Institute Of Nanociencia I Nanotecnologia In2Ub

Sant Martí, Spain

Institute Of Nanociencia I Nanotecnologia In2Ub

Sant Martí, Spain
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Catala F.,University of Barcelona | Catala F.,Institute Of Nanociencia I Nanotecnologia In2Ub | Marsa F.,Institute Of Nanociencia I Nanotecnologia In2Ub | Marsa F.,Optics 1 | And 6 more authors.
Scientific Reports | Year: 2017

Optical trapping has become an optimal choice for biological research at the microscale due to its non-invasive performance and accessibility for quantitative studies, especially on the forces involved in biological processes. However, reliable force measurements depend on the calibration of the optical traps, which is different for each experiment and hence requires high control of the local variables, especially of the trapped object geometry. Many biological samples have an elongated, rod-like shape, such as chromosomes, intracellular organelles (e.g., peroxisomes), membrane tubules, certain microalgae, and a wide variety of bacteria and parasites. This type of samples often requires several optical traps to stabilize and orient them in the correct spatial direction, making it more difficult to determine the total force applied. Here, we manipulate glass microcylinders with holographic optical tweezers and show the accurate measurement of drag forces by calibration-free direct detection of beam momentum. The agreement between our results and slender-body hydrodynamic theoretical calculations indicates potential for this force-sensing method in studying protracted, rod-shaped specimens. © The Author(s) 2017.

Suarez-Germa C.,University of Barcelona | Suarez-Germa C.,Institute Of Nanociencia I Nanotecnologia In2Ub | Loura L.M.S.,University of Coimbra | Domenech O.,University of Barcelona | And 6 more authors.
Journal of Physical Chemistry B | Year: 2012

In this work we have investigated the selectivity of lactose permease (LacY) of Escherichia coli (E. coli) for its surrounding phospholipids when reconstituted in binary mixtures of 1-palmitoyl-2-oleoyl-sn-glycero-3- phosphoethanolamine (POPE), 1,2-Palmitoyl-sn-glycero-3-phosphoethanolamine (DPPE), or 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine (DOPE) with 1-palmitoyl-2-oleoyl-sn-glycero-3-(phospho-rac-(1-glycerol)) (POPG). Förster resonance energy transfer (FRET) measurements have been performed to investigate the selectivity between a single tryptophan mutant of LacY used as donor (D), and two analogues of POPE and POPG labeled with pyrene in the acyl chains (Pyr-PE and Pyr-PG) used as acceptors. As a difference from previous works, now the donor has been single-W151/C154G/D68C LacY. It has been reported that the replacement of the aspartic acid in position 68 by cysteine inhibits active transport in LacY. The objectives of this work were to elucidate the phospholipid composition of the annular region of this mutant and to determine whether the mutation performed, D68C, induced changes in the protein-lipid selectivity. FRET efficiencies for Pyr-PE were always higher than for Pyr-PG. The values of the probability of each site in the annular ring being occupied by a label (μ) were similar at the studied temperatures (24 °C and 37 °C), suggesting that the lipid environment is not significantly affected when increasing the temperature. By comparing the results with those obtained for single-W151/C154G LacY, we observe that the mutation in the 68 residue indeed changes the selectivity of the protein for the phospholipids. This might be probably due to a change in the conformational dynamics of LacY. © 2012 American Chemical Society.

Espargaro A.,Autonomous University of Barcelona | Villar-Pique A.,Autonomous University of Barcelona | Sabate R.,University of Barcelona | Sabate R.,Institute Of Nanociencia I Nanotecnologia In2Ub | Ventura S.,Autonomous University of Barcelona
Microbial Cell Factories | Year: 2012

Background: Prions were first identified as infectious proteins associated with fatal brain diseases in mammals. However, fungal prions behave as epigenetic regulators that can alter a range of cellular processes. These proteins propagate as self-perpetuating amyloid aggregates being an example of structural inheritance. The best-characterized examples are the Sup35 and Ure2 yeast proteins, corresponding to [PSI+] and [URE3] phenotypes, respectively.Results: Here we show that both the prion domain of Sup35 (Sup35-NM) and the Ure2 protein (Ure2p) form inclusion bodies (IBs) displaying amyloid-like properties when expressed in bacteria. These intracellular aggregates template the conformational change and promote the aggregation of homologous, but not heterologous, soluble prionogenic molecules. Moreover, in the case of Sup35-NM, purified IBs are able to induce different [PSI+] phenotypes in yeast, indicating that at least a fraction of the protein embedded in these deposits adopts an infectious prion fold.Conclusions: An important feature of prion inheritance is the existence of strains, which are phenotypic variants encoded by different conformations of the same polypeptide. We show here that the proportion of infected yeast cells displaying strong and weak [PSI+] phenotypes depends on the conditions under which the prionogenic aggregates are formed in E. coli, suggesting that bacterial systems might become useful tools to generate prion strain diversity. © 2012 Espargaró et al.; licensee BioMed Central Ltd.

Cortes M.,Institute Of Nanociencia I Nanotecnologia In2Ub | Gomez E.,Institute Of Nanociencia I Nanotecnologia In2Ub | Valles E.,Institute Of Nanociencia I Nanotecnologia In2Ub
Electrochemistry Communications | Year: 2010

CoPt particles of different size and modulate magnetic properties have been prepared by electrodeposition. Particles of growing size from 50 nm until continuous deposits have been obtained and their composition, crystalline structure and magnetic properties have been analyzed. The prepared CoPt particles from 50 nm to 250 nm showed ferromagnetic behaviour so did the continuous deposits. However, drastic changes in magnetism have been detected related to the size of the particles: the smallest particles presented lower coercivity which increases with increasing size, with a maximum value for particles of 150-250 nm diameter. The coercivity decreased when continuous deposits were attained due to the disordered growing and the loss of the surface anisotropy. © 2009 Elsevier B.V. All rights reserved.

Suarez-Germa C.,Facultat de Farmacia | Suarez-Germa C.,Institute Of Nanociencia I Nanotecnologia In2Ub | Morros A.,Unitat de Biofisica | Montero M.T.,Facultat de Farmacia | And 5 more authors.
Chemistry and Physics of Lipids | Year: 2014

In this work we studied a binary lipid matrix of 1-palmitoyl-2-oleoyl-sn- glycero-3-phosphoethanolamine (POPE) and 1-palmitoyl-2-oleoyl-sn-glycero-3- phospho-(1′-rac-glycerol) (POPG), a composition that mimics the inner membrane of Escherichia coli. More specifically, liposomes with varying fractions of POPG were analysed by differential scanning calorimetry (DSC) and a binary phase diagram of the system was created. Additionally, we performed atomic force microscopy (AFM) imaging of supported lipid bilayers (SLBs) of similar compositions at different temperatures, in order to create a pseudo-binary phase diagram specific to this membrane model. AFM study of SLBs is of particular interest, as it is conceived as the most adequate technique not only for studying lipid bilayer systems but also for imaging and even nanomanipulating inserted membrane proteins. The construction of the above-mentioned phase diagram enabled us to grasp better the thermodynamics of the thermal lipid transition from a gel-like POPE:POPG phase system to a more fluid phase system. Finally, AFM force spectroscopy (FS) was used to determine the nanomechanics of these two lipid phases at 27 °C and at different POPG fractions. The resulting data correlated with the specific composition of each phase was calculated from the AFM phase diagram obtained. All the experiments were done in the presence of 10 mM of Ca2+, as this ion is commonly used when performing AFM with negatively charged phospholipids. © 2014 Elsevier Ireland Ltd.

Serra-Peinado C.,University of Barcelona | Sicart A.,University of Barcelona | Sicart A.,Catholic University of Leuven | Llopis J.,University of Castilla - La Mancha | And 3 more authors.
Journal of Biological Chemistry | Year: 2016

We previously reported that actin-depolymerizing agents promote the alkalization of the Golgi stack and the trans-Golgi network. The main determinant of acidic pH at the Golgi is the vacuolar-type H+-translocating ATPase (V-ATPase), whose V1 domain subunits B and C bind actin. We have generated a GFPtagged subunit B2 construct (GFP-B2) that is incorporated into theV1 domain, which in turn is coupled to theV0 sector. GFP-B2 subunit is enriched at distal Golgi compartments in HeLa cells. Subcellular fractionation, immunoprecipitation, and inversal FRAP experiments show that the actin depolymerization promotes the dissociation of V1-V0 domains, which entails subunit B2 translocation from Golgi membranes to the cytosol. Moreover, molecular interaction between subunits B2 and C1 and actin were detected. In addition, Golgi membrane lipid order disruption by D-ceramide-C6 causes Golgi pH alkalization. We conclude that actin regulates the Golgi pH homeostasis maintaining the coupling of V1-V0 domains of V-ATPase through the binding of microfilaments to subunits B and C and preserving the integrity of detergent-resistant membrane organization. These results establish the Golgi-associated V-ATPase activity as the molecular link between actin and the Golgi pH. © 2016 by The American Society for Biochemistry and Molecular Biology, Inc.

Suarez-Germa C.,Institute Of Nanociencia I Nanotecnologia In2Ub | Domenech O.,Institute Of Nanociencia I Nanotecnologia In2Ub | Montero M.T.,Institute Of Nanociencia I Nanotecnologia In2Ub | Hernandez-Borrell J.,Institute Of Nanociencia I Nanotecnologia In2Ub
Biochimica et Biophysica Acta - Biomembranes | Year: 2014

In this paper we present a comparative study of supported lipid bilayers (SLBs) and proteolipid sheets (PLSs) obtained from deposition of lactose permease (LacY) of Escherichia coli proteoliposomes in plane. Lipid matrices of two components, phosphatidylethanolamine (PE) and phosphatidylglycerol (PG), at a 3:1, mol/mol ratio, were selected to mimic the inner membrane of the bacteria. The aim was to investigate how species of different compactness and stiffness affect the integration, distribution and nanomechanical properties of LacY in mixtures of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphoethanolamine (POPE) or 1,2-palmitoyl-sn-glycero-3-phosphoethanolamine (DPPE) with 1-palmitoyl-2-oleoyl- sn-glycero-3-[phospho-rac-(1-glycerol)] (POPG). Both compositions displayed phase separation and were investigated by atomic force microscopy (AFM) imaging and force-spectroscopy (FS) mode. PLSs displayed two separated, segregated domains with different features that were characterised by FS and force-volume mode. We correlated the nanomechanical characteristics of solid-like gel phase (Lβ) and fluid liquid-crystalline phase (Lα) with phases emerging in presence of LacY. We observed that for both compositions, the extended PLSs showed a Lβ apparently formed only by lipids, whilst the second domain was enriched in LacY. The influence of the lipid environment on LacY organisation was studied by performing protein unfolding experiments using the AFM tip. Although the pulling experiments were unspecific, positive events were obtained, indicating the influence of the lipid environment when pulling the protein. A possible influence of the lateral surface pressure on this behaviour is suggested by the higher force required to pull LacY from DPPE:POPG than from POPE:POPG matrices. This is related to higher forces governing protein-lipid interaction in presence of DPPE. © 2013 Elsevier B.V.

Garcia-Torres J.,Institute Of Nanociencia I Nanotecnologia In2Ub | Gomez E.,Institute Of Nanociencia I Nanotecnologia In2Ub | Valles E.,Institute Of Nanociencia I Nanotecnologia In2Ub
Materials Chemistry and Physics | Year: 2010

The influence of sulphur incorporation during electrodeposition on the structural and magnetic properties of both Co and Co-Ag thin films from aqueous thiosulphate solutions has been investigated. Co-Ag deposits containing sulphur showed granular morphology and varying cobalt and sulphur contents as a function of the applied potential. Nanocrystalline soft-magnetic deposits whose coercivity decreased as sulphur incorporation increased were obtained. More influence of the sulphur presence on the cobalt thin film magnetic properties was observed due to the significant structural changes induced by sulphur incorporation into the crystalline lattice. When high amounts of S were present, soft-magnetic amorphous cobalt coatings were obtained. On the other hand, stronger hard-magnetic behaviour was detected on those crystalline thin films where S content was lesser. © 2010 Elsevier B.V. All rights reserved.

Estelrich J.,University of Barcelona | Estelrich J.,Institute Of Nanociencia I Nanotecnologia In2Ub | Sanchez-Martin M.J.,University of Barcelona | Busquets M.A.,University of Barcelona | Busquets M.A.,Institute Of Nanociencia I Nanotecnologia In2Ub
International Journal of Nanomedicine | Year: 2015

Magnetic resonance imaging (MRI) has become one of the most widely used and powerful tools for noninvasive clinical diagnosis owing to its high degree of soft tissue contrast, spatial resolution, and depth of penetration. MRI signal intensity is related to the relaxation times (T1, spin–lattice relaxation and T2, spin–spin relaxation) of in vivo water protons. To increase contrast, various inorganic nanoparticles and complexes (the so-called contrast agents) are administered prior to the scanning. Shortening T1 and T2 increases the corresponding relaxation rates, 1/T1 and 1/T2, producing hyperintense and hypointense signals respectively in shorter times. Moreover, the signal-to-noise ratio can be improved with the acquisition of a large number of measurements. The contrast agents used are generally based on either iron oxide nanoparticles or ferrites, providing negative contrast in T2-weighted images; or complexes of lanthanide metals (mostly containing gadolinium ions), providing positive contrast in T1-weighted images. Recently, lanthanide complexes have been immobilized in nanostructured materials in order to develop a new class of contrast agents with functions including blood-pool and organ (or tumor) targeting. Meanwhile, to overcome the limitations of individual imaging modalities, multimodal imaging techniques have been developed. An important challenge is to design all-in-one contrast agents that can be detected by multimodal techniques. Magnetoliposomes are efficient multimodal contrast agents. They can simultaneously bear both kinds of contrast and can, furthermore, incorporate targeting ligands and chains of polyethylene glycol to enhance the accumulation of nanoparticles at the site of interest and the bioavailability, respectively. Here, we review the most important characteristics of the nanoparticles or complexes used as MRI contrast agents. © 2015 Estelrich et al.

PubMed | Institute Of Nanociencia I Nanotecnologia In2Ub
Type: Journal Article | Journal: The journal of physical chemistry. B | Year: 2012

Frster resonance energy transfer (FRET) is a powerful method for the characterization of membrane proteins lipid selectivity. FRET can be used to quantify distances between a single donor and a single acceptor molecule; however, for FRET donors and acceptors scattered in the bilayer plane, multiple donor-acceptor pairs and distances are present. In addition, when studying protein/lipid selectivity, for a single tryptophan used as a donor; several lipid acceptors may be located at the boundary region (annular lipids) of the protein. Therefore, in these experiments, a theoretical analysis based on binomial distribution of multiple acceptors around the membrane proteins is required. In this work, we performed FRET measurements between single tryptophan lactose permease (W151/C154G LacY) of Escherichia coli and pyrene-labeled phospholipids (Pyr-PE, Pyr-PG, and Pyr-PC) reconstituted in palmitoyl-2-oleoyl-sn-glycero-3-phosphoethanolamine, 1-palmitoyl-2-oleoyl-sn-glycero-3-[phospho-rac-(1-glycerol)] (sodium salt), 1-palmitoyl-2-oleoyl-sn-glycero-3-phospho-choline, and 1,2-dioleoyl-sn-glycero-3-phospho-choline at 25 and 37 C. To increase the sensitivity of the method and to ascertain the lipid selectivity for LacY, we reconstituted the protein in the pure phospholipids doped with 1.5% of labeled phospholipids. From fitting the theoretical model to the experimental FRET efficiencies, two parameters were calculated: the probability of a site in the annular ring being occupied by a labeled pyrene phospholipid and the relative association constant between the labeled and unlabeled phospholipids. The experimental FRET efficiencies have been interpreted taking into account the particular folding of the protein in each phospholipid matrix. Additional information on the annular lipid composition for each system has been obtained by exciting W151/C154G LacY and monitoring the emission intensities for monomer and excimer of the pyrene spectra. The results obtained indicate a higher selectivity of LacY for PE over PG and PC and pointed to a definite role of the acyl chains in the overall phospholipid-protein interaction.

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