Bacteria‐Based Production of Thiol‐Clickable, Genetically Encoded Lipid Nanovesicles

International audienceDespite growing research efforts on the preparation of (bio)functional liposomes, synthetic capsules cannot reach the densities of protein loading and the control over peptide display that is achieved by natural vesicles. Here we present a microbial platform for high yield production of lipidic nanovesicles, with clickable thiol moieties in their outer corona. These nanovesicles show low size dispersity, are decorated with a dense, perfectly oriented and customizable corona of transmembrane polypeptides. In addition, this approach enables encapsulation of soluble proteins into the nanovesicles. Due to the mild preparation and loading conditions (absence of organic solvents, pH gradients or detergents) and their straightforward surface functionalization taking advantage of the diversity of commercially-available maleimide derivatives, engineering bacterial-based proteoliposomes are an attractive eco-friendly alternative that can outperform current liposome preparation methods

Polímeros y geles supramoleculares fotosensibles aquirales precursores de materiales quirales

Desde que Pasteur descubrió el fenómeno de la quiralidad en la primera mitad del siglo XIX, al observar la resolución espontánea en cristales de ácido tartárico proveniente del vino, esta se ha convertido en un campo muy estudiado de la química orgánica. Prueba de ello es la gran cantidad de metodologías sintéticas asimétricas y de métodos de separación o resolución de enantiómeros que se han desarrollado y utilizado desde entonces para obtener compuestos químicos quirales. Cuando se logra transferir la quiralidad desde el nivel molecular hasta el nivel supramolecular, se obtienen materiales quirales. Estos materiales a menudo presentan propiedades más interesantes que sus análogos aquirales, lo que hace que sean muy adecuados para aplicaciones avanzadas, como la fabricación de dispositivos ópticos, sensores quirales, catalizadores asimétricos, materiales biomiméticos o materiales con propiedades mecánicas mejoradas. La forma más evidente de preparar materiales quirales es la utilización de compuestos químicos con átomos asimétricos, es decir, moléculas quirales. Sin embargo, en los últimos años la inducción de quiralidad en materiales aquirales utilizando un estímulo quiral externo ha despertado un creciente interés, porque permite obtener materiales quirales sin necesidad de utilizar costosos procedimientos de síntesis o separación asimétricas. De todos los estímulos externos quirales, la luz circularmente polarizada es uno de los más convenientes ya que, ajustando parámetros como la longitud de onda, intensidad y focalización, permite producir cambios localizados en los materiales, tanto en el espacio como en el tiempo. Además, cambiando la helicidad de la luz circularmente polarizada empleada se puede conmutar la quiralidad del material de manera reversible. Nikolova et al. demostraron por primera vez la viabilidad de la utilización de luz circularmente polarizada para fotoinducir quiralidad en materiales fotoactivos, en concreto azopolímeros. Tomando como referencia estos trabajos, en el grupo de Cristales Líquidos y Polímeros de la Universidad de Zaragoza se ha utilizado esta estrategia para obtener materiales quirales a partir de precursores cristales líquido y azopolímeros aquirales, dando lugar a varios capítulos de tesis doctorales y artículos de investigación. Teniendo en cuenta la experiencia adquirida y los antecedentes anteriores, esta tesis doctoral se ha realizado con el objetivo de avanzar en la fabricación de nuevos materiales quirales para aplicaciones ópticas a partir materiales inicialmente aquirales utilizando luz circularmente polarizada. Para ello, se han preparado geles moleculares y polímeros que contienen unidades fotoactivas derivadas de azobenceno, ácido (E)-cinámico y (E,E)-1,4-difenil-1,3-butadieno y se ha utilizado la luz circularmente polarizada como estímulo físico quiral para inducir quiralidad en los mismos. Cabe destacar que, aunque existen un número considerable de ejemplos que describen la fotoinducción de quiralidad en azopolímeros aquirales, prácticamente no existen ejemplos de la fotoinducción de quiralidad empleando otras unidades fotoactivas. Tampoco existen antecedentes, hasta el momento, en los que se utilice la luz circularmente polarizada para fotoinducir quiralidad en geles moleculares aquirales.Peer reviewe

Polarization holograms in a bifunctional amorphous polymer exhibiting equal values of photoinduced linear and circular birefringences

Light-controlled molecular alignment is a flexible and useful strategy introducing novelty in the fields of mechanics, self-organized structuring, mass transport, optics, and photonics and addressing the development of smart optical devices. Azobenzene-containing polymers are well-known photocontrollable materials with large and reversible photoinduced optical anisotropies. The vectorial holography applied to these materials enables peculiar optical devices whose properties strongly depend on the relative values of the photoinduced birefringences. Here is reported a polarization holographic recording based on the interference of two waves with orthogonal linear polarization on a bifunctional amorphous polymer that, exceptionally, exhibits equal values of linear and circular birefringence. The peculiar photoresponse of the material coupled with the holographic technique demonstrates an optical device capable of decomposing the light into a set of orthogonally polarized linear components. The holographic structures are theoretically described by the Jones matrices method and experimentally investigated.The work was supported by European Commission, FSE Regione Calabria and Spanish MINECO project MAT2011-27978-C02-01.Peer Reviewe

Strategies to Stabilize the Photoinduced Supramolecular Chirality in Azobenzene Liquid Crystalline Polymers

This paper describes the synthesis, thermal characterization and optical properties of liquid crystalline homopolymers and block copolymers with a repeating unit consisting of two functional units, with at least one of them being an azobenzene. Films of these polymers have been irradiated with circularly polarized light at room temperature, evaluating the intensity of the photoinduced chiral signal and its temporal stability upon storage. The paper also explores two different strategies to restrict the relaxation of the photoinduced order. Firstly, block copolymers have been prepared to confine the photoaddressable segments into nanoscopic domains where relaxation should be restricted. Secondly, an alternative homopolymer has been synthesized where the repeating unit combines two chromophores that can be separately photoaddressed, an azobenzene unit to efficiently photoinduce chirality and a cinnamate to fix the chiral signal by photocrosslinking

Inducible intracellular membranes: molecular aspects and emerging applications

International audienceMembrane remodeling and phospholipid biosynthesis are normally tightly regulated to maintain the shape and function of cells. Indeed, different physiological mechanisms ensure a precise coordination between de novo phospholipid biosynthesis and modulation of membrane morphology. Interestingly, the overproduction of certain membrane proteins hijack these regulation networks, leading to the formation of impressive intracellular membrane structures in both prokaryotic and eukaryotic cells. The proteins triggering an abnormal accumulation of membrane structures inside the cells (or membrane proliferation) share two major common features: (1) they promote the formation of highly curved membrane domains and (2) they lead to an enrichment in anionic, cone-shaped phospholipids (cardiolipin or phosphatidic acid) in the newly formed membranes. Taking into account the available examples of membrane proliferation upon protein overproduction, together with the latest biochemical, biophysical and structural data, we explore the relationship between protein synthesis and membrane biogenesis. We propose a mechanism for the formation of these non-physiological intracellular membranes that shares similarities with natural inner membrane structures found in α-proteobacteria, mitochondria and some viruses-infected cells, pointing towards a conserved feature through evolution. We hope that the information discussed in this review will give a better grasp of the biophysical mechanisms behind physiological and induced intracellular membrane proliferation, and inspire new applications, either for academia (high-yield membrane protein production and nanovesicle production) or industry (biofuel production and vaccine preparation)

Preparation of side-chain liquid crystalline Azopolymers by CuAAC postfunctionalization using bifunctional azides: Induction of chirality using circularly polarized light

Well-defined side-chain liquid crystal azopolymers have been synthesized by click chemistry of poly(propargyl methacrylate) with bifunctional liquid crystalline azides to produce materials with large degrees of functionalization. A polymeric scaffold having pendant alkyne groups was prepared by atom transfer radical polymerization (ATRP) and postfunctionalized by copper(I)-catalyzed azide-alkyne cycloaddition (CuAAC) using homo- and heterobifunctional azides. The azides are derivatives of 2,2-bis(hydroxymethyl)propanoic acid (bis-MPA) containing photoresponsive azobenzene and/or liquid crystalline biphenyl moieties. The approach is a convenient alternative to increase the density of functional units in side-chain polymers having moderate polymerization degrees and to modulate the properties of the final material. The article describes the synthesis, characterization, and liquid crystalline properties of the obtained polymers. The effect of the chemical structure and the possible cooperative effects between functional units in the photo-induction of chirality are also evaluated. A switchable photo-transference of chirality from the circularly polarized light (CPL) to material has been achieved. © 2012 Wiley Periodicals, Inc.This work was supported by the Ministerio de Ciencia e Innovación (MICINN), under the project MAT2008-06522- C01, Fondo Europeo de Desarrollo Regional (FEDER), and Gobierno de Aragón funding. N. Gimeno acknowledges CSIC for a JAE-DOC contract.Peer Reviewe

Chiral supramolecular organization from a sheetlike achiral gel: a study of chiral photoinduction

Chiral photoinduction in a photoresponsive gel based on an achiral 2D architecture with high geometric anisotropy and low roughness has been investigated. Circularly polarized light (CPL) was used as a chiral source and an azobenzene chromophore was employed as a chiral trigger. The chiral photoinduction was studied by evaluating the preferential excitation of enantiomeric conformers of the azobenzene units. Crystallographic data and density functional theory (DFT) calculations show how chirality is transferred to the achiral azomaterials as a result of the combination of chiral photochemistry and supramolecular interactions. This procedure could be applied to predict and estimate chirality transfer from a chiral physical source to a supramolecular organization using different light-responsive units.This work was supported by the Ministerio de Economia y Competitividad, under the project MAT2014-55205-P, Fondo Europeo de Desarrollo Regional (FEDER) and Gobierno de Aragon. The authors acknowledge the Laboratory of Advanced Microscopy Laboratory (LMA) of the Universidad de Zaragoza (Unizar) and CEQMA (CSIC-Unizar) for the NMR, MS, EA and thermal analysis general facilities. The authors additionally acknowledge the use of the Servicio General de Apoyo a la Investigacion of the Universidad de Zaragoza. General Research Services SGIker technical support from UPV/EHU (MEC, GV/EJ, European Social Fund) is gratefully acknowledged.Peer reviewe

Effect of the polymer architecture on the photoinduction of stable chiral organizations

The paper presents a series of light responsive block copolymers that have been prepared by sequential polymerization of propargyl methacrylate and methyl methacrylate by atom transfer radical polymerization (ATRP). The pendant alkyne groups of the poly (propargyl methacrylate) block have been subsequently modified with azides from 2,2-bis(hydroxymethyl)propanoic acid decorated with two motifs, either two azobenzenes or one azobenzene and one biphenyl. This general and versatile synthetic approach simplifies the rational inclusion of structural modifications onto these polymers and, thus, establishing structure-properties relationships as a way to tailor the final properties of the material. By polymerizing the poly(propargyl methacrylate) firstly and poly(methyl methacrylate) secondly, block copolymers with low mass fractions, i.e. highly diluted contents, of the photoresponsive block have been achieved where the effect of the polymeric architecture on the induction of chirality using circularly polarized light (CPL) and its temporal stability has been evaluated. The relevance of the liquid crystallinity on the photoinduction of chirality in the block copolymers has also been investigated mainly in relation to thick films of good optical quality.This work was supported by the Ministerio de Economía y Competitividad, under the project MAT2014-55205-P, Fondo Europeo de Desarrollo Regional (FEDER) and Gobierno de Aragón.The authors acknowledge the Laboratory of Advanced MicroscopyLaboratory (LMA) of the Universidad de Zaragoza and CEQMA(Consejo Superior de Investigaciones Científicas-Universidad deZaragoza) for the NMR, MS, EA and thermal analysis general facil-ities. The authors thank M. Sztucki for assistance during measure-ments in ID2 at ESRF. The authors additionally acknowledge the use of the Servicio General de Apoyo a la Investigación of the Universidad de ZaragozaPeer Reviewe

Quantitative kinetic modeling in photoresponsive supramolecular chemistry: the case of water-soluble azobenzene/cyclodextrin complexes

International audienc

Bacteria-Based Production of Thiol-Clickable, Genetically Encoded Lipid Nanovesicles

Despite growing research efforts on the preparation of (bio)functional liposomes, synthetic capsules cannot reach the densities of protein loading and the control over peptide display that is achieved by natural vesicles. Herein, a microbial platform for high-yield production of lipidic nanovesicles with clickable thiol moieties in their outer corona is reported. These nanovesicles show low size dispersity, are decorated with a dense, perfectly oriented, and customizable corona of transmembrane polypeptides. Furthermore, this approach enables encapsulation of soluble proteins into the nanovesicles. Due to the mild preparation and loading conditions (absence of organic solvents, pH gradients, or detergents) and their straightforward surface functionalization, which takes advantage of the diversity of commercially available maleimide derivatives, bacteria-based proteoliposomes are an attractive eco-friendly alternative that can outperform currently used liposomes