Any chemist studying the interaction of molecules with lipid assemblies will eventually be confronted by the topic of membrane bilayer heterogeneity and may ultimately encounter the heterogeneity of natural membranes. In artificial bilayers, heterogeneity is defined by phase segregation that can be in the nano-and micrometer range. In biological bilayers, heterogeneity is considered in the context of small (10-200 nm) sterol and sphingolipid-enriched heterogeneous and highly dynamic domains. Several techniques can be used to assess membrane heterogeneity in living systems. Our approach is to use a fluorescent reporter molecule immersed in the bilayer, which, by changes in its spectroscopic properties, senses physical-chemistry aspects of the membrane. This dye in combination with microscopy and fluctuation techniques can give information about membrane heterogeneity at different temporal and spatial levels: going from average fluidity to number and diffusion coefficient of nanodomains. LAURDAN (6 dodecanoyl-2-(dimethylamino) naphthalene), is a fluorescent probe designed and synthesized in 1979 by Gregorio Weber with the purpose to study the phenomenon of dipolar relaxation. The spectral displacement observed when LAURDAN is either in fluid or gel phase permitted the use of the technique in the field of membrane dynamics. The quantitation of the spectral Corresponding AuthorSusana A. Sánchez -

A novel strategy to control the generation of singlet oxygen by a photosensitizer using cucurbit[n]urils inclusion complexes is shown herein, and the strategy has great potential for therapeutic applications. We show the basic requirements of the photosensitizer complexes in order to develop an on−off switch for singlet oxygen that is reversible using competitive binding. The supramolecular strategy proposed in this paper avoids complex synthetic schemes in order to activate or deactivate the photosensitizer as previous work has shown and supports the use of biocompatible materials. Mechanistic insights into the control over the generation of singlet oxygen are provided, which strongly emphasize the key role of the cucurbit[n]uril macrocycles in the stabilization or deactivation of the triplet excited state.

Methyl-β-cyclodextrins (MβCDs) are molecules that are extensively used to remove and to load cholesterol (Chol) from artificial and natural membranes; however, the mechanism of Chol extraction by MβCD from pure lipids or from complex mixtures is not fully understood. One of the outstanding questions in this field is the capability of MβCD to remove Chol from lipid domains having different packing. Here, we investigated the specificity of MβCD to remove Chol from coexisting macrodomains with different lipid packing. We used giant unilamellar vesicles (GUVs) made of 1,2-dioleoylphosphatidylcholine:1,2-dipalmitoylphatidylcholine:free cholesterol, 1:1:1 molar ratio at 27°C. Under these conditions, individual GUVs present Chol distributed into lo and ld phases. The two phases can be distinguished and visualized using Laurdan generalized polarization and two-photon excitation fluorescence microscopy. Our data indicate that MβCD removes Chol preferentially from the more disordered phase. The process of selective Chol removal is dependent on the MβCD concentration. At high concentrations, MβCD also removes phospholipids.

Detection of singlet oxygen emission, λmax = 1270 nm, following laser excitation and steady-state methods were employed to measure the total reaction rate constant, kT, and the reactive reaction rate constant, kr, for the reaction between singlet oxygen and several flavonoids. Values of kT determined in deuterated water, ranging from 2.4×107 M−1s−1 to 13.4×107 M−1s−1, for rutin and morin, respectively, and the values measured for kr, ranging from 2.8×105 M−1s−1 to 65.7×105 M−1s−1 for kaempferol and morin, respectively, being epicatechin and catechin chemically unreactive. These results indicate that all the studied flavonoids are good quenchers of singlet oxygen and could be valuable antioxidants in systems under oxidative stress, in particular if a flavonoid-rich diet was previously consumed. Analysis of the dependence of rate constant values with molecular structure in terms of global descriptors and condensed Fukui functions, resulting from electronic structure calculations, supports the formation of a charge transfer exciplex in all studied reactions. The fraction of exciplex giving reaction products evolves through a hydroperoxide and/or an endoperoxide intermediate produced by singlet oxygen attack on the double bond of the ring C of the flavonoid.

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Artículo de publicación ISIRhenium complexes are versatile molecular building blocks whose tunable photophysical properties are useful in diverse opto-related applications. Herein we report the synthesis and characterization of a novel ReI tricarbonyldiimine complex, [(phen)Re(CO)3Br] (phen: 1,10-phenanthroline), which was found to be an efficient singlet oxygen [O2(1Δg)] photosensitizer in homogeneous solution [ΦO2(1Δg) = 0.55 (dichloromethane) and 0.16 (dimethylformamide)]. The photophysical properties of [(phen)Re(CO)3Br] were thoroughly characterized in solution and modeled by means of density functional theory (DFT) and time-dependent (TD)-DFT quantum mechanical calculations. The Re complex was incorporated into a flexible polymeric silsesquioxane (SSO) film, which has excellent dopant compatibility, chemical resistance, and mechanical properties. When [(phen)Re(CO)3Br] is embedded in the SSO film, it is found to retain most of the photophysical characteristics observed for the complex in solution. In particular, the [(phen)Re(CO)3Br]-doped SSO films were able to photosensitize O2(1Δg) when illuminated with blue light (∼405 nm). The O2(1Δg) sensitization by films in acetonitrile was followed by the photooxidation of the well-known O2(1Δg) chemical trap 9,10-dimethylanthracene (DMA) and confirmed by the direct observation of the O2(1Δg) luminescence spectrum (centered at 1270 nm) and the measurement of its kinetic profile. These results highlight the potential application of this type of polymeric material in the production of biological- or microbial-photoinactivating flexible surfaces or in the implementation of interfacial solid/liquid strategies for the photoinduced oxidation of organic compounds in solution.CONICYT 7913003

The design of efficient, biocompatible, and easily prepared vehicles for drug delivery is a subject of great interest for medicine and pharmaceutical sciences. To achieve the above goals, surface functionalization is critical. Here, we report a hybrid nanocarrier consisting of core–shell silica nanospheres and the antioxidant caffeic acid linked to the surface, to evaluate their in vitro antioxidant capacity, their capability to protect oxidation-sensitive compounds incorporated in nanoparticles, and to study the interaction with bovine serum albumin protein. The results show that the radical-scavenging activity of immobilized caffeic acid is attenuated in the silica nanospheres; however, other antioxidant properties such as Fe2+-chelating activity and singlet oxygen quenching are enhanced. In addition, caffeic acid is protected from binding to proteins by the nanoparticle, suggesting that this nanosystem is more likely to maintain the antioxidant activity of caffeic acid in biological media. Finally, the natural antioxidant barrier on the nanocarrier is able to delay the degradation of a compound incorporated into this nanovehicle. Considering all findings, this work proposes a suitable tool for pharmaceutical and cosmetic industries as an antioxidant nanocarrier for oxidation-sensitive drugs.