RESUMO
In eukaryotic cells, many macromolecules are organized as membraneless biomolecular condensates (or biocondensates). Liquid-liquid and liquid-solid phase transitions are the drivers of the condensation process. The absence of membrane borders makes biocondensates very flexible in their composition and functions, which vary in different cells and tissues. Some biocondensates are specific for germ line cells and are, thus, termed germ granules. This review summarizes the recent data on the composition of germ granules and their functions in gametes. According to these data, germ granules are involved in the determination of germline cells in some animals, such as Amphibia. In other animals, such as Mammalia, germ granules are involved in the processes of transposons inactivation and sequestration of mRNA and proteins to temporarily decrease their activity. The new data on germ granules composition and functions sheds light on germ cell differentiation and maturation properties.
RESUMO
C,N-Chelate deprotonated diaminocarbene platinum(II) complexes were synthesized by coupling coordinated isocyanides and azinyl-substituted ureas. The complexes act as catalysts of α,ω-divinylpolydimethylsiloxane and poly(dimethylsiloxane-co-methylhydrosiloxane) hydrosilylation cross-linking. Silicone rubbers obtained with (aminoisoquinoline)-containing complex 3d exhibit temperature-responsive luminescence. Their emission changes irreversibly when heated from 80-100 °C (green radiation) to 120 °C or more (blue radiation).
RESUMO
Membraneless organelles (bodies, granules, etc.) are spatially distinct sub-nuclear and cytoplasmic foci involved in all the processes in a living cell, such as development, cell death, carcinogenesis, proliferation, and differentiation. Today the list of the membraneless organelles includes a wide spectrum of intranuclear and cytoplasmic bodies. Proteins with intrinsically disordered regions are the key players in the membraneless body assembly. However, recent data assume an important role of RNA molecules in the process of the liquid-liquid phase separation. High-level expression of RNA above a critical concentration threshold is mandatory to nucleate interactions with specific proteins and for seeding membraneless organelles. RNA components are considered by many authors as the principal determinants of organelle identity. Tandemly repeated (TR) DNA of big satellites (a TR family that includes centromeric and pericentromeric DNA sequences) was believed to be transcriptionally silent for a long period. Now we know about the TR transcription upregulation during gameto- and embryogenesis, carcinogenesis, stress response. In the review, we summarize the recent data about the involvement of TR RNA in the formation of nuclear membraneless granules, bodies, etc., with different functions being in some cases an initiator of the structures assembly. These RNP structures sequestrate and inactivate different proteins and transcripts. The TR induced sequestration is one of the key principles of nuclear architecture and genome functioning. Studying the role of the TR-based membraneless organelles in stress and disease will bring some new ideas for translational medicine.
Assuntos
Carcinogênese , Diferenciação Celular/genética , Proliferação de Células/genética , Desenvolvimento Embrionário/genética , Regulação Neoplásica da Expressão Gênica , Organelas , RNA Neoplásico , RNA , Animais , Carcinogênese/genética , Carcinogênese/metabolismo , Humanos , Organelas/genética , Organelas/metabolismo , RNA/biossíntese , RNA/genética , RNA Neoplásico/biossíntese , RNA Neoplásico/genéticaRESUMO
A new method was developed for the metal-free cross-linking of silicone rubbers. This process uses azobisisobutyronitrile (AIBN) to selectively react with Si-H and vinyl groups as a free-radical initiator for the thermal curing of polymethylhydrosiloxane (PMHS) and polymethylvinylsiloxane (PMVS). The AIBN-initiated curing reaction between the Si-H groups of PMHS generated Si-O-Si and Si-Si cross-links. In contrast, PMVS was cured via the formation of C-C bonds through "methyl-vinyl" and "vinyl-vinyl" mechanisms. Curing reactions were performed at 80-120 °C in air and confirmed by 13C and 29Si solid state NMR analyses and swelling trials.
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Hydrosilylation catalyzed by the rhodium(I) complex [Rh(acac)(CO)2] or platinum(0)-based Karstedt's catalyst was employed to combine hydrophilic propargylated hydroxyethyl cellulose and hydrophobic hydride-terminated polydimethylsiloxane to give polymer hybrid structures. The final polymers were characterized by FTIR, solid state 1H, 13C and 29Si NMR, contact angle, microcalorimetry and thermogravimetry measurements. The grafting degree was controlled by the catalyst choice and by the reagent load variations; an increase of the polysiloxane load and a change from Karstedt's to the rhodium catalyst led to a higher (from 2 to 7%) silicon content in the glycosilicones. The glycosilicones were insoluble in water, but swelled in organic solvents (DMSO, DMF, and chloroform). The hydrophilicity of the glycosilicones decreased with incrementing silicon content: the contact angles increased from 30 (cellulose) to 103-131° in the hybrids. The glycosilicones obtained via the hydrosilylation are less toxic toward algae Chlorella vulgaris and infusoria Paramecium caudatum than those obtained with CuAAC.
Assuntos
Celulose/análogos & derivados , Dimetilpolisiloxanos , Catálise , Celulose/síntese química , Celulose/química , Chlorella vulgaris , Dimetilpolisiloxanos/síntese química , Dimetilpolisiloxanos/química , Paramecium caudatum , Testes de ToxicidadeRESUMO
This dataset, produced through the Coordinated Ocean Wave Climate Project (COWCLIP) phase 2, represents the first coordinated multivariate ensemble of 21st Century global wind-wave climate projections available (henceforth COWCLIP2.0). COWCLIP2.0 comprises general and extreme statistics of significant wave height (HS), mean wave period (Tm), and mean wave direction (θm) computed over time-slices 1979-2004 and 2081-2100, at different frequency resolutions (monthly, seasonally and annually). The full ensemble comprising 155 global wave climate simulations is obtained from ten CMIP5-based state-of-the-art wave climate studies and provides data derived from alternative wind-wave downscaling methods, and different climate-model forcing and future emissions scenarios. The data has been produced, and processed, under a specific framework for consistency and quality, and follows CMIP5 Data Reference Syntax, Directory structures, and Metadata requirements. Technical comparison of model skill against 26 years of global satellite measurements of significant wave height has been undertaken at global and regional scales. This new dataset provides support for future broad scale coastal hazard and vulnerability assessments and climate adaptation studies in many offshore and coastal engineering applications.
RESUMO
cis- and trans-Isomers of the platinum(II) nitrile complexes [PtCl2(NCR)2] (R = NMe2, N(C5H10), Ph, CH2Ph) were examined as catalysts for hydrosilylation cross-linking of vinyl-terminated polydimethylsiloxane and trimethylsilyl-terminated poly(dimethylsiloxane-co-ethylhydrosiloxane) producing high quality silicone rubbers. Among the tested platinum species the cis-complexes are much more active catalysts than their trans-congeners and for all studied platinum complexes cis-[PtCl2(NCCH2Ph)2] exhibits the best catalytic activity (room temperature, c = 1.0 × 10(-4) mol/L, τpot-life 60 min, τcuring 6 h). Although cis-[PtCl2(NCCH2Ph)2] is less active than the widely used Karstedt's catalyst, its application for the cross-linking can be performed not only at room temperature (c = 1.0 × 10(-4) mol/L), but also, more efficiently, at 80 °C (c = 1.0 × 10(-4)-1.0 × 10(-5) mol/L) and it prevents adherence of the formed silicone rubbers to equipment. The usage of the cis- and trans-[PtCl2(NCR)2] complexes as the hydrosilylation catalysts do not require any inhibitors and, moreover, the complexes and their mixtures with vinyl- and trimethylsilyl terminated polysiloxanes are shelf-stable in air. Tested catalysts do not form colloid platinum particles after the cross-linking.