Melanopsin and the Non‐visual Photochemistry in the Inner Retina of Vertebrates

Melanopsin (Opn4), a member of the G‐protein‐coupled receptor family, is a vitamin A‐based opsin in the vertebrate retina that has been shown to be involved in the synchronization of circadian rhythms, pupillary light reflexes, melatonin suppression and other light‐regulated tasks. In nonmammalian vertebrates there are two Opn4 genes, Opn4m and Opn4x, the mammalian and Xenopus orthologs respectively. Opn4x is only expressed in nonmammalian vertebrates including reptiles, fish and birds, while Opn4m is found in a subset of retinal ganglion cells (RGCs), the intrinsically photosensitive (ip) RGCs of the inner retina of both mammals and nonmammalian vertebrates. All opsins described utilize retinaldehyde as chromophore, photoisomerized from 11‐cis‐ to all‐trans‐retinal upon light exposure. Visual retinal photoreceptor cones and rods, responsible for day and night vision respectively, recycle retinoids through a process called the visual cycle that involves the retinal pigment epithelium or glial Müller cells. Although Opn4 has been characterized as a bistable photopigment, little is known about the mechanism/s involved in its chromophore regeneration. In this review, we will attempt to shed light on the visual cycle taking place in the inner retina and discuss the state of the art in the nonvisual photochemistry of vertebrates.     

Synthesis and characterization of polyesters derived from sebacic acid,hexanediol, and hydroquinone

Oils and fats derived from animals and plants provide a good renewable source for polymer precursors. In this investigation, fatty acids derived from plant oils and diols were used as monomers to produce polyesters by melt polycondensation. Sebacic acid, hexanediol, and hydroquinone were used as precursors in the polymer synthesis. The polymers were characterized by gel permeation chromatography, Fourier transform infrared spectroscopy, three-bending point flexural test, X-ray diffraction, tensile testing, and contact angle. The resulting polyesters were blended with epoxies to create materials with an increased elongation at break without affecting other mechanical properties.     

Sequential Voltammetric Determination of Uranium,Cadmium and Lead by Using the ex situ Bismuth Film Electrode: Application to Phosphate Fertilizers

A sequential voltammetric procedure for the determination of uranium, cadmium and lead was investigated at an ex situ bismuth film electrode (BiFE). First, the adsorptive stripping voltammetry was applied to assay the U(VI)‐cupferron complex in the differential pulse mode (detection limit of 1.0 µg L^?1, 200 s accumulation time). Through the manipulation of the same aliquot of the sample, efforts were made to quantify cadmium and lead by square wave anodic stripping voltammetry. Detection limits of 2.03 µg L^?1 for Cd (II) and 2.43 µg L^?1 for Pb (II) were calculated (100 s accumulation time). The methodology was successfully applied to phosphate fertilizer samples after open vessel wet decomposition (HNO₃/H₂O₂). The following value ranges were evaluated: U (VI) 37.2–150 mg kg^?1, Pb (II) 78.3–204 mg kg^?1 and Cd (II) 44.1–71.6 mg kg^?1. Validation was performed by using the standard reference materials SRM‐695 – phosphate fertilizer – and SRM‐1643e – water.     

Benign‐by‐Design Solventless Mechanochemical Synthesis of Three‐, Two‐, and One‐Dimensional Hybrid Perovskites

Organic–inorganic hybrid perovskites have attracted significant attention owing to their extraordinary optoelectronic properties with applications in the fields of solar energy, lighting, photodetectors, and lasers. The rational design of these hybrid materials is a key factor in the optimization of their performance in perovskite‐based devices. Herein, a mechanochemical approach is proposed as a highly efficient, simple, and reproducible method for the preparation of four types of hybrid perovskites, which were obtained in large amounts as polycrystalline powders with high purity and excellent optoelectronics properties. Two archetypal three‐dimensional (3D) perovskites (MAPbI₃ and FAPbI₃) were synthesized, together with a bidimensional (2D) perovskite (Gua₂PbI₄) and a “double‐chain” one‐dimensional (1D) perovskite (GuaPbI₃), whose structure was elucidated by X‐ray diffraction.     

Uniqueness of Radial Solutions for the Fractional Laplacian

We prove general uniqueness results for radial solutions of linear and nonlinear equations involving the fractional Laplacian (?Δ)^s with s ? (0,1) for any space dimensions N ≥ 1. By extending a monotonicity formula found by Cabré and Sire , we show that the linear equation has at most one radial and bounded solution vanishing at infinity, provided that the potential V is radial and nondecreasing. In particular, this result implies that all radial eigenvalues of the corresponding fractional Schrödinger operator H = (?Δ)^s + V are simple. Furthermore, by combining these findings on linear equations with topological bounds for a related problem on the upper half‐space , we show uniqueness and nondegeneracy of ground state solutions for the nonlinear equation for arbitrary space dimensions N ≥ 1 and all admissible exponents α > 0. This generalizes the nondegeneracy and uniqueness result for dimension N = 1 recently obtained by the first two authors and, in particular, the uniqueness result for solitary waves of the Benjamin‐Ono equation found by Amick and Toland .© 2016 Wiley Periodicals, Inc.     

Oxidative degradations of the side chain of unsaturated ent-labdanes. Part II

A route for the degradation of the side chain of ent-labdane derivatives has been devised, giving the useful synthon 2beta,12-dihydroxy-13,14,15,16,17-pentanor-ent-labdane-8-one (8). The use of this compound in the preparation of terpenylquinone derivatives shall be reported elsewhere. In addition we have synthesized the compound 2beta,12-diacetoxy-8beta,17-epoxy-13,14,15,16-tetranor-ent-labdane (10), which upon catalytic epoxide ring opening in alkaline or acid media gave rise in all cases to the formation of tricyclicc ompounds.     

Photodissociation of uracil

We investigate the photochemistry and photodissociation dynamics of uracil by two-colour photofragment Doppler spectroscopy and by two-colour slice imaging at excitation wavelengths between 268 and 235 nm. We observe the loss of a hydrogen atom upon excitation into the pipi* state. The angular distribution indicates a statistical process, while the translational energy distribution agrees with a dissociation that takes place on the electronic ground state. The pipi* state most likely deactivates via the lower-lying npi* state. In addition there is evidence for a second pathway: direct decay of the pipi* state to the electronic ground state with subsequent dissociation. Experiments on uracil-1,3-D(2) show that there is no site selectivity in the dissociation process. No evidence was found for the direct dissociation via a pisigma* excited state that seems to be relevant in the photochemistry of adenine and many other heterocyclic molecules. Overall, the photochemistry of uracil is similar to that of thymine.     

Oxaaza cyclophanes in the recognition of nucleotides. The role of oxygen and electron-rich aromatic rings

Dioxapolyaza cyclophanes derived from resorcinol and different polyamine chains have been studied in aqueous solution as abiotic receptors for nucleotides. The presence of the additional ethyleneoxy subunits is reflected in a higher basicity and in a significant increase in the log K values for the interaction with nucleotides relative to that of related polyazacyclophanes.