interference patterns in the fragment's kinetic energy
spectrum, viewed as a function of the time delay between the pump and the
probe pulses
A quantitative theory-versus-experiment comparison for the intense laser dissociation of H2+
A detailed theory-versus-experiment comparison is worked out for H
intense laser dissociation, based on angularly resolved photodissociation
spectra recently recorded in H.Figger's group. As opposite to other
experimental setups, it is an electric discharge (and not an optical
excitation) that prepares the molecular ion, with the advantage for the
theoretical approach, to neglect without lost of accuracy, the otherwise
important ionization-dissociation competition. Abel transformation relates the
dissociation probability starting from a single ro-vibrational state, to the
probability of observing a hydrogen atom at a given pixel of the detector
plate. Some statistics on initial ro-vibrational distributions, together with a
spatial averaging over laser focus area, lead to photofragments kinetic
spectra, with well separated peaks attributed to single vibrational levels. An
excellent theory-versus-experiment agreement is reached not only for the
kinetic spectra, but also for the angular distributions of fragments
originating from two different vibrational levels resulting into more or less
alignment. Some characteristic features can be interpreted in terms of basic
mechanisms such as bond softening or vibrational trapping.Comment: submitted to PRA on 21.05.200
New conditional symmetries and exact solutions of nonlinear reaction-diffusion-convection equations. II
In the first part of this paper math-ph/0612078, a complete description of
Q-conditional symmetries for two classes of reaction-diffusion-convection
equations with power diffusivities is derived. It was shown that all the known
results for reaction-diffusion equations with power diffusivities follow as
particular cases from those obtained in math-ph/0612078 but not vise versa. In
the second part the symmetries obtained in are successfully applied for
constructing exact solutions of the relevant equations. In the particular case,
new exact solutions of nonlinear reaction-diffusion-convection (RDC) equations
arising in application and their natural generalizations are found
The C-H bond activation in 1-ethyl-3-methylimidazolium acetate-copper(ii) acetate-water-air (dioxygen) systems
Ionic liquid (1-ethyl-3-methylimidazolium acetate, [C2C 1im][AcO])-copper(ii) diacetate monohydrate-water-air (O2) systems have been investigated by 13C NMR, EPR, spectrophotometry, HPLC, and synthetic chemistry methods at different temperatures. The C-H bond activation of [C2C1im]+ with the formation of the unusual dication 1,1′-diethyl-3,3′-dimethyl-2,2′- biimidazolium ([(C2C1im)2]2+) at 50°C and 1-ethyl-3-methyl-1H-imidazol-2(3H)-one (C2C 1imO) at 50-85°C was revealed. Two new complexes with the above compounds, [(C2C1im)2][Cu(AcO)4] and Cu2(AcO)4(C2C1imO)2, were isolated from the systems and characterized by X-ray structural analysis. Catalytic cycles with the participation of copper(ii) acetate and dioxygen and the production of [(C2C1im)2]2+ and C2C1imO have been proposed. The catalysis presumably includes the formation of the CuII(O2)CuII active centre with μ-η2:η2-peroxide bridging in analogy with tyrosinase and catechol oxidase activity. © 2014 The Royal Society of Chemistry
Enhanced Group Analysis and Exact Solutions of Variable Coefficient Semilinear Diffusion Equations with a Power Source
A new approach to group classification problems and more general
investigations on transformational properties of classes of differential
equations is proposed. It is based on mappings between classes of differential
equations, generated by families of point transformations. A class of variable
coefficient (1+1)-dimensional semilinear reaction-diffusion equations of the
general form () is studied from the
symmetry point of view in the framework of the approach proposed. The singular
subclass of the equations with is singled out. The group classifications
of the entire class, the singular subclass and their images are performed with
respect to both the corresponding (generalized extended) equivalence groups and
all point transformations. The set of admissible transformations of the imaged
class is exhaustively described in the general case . The procedure of
classification of nonclassical symmetries, which involves mappings between
classes of differential equations, is discussed. Wide families of new exact
solutions are also constructed for equations from the classes under
consideration by the classical method of Lie reductions and by generation of
new solutions from known ones for other equations with point transformations of
different kinds (such as additional equivalence transformations and mappings
between classes of equations).Comment: 40 pages, this is version published in Acta Applicanda Mathematica
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