RESUMEN

The zwitterions resulting from the covalent attachment of 3- or 4-hydroxy benzene to the 1,3-dimethylimidazolium cation represent basic compounds (pKa of 8.68 and 8.99 in aqueous solutions, respectively) that chemisorb in aqueous solutions 0.58 mol/mol of carbon dioxide at 1.3 bar (absolute) and 40 °C. Equimolar amounts of chemisorbed CO2 in these solutions are obtained at 10 bar and 40 °C. Chemisorption takes place through the formation of bicarbonate in the aqueous solution using imidazolium-containing phenolate. CO2 is liberated by simple pressure relief and heating, regenerating the base. The enthalpy of absorption was estimated to be -38 kJ/mol, which is about 30 % lower than the enthalpy of industrially employed aqueous solutions of MDEA (estimated at -53 kJ/mol using the same experimental apparatus). The physisorption of CO2 becomes relevant at higher pressures (>10 bar) in these aqueous solutions. Combined physio- and chemisorption of up to 1.3 mol/mol at 40 bar and 40 °C can be attained with these aqueous zwitterionic solutions that are thermally stable and can be recycled at least 20 times.

RESUMEN

The simple photolysis of CO2 in aqueous solutions to generate CO and/or hydrocarbons and derivatives in the presence of a catalyst is considered to be a clean and efficient approach for utilizing CO2 as a C1 building block. Despite the huge efforts dedicated to this transformation using either semiconductors or homogeneous catalysts, only small improvements of the catalytic activity have been achieved so far. This article reports that simple aqueous solutions of organic salts-denominated as ionic liquids-can efficiently photo-reduce CO2 to CO without using photosensitizers or sacrificial agents. The system relies on the formation of the [CO2 ].- intermediate through homolytic C-C bond cleavage in a cation-CO2 adduct of imidazolium-based ionic liquids (ILs). The system continuously produced CO up to 2.88 mmol g-1 of IL after 40 h of irradiation by using an aqueous solution of 1-n-butyl-3-methylimidazolium-2-carboxylate (BMIm.CO2 ) IL, representing an apparent quantum yield of 3.9 %. The organophotocatalytic principles of our system may help to develop more simple and efficient organic materials for the production of solar fuels from CO2 under mild conditions, which represents a real alternative to those based on semiconductors and homogeneous metal-based catalysts.

RESUMEN

Echinococcus granulosus antigen B is an oligomeric protein of 120-160 kDa composed by 8-kDa (AgB8) subunits. Here, we demonstrated that the AgB8 recombinant subunits AgB8/1, AgB8/2 and AgB8/3 are able to self-associate into high order homo-oligomers, showing similar properties to that of parasite-produced AgB, making them valuable tools to study AgB structure. Dynamic light scattering, size exclusion chromatography and cross-linking assays revealed approximately 120- to 160-kDa recombinant oligomers, with a tendency to form populations with different aggregation states. Recombinant oligomers showed helical circular dichroism spectra and thermostability similar to those of purified AgB. Cross-linking and limited proteolysis experiments indicated different degrees of stability and compactness between the recombinant oligomers, with the AgB8/3 one showing a more stable and compact structure. We have also built AgB8 subunit structural models in order to predict the surfaces possibly involved in electrostatic and hydrophobic interactions during oligomerization.

Asunto(s)

Antígenos Helmínticos/química , Echinococcus granulosus/inmunología , Secuencia de Aminoácidos , Animales , Antígenos Helmínticos/inmunología , Biopolímeros , Cromatografía en Gel , Dicroismo Circular , Modelos Moleculares , Datos de Secuencia Molecular , Conformación Proteica , Estructura Secundaria de Proteína , Proteínas Recombinantes/química , Proteínas Recombinantes/inmunología , Homología de Secuencia de Aminoácido , Espectrometría de Fluorescencia , Electricidad Estática