26 research outputs found
Studying synthesis confinement effects on the internal structure of nanogels in computer simulations
We study the effects of droplet finite size on the structure of nanogel
particles synthesized by random crosslinking of molecular polymers diluted in
nanoemulsions. For this, we use a bead-spring computer model of polymer-like
structures that mimics the confined random crosslinking process corresponding
to irradiation- or electrochemically-induced crosslinking methods. Our results
indicate that random crosslinking under strong confinement can lead to unusual
nanogel internal structures, with a central region less dense than the external
one, whereas under moderate confinement the resulting structure has a denser
central region. We analyze the topology of the polymer networks forming nanogel
particles with both types of architectures, their overall structural
parameters, their response to the quality of the solvent and compare the cases
of non-ionic and ionic systems
Suspensions of magnetic nanogels at zero field: equilibrium structural properties
Magnetic nanogels represent a cutting edge of magnetic soft matter research
due to their numerous potential applications. Here, using Langevin dynamics
simulations, we analyse the influence of magnetic nanogel concentration and
embedded magnetic particle interactions on the self-assembly of magnetic
nanogels at zero field. For this, we calculated radial distribution functions
and structure factors for nanogels and magnetic particles within them. We found
that, in comparison to suspensions of free magnetic nanoparticles, where the
self-assembly is already observed if the interparticle interaction strength
exceeds the thermal fluctuations by approximately a factor of three,
self-assembly of magnetic nanogels only takes place by increasing such ratio
above six. This magnetic nanogel self-assembly is realised by means of
favourable close contacts between magnetic nanoparticles from different
nanogels. It turns out that for high values of interparticle interactions,
corresponding to the formation of internal rings in isolated nanogels, in their
suspensions larger magnetic particle clusters with lower elastic penalty can be
formed by involving different nanogels. Finally, we show that when the
self-assembly of these nanogels takes place, it has a drastic effect on the
structural properties even if the volume fraction of magnetic nanoparticles is
low.Comment: International Conference on Magnetic Fluids - ICMF 201
Compressibility of ferrofluids: Towards a better understanding of structural properties
Derivation, Characterization, and Stable Transfection of Induced Pluripotent Stem Cells from Fischer344 Rats
The rat represents an important animal model that, in many respects, is superior to the mouse for dissecting behavioral, cardiovascular and other physiological pathologies relevant to humans. Derivation of induced pluripotent stem cells from rats (riPS) opens the opportunity for gene targeting in specific rat strains, as well as for the development of new protocols for the treatment of different degenerative diseases. Here, we report an improved lentivirus-based hit-and-run riPS derivation protocol that makes use of small inhibitors of MEK and GSK3. We demonstrate that the excision of proviruses does not affect either the karyotype or the differentiation ability of these cells. We show that the established riPS cells are readily amenable to genetic manipulations such as stable electroporation. Finally, we propose a genetic tool for an improvement of riPS cell quality in culture. These data may prompt iPS cell-based gene targeting in rat as well as the development of iPS cell-based therapies using disease models established in this species
Suppression of Metacaspase- and Autophagy-Dependent Cell Death Improves Stress-Induced Microspore Embryogenesis in Brassica napus
Microspore embryogenesis is a biotechnological process that allows us to rapidly obtain doubled-haploid plants for breeding programs. The process is initiated by the application of stress treatment, which reprograms microspores to embark on embryonic development. Typically, a part of the microspores undergoes cell death that reduces the efficiency of the process. Metacaspases (MCAs), a phylogenetically broad group of cysteine proteases, and autophagy, the major catabolic process in eukaryotes, are critical regulators of the balance between cell death and survival in various organisms. In this study, we analyzed the role of MCAs and autophagy in cell death during stress-induced microspore embryogenesis in Brassica napus. We demonstrate that this cell death is accompanied by the transcriptional upregulation of three BnMCA genes (BnMCA-Ia, BnMCA-IIa and BnMCA-IIi), an increase in MCA proteolytic activity and the activation of autophagy. Accordingly, inhibition of autophagy and MCA activity, either individually or in combination, suppressed cell death and increased the number of proembryos, indicating that both components play a pro-cell death role and account for decreased efficiency of early embryonic development. Therefore, MCAs and/or autophagy can be used as new biotechnological targets to improve in vitro embryogenesis in Brassica species and doubled-haploid plant production in crop breeding and propagation programs
Compressibility of ferrofluids: Towards a better understanding of structural properties
This paper addresses a computational method aimed at obtaining the isothermal compressibility of ferrofluids by means of molecular dynamics (MD) simulations. We model ferrofluids as a system of dipolar soft spheres and carry out MD simulations in the NPT ensemble. The obtained isothermal compressibility computed via volume fluctuations provides us with a strong evidence that dipolar interactions lead to a higher compressibility of dipolar soft sphere systems: the stronger the dipolar interactions, the bigger is the deviation of the compressibility from the one of a system with no dipoles. Furthermore, we use the isothermal compressibility to calculate the structure factor of ferrofluids at low values of wave vectors, i.e. in the range where it is difficult to predict its behaviour because of a problem with accounting for long-range particle correlations that give the main contribution to the structure factor in this range. Our approach based on the interpolation of the structure factor and the computed isothermal compressibility allows us to obtain the smooth structure factor in the range of low wave vectors and the reliable fractal dimension of the clusters formed in the system
Metacaspases versus caspases in development and cell fate regulation
Initially found to be critically involved in inflammation and apoptosis, caspases have since then been implicated in the regulation of various signaling pathways in animals. How caspases and caspase-mediated processes evolved is a topic of great interest and hot debate. In fact, caspases are just the tip of the iceberg, representing a relatively small group of mostly animal-specific enzymes within a broad family of structurally related cysteine proteases (family C14 of CD clan) found in all kingdoms of life. Apart from caspases, this family encompasses para- and metacaspases, and all three groups of proteases exhibit significant variation in biochemistry and function in vivo. Notably, metacaspases are present in all eukaryotic lineages with a remarkable absence in animals. Thus, metacaspases and caspases must have adapted to operate under distinct cellular and physiological settings. Here we discuss biochemical properties and biological functions of metacaspases in comparison to caspases, with a major focus on the regulation of developmental aspects in plants versus animals.Research in our laboratories is supported by grants from Carl Tryggers Foundation (to EAM), the Swedish Research Council (to HT and PVB), Knut and Alice Wallenberg Foundation (to PVB), Olle Engkvist Foundation (to PVB), the Swedish Foundation for Strategic Research (to PVB), the Trees and Crops for the Future (TC4F) programme (to PVB), Spanish Ministry of Economy, Industry and Competitiveness (projects AGL2016-78002, RyC 2014-1658 SEV‐2015‐0533; to NSC) and the CERCA Programme/Generalitat de Catalunya (to NSC).Peer reviewe
Running Head: Metacaspases and autophagy in microspore embryogenesis
14 p.-7 fig.Microspore embryogenesis is a biotechnological process that allows to rapidly obtain doubled haploid plants for breeding programs. The process is initiated by the application of stress treatment which reprograms microspores to embark on embryonic development. Typically, a part of the microspores undergoes cell death that reduces the efficiency of the process. Metacaspases (MCAs), a phylogenetically broad group of cysteine proteases, and autophagy, the major catabolic process in eukaryotes, are critical regulators of the balance between cell death and survival in various organisms. In this study we analyzed the role of MCAs and autophagy in cell death during stress-induced microspore embryogenesis in Brassica napus. We demonstrate that this cell death is accompanied by transcriptional upregulation of three BnMCA genes (BnMCA-Ia, BnMCA-IIa and BnMCA-IIi), increase in MCA proteolytic activity, and activation of autophagy. Accordingly, inhibition of autophagy and MCA activity, either individually or in combination, suppressed cell death and increased the number of proembryos, indicating that both components play a pro-cell death role and account for decreased efficiency of early embryonic development. Therefore, MCAs and/or autophagy can be used as new biotechnological targets to improve in vitro embryogenesis in Brassica species and doubled-haploid plant production in crop breeding and propagation programmes.The work was supported by the Spanish National Agency of Research (Agencia Estatal
de Investigación, AEI) and European Regional Development Fund (ERDF/FEDER)
[grant AGL2017- 82447-R to PST], and by the Swedish Foundation for Strategic
Research and the research program “Crops for the future” [grants to PVB].Peer reviewe