https://www.selleckchem.com/products/CP-690550.html SIGNIFICANCE Selenenyl sulfides and thioseleninic acids are the mono-selenium analogues of disulfides and persulfides that contain Se-S bonds. These bonds are found in several antioxidant regenerating enzymes as derivatives of selenocysteine, making them an important player in redox biology as it pertains to sulfur redox regulation. Recent Advances Mechanistic studies of redox regulating selenoenzymes like thioredoxin reductase and glutathione peroxidase suggest crucial Se-S bonds in the active sites. Peptide models and small molecule mimics of these active sites have been prepared to study their fundamental chemistry. These advances help pave the road to better understand the functions of the Se-S bond in the body. CRITICAL ISSUES The Se-S bond is unstable in atmospheric temperatures and pressures. Therefore, studying their properties proposes a major challenge. Currently there are no trapping reagent specific to selenenyl sulfides or thioseleninic acids, making their presence, identity, and fates in biological environments difficult to track. Future Direction Further understanding the fundamental chemistry/biochemistry of selenenyl sulfides and thioseleninic acids are needed to understand what their intracellular targets are and to what extent they impact signaling. Besides antioxidant regeneration and peroxide radical reduction, the roles of selenenyl sulfide and thioseleninic acids in other systems need to be further explored.SIGNIFICANCE The p53 tumor suppressor has been dubbed the "guardian of genome" because of its various roles in the response to DNA damage such as DNA damage repair, cell cycle arrest, senescence and apoptosis, all of which are in place to prevent mutations from being passed on down the lineage. Recent Advances Reactive oxygen species (ROS), for instance H2O2 derived from mitochondrial respiration, have long been regarded mainly as a major source of cellular damage to DNA and other macro mo