Photoactivation and Detection of Photoexcited Molecules and Photochemical Products

Abstract

Aerobic photoactivation of photosensitizing dye molecules can lead to the formation of oxygen radicals, singlet oxygen and other partially reduced oxygen species, collectively called reactive oxygen species (ROS), which are responsible for photodynamic damage and the accompanying cytotoxicity. This review briefly describes basic photophysical phenomena involved in the formation of electronically excited states and photochemical processes that play a key role in the generation of ROS. Physicochemical properties of the excited states of the photosensitizing dye molecules and of ROS, particularly their chemical reactivity with selected substrate molecules, as well as major spectroscopic and analytical methods used for the detection and characterization of reactive intermediates involved in photodynamic phenomena, are critically discussed in this paper.

Changes in production of reactive oxygen species in illuminated thylakoids isolated during development and senescence of barley

“…However, at longer times, particularly between 10 and 50 microseconds, the two decay curves recorded at 1355 nm and in the presence of NaN 3 significantly differ from the one recorded at 1270 nm. The higher luminescence intensity in this time domain, observed at 1270 nm, is due to singlet oxygen phosphorescence, which shows an apparent lifetime of ≈55 s. The measurement of singlet oxygen phosphorescence was carried out in a D 2 O-phosphate buffer, in which the singlet oxygen lifetime was reported to be 50-60 s (Kozinska et al, 2012). The shortened lifetime of singlet oxygen indicates that it interacts with the quenching molecules present in the microenvironment where this reactive oxygen species is photogenerated.…”

“…The production of 1 O 2 during the development and senescence of barley was determined by direct spectroscopic measurements (Kozinska et al, 2012). The experimental set-up has been described elsewhere (Grinholc et al, 2015).…”

“…Although in condensed phase, in the absence of appropriate chemical acceptors, 1 O 2 predominantly decays via thermal relaxation, and very weak phosphorescence, centred at 1270 nm, accompanies this process (Kozinska et al, 2012). The intensity of this emission is proportional to the momentary concentration of singlet oxygen.…”

Photodegradation of Eumelanin and Pheomelanin and Its Pathophysiological Implications

“…1/3) than with UVA at a dose 20% that of UVA . In addition, unlike the generally accepted mechanism of photosensitized generation of ROS mediated by UVA , the UVB‐induced generation of ROS is poorly understood and may involve such adverse processes as activation of the cellular catalase or elevation of the intracellular Ca 2+ levels .…”

Photodynamic Inactivation of Candida albicans with Imidazoacridinones: Influence of Irradiance, Photosensitizer Uptake and Reactive Oxygen Species Generation

“…The quantum yield of singlet oxygen production upon the photoexcitation of imidazoacridinone derivatives was low compared with the known efficient producers of singlet oxygen, such as TMPyP or Rose Bengal photosensitizers ( Fig 5 ). However, even the relatively inefficient production of singlet oxygen could have significant biological impact when this species is generated in proximity to molecular targets that readily undergo oxidative modifications [ 50 – 51 ]. This phenomenon was observed in the case of 1330 and 1330H,which produced similar amounts of singlet oxygen, and showed similar levels of accumulation in yeasts cells, but have different localization pattern.…”