Reactive oxygen species: Re-evaluation of generation, monitoring and role in stress-signaling in phototrophic organisms

Abstract

This review provides an overview about recent developments and current knowledge about monitoring, generation and the functional role of reactive oxygen species (ROS) - H2O2, HO2, HO, OH(-), (1)O2 and O2(-) - in both oxidative degradation and signal transduction in photosynthetic organisms including microscopic techniques for ROS detection and controlled generation. Reaction schemes elucidating formation, decay and signaling of ROS in cyanobacteria as well as from chloroplasts to the nuclear genome in eukaryotes during exposure of oxygen-evolving photosynthetic organisms to oxidative stress are discussed that target the rapidly growing field of regulatory effects of ROS on nuclear gene expression.

Imaging short‐lived reactive oxygen species (ROS) with endogenous contrast MRI

“…According to Rosen criteria, requiring CNR >5, the detection sensitivity of ROS imaging was around 10 pM assuming a lifetime of 1 ls for the hydroxyl radicals. [8][9][10][11][12][13] With the estimated ROS concentrations over time and the corresponding T 1 relaxation times, the T 1 relaxivity of ROS was computed to be 3.4 3 10 7 s 21 ÁmM 21 , which is much larger than that of Gd-DTPA (0.9 s 21 ÁmM 21 ) (Fig. 5).…”

“…[8][9][10][11][12][13] Instead of developing an MRI technique with submicrosecond temporal resolution to study its MRI properties, we alternatively established an imaging platform that sustainably produces ROS. Fresh egg white treated with H 2 O 2 prolongs ROS production for hours, with quantifiable ROS concentrations over time.…”

“…Based on this simple model, we estimated the detection sensitivity of ROS MRI is at the pM level under the assumption of a 1 ls lifetime for hydroxyl radicals. [8][9][10][11][12][13] Under shorter lifetimes (eg, 1 ns), the detection sensitivity will be proportionally higher (eg, 10 23 pM level). Given that the physiological concentrations of ROS is in the lM level 14 and their concentration can be elevated by over 100 times under conditions such as inflammation or stroke and reperfusion, 14,31,32 the pM detection sensitivity provides the capability to detect ROS under both physiological and pathological conditions.…”

“…For example, the lifetime of singlet oxygen, superoxide, and hydroxyl radical in aqueous solutions is within the ls regime. [8][9][10][11][12][13] In addition, The power of MRI resides in providing superb softtissue structural contrast for clinical diagnosis. In addition to the anatomical information provided by MRI, molecular information may also be obtained.…”

“…For example, the lifetime of singlet oxygen, superoxide, and hydroxyl radical in aqueous solutions is within the ls regime. [8][9][10][11][12][13] In addition, the in vivo concentration of ROS is generally low (lM level), 14 making the detection more challenging. In order to measure ROS, several methods have been developed including optical redox scanning 15 and exogenous contrast magnetic resonance imaging (MRI)-based methods.…”