Lipid packing determines protein-membrane interactions: Challenges for apolipoprotein A-I and high density lipoproteins

Protein and protein-lipid interactions, with and within specific areas in the cell membrane, are critical in order to modulate the cell signaling events required to maintain cell functions and viability. Biological bilayers are complex, dynamic platforms, and thus in vivo observations usually need to be preceded by studies on model systems that simplify and discriminate the different factors involved in lipid-protein interactions. Fluorescence microscopy studies using giant unilamellar vesicles (GUVs) as membrane model systems provide a unique methodology to quantify protein binding, interaction, and lipid solubilization in artificial bilayers. The large size of lipid domains obtainable on GUVs, together with fluorescence microscopy techniques, provides the possibility to localize and quantify molecular interactions. Fluorescence Correlation Spectroscopy (FCS) can be performed using the GUV model to extract information on mobility and concentration. Two-photon Laurdan Generalized Polarization (GP) reports on local changes in membrane water content (related to membrane fluidity) due to protein binding or lipid removal from a given lipid domain. In this review, we summarize the experimental microscopy methods used to study the interaction of human apolipoprotein A-I (apoA-I) in lipid-free and lipid-bound conformations with bilayers and natural membranes. Results described here help us to understand cholesterol homeostasis and offer a methodological design suited to different biological systems.Instituto de Investigaciones Bioquímicas de La PlataFacultad de Ciencias Médica

Lipid—Protein Interactions Revealed by Two-Photon Microscopy and Fluorescence Correlation Spectroscopy

Cellular processes involve a multitude of chemical reactions that must be kept in delicate equilibrium to maintain cellular homeostasis. Powerful biophysical techniques are needed to measure the localization and concentration of target molecules as well as to quantify complex molecular processes in model and in vivo systems. Two-photon microscopy and fluorescence correlation spectroscopy (FCS) can measure association and dynamics of appropriate molecules under equilibrium conditions. FCS provides information on motility (diffusion coefficients), concentration (number of particles), association (molecular brightness), and localization (image) of the target molecules. All of this information, in conjunction with computational modeling techniques, can help us to better understand the network of complex molecular interactions, which are at the basis of cellular processes. Fluorescence imaging techniques add the beauty of visualization to the scientific information. Photons emitted by a fluorescent dye are digitized, and the associated spatial information and intensity can be translated into different colors and shades providing the researcher not only with quantitative intensity information but also with spatial resolution and visual comprehension of two- or three-dimensional images. In this Account, we review the use of two-photon excitation microscopy and FCS in the study of lipid-protein interactions. We discuss these new methodologies and techniques, and we present examples of different complexity from qualitative to quantitative, from simple model systems to studies in living cells

Visualization and analysis of lipopolysaccharide distribution in binary phospholipid bilayers

Lipopolysaccharide (LPS) is an endotoxin released from the outer membrane of Gram-negative bacteria during infections. It have been reported that LPS may play a role in the outer membrane of bacteria similar to that of cholesterol in eukaryotic plasma membranes. In this article we compare the effect of introducing LPS or cholesterol in liposomes made of dipalmitoylphosphatidylcholine/dioleoylphosphatidylcholine on the solubilization process by Triton X-100. The results show that liposomes containing LPS or cholesterol are more resistant to solubilization by Triton X-100 than the binary phospholipid mixtures at 4 °C. The LPS distribution was analyzed on GUVs of DPPC:DOPC using FITC-LPS. Solid and liquid-crystalline domains were visualized labeling the GUVs with LAURDAN and GP images were acquired using a two-photon microscope. The images show a selective distribution of LPS in gel domains. Our results support the hypothesis that LPS could aggregate and concentrate selectively in biological membranes providing a mechanism to bring together several components of the LPS-sensing machinery.Instituto de Investigaciones Bioquímicas de La Plat

Charge ordering and dielectric properties in the near half-doped Pr0.79Na0.21MnO3 perovskite

[Abstract] The Pr0.79Na0.21MnO3 perovskite has been prepared in polycrystalline form by a ceramic method. We have carried out its structural characterization by synchrotron X-ray powder diffraction (SXRPD) at room temperature and at 150 K (T<TCO). In the charge ordering (CO) state, the SXRPD data can be refined both on the basis of the site-centred model and the bond-centred model proposed for half-doped manganites, without a clear advantage of one model over the other. From the dielectric point of view, at the CO temperature this manganite shows a maximum in the dielectric constant whose origin is intrinsic, and cannot be attributed to the presence of extrinsic factors. We relate this dielectric behaviour to the formation of polar entities at the temperature of charge condensation, due to an asymmetric charge distribution intermediate between site-centred and bond-centred type.Xunta de Galicia; PGIDIT06PXB103298PRMinisterio de Educación y Ciencia; Project FEDER MAT 2004-0513

PEO: An immobile solvent?

Despite used for half a century as host for salt-polymer complexes, PEO is still not a fossil and due to its availability, remains regularly used as a reference in solvent-free polymer electrolytes and related electrochemical cells. Often qualified as macromolecular solvent or immobile solvent, its drawbacks (crystallinity, mechanical strength) are well identified. On the other hand, its electrolyte conductivity maxima are considered as the best possible in absence of molecular solvents or ionic liquids. The comparison of PEO/LiTFSI based on raw PEO and ultrafiltrated one, shows unambiguously the impact of unentangled oligomers not only on ionic transport but also on mechanical behavior. Conductivity, cationic transference numbers and storage modulus data go in the same direction and the cationic conductivity (O/Li = 30) is divided by 2, following PEO purification.Jean-Yves Sanchez acknowledges the CONEX Programme, funding received from Universidad Carlos III de Madrid, the European Union's Seventh Framework Programme for research, technological development and demonstration (Grant agreement nº 600371), Spanish Ministry of Economy and Competitiveness (COFUND2013-40258) and Banco Santander. Amadou Thiam acknowledges ANR for his fellowship. Yannick Molméret acknowledges KICINNO Energy for the granting of his post-doc fellowship, in the frame of the project PENLiB coordinated by Prof. Jean-Yves Sanchez

Emergency agreements. Covid-19 and women in federal prison

En el siguiente trabajo, nos proponemos analizar las Acordadas 2, 3, y 9 de la Cámara Federal de Casación Penal, con la impronta de hacer explicitas las razones dadas por parte de este tribunal respecto a las cuestiones referentes a la situación de las mujeres en cárceles en el contexto de la pandemia COVID-19.Dossier: Covid-19 y DerechoFacultad de Ciencias Jurídicas y Sociale

Acuerdos de emergencia

&nbsp; &nbsp;En el siguiente trabajo, nos proponemos analizar las Acordadas 2, 3, y 9 de la Cámara Federal de Casación Penal, con la impronta de hacer explicitas las razones dadas por parte de este tribunal respecto a las cuestiones referentes a la situación de las mujeres en cárceles en el contexto de la pandemia COVID-19. Esto es, detallar cuáles son las medidas de protección adoptadas y, además, cuáles deberían ser los procedimientos a seguir toda vez que se requiera hacer efectiva alguna protección de derechos y garantías en el ámbito carcelario, respecto a mujeres privadas de su libertad, mujeres embarazadas o con hijos a cargo, haciendo una distinción respecto de aquellos niños/as que se encuentren o no alojados en prisión. Para este último supuesto, nos valdremos del análisis de los argumentos de dos fallos resueltos por la Cámara Federal de Casación Penal, en el período del aislamiento preventivo y obligatorio, tomando como muestra dos casos en los que se resolvió de manera divergente

Investigating the electronic properties and structural features of MgH and of MgH−anions

[EN]In the present paper we analyze in detail several properties of the MgH − anion and the MgH neutral molecule using accurate ab initio quantum computational methods in order to establish with a higher reliability specific molecular features like the gas-phase electron affinity, the Franck-Condon factors for excitation of the neutral and of its anion to their lower electronic states, and the general feasibility of employing the anion in photodetachment experiments after its confinement in cold ion traps. The calculations suggest that the electron affinity value is in agreement with an existing early experiment and, further, places on it an error bar smaller than that given before. Accurate zero-point-energy corrections are also included in our calculations and their effects discussed

The Role of Developmental Assets in Gender Differences in Anxiety in Spanish Youth

Anxiety disorders are the most prevalent psychological disorders during emerging adulthood. Some consistent gender differences have been reported in anxiety with women suffering more anxiety than men, which has detrimental consequences in most life spheres in the youth and later life stages. The understanding of the development of anxiety in emerging adulthood requires a developmental perspective. The Developmental Assets Theory was postulated to describe the individual and the contextual resources which may foster positive youth development and mental health. The present study aims to analyze to what extent the gender differences in anxiety may be partly explained by gender differences in developmental assets. For this purpose, a cross-sectional study was conducted in which a sample of 1,044 youths (75.5% women; age range = 18–28; M age = 20.47, SD = 3.08) enrolled in 11 universities from different regions in Spain filled in self-report measures of developmental assets and anxiety symptoms. The participants completed an online survey with the scales, Developmental Assets Profile developed by the Search Institute (1) and Generalized Anxiety Disorder-7 (GAD-7) (2). The results showed more anxiety in the female subsample (at both the symptoms and clinical levels). Some gender differences in developmental assets were also observed. A partial mediation model, based on regression analyses, indicated that gender differences in anxiety were partly explained by gender differences in developmental assets. Thus, higher anxiety in the women was partly due to lower scores in positive identity and higher scores in positive values. These results suggested the need to design programs to prevent anxiety with specific measures for women youth to nurture positive identity and promote strengths and coping skills that allow them to get the benefits of well-being derived from positive values, thus, preventing worry and stress overload, which may lead to anxiety.This research received funding from Research, Development and Innovation Projects of European Regional Development Fund in Andalusia 2014–2020. Grant number UHU-1259711, awarded to the first and last authors