Cyclic electron flow (CEF) around photosystem I has a role in avoiding photoinhibition of photosystem II (PSII), which occurs under conditions in which the rate of photodamage to PSII exceeds the rate of its repair. However, the molecular mechanism underlying how CEF contributes to photoprotection is not yet well understood. We examined the effect of impairment of CEF and thermal energy dissipa...

BACKGROUND The vitamin D endocrine system, besides multiple other functions, regulates aging in many tissues, including the skin. It protects the skin against the hazardous effects of many skin age-inducing agents, including ultraviolet radiation. Thus, in the present study we aimed to investigate the relationship between facial skin aging and 25-hydroxyvitamin D [25(OH)D] serum levels in healt...

Light-harvesting complex II (LHCII) is pivotal both for collecting solar radiation for photosynthesis, and for protection against photodamage under high light intensities (via a process called nonphotochemical quenching, NPQ). Aggregation of LHCII is associated with fluorescence quenching, and is used as an in vitro model system of NPQ. However, there is no agreement on the nature of the quench...

A novel treatment serum formulated to target multiple pathways in the anti-ageing cascade was tested both in vitro and in clinical settings. In vitro testing was performed to assess the ability to stimulate key proteins and genes fundamental to the anti-ageing cascade. The antioxidant potential of the formulation was studied in a UV-irradiation clinical study. A 12-week, open-label, single-cent...

BACKGROUND Characterization of mechanisms that can reverse residual damage from prior skin exposure to ultraviolet (UV) would be of considerable biological and therapeutic interest. Topical caffeine application to mouse skin that had previously been treated with UV has been shown to inhibit the subsequent development of squamous cell carcinomas. OBJECTIVES We used an established mouse photoda...

The main function of the photosynthetic process is to capture solar energy and to store it in the form of chemical 'fuels'. Increasingly, the photosynthetic machinery is being used for the production of biofuels such as bio-ethanol, biodiesel and bio-H2. Fuel production efficiency is directly dependent on the solar photon capture and conversion efficiency of the system. Green algae (e.g. Chlamy...

UVA accounts for about 95% of the solar ultraviolet (UV) radiation that reaches Earth and most likely contributes to human skin cancer risk. In contrast to UVB, which comprises the remaining 5% and is absorbed by DNA nucleobases to cause direct photodamage, UVA damages DNA indirectly. It does this largely through its interactions with cellular chromophores that act as photosensitisers to genera...

Light-induced damage to photosystem I (PSI) was studied during low-light illumination of barley (Hordeum vulgare L.) at chilling temperatures. A 4-h illumination period induced a significant inactivation of PSI electron transport activity. Flash-induced P700 absorption decay measurements revealed progressive damage to (a) the iron-sulfur clusters FA and FB, (b) the iron-sulfur clusters FA, FB, ...

Under high-irradiance conditions, plants must efficiently protect photosystem II (PSII) from damage. In this study, we demonstrate that the chloroplast protein HYPERSENSITIVE TO HIGH LIGHT1 (HHL1) is expressed in response to high light and functions in protecting PSII against photodamage. Arabidopsis thaliana hhl1 mutants show hypersensitivity to high light, drastically decreased PSII photosynt...

Although cyclic electron flow (CEF) is essential for repair of PSII, it is unclear whether the CEF is stimulated and what the role of stability of PSI is during the recovery. In order to explore these two questions, mature leaves of Dalbergia odorifera were treated with the chilling temperature of 4°C under a photosynthetic flux density (PFD) of 650 μmol m(-2) s(-1) for 2 h and then were transf...