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Nitric Oxide-Induced Tolerance in Plants under Adverse Environmental Conditions
Published in Hasanuzzaman Mirza, Nahar Kamrun, Fujita Masayuki, Oku Hirosuke, Tofazzal M. Islam, Approaches for Enhancing Abiotic Stress Tolerance in Plants, 2019
Neidiquele M. Silveira, Amedea B. Seabra, Eduardo C. Machado, John T. Hancock, Rafael V. Ribeiro
S-nitrosothiols (RSNOs) belong to an important group of NO• donors, and the most frequently used RSNOs in plants are S-nitrosoglutathione (GSNO) and S-nitroso-N-acetylpenicillamine (SNAP). Nonreductive decomposition of RSNOs leads to the formation of disulfides and release of NO•, which are dependent on light, temperature, the presence of metal ions (Cu2+), and pH (Hou et al., 1999). In addition, oxidized forms of endogenous NO• (such as N2O3) may react with the thiol group (SH) of cysteine residues (Cys) present in proteins, forming an S-nitrosothiol (SNO), a reaction called S-nitrosation or S-nitrosylation (Lindermayr et al., 2005; Aracena-Parks et al., 2006). Thus, RSNOs, such as GSNO, are the natural reservoir of NO• in biological systems, releasing free NO• during its degradation. The GSNO is an S-nitrosated derivative of the most abundant cellular thiol, the glutathione (GSH), which intracellular concentrations may be greater than 10 mM (Hancock and Whiteman, 2018). GSNO itself is not directly absorbed into cells; however, GSNO treatment does cause increases in cellular S-nitrosothiol levels under many conditions. It was hypothesized that GSNO decomposes in the extracellular space to release NO•, which is then able to diffuse across the cell membrane to S-nitrosate protein targets (Broniowska et al., 2013).
Toxicity of Carbon Monoxide: Hemoglobin vs. Histotoxic Mechanisms
Published in David G. Penney, Carbon Monoxide, 2019
The role of NO in CO poisoning has not been well defined. CO poisoning causes profound increases in cerebral blood flow, and consequently, levels of tissue oxygen and glucose delivery and lactate clearance are higher compared to brain ischemia. These conditions, accompanied by interstitial EAA accumulation, may facilitate NO production after CO exposure. In addition, both NO and CO activate guanylyl cyclase causing increases in cGMP (Verma et al., 1993). This cellular effect of CO may be responsible for vasodilation during CO poisoning (Ramos et al., 1989). In preliminary experiments, however, NOS inhibitors appear to interfere with the vascular effects of CO in the rat. The exact biological role of NO remains unclear because its fate is complex; it is susceptible to both oxidation and reduction, and interactions occur with biological metals and thiols (Stamler et al., 1992). Some redox forms of NO retain NO-like activity as demonstrated by the potent bioactivity of S-nitrosothiols (RS-NO) (Mohr et al., 1994). To understand the role of NO production in CO hypoxia, it will be necessary to examine the extent to which NO production increases, and determine how NOS inhibition alters interstitial EAA accumulation and changes in RS-NO pools during and after CO exposure. It is also important to determine how much CO alters the activities of guanylyl cyclase and NOS in vivo. NO overproduction also may lead to direct cytotoxicity in the presence of superoxide due to the formation of peroxynitrite anion (ONOO-), which is a strong oxidant with reactive hydroxyl radical-like activity (Beckman et al., 1990).
Structural properties and isomerisation of simple S-nitrosothiols: ab initio studies with a simplified treatment of correlation effects
Published in Molecular Physics, 2020
Shovan Manna, Suvonil Sinha Ray, Pradipta Ghosh, Sudip Chattopadhyay
The class of compounds called the S-Nitrosothiols or thionitrites (RSNOs) have recently emerged as major players in the NO regulated biochemical processes. By suitably tuning the chemical nature of the substituent R, one can play with the RSNOs to efficiently release NO, act as specific trans-S-nitrosation reagents, or, possibly, as biologically compatible HNO/NO-donors. To this end, a detailed theoretical understanding of the RSNO structure, stability, and chemical properties is essential. The properties of RSNOs can be described by inspecting the S-N bond properties. The results of Timerghazin and coworkers are very useful to judge the out come of the present IVO-SS-MRMPPT results. The main features of the present work may be summed up as follows: