Journal of Photochemistry and Photobiology最新文献

Covalently linked peptide-porphyrin compounds are most suitable systems for fundamental studies aiming to the comprehension of the mechanisms driving photoinduced energy/electron transfer processes. Mimicking photosynthetic units, the porphyrin groups act as antenna moieties while the peptide chain is the active medium through which energy and/or electron funneling occur. In this contribution we studied the transfer of excitation between two identical tetraphenylporphyrin groups connected by short peptide chains of different length formed by non-coded conformationally constrained α-amino acids, i.e., C^α-methylvaline. The photophysical events following porphyrin photoexcitation were characterized from the microsecond to the picosecond time region by time-resolved spectroscopy techniques. Ultrafast transient absorption measurements revealed the presence of a transient species that we assign to a self-trapped exciton migrating through the peptide chain. The exciton species propagates the electronic coupling between the two porphyrin groups giving rise to a characteristic bisignate band measured by circular dichroism experiments. Molecular dynamics simulations strongly suggest that the long lifetime (hundreds of picoseconds) of the exciton species is determined by the rigidity of the C^α-methylvaline residues, that inhibited energy relaxation pathways coupled to torsional motions of the peptide chain.

The reactions involving aryl radicals is an efficient strategy for the synthesis of a wide variety of important molecules. We have highlighted here recent developments on the generation of aryl radicals from various substrates by visible light mediated photocatalysis and their reactions with different substrates to produce a library of arylated and het-arylated compounds. These reactions are performed at room temperature using LED bulbs. Thus, this strategy is green involving less energy.

Seaweeds play an important role for the environment, since they are photosynthetic organisms, contributing to the cycling of nutrients and to the protection and feeding of several animals. The potential for biotechnological applications of marine macroalgae biomass is enormous, and to attend the demand of the current market, the knowledge of the physiological characteristics of these organisms is essential to ensure a high productivity in cultivation systems. In this review, we contribute to the knowledge about the photosynthetic characteristics of seaweeds, describing relevant aspects of marine macroalgae and photosynthesis, and the biotechnological use of these organisms.

Prior to the coronavirus disease-19 (COVID-19) pandemic, the germicidal effects of visible light (λ = 400 – 700 nm) were well known. This review provides an overview of new findings that suggest there are direct inactivating effects of visible light – particularly blue wavelengths (λ = 400 – 500 nm) – on exposed severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virions, and inhibitory effects on viral replication in infected cells. These findings complement emerging evidence that there may be clinical benefits of orally administered blue light for limiting the severity of COVID-19. Possible mechanisms of action of blue light (e.g., regulation of reactive oxygen species) and important mediators (e.g., melatonin) are discussed.

The pupil reacts to the amount of light reaching the eye. It reduces its size when the light is high and dilates at low light levels to allow the entrance of more photons. This behavior is called pupil light reflex (PLR). Recent investigations in humans were conducted to understand how the photoreceptor signals are combined to drive the pupil light reflex. This review is about the physiological processes that govern the pupil in humans. In particular, how cone-opsins, rhodopsin, and melanopsin photoreception contribute to governing the PLR. We also summarize investigations on the assessment of the PLR in clinical settings.

Our laboratory has been studying the strong enhancement in the fluorescence quantum yield and an excited lifetime of the organic dye molecules on the clay nanosheets and refer to as “Surface-Fixation Induced Emission”. In this study, Safranine-O which is a mono-cationic phenazine-based dye molecule, was used as the organic dye. It has fluorescence enhancement properties on the clay surface due to the suppression of the non-radiative deactivation rate constant (k_nr) on the clay nanosheets. While Safranine-O in water in the absence of clay nanosheets exhibited the values as 0.068 and 1.09 × 10⁻⁹ s for ϕ_f and τ, those on the clay surface are 0.121 and 1.96 × 10⁻⁹ s. k_nr values in water and on the clay were calculated to be 8.6 × 10⁸ s ^− 1 and 4.5 × 10⁸ s ^− 1, respectively. These results can be explained well by the structure fixing and structure resembling effect. This study helps to explore the possibility of utilizing mono-cationic dye molecules for the realization of desired photo-functional materials and photochemical reactions.

Opsins are light-sensitive proteins that are found across the animal kingdom. In mammals, opsins are classically associated with image-forming processes, a function exerted by cone and rod opsins. In early 2000, melanopsin was identified in the human retina as an important regulator of non-image forming events such as melatonin suppression, pupillary constriction, and circadian rhythm adjustment. The presence of different opsins and the biological processes that these proteins regulate in the skin are increasingly being described. Currently, opsins are considered light as well as thermosensors in the skin. However, additional regulatory functions, in a light and thermo-independent fashion, mostly likely via protein-protein interaction have set a new field of study. The goal of this review is to critically revise the literature on the role of opsins in skin physiology as well as in melanoma cancer.

Phlorotannins are believed to provide UV protection in brown algae. In Fucus species, phlorotannin-rich vesicles (“physodes”) form an “epidermal physode layer”, which might represent the anatomical structure responsible for UV protection. However, this layer has been neglected so far; instead, phlorotannin contents of entire thalli were studied in UV exposure experiments.

We employed fluorometric methods to investigate in which wavelength region and to which degree the epidermal physode layer of two Fucus species reduces the transmittance of UV radiation. For comparison, we also studied Saccharina latissima, a brown algal species without epidermal physode layer.

We could show that the epidermal physode layer absorbs throughout the entire UV wavelength range and reduces the epidermal UV-B transmittance into the thallus strongly (15% transmitted in F. vesiculosus vs. 80–100% in S. latissima). UV-B transmittances varied with growth depth and the variations correlated with photosystem II (PSII) stress responses upon artificial UV-B illumination. We found that the UV-B protection is more than sufficient for natural UV-B levels and of rather constitutive nature.

In conclusion, the epidermal physode layer appears to be the anatomical feature exerting UV protection by phlorotannins in Fucus species and might thus be a core adaptation that enables Fucales the colonization of the intertidal habitat.

Studying the uptake mechanism of photosensitizers is an important step in developing an ideal photosensitizer for use in photodynamic therapy (PDT). Understanding the uptake mechanism can help design novel photosensitizers that are selectively accumulated in the target tissue, with improved pharmacokinetics, and are dosed optimally to maximize the efficacy of the treatment. In our previous studies we synthesized and characterized the use of chitosan nanoparticles functionalized with rose bengal (CSRBnp) as a photosensitizer against dental biofilm. The aim of this study is to analyze the internalization mechanism and cellular proinflammatory activities of CSRBnps on fibroblasts. Fibroblasts (NIH 3T3) were incubated with chlorpromazine (5 µg/ml), nystatin (5 µg/ml), wortmannin (100 ng/ml) and at 4 °C for 30 min followed by CSRBnp (0.3 mg/ml). Cell viability (MTS assay), intracellular adenosine triphosphate content (Luminescence assay), cytokine expression (TNF-α) using ELISA and nitric oxide (NO) production by Griess reaction system were conducted at different time intervals (30 min, 1, 4, and 12 h). The internalization of CSRBnps was analyzed using live cell imaging confocal microscope with excitation wavelengths of 405 and 568 to detect nuclei (Hoechst 33,342) and CSRBnps respectively. CSRBnps and inhibitors at the applied concentrations were not cytotoxic. ATP content in chlorpromazine and without inhibitors groups were significantly lower than the control group at 12 h. All inhibitors showed significantly lower CSRBnps uptake compared to the control group at 30 min, 1 h, and 4 h time. Wortmannin resulted in the most significant inhibition of CSRBnps uptake as compared to chlorpromazine and nystatin (P < 0.05). TNF-α expression and NO production were not significant during the entire CSRBnps uptake. The results showed macropinocytosis was a dominant CSRBnps uptake mechanism by fibroblasts in the early stages and non-specific uptake pathways were activated after prolonged incubation time. CSRBnps uptake by fibroblasts was energy dependent and did not cause any proinflammatory response.

A series of 3,6-diamino-9-naphthylcarbazole derivatives were synthesized and characterized experimentally and computationally. As the lowest unoccupied molecular orbital of the naphthyl group has lower energy than that of the phenyl group, a charge transfer from carbazole to naphthyl in the excited states occurred causing solvatofluorochromism and solvent-dependency in fluorescence quantum yields. A molecule having two carbazole substituents sandwiching the central naphthyl ring had absorption reaching 470 nm and a high reducing capability in the excited state. This molecule could successfully photosensitize the hydrodehalogenation of haloarenes under visible light irradiation.