Structures properties and reactions of some biologically important molecules and other molecules

Abstract

Large abundance of certain chemical species most of which are free radicals and are called newlinereactive oxygen species (ROS) and reactive nitrogen oxide species (RNOS) damage newlinebiomolecules in living organisms. The ROS and RNOS include superoxide radical anion (O2 newline.-), newlinehydroxyl radical (OH.), methoxy radical (OCH3 newline.), nitrogen di-oxide radical (NO2 newline.), carbonate newlineradical anion (CO3 newline.-) etc. Reactions of ROS and RNOS with the DNA bases, particularly newlineguanine, lead to formation of different products. For example, when guanine reacts with OH. and newlineNO2 newline. radicals, 8-oxoguanine (8-oxoG) and 8-nitroguanine (8-nitroG) are formed respectively. newlineThe guanine base of DNA, among the four bases, is most susceptible to attack by ROS and newlineRNOS. Modified forms of guanine can mispair with the other bases including adenine during newlineDNA replication and thus cause GC and#8594; AT transversion mutation. Such mutations can eventually newlinecause numerous diseases involving all vital organs of the human body including cancer, the newlineAlzheimer s and Parkinson s diseases. The ROS and RNOS mediated DNA damages are newlinecontinuously prevented inside biological systems by scavenging these species by anti-oxidants. newlineThe endogenous anti-oxidants include the enzymes superoxide dismutase, catalase, glutathione newlineperoxidase and glutathione reductase as well as certain other molecules e.g. glutathione, alphalipoic newlineacid, ferritin, uric acid, bilirubin etc. while the exogenous anti-oxidants include ascorbic newlineacid (vitamin C), and#945;-tocopherol (vitamin E), curcumin, 6-gingerol, lycopene etc. In the state of newlinedisease, the endogenous anti-oxidants are insufficient to scavenge the ROS and RNOS newlineefficiently. Therefore, the exogenous anti-oxidants are taken as supplements of food. newline