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1.
Nat Commun ; 11(1): 4628, 2020 09 15.
Artigo em Inglês | MEDLINE | ID: mdl-32934220

RESUMO

Liquid phase separation into two or more coexisting phases has emerged as a new paradigm for understanding subcellular organization, prebiotic life, and the origins of disease. The design principles underlying biomolecular phase separation have the potential to drive the development of novel liquid-based organelles and therapeutics, however, an understanding of how individual molecules contribute to emergent material properties, and approaches to directly manipulate phase dynamics are lacking. Here, using microrheology, we demonstrate that droplets of poly-arginine coassembled with mono/polynucleotides have approximately 100 fold greater viscosity than comparable lysine droplets, both of which can be finer tuned by polymer length. We find that these amino acid-level differences can drive the formation of coexisting immiscible phases with tunable formation kinetics and can be further exploited to trigger the controlled release of droplet components. Together, this work provides a novel mechanism for leveraging sequence-level components in order to regulate droplet dynamics and multiphase coexistence.


Assuntos
Arginina/química , Lisina/química , Cinética , Transição de Fase , Polinucleotídeos/química , Viscosidade
2.
Nat Commun ; 11(1): 4616, 2020 09 15.
Artigo em Inglês | MEDLINE | ID: mdl-32934229

RESUMO

Para-nematic phases, induced by unwinding chiral helices, spontaneously relax to a chiral ground state through phase ordering dynamics that are of great interest and crucial for applications such as stimuli-responsive and biomimetic engineering. In this work, we characterize the cholesteric phase relaxation behaviors of ß-lactoglobulin amyloid fibrils and cellulose nanocrystals confined into cylindrical capillaries, uncovering two different equilibration pathways. The integration of experimental measurements and theoretical predictions reveals the starkly distinct underlying mechanism behind the relaxation dynamics of ß-lactoglobulin amyloid fibrils, characterized by slow equilibration achieved through consecutive sigmoidal-like steps, and of cellulose nanocrystals, characterized by fast equilibration obtained through smooth relaxation dynamics. Particularly, the specific relaxation behaviors are shown to emerge from the order parameter of the unwound cholesteric medium, which depends on chirality and elasticity. The experimental findings are supported by direct numerical simulations, allowing to establish hard-to-measure viscoelastic properties without applying magnetic or electric fields.


Assuntos
Lactoglobulinas/química , Cristais Líquidos/química , Amiloide/química , Coloides/química , Elasticidade , Cinética , Nanopartículas/química , Transição de Fase , Temperatura
4.
Science ; 369(6509): 1304-1305, 2020 09 11.
Artigo em Inglês | MEDLINE | ID: mdl-32913090
5.
Phys Rev Lett ; 125(3): 038003, 2020 Jul 17.
Artigo em Inglês | MEDLINE | ID: mdl-32745423

RESUMO

Experiments and theory have shown that cell monolayers and epithelial tissues exhibit solid-liquid and glass-liquid transitions. These transitions are biologically relevant to our understanding of embryonic development, wound healing, and cancer. Current models of confluent epithelia have focused on the role of cell shape, with less attention paid to cell extrusion, which is key for maintaining homeostasis in biological tissue. Here, we use a multiphase field model to study the solid-liquid transition in a confluent monolayer of deformable cells. Cell overlap is allowed and provides a way for modeling the precursor for extrusion. When cells overlap rather than deform, we find that the melting transition changes from continuous to first order like, and that there is an intermittent regime close to the transition, where solid and liquid states alternate over time. By studying the dynamics of five- and sevenfold disclinations in the hexagonal lattice formed by the cell centers, we observe that these correlate with spatial fluctuations in the cellular overlap, and that cell extrusion tends to initiate near fivefold disclinations.


Assuntos
Células Epiteliais/química , Células Epiteliais/citologia , Rim/química , Rim/citologia , Modelos Biológicos , Animais , Fenômenos Biofísicos , Movimento Celular/fisiologia , Forma Celular/fisiologia , Cães , Transição Epitelial-Mesenquimal , Células Madin Darby de Rim Canino , Transição de Fase
6.
Nat Commun ; 11(1): 3859, 2020 07 31.
Artigo em Inglês | MEDLINE | ID: mdl-32737298

RESUMO

Non-enzymatic proteins including antibodies function as biomarkers and are used as biopharmaceuticals in several diseases. Protein-responsive soft materials capable of the controlled release of drugs and proteins have potential for use in next-generation diagnosis and therapies. Here, we describe a supramolecular/agarose hydrogel composite that can release a protein in response to a non-enzymatic protein. A non-enzymatic protein-responsive system is developed by hybridization of an enzyme-sensitive supramolecular hydrogel with a protein-triggered enzyme activation set. In situ imaging shows that the supramolecular/agarose hydrogel composite consists of orthogonal domains of supramolecular fibers and agarose, which play distinct roles in protein entrapment and mechanical stiffness, respectively. Integrating the enzyme activation set with the composite allows for controlled release of the embedded RNase in response to an antibody. Such composite hydrogels would be promising as a matrix embedded in a body, which can autonomously release biopharmaceuticals by sensing biomarker proteins.


Assuntos
Anidrase Carbônica II/química , Preparações de Ação Retardada/síntese química , Hidrogéis/química , Ribonucleases/química , Sefarose/química , Animais , Anticorpos/química , Avidina/química , Biotina/química , Anidrase Carbônica II/antagonistas & inibidores , Inibidores da Anidrase Carbônica/química , Bovinos , Ativação Enzimática , Transição de Fase , Reologia , Ribonucleases/antagonistas & inibidores , Sulfonamidas/química
7.
Nature ; 585(7824): 256-260, 2020 09.
Artigo em Inglês | MEDLINE | ID: mdl-32848244

RESUMO

Temperature controls plant growth and development, and climate change has already altered the phenology of wild plants and crops1. However, the mechanisms by which plants sense temperature are not well understood. The evening complex is a major signalling hub and a core component of the plant circadian clock2,3. The evening complex acts as a temperature-responsive transcriptional repressor, providing rhythmicity and temperature responsiveness to growth through unknown mechanisms2,4-6. The evening complex consists of EARLY FLOWERING 3 (ELF3)4,7, a large scaffold protein and key component of temperature sensing; ELF4, a small α-helical protein; and LUX ARRYTHMO (LUX), a DNA-binding protein required to recruit the evening complex to transcriptional targets. ELF3 contains a polyglutamine (polyQ) repeat8-10, embedded within a predicted prion domain (PrD). Here we find that the length of the polyQ repeat correlates with thermal responsiveness. We show that ELF3 proteins in plants from hotter climates, with no detectable PrD, are active at high temperatures, and lack thermal responsiveness. The temperature sensitivity of ELF3 is also modulated by the levels of ELF4, indicating that ELF4 can stabilize the function of ELF3. In both Arabidopsis and a heterologous system, ELF3 fused with green fluorescent protein forms speckles within minutes in response to higher temperatures, in a PrD-dependent manner. A purified fragment encompassing the ELF3 PrD reversibly forms liquid droplets in response to increasing temperatures in vitro, indicating that these properties reflect a direct biophysical response conferred by the PrD. The ability of temperature to rapidly shift ELF3 between active and inactive states via phase transition represents a previously unknown thermosensory mechanism.


Assuntos
Proteínas de Arabidopsis/química , Proteínas de Arabidopsis/metabolismo , Arabidopsis/metabolismo , Proteínas Priônicas/química , Temperatura , Fatores de Transcrição/química , Fatores de Transcrição/metabolismo , Aclimatação/fisiologia , Arabidopsis/química , Temperatura Alta , Modelos Moleculares , Peptídeos/metabolismo , Transição de Fase , Domínios Proteicos , Proteínas Repressoras/química , Proteínas Repressoras/metabolismo
8.
Mol Cell ; 79(2): 293-303.e4, 2020 07 16.
Artigo em Inglês | MEDLINE | ID: mdl-32679076

RESUMO

Liquid-liquid phase-separated (LLPS) states are key to compartmentalizing components in the absence of membranes; however, it is unclear whether LLPS condensates are actively and specifically organized in the subcellular space and by which mechanisms. Here, we address this question by focusing on the ParABS DNA segregation system, composed of a centromeric-like sequence (parS), a DNA-binding protein (ParB), and a motor (ParA). We show that parS and ParB associate to form nanometer-sized, round condensates. ParB molecules diffuse rapidly within the nucleoid volume but display confined motions when trapped inside ParB condensates. Single ParB molecules are able to rapidly diffuse between different condensates, and nucleation is strongly favored by parS. Notably, the ParA motor is required to prevent the fusion of ParB condensates. These results describe a novel active mechanism that splits, segregates, and localizes non-canonical LLPS condensates in the subcellular space.


Assuntos
Trifosfato de Adenosina/fisiologia , Fenômenos Fisiológicos Bacterianos , Proteínas de Escherichia coli/fisiologia , Transição de Fase , DNA Primase/fisiologia , DNA Bacteriano , Microscopia/métodos , Nanopartículas , Imagem Individual de Molécula/métodos
9.
J Chromatogr A ; 1625: 461295, 2020 Aug 16.
Artigo em Inglês | MEDLINE | ID: mdl-32709338

RESUMO

In addition to the diverse extraction techniques available, capsule phase microextraction (CPME), which uses a microextraction capsule (MEC), has recently been introduced as a sorptive-based sample preparation technique. In this study, two different MECs (MEC-C18/SAX and MEC-C18/SCX) based on mixed-mode ion-exchange technology were synthesized and evaluated for the selective extraction of a group of ionizable compounds, including acidic and basic analytes. A sulfonic acid was used as the cation-exchange group in MEC-C18/SCX, and a quaternary amine as the anion-exchange group in MEC-C18/SAX. The extraction parameters optimized were sample pH, elution solvent, sample/elution volume and extraction/elution time. The optimized CPME method followed by LC-MS/MS was used to determine the ionizable compounds in environmental water samples, including river water and effluent wastewater, with excellent selectivity and matrix effect values below -30% (except -33% for mephedrone) and apparent recovery results ranging from 40% to 69%, except for ibuprofen (< 35%) and atenolol (< 25%). The analytical method was validated for environmental water samples, and used in the analysis of several samples in which some of the target compounds were found at ng L-1 concentration levels.


Assuntos
Microextração em Fase Líquida/métodos , Transição de Fase , Espectrometria de Massas em Tandem/métodos , Poluentes Químicos da Água/análise , Cromatografia Líquida , Concentração de Íons de Hidrogênio , Reprodutibilidade dos Testes , Rios/química , Extração em Fase Sólida/métodos , Fatores de Tempo , Eliminação de Resíduos Líquidos , Águas Residuárias/química , Água/análise
10.
Proc Natl Acad Sci U S A ; 117(28): 16160-16166, 2020 07 14.
Artigo em Inglês | MEDLINE | ID: mdl-32601183

RESUMO

Biomolecules can undergo liquid-liquid phase separation (LLPS), forming dense droplets that are increasingly understood to be important for cellular function. Analogous systems are studied as early-life compartmentalization mechanisms, for applications as protocells, or as drug-delivery vehicles. In many of these situations, interactions between the droplet and enzymatic solutes are important to achieve certain functions. To explore this, we carried out experiments in which a model LLPS system, formed from DNA "nanostar" particles, interacted with a DNA-cleaving restriction enzyme, SmaI, whose activity degraded the droplets, causing them to shrink with time. By controlling adhesion of the DNA droplet to a glass surface, we were able to carry out time-resolved imaging of this "active dissolution" process. We found that the scaling properties of droplet shrinking were sensitive to the proximity to the dissolution ("boiling") temperature of the dense liquid: For systems far from the boiling point, enzymes acted only on the droplet surface, while systems poised near the boiling point permitted enzyme penetration. This was corroborated by the observation of enzyme-induced vacuole-formation ("bubbling") events, which can only occur through enzyme internalization, and which occurred only in systems poised near the boiling point. Overall, our results demonstrate a mechanism through which the phase stability of a liquid affects its enzymatic degradation through modulation of enzyme transport properties.


Assuntos
DNA/química , DNA/metabolismo , Biopolímeros/química , Biopolímeros/metabolismo , Enzimas de Restrição do DNA/metabolismo , Transição de Fase , Temperatura
11.
Environ Sci Pollut Res Int ; 27(30): 38221-38240, 2020 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-32621198

RESUMO

The performance of single slope solar still with an enhanced condenser at different saline water mediums in the basin is studied and assessed based on productivity, energy, exergy, economic, and enviroeconomic methodologies. Six solar still configurations are considered: conventional solar still (CSS); modified solar still (MSS) which is a still with heat sink condenser; MSS having an umbrella (MSS + U); MSS with forced-air cooling (MSS + FA); MSS with forced-water cooling (MSS + FW); and finally, MSS with forced-water cooling and contains sand in the basin (MSS + FW + SD). Experiments are conducted under hot and cold climate conditions of Sohag city, Egypt. The results indicate that the MSS + FW + SD has a maximum daily yield of 5.37 kg/m2 in summer and 2.74 kg/m2 in winter with an increase of 36% in summer and 26% in winter compared with CSS. It was found that the maximum increase of the energy and exergy efficiency compared with CSS is achieved in the case of MSS + FW + SD of 39% and 33%, respectively. Furthermore, the maximum and minimum cost of freshwater is achieved in cases of MSS + U and MSS + FW + SD, respectively. Finally, among all studied systems, MSS + FW + SD achieves the best performance based on the exergoeconomic approach.


Assuntos
Energia Solar , Luz Solar , Temperatura Baixa , Egito , Transição de Fase , Porosidade
12.
Food Chem ; 333: 127538, 2020 Dec 15.
Artigo em Inglês | MEDLINE | ID: mdl-32712546

RESUMO

The effects of water content; 15, 30, and 40% (w/w), water droplet size; d43 15.0-19.6 µm (larger) and d43 1.2-2.7 µm (smaller), and sodium alginate (0.5%, w/w) induced water gelation on crystallization kinetics and water and fat proton relaxation were studied in water-in-milk fat emulsions during in situ cooling from 40 °C to 5 °C. Anhydrous milk fat (AMF) and commercial butter were employed as two separate fat sources. Although emulsions were crystallized faster than the bulk fat, the variations in the water fraction and droplet size did not show major influence on crystallization properties. Smaller droplet size induced significant (p < 0.05) reduction in water mobility with a minimal effect of the temperature. In AMF-based emulsions, gelation of water phase not only immobilized the water molecules but also enhanced the rate of fat crystallization. Globular fat and serum solids in butter-based emulsions showed to fasten the water proton relaxation.


Assuntos
Ácidos Graxos/química , Leite/química , Movimento (Física) , Transição de Fase , Água/química , Animais , Manteiga/análise , Cristalização , Emulsões , Géis , Cinética , Temperatura
13.
Proc Natl Acad Sci U S A ; 117(27): 15650-15658, 2020 07 07.
Artigo em Inglês | MEDLINE | ID: mdl-32571937

RESUMO

Liquid-liquid phase separation of multivalent intrinsically disordered protein-RNA complexes is ubiquitous in both natural and biomimetic systems. So far, isotropic liquid droplets are the most commonly observed topology of RNA-protein condensates in experiments and simulations. Here, by systematically studying the phase behavior of RNA-protein complexes across varied mixture compositions, we report a hollow vesicle-like condensate phase of nucleoprotein assemblies that is distinct from RNA-protein droplets. We show that these vesicular condensates are stable at specific mixture compositions and concentration regimes within the phase diagram and are formed through the phase separation of anisotropic protein-RNA complexes. Similar to membranes composed of amphiphilic lipids, these nucleoprotein-RNA vesicular membranes exhibit local ordering, size-dependent permeability, and selective encapsulation capacity without sacrificing their dynamic formation and dissolution in response to physicochemical stimuli. Our findings suggest that protein-RNA complexes can robustly create lipid-free vesicle-like enclosures by phase separation.


Assuntos
Proteínas Intrinsicamente Desordenadas/química , Lipídeos/química , Nucleoproteínas/química , RNA/química , Anisotropia , Proteínas Intrinsicamente Desordenadas/genética , Lipídeos/genética , Complexos Multiproteicos/química , Complexos Multiproteicos/genética , Nucleoproteínas/genética , Pinças Ópticas , Transição de Fase , RNA/genética
14.
Nature ; 581(7807): 209-214, 2020 05.
Artigo em Inglês | MEDLINE | ID: mdl-32405004

RESUMO

Intracellular bodies such as nucleoli, Cajal bodies and various signalling assemblies represent membraneless organelles, or condensates, that form via liquid-liquid phase separation (LLPS)1,2. Biomolecular interactions-particularly homotypic interactions mediated by self-associating intrinsically disordered protein regions-are thought to underlie the thermodynamic driving forces for LLPS, forming condensates that can facilitate the assembly and processing of biochemically active complexes, such as ribosomal subunits within the nucleolus. Simplified model systems3-6 have led to the concept that a single fixed saturation concentration is a defining feature of endogenous LLPS7-9, and has been suggested as a mechanism for intracellular concentration buffering2,7,8,10. However, the assumption of a fixed saturation concentration remains largely untested within living cells, in which the richly multicomponent nature of condensates could complicate this simple picture. Here we show that heterotypic multicomponent interactions dominate endogenous LLPS, and give rise to nucleoli and other condensates that do not exhibit a fixed saturation concentration. As the concentration of individual components is varied, their partition coefficients change in a manner that can be used to determine the thermodynamic free energies that underlie LLPS. We find that heterotypic interactions among protein and RNA components stabilize various archetypal intracellular condensates-including the nucleolus, Cajal bodies, stress granules and P-bodies-implying that the composition of condensates is finely tuned by the thermodynamics of the underlying biomolecular interaction network. In the context of RNA-processing condensates such as the nucleolus, this manifests in the selective exclusion of fully assembled ribonucleoprotein complexes, providing a thermodynamic basis for vectorial ribosomal RNA flux out of the nucleolus. This methodology is conceptually straightforward and readily implemented, and can be broadly used to extract thermodynamic parameters from microscopy images. These approaches pave the way for a deeper understanding of the thermodynamics of multicomponent intracellular phase behaviour and its interplay with the nonequilibrium activity that is characteristic of endogenous condensates.


Assuntos
Espaço Intracelular/química , Espaço Intracelular/metabolismo , Organelas/química , Organelas/metabolismo , Termodinâmica , Proteínas Adaptadoras de Transdução de Sinal/deficiência , Nucléolo Celular/química , Nucléolo Celular/metabolismo , Corpos Enovelados/química , Corpos Enovelados/metabolismo , Grânulos Citoplasmáticos/química , Grânulos Citoplasmáticos/metabolismo , DNA Helicases/deficiência , Células HeLa , Humanos , Proteínas Nucleares/química , Proteínas Nucleares/metabolismo , Transição de Fase , Proteínas de Ligação a Poli-ADP-Ribose/deficiência , RNA Helicases/deficiência , Proteínas com Motivo de Reconhecimento de RNA/deficiência , RNA Ribossômico/química , RNA Ribossômico/metabolismo , Proteínas de Ligação a RNA , Ribossomos/química , Ribossomos/metabolismo
15.
Proc Natl Acad Sci U S A ; 117(21): 11421-11431, 2020 05 26.
Artigo em Inglês | MEDLINE | ID: mdl-32393642

RESUMO

Phase separation of intrinsically disordered proteins (IDPs) commonly underlies the formation of membraneless organelles, which compartmentalize molecules intracellularly in the absence of a lipid membrane. Identifying the protein sequence features responsible for IDP phase separation is critical for understanding physiological roles and pathological consequences of biomolecular condensation, as well as for harnessing phase separation for applications in bioinspired materials design. To expand our knowledge of sequence determinants of IDP phase separation, we characterized variants of the intrinsically disordered RGG domain from LAF-1, a model protein involved in phase separation and a key component of P granules. Based on a predictive coarse-grained IDP model, we identified a region of the RGG domain that has high contact probability and is highly conserved between species; deletion of this region significantly disrupts phase separation in vitro and in vivo. We determined the effects of charge patterning on phase behavior through sequence shuffling. We designed sequences with significantly increased phase separation propensity by shuffling the wild-type sequence, which contains well-mixed charged residues, to increase charge segregation. This result indicates the natural sequence is under negative selection to moderate this mode of interaction. We measured the contributions of tyrosine and arginine residues to phase separation experimentally through mutagenesis studies and computationally through direct interrogation of different modes of interaction using all-atom simulations. Finally, we show that despite these sequence perturbations, the RGG-derived condensates remain liquid-like. Together, these studies advance our fundamental understanding of key biophysical principles and sequence features important to phase separation.


Assuntos
Proteínas de Caenorhabditis elegans/química , Proteínas Intrinsicamente Desordenadas/química , Substituição de Aminoácidos , Arginina/química , Proteínas de Caenorhabditis elegans/genética , Proteínas de Caenorhabditis elegans/metabolismo , Citoplasma/metabolismo , Interações Hidrofóbicas e Hidrofílicas , Proteínas Intrinsicamente Desordenadas/genética , Proteínas Intrinsicamente Desordenadas/metabolismo , Microrganismos Geneticamente Modificados , Simulação de Dinâmica Molecular , Transição de Fase , Domínios Proteicos , Saccharomyces cerevisiae/genética , Saccharomyces cerevisiae/metabolismo , Temperatura , Tirosina/química
16.
AAPS PharmSciTech ; 21(5): 152, 2020 May 21.
Artigo em Inglês | MEDLINE | ID: mdl-32440782

RESUMO

The present study investigates concomitant processes of solid-state disordering and oxidation of simvastatin during milling. The separate dry ball milling of crystalline and amorphous powders of simvastatin were conducted at ambient temperature for 10 and 60 min each. The relative crystallinity was determined using X-ray scattering and oxidative degradation was analyzed using liquid chromatography. The physical and chemical transformations in the milled powder were evaluated using modulated differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy. The disordering during milling of the crystalline powder was found to progressively decrease the crystallinity. For the amorphous starting material, milling for 10 min induced a large extent of recrystallization, while milling for 60 min largely re-amorphized the powder. This solid-state disordering and/or ordering were accompanied by progressive air oxidation during milling. The infrared spectroscopic analysis revealed the molecular manifestations associated with the physicochemical transformations in the disordered solid states. The melting point of simvastatin depressed systematically with the increase in the degree of disorder as well as the degradation. The in situ cooling in DSC of milled samples from their molten state led to the formation of the co-amorphous phase between the drug and degradation products, which showed a consistent increase in glass transition temperature with the increase in the content of degradation products. The study overall demonstrates the solid-state re-ordering and disordering of crystalline and amorphous simvastatin accompanied by chemical degradation as the consequence of the mechano-activation.


Assuntos
Inibidores de Hidroximetilglutaril-CoA Redutases/química , Sinvastatina/química , Varredura Diferencial de Calorimetria , Análise Diferencial Térmica , Composição de Medicamentos , Inibidores de Hidroximetilglutaril-CoA Redutases/administração & dosagem , Luz , Transição de Fase , Pós , Espalhamento de Radiação , Sinvastatina/administração & dosagem , Espectrofotometria Infravermelho , Raios X
17.
J Oleo Sci ; 69(6): 569-572, 2020 Jun 09.
Artigo em Inglês | MEDLINE | ID: mdl-32404553

RESUMO

The effect of solvent species and quantity of solvent used for spreading on the morphology of Langmuir monolayer composed of palmitic and lignoceric acids was investigated based on atomic force microscopy observations. The variation in domain size depending on the evaporation time of the spreading solution indicated that the mixed monolayer was in a non-equilibrium phase-separated state.


Assuntos
Ácidos Graxos/química , Bicamadas Lipídicas/química , Ácido Palmítico/química , Transição de Fase , Microscopia de Força Atômica , Soluções , Solventes , Propriedades de Superfície , Fatores de Tempo , Volatilização
18.
Artigo em Inglês | MEDLINE | ID: mdl-32375002

RESUMO

Lipid nanoparticle (LNP) packaged mRNA vaccines have been deployed against infectious diseases such as COVID-19, yet their structural features remain unclear. Cholesterol, a major constituent within LNPs, contributes to their morphology that influences gene delivery. Herein, we examine the structure of LNPs containing cholesterol derivatives using electron microscopy, differential scanning calorimetry, and membrane fluidity assays. LNPs formulated with C24 alkyl derivatives of cholesterol show a polymorphic shape and various degrees of multilamellarity and lipid partitioning, likely due to phase separation. The addition of methyl and ethyl groups to the C24 alkyl tail of the cholesterol backbone induces multilamellarity (>50% increase compared to cholesterol), while the addition of a double bond induces lipid partitioning (>90% increase compared to cholesterol). LNPs with multilamellar and faceted structures, as well as a lamellar lipid phase, showed higher gene transfection. Unraveling the structure of mRNA-LNPs can enable their rational design toward enhanced gene delivery.


Assuntos
Colesterol/análogos & derivados , Infecções por Coronavirus/prevenção & controle , Portadores de Fármacos/química , Nanopartículas/química , Pandemias/prevenção & controle , Pneumonia Viral/prevenção & controle , RNA Mensageiro/administração & dosagem , Vacinas Virais/administração & dosagem , Betacoronavirus/isolamento & purificação , Infecções por Coronavirus/genética , Técnicas de Transferência de Genes , Células HeLa , Humanos , Lipídeos/química , Nanopartículas/ultraestrutura , Transição de Fase , Fitosteróis/química , RNA Mensageiro/genética , Transfecção , Vacinas Virais/genética
19.
Nat Chem Biol ; 16(6): 644-652, 2020 06.
Artigo em Inglês | MEDLINE | ID: mdl-32367017

RESUMO

A fundamental feature of cellular plasma membranes (PMs) is an asymmetric lipid distribution between the bilayer leaflets. However, neither the detailed, comprehensive compositions of individual PM leaflets nor how these contribute to structural membrane asymmetries have been defined. We report the distinct lipidomes and biophysical properties of both monolayers in living mammalian PMs. Phospholipid unsaturation is dramatically asymmetric, with the cytoplasmic leaflet being approximately twofold more unsaturated than the exoplasmic leaflet. Atomistic simulations and spectroscopy of leaflet-selective fluorescent probes reveal that the outer PM leaflet is more packed and less diffusive than the inner leaflet, with this biophysical asymmetry maintained in the endocytic system. The structural asymmetry of the PM is reflected in the asymmetric structures of protein transmembrane domains. These structural asymmetries are conserved throughout Eukaryota, suggesting fundamental cellular design principles.


Assuntos
Membrana Celular/metabolismo , Bicamadas Lipídicas/química , Proteínas de Membrana/química , Fosfolipídeos/química , Difusão , Eritrócitos/metabolismo , Corantes Fluorescentes/química , Humanos , Metabolismo dos Lipídeos , Fluidez de Membrana , Microdomínios da Membrana , Imagem Óptica , Transição de Fase , Conformação Proteica , Compostos de Piridínio/química
20.
Sci China Life Sci ; 63(6): 795-810, 2020 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-32249389

RESUMO

Eukaryotic genomes are densely packaged into hierarchical three-dimensional (3D) structures that contain information about gene regulation and many other biological processes. With the development of imaging and sequencing-based technologies, 3D genome studies have revealed that the high-order chromatin structure is composed of hierarchical levels, including chromosome territories, A/B compartments, topologically associated domains, and chromatin loops. However, how this chromatin architecture is formed and maintained is not completely clear. In this review, we introduce experimental methods to investigate the 3D genome, review major architectural proteins that regulate 3D chromatin organization in mammalian cells, such as CTCF (CCCTC-binding factor), cohesin, lamins, and transcription factors, and discuss relevant mechanisms such as phase separation.


Assuntos
Cromatina/genética , Genoma/genética , Animais , Fator de Ligação a CCCTC/genética , Fator de Ligação a CCCTC/metabolismo , Proteínas de Ciclo Celular/genética , Proteínas de Ciclo Celular/metabolismo , Proteínas Cromossômicas não Histona/genética , Proteínas Cromossômicas não Histona/metabolismo , Regulação da Expressão Gênica , Humanos , Laminas/genética , Laminas/metabolismo , Conformação de Ácido Nucleico , Transição de Fase , Fatores de Transcrição/genética , Fatores de Transcrição/metabolismo
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