Journal of Photochemistry and Photobiology最新文献

The electron transfer reaction between C₆₀ and SWCNTs in D₂O was investigated. Repeated laser irradiation of water-soluble C₆₀ encapsulated in γ-cyclodextrin and SWCNTs with carboxymethylcellulose dispersed in D₂O resulted in the accumulation of C₆₀ anion radicals and a decrease in the E₁₁ absorption band of SWCNTs, strongly suggesting electron transfer between C₆₀ and SWCNTs. Transient absorption techniques revealed that this electron transfer occurred through the excited triplet of C₆₀.

Mammals use social thermoregulation to maintain the core body temperature (Tc) at a lower energy cost. Brown adipose tissue (BAT) plays a crucial role in thermoregulation. This study tested the hypothesis that social isolation induces alterations in thermogenesis and metabolism to maintain the rhythm of Tc throughout the day. Adult male mice (C57BLJ/6) were maintained in groups of 4–5 (group-housed) or isolated (single-housed) for 28 days. Telemetric probes recorded spontaneous locomotor activity (SLA) and Tc to analyze SLA and Tc daily rhythms. Body weight was measured weekly. VO2 consumption was analyzed at zeitgeber time (ZT) 1–3 (beginning of light phase) or ZT10–14 (beginning of dark phase). The expression of thermogenic-related and clock genes in the BAT occurred at ZT2, ZT8, ZT14, and ZT20. The β3 adrenergic agonist CL-316,243 was i.p. injected in the group- or single-housed mice. Social isolation increased the amplitude of Tc rhythm but decreased the amplitude of SLA oscillation. Nevertheless, in single-housed mice, the circadian peak of Tc and SLA was unaltered, with reduced body weight gain, increased VO2 consumption, and BAT Ucp1 expression at ZT14. Isolation advanced the BAT Rev-erb-ɑ peak of expression and phased-shift the peak of expression in BAT Bmal1, while it abolished the daily BAT Per2 oscillation. Isolation also abolished the BAT Ucp1 and hormone-sensitive lipase (Hsl) expression induced by stimulation of the β3ADR, but it increased Rev-erb-ɑ and Pgc1α. Thus, alterations in Ucp1, Reverb-α, Bmal1, and Per2 daily expression may favor an increased metabolic rate at the beginning of the dark, which, in turn, contributes to maintaining the daily Tc rhythm at the expense of reduced body weight gain in isolated mice. In addition, at least at the transcription level, the response of BAT from isolated mice to adrenergic agonist seems to be via a non-canonical mechanism involving Rev-erb-α and Pgc1α.

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.

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.

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.

Photobiomodulation (PBM) is a noninvasive photonic-based therapy, capable of dealing with immune-inflammatory, neurological, and musculoskeletal disorders, as well as healing oral and chronic skin wounds. During PBM light is applied at a specific wavelength, either in the visible or near-infrared (NIR) ranges. Photophysical and photochemical processes might stimulate or inhibit various biological processes, depending on the target tissue, the wavelength of light, irradiance, fluence, repetition rate (pulse frequency), spot size, optical data of the tissue to be irradiated and treatment regimen. There are several randomized clinical studies demonstrating the PBM benefits as main or adjuvant therapies. Of importance to this review, there is a large piece of evidence in the management of skin or venous ulcers, and diabetic foot. In this review, the PBM´s efficacy as adjuvant therapy to deal with chronic human ulcers were discussed concerning the photophysical parameters and clinical aspects. Beside, we overview the state-of-the-art regarding the cellular and molecular modulatory mechanisms photoactivated by red and NIR light.

Electron donor and acceptor undergo association in solution to form a weak molecular complex, namely a charge transfer complex. The formation of the complex is apparent by its new low-energy absorption band. Upon photoexcitation of this charge transfer band, an intracomplex electron transfer is facilitated to form a contact ion radical pair. The theoretical basis for the complex formation and the subsequent photoinduced electron transfer process has been well established already half a century ago. Nevertheless, the charge transfer complex photochemistry is now in a renaissance, due to its synthetic utility of its radical ion pair. By intentionally sidestepped unproductive back electron transfer process, a desired product is effectively obtained with or without external reagent and/or catalyst. In addition, the photoexcitation of the complex does not require any additional photocatalyst and often conceivable with the visible light. Accordingly, various donor/acceptor pairs and synthetic applications have been emerged as novel photoreaction systems in the last two decades. Some have also addressed the stereoselective transformations. This mini review highlights the recent progress of the asymmetric photoreaction, in particular in synthetic applications, based on the photoexcitation of the charge transfer complex, in comparison with photoredox catalysis.

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.

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.

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.