Associate Research Scientist
B.S., 1982, Madurai Kamaraj University, India
M.S., 1985, Madurai Kamaraj University, India
Ph.D., 1991, University of Hyderabad, India
Postdoctoral Fellow, 1991-1994, University of Wyoming
Postdoctoral Fellow, 1994-1996, University of Iowa
Nitric oxide (NO) is a neurotransmitter, and a potent therapeutic agent capable of fighting tumor (cytostasis) and inhibiting platelet aggregation. There are also well documented deleterious effects arising from the overproduction of NO. For example, undesired consequences such as vascular diseases (septic shock, post-ischemic cerebral damage, etc.), immuno-pathological diseases and neurodegenerative diseases (cerebral ischemia, Alzheimer disease and Huntington disease) are attributed to NO overproduction. Recent evidences suggest that the closely related redox partner, nitroxyl (HNO, also known as nitrosyl hydride), produced during the biosynthesis of NO from L-arginine or by the one-electron reduction of NO under physiological conditions is also responsible for some of the physiological functions attributed to NO. Therefore, there is new impetus given to the biological chemistry of HNO. In contrast to the rapid growth of biochemical and pharmacological studies of HNO, there is little attention given to the fundamental reactivity studies of NO and HNO. The continued use of classic compounds such as sodium hyponitrate (Na2N2O3, Angeli's salt) and N-hydroxybenzenesulfamide (C6H5SO2NHOH, Piloty's acid), for the in situ generation of the nitroxyl anion (NO-) in various biochemical studies illustrates the status of fundamental research toward the synthesis and characterization of HNO and NO-. The biosynthesis of NO involves the formation of HNO as a byproduct, and there is evidence for the preferential formation of HNO over NO under certain cellular conditions. The capricious biosynthesis of HNO in lieu of NO has blurred the physiological roles of NO and HNO. Studies aimed at distinguishing their chemical properties are complicated by the ready inter-conversion of NO and NO-. The complexity of HNO reactivity still remains poorly understood.
Our research is focused on the chemical reactivity of NO- in conjunction with that of NO. We have observed that NO consistently adds to a variety of carbanions as a dimeric molecule, [NO]2. We believe that the key to the understanding of NO- reactivity lies with the dimeric reactivity of NO. A scrutiny of the existing chemical literature reveals that NO exhibits conflicting reactivity: it acts both as a Lewis base (in reaction with ligand-bound metal ions) and as a Lewis acid (in reaction with dialkylamines). Although the Lewis base reactivity of NO is well-recognized, except for the early studies of Drago et al and our recent work no detailed studies on the Lewis acidity of NO are available. Interestingly, physical chemists have observed the adsorption and reduction of dimeric NO on "electron-rich" surfaces of metallic copper, palladium and silver, and aluminum oxide and magnesium oxide surfaces at ambient conditions. But the chemical implications of the behavior are yet to be investigated. Our current work aims to verify the hypothesis that the formation of NO- from NO and the Lewis acidity of NO are related, and that the observed inconsistency in NO reactivity arises from the molecule's ability to act as a monomer and dimer. As a monomer NO acts as a Lewis base, and as a dimer it acts as a Lewis acid.