Nitric oxide (NO) is a simple odd-electron molecule that is a primary pollutant. It transmits signals between neurons; playing a role in blood flow and sexual arousal. In this mini review we try to make accessible the properties and functions of this lipophilic molecule to non-specialists

Eluagwule, Arnold N.

Mordi, Raphael C.

Odede, Towojesudunjoyinlo D.

Okedere, Adebola P.

Covenant University Repository

        REVIEW ARTICLE  SOME CHEMICAL AND PHYSIOLOGICAL PROPERTIES OF NITRIC OXIDE: A MINI REVIEW  Adebola P. Okedere, Towojesudunjoyinlo D. Odede, Arnold N. Eluagwule and *Raphael C. Mordi  Chemistry Department, College of Science and Technology, Covenant University, Km 10 Idiroko Road, OTA,  Ogun State, Nigeria    ARTICLE INFO                                         ABSTRACT     Nitric oxide (NO) is a simple odd-electron molecule that is a primary pollutant. It transmits signals between neurons; playing a role in blood flow and sexual arousal. In this mini review we try to make accessible the properties and functions of this lipophilic molecule to non-specialists.              Copyright©2017, Adebola P. Okedere et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution and reproduction in any medium, provided the original work is properly cited.    INTRODUCTION    Some Chemistry of NO: Nitric oxide is a colorless, paramagnetic gas that is moderately soluble in water. It is produced in the body to help the millions of cells communicate with one another by transmitting signals throughout the entire body system (Clark, 2017). Nitric oxide is a radical that does not dimerize unless cooled to very low temperature at high pressure (Housecroft & Sharpe, 2012; Weller et al., 2010). Nitric oxide is a stable molecule with an odd number of electrons (11 valence electrons), •N═O; with an unpaired electron in one of the pi (π) antibonding orbital, which means that the molecule is paramagnetic. The bonding between nitrogen and oxygen is intermediate between a double bond and triple bond. The molecular electron configuration for NO is:   [Core electrons](σ2s)2(σ*2s)2(π2p)4(σ2p)2(π*2p)1. The net bond order is 2.5 and the oxidation state of nitrogen is +2. The molecular orbital description of the bonding in NO is shown below (Figure 1).  NON O(2s2 2p3) (2s2 2p4)32p 2p2p2p2  Figure 1. Molecular orbital energy level diagram for NO (Burrow et al., 2013)  *Corresponding author: Raphael C. Mordi,        International Journal of Information Research and Review Vol. 04, Issue, 07, pp.xxx-xxxx, July, 2017   Article History:   Received xxxxxxxxxx, 2016 Received in revised form xxxxxxxxxx, 2017 Accepted xxxxxxxxxxxx, 2017 Published online xxxxxxxx, 2017       International Journal of Information Research and Review, June, 2017  Keywords:  Nitric oxide, Structure,  Synthesis, Messenger molecule, Chemical properties,  Physiological properties. Chemistry Department, College of Science and Technology, Covenant University, Km 10 Idiroko Road, OTA, Ogun State, Nigeria Some physical properties of NO are presented in Table 1 below, where it can be seen that its solubility in water is low and heavier than water.  Table 1. Some physical properties of nitric oxide  Chemical formula NO Density 1.3402 g dm−3 Boiling point −152 oC Melting point −164 oC Appearance Colorless gas Molar mass 30.01 g·mol−1 Solubility in water 0.0098 g/100 mL (0 oC) 0.0056 g/100 mL (20 oC) Molecular shape Linear  Nitric oxide is prepared industrially by the oxidation of ammonia; catalyzed by Pt/Rh catalyst at between 820oC to 950oC and at pressures between 1 atm and 12 atm.  4 NH3(g) + 5 O2(g) 4 NO(g) + 6 H2O(l)∆Pt/Rh catalyst  It can be prepared by the reduction of nitrite ions with iodide ions:  KNO2(aq) + KI(aq) + H2SO4(aq) NO(g) + K2SO4(aq) + H2O(l) + 1/2 I2(aq)  The formation of NO from its elements is unfavorable, that is, its enthalpy of formation, ∆Hf is positive, ∆Hf = +90.2 kJ/mol (Housecroft & Sharpe, 2012; Weller et al., 2010). Nitric oxide, NO, is a primary pollutant, produced in the high temperature combustion cylinders of cars and jet engines.  N2(g) + O2(g) ∆ 2 NO(g)  In the atmosphere, it is oxidized to nitrogen dioxide, a brown gas, which is a major contributor to smog.  2 NO(g) + O2(g) 2 NO2(g) Hr = -114.1 kJ The NO2 absorbs ultraviolet light dissociating into NO molecules and O atoms. NO2(g) NO + Ohνλ < 400 nm Nitric oxide undergoes a series of reactions to produce other chemical compounds and some of the reactions include:  Its reaction with oxygen to give nitrogen dioxide, NO2, which when added to water gives nitric acid.  2 NO 2(g) + H2O(l) HNO3(aq) + HNO2(aq)  It reacts with hydrogen gas to form nitrogen and water  2 NO(g) + 2 H2(g) N2(g) + 2 H2O(g)  NO reacts with the halogens to form nitrosyl halides, of general formula XNO. For example, nitrosyl chloride, NOCl, this is a very toxic gas (Jones & Atkins, 1999; Kotz & Treichel Jr, 1999). 2 NO + Cl2 2 NOCl  When nitric oxide reacts with transition metals, metal nitrosyls are formed. The metal nitrosyls are highly colored, deep reds, browns, purples or even black. The NO molecule binds to a low oxidation state metal atom. The most common bonding mode of NO is the terminal linear type (M—NO). The angle of the M—N—O varies from 160º to 180º. Here NO is behaving as a 3-electron donor.  M══N══O                                                   M——N≡≡O  Classic examples of this type of bonding are found in the qualitative test for nitrates, “brown-ring” complex [Fe(H2O)5NO]2+; Roussin’s red and black salts K2[Fe2(NO)4S2] and K[Fe4(NO)7S3] obtained by the action of NO on FeII ion the presence of S2−; and sodium nitroprusside, Na2[Fe(CN)5NO].H2O.  In the bent M—N—O conformation the NO group behaves as a one electron donor. The bond angle is in the range 120 – 140º (Greenwood & Earnshaw, 1989).  M NO   NO causes a wide range of health and environmental effects as a result of the various compounds and derivatives of the family of nitrogen oxides. In a series of reactions that occurs in the troposphere as shown in the reaction equations below, NO increases the concentration of HO• and O3. Ozone is formed when NO and volatile organic compounds (VOCs) react in the presence of heat and sunlight. Nitric oxide reacts with stratospheric ozone to form O2 and nitrogen dioxide (Jones & Atkins, 1999).  CO + HO + O2 HO2 + CO2HO2 + ON HO + NO2NO2 ON +O2 + O3OO  NO acts as catalyst for the conversion of O3 to O2 and is therefore considered as a contributor to the depletion of the ozone layer.  NO + O3 NO2 + O2  Some Physiological Properties of NO  In 1998 Furchgott, Ignarro and Murad won the Nobel Prize for medicine and Physiology for their earlier discovery in 1986 that NO acted as a signaling agent in biological systems. The molecule penetrates membranes and regulates the functions of the cell (Furchgott, 1999; Ignarro, 1999; Murad, 1999). The ability of NO to act as a neurotransmitter arises from its small molecular size and high lipophilicity which allows it to pass through cell walls. It plays a role in a wide range of biological processes such as blood flow and sexual arousal, blood clotting, blood pressure control by dilating arteries; assisting in gastric motility and the immune system’s ability to kill tumor cells and intracellular parasites when it is produced in the macrophage, acting as a toxin (C&EN, 1993). NO has been implicated in the mechanism by which nitroglycerin, which has been used in the treatment of angina. It works by dilating the blood vessels, thereby decreasing the pressure and increasing blood flow.The brain has been found to be a rich source of nitric oxide synthase (NOS) and so it has been postulated that NO may be involved in long-term memory.  NO is synthesized in vivo from the amino acid L-arginine, which is catalysed by the haem-containing NO synthase (NOS) enzymes. There are three forms of NO synthases: neuronal NOS (nNOS), inducible NOS (iNOS) and endothelial NOS (eNOS). Inducible NOS (iNOS) is a high-output enzyme and its activity does not depend on the presence of Ca2+ ions whereas the isoforms nNOS and eNOS depend on Ca2+ for their activity. It has been shown that eNOS and nNOS synthesize NO in response to intracellular Ca2+ levels and the effectiveness of NOS isoforms depends on their binding with calmodulin (Omer et al., 2012). L-arginine is converted to L-citrulline and NO, in a two-step reaction, involving a 5-electron oxidation process, which requires oxygen in addition to the cofactor NADPH.  NHNHNH2NH2COOHNHNH2ONH2COOHL-Arginine L-Citrulline+ + +NO 2NADP 2H2ONO synthase2 NADPH; 2 O2  Figure 2. Synthesis of NO through the conversion of L-arginine to L-citrulline  NO has been linked with some non-human activities, for example, when the blood-sucking insect Rhodnius prolixus attacks a victim. Once its saliva is injected into its victim NO causes the blood vessels to expand and inhibiting blood clotting, making the victim an effective blood donor. The victim now releases histamine to aid healing of the wound but this favors the attacking insect (Burrow et al., 2013; Anderson, 2010). NO activities have been implicated in plant physiological and biochemical processes, which has led to its classification as a phytohormone (Pagnussat et al., 2002; Lamattina et al., 2003; Stohr & Stremlau, 2006; Leshem, 2000). NO in plants is thought to be generated through enzymatic and non-enzymatic pathways. The enzymatic pathway seems to be catalysed by cytosolic nitrate reductase (cNR), NOS or NOS-like enzymes and nitrite:NO reductase (N:NOR). Non-enzymatic pathway is nitrite dismutation to NO and nitrate at acidic pH values (Stohr & Ullrich, 2002; Neill et al., 2003; Graziano & Lamattina, 2005; Hayat et al., 2010; Besson-Bard et al., 2008). Even though NOS-like activity has been detected in plants, animal-type NOS has not been found. NO has been found to have significant effect on seed dormancy, growth, senescence, nitrate reductase activity, respiration, stomatal movement, chlorophyll content, photosynthesis and antioxidant system (Hayat et al., 2010). NO is also related to the function of the well-known anti-impotence drug Viagra® (sildenafil), which works by affecting the concentration of cyclic guanosine monophosphate (cGMP) in the body. On sexual stimulation, NO is released in the body and this leads to the production of cGMP. cGMP triggers relaxation of smooth muscle and an increase in blood flow in the penis, which causes and erection. However an enzyme cGMP phosphodiesterase type 5 (PDE5) destroys cGMP and this causes loss of erection. Viagra® inhibits PDE5, thereby maintaining the concentration of cGMP in the body and duration of erection.  SNNONNH NNOOONHNNNOOOPOOHONH2OHSexual stimulationNOcGMPGMPPDE5an erectionViagra inhibits PDE5no erectionViagra (sildenafil)cGMP Figure 3. Role of Viagra® in erectile dysfunction; note that both Viagra and cGMP have similar heterocyclic rings [4]  Conclusion  Nitric oxide has been shown to play a remarkable role in living systems, as it is involved in blood pressure regulation and blood clotting, neurotransmission. With its involvement in this biochemical and physiological processes in both humans and plants, NO, a small inorganic substance deserves the attention it received which led to the award of the Nobel Prize and the attention it continues to receive. However, the mechanism of its action in plants still requires attention as NO-like protein has not been identified.  REFERENCES  Anderson JF.Structure and Mechanism in salivary proteins from blood-feeding arthropods, Toxicon 2010, 56, 1120 – 1129 doi.org/10.1016/j.toxicon.2009.11.002 Besson-Bard A, Pugin A and Wendehenne D. New insights into Nitrix oxide signaling in plants, Ann Rev Plant Biol, 2008, 59, 21 – 39 DOI:10.1146/annurev.arplant.59.032607.092830 Burrow A, Holman J, Parsons A, Pilling G and Price G. Chemistry3 Introducing Inorganic, Organic and Physical Chemistry, 2nd Edition, Oxford University Press, 2013: Oxford Chemical and Engineering News: The surprising life of nitric oxide Small, reactive and containing no carbon atoms, nitric oxide is nevertheless emerging as a biochemical of major importance, 1993, 71(51) 26 – 38 DOI: 10.1021/cen-v071no051.p026 Clark J What is nitric oxide and how does it work? (assessed 17 April 2017) http://www.nutritionexpress.com/ showarticle.aspx?articleid=286 Furchgott RF.Endothelium-Derived Relaxing Factor: Discovery, Early Studies, and Identifcation as Nitric Oxide, Angew. Chem. Int. Ed. 1999, 38, 1870 – 1880 Graziano M and Lamattina L. Nitric oxide and iron in plants: an emerging and converging story, Trends Plant Sci, 2005, 10, 4 – 8 doi.org/10.1016.j.tplants.2004.12.004 Greenwood NN and Earnshaw A. Chemistry of the Elements, Pergamon Press, Oxford, 1989 Hayat S, Hasan SA, Mori M, Fariduddin Qand Ahmad A. Nitric oxide: Chemistry, biosynthesis and physiological role, in Nitric oxide in plant physiology, Ed. S Hayat, M Mori, J Pichtel and A Ahmad, Wiley-VCH Verlag GmbH & Co, KGaAWeinhelm, 2010: pp 1 – 16 Housecroft CE and Sharpe AG. Inorganic Chemistry, 4th Edition, Pearson: 2012 London Ignarro LJ. Nitric Oxide: A Unique Endogenous Signaling Molecule in Vascular Biology, Angew. Chem. Int. Ed. 1999, 38, 1882 – 1892 Jones L and Atkins P. Chemistry Molecules, Matter and Change, 4th Edition, WH Freeman and Company, New York, 1999 Kotz JC and Treichel P, Jr. Chemistry and Chemical Reactivity, 4th Edition, Saunders Golden Sunburst Series, Saunders College Publishing, Harcourt Brace College Publishers, Forth Worth, 1999 Lamattina L, Garcia-Mata C, Graziano M and Pagnussat GC. Nitric oxide: The versatility of an extensive signal molecule, Annu Rev Plant Biol 2003, 54 109 – 136 DOI:10.1146/annurev.arplant.54.031902.134752 Leshem YY. Nitric oxide in plants, in occurrence, Function and Use, 2000, Kluwer Academic Publishers, Dordrecht, The Netherlands Murad F. Discovery of Some of the Biological Effects of Nitric Oxide and Its Role in Cell Signaling, Angew. Chem. Int. Ed. 1999, 38, 1856 – 1868 Neill SJ, Desikan R and Hancock JT. Nitric oxide signaling in plants, New Phytol 2003, 159, 11 – 35 DOI:10.1046.j.1469-8137.2003.00804.x Omer N, Rohilla A, Rohilla S and Kushnoor A. Nitric oxide: role in human biology. Int J Pharm Sci Drug Res, 2012, 4(2), 105 – 109. Pagnussat GC, Simontacchi M, Puntarulo S and Lamattina, L. Nitric Oxide Is Required for Root Organogenesis. Plant Physiology, 2002, 129, 954 – 956 doi.10.1104/pp.004036 Stohr C and Ullrich WR. Generation and possible roles of nitric oxide in plant and roots and their apoplastic space, J Exp Bot 2002, 53, 2293 – 2303 DOI.org/10.1093.jxb/erf110 Stohr C and Stremlau S. Formation and possible roles of nitric oxide in plant roots, J Exp Bot, 2006, 57, 463 – 470 doi.org/10.1093/jxb/erj058 Weller M, Overton T, Burke J, and Armstrong F.Inorganic Chemistry, 6th Edition, Oxford University Press: 2010 Oxford  ******* 

SOME CHEMICAL AND PHYSIOLOGICAL PROPERTIES OF NITRIC OXIDE: A MINI REVIEW

        REVIEW ARTICLE  SOME CHEMICALAND PHYSIOLOGICAL PROPERTIES OF NITRIC OXIDE: A MINI REVIEW  Adebola P. Okedere, Towojesudunjoyinlo D.Odede, ArnoldN. Eluagwule and *Raphael C. Mordi  Chemistry Department, College of Science and Technology, Covenant University, Km 10 Idiroko Road, OTA,  Ogun State, Nigeria    ARTICLE INFO                                         ABSTRACT     Nitric oxide (NO) is a simple odd-electron molecule that is a primary pollutant. It transmits signals between neurons; playing a role in blood flow and sexual arousal. In this mini review we try to make accessible the properties and functions of this lipophilic molecule to non-specialists.              Copyright©2017, Adebola P. Okedere et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution and reproduction in any medium, provided the original work is properly cited.    INTRODUCTION    Some Chemistry of NO: Nitric oxide is a colorless, paramagnetic gas that is moderately soluble in water.It is produced in the body to help the millions of cells communicate with one another by transmitting signals throughout the entire body system[1]. Nitric oxideis a radical that does not dimerize unless cooled to very low temperature at high pressure[2,3]. Nitric oxide is a stable molecule with an odd number of electrons (11 valence electrons), •N═O; with an unpaired electron in one of the pi () antibonding orbital, which means that the molecule is paramagnetic. The bonding between nitrogen and oxygen is intermediate between a double bond and triple bond. The molecular electron configuration for NO is:   [Core electrons](2s)2(*2s)2(2p)4(2p)2(*2p)1. The net bond order is 2.5 and the oxidation state of nitrogen is +2. The molecular orbital description of the bonding in NO is shown below (Figure 1).  NON O(2s2 2p3) (2s2 2p4)32p 2p2p2p2  Figure 1. Molecular orbital energy level diagram for NO[4]  *Corresponding author: Raphael C. Mordi, Chemistry Department, College of Science and Technology, Covenant University, Km 10 Idiroko Road, OTA, Ogun State, Nigeria        International Journal of Information Research and Review Vol. 04, Issue, 07, pp.4294-4298, July, 2017  Article History:   Received 17th April, 2017 Received in revised form 26th May, 2017 Accepted 14th June, 2017 Published online 26th July, 2017  International Journal of Information Research and Review, July, 2017 Keywords:  Nitric oxide, Structure,  Synthesis, Messenger molecule, Chemical properties,  Physiological properties. Some physical properties of NO are presented in Table 1 below, where it can be seen that its solubility in water is low and heavier than water.  Table 1. Some physical properties of nitric oxide  Chemical formula NO Density 1.3402 g dm−3 Boiling point −152 oC Melting point −164 oC Appearance Colorless gas Molar mass 30.01 g·mol−1 Solubility in water 0.0098 g/100 mL (0 oC) 0.0056 g/100 mL (20 oC) Molecular shape Linear  Nitric oxide is prepared industrially by the oxidation of ammonia; catalyzed by Pt/Rh catalyst at between 820oC to 950oC and at pressures between 1 atm and 12 atm.  4 NH3(g) + 5 O2(g) 4 NO(g) + 6 H2O(l)Pt/Rh catalyst  It can be prepared by the reduction of nitrite ions with iodide ions:  KNO2(aq) + KI(aq) + H2SO4(aq) NO(g) + K2SO4(aq) + H2O(l) + 1/2 I2(aq)  The formation of NO from its elements is unfavorable, that is, its enthalpy of formation,Hfis positive, Hf= +90.2 kJ/mol[2,3]. Nitric oxide, NO, is a primary pollutant, produced in the high temperature combustion cylinders of cars and jet engines  N2(g) + O2(g)2 NO(g)  In the atmosphere, it is oxidized to nitrogen dioxide, a brown gas, which is a major contributor to smog.  2 NO(g) + O2(g) 2 NO2(g) Hr = -114.1 kJ The NO2 absorbs ultraviolet light dissociating into NO molecules and O atoms. NO2(g) NO + Oh < 400 nm Nitric oxide undergoes a series of reactions to produce other chemical compounds and some of the reactions include:  Its reaction with oxygen to give nitrogen dioxide, NO2, which when added to water gives nitric acid.  2 NO 2(g) + H2O(l) HNO3(aq) + HNO2(aq)  It reacts with hydrogen gas to form nitrogen and water  2 NO(g) + 2 H2(g) N2(g) + 2 H2O(g)  NO reacts with the halogens to form nitrosyl halides, of general formula XNO. For example, nitrosyl chloride,NOCl, this is a very toxic gas [5,6]. 2 NO + Cl2 2 NOCl  When nitric oxide reacts with transition metals, metal nitrosyls are formed. The metal nitrosyls are highly colored, deep reds, browns, purples or even black. The NO molecule binds to a low oxidation state metal atom. The most common bonding mode of NO is the terminal linear type (M—NO). The angle of the M—N—O varies from 160º to 180º. Here NO is behaving as a 3-electron donor.  M══N══O                                                   M——N≡≡O  4295                                  Adebola P. Okedere et al. Some chemicaland physiological properties of nitric oxide: A mini review  Classic examples of this type of bonding are found in the qualitative test for nitrates, “brown-ring” complex [Fe(H2O)5NO]2+;Roussin’s red and black salts K2[Fe2(NO)4S2] and K[Fe4(NO)7S3] obtained by the action of NO on FeII ion the presence of S2; and sodium nitroprusside, Na2[Fe(CN)5NO].H2O.  In the bent M—N—O conformation the NO group behaves as a one electron donor. The bond angle is in the range 120 – 140º [7].  M NO  NO causes a wide range of health and environmental effects as a result of the various compounds and derivatives of the family of nitrogen oxides.In a series of reactions that occurs in the troposphere as shown in the reaction equations below,NO increases the concentration of HO• and O3. Ozone is formed when NO and volatile organic compounds (VOCs) react in the presence of heat and sunlight. Nitric oxide reacts with stratospheric ozone to form O2 and nitrogen dioxide [6].  CO + HO + O2 HO2 + CO2HO2 + ON HO + NO2NO2 ON +O2 + O3OO  NO acts as catalyst for the conversion of O3 to O2 and is therefore considered as a contributor to the depletion of the ozone layer.  NO + O3 NO2 + O2  Some Physiological Properties of NO  In 1998 Furchgott, Ignarro and Murad won the Nobel Prize for medicine and Physiology for their earlier discovery in 1986 that NO acted as a signaling agent in biological systems. The molecule penetrates membranes and regulates the functions of the cell [8,9,10]. The ability of NO to act as a neurotransmitter arises from its small molecular size and high lipophilicity which allows it to pass through cell walls. It plays a role in a wide range of biological processes such as blood flow and sexual arousal, blood clotting, blood pressure control by dilating arteries; assisting in gastric motility and the immune system’s ability to kill tumor cells and intracellular parasites when it is produced in the macrophage, acting as a toxin[11].NO has been implicated in the mechanism by which nitroglycerin, which has been used in the treatment of angina.Itworks by dilating the blood vessels, thereby decreasing the pressure and increasing blood flow.The brain has been found to be a rich source of NOS and so it has been postulated that NO may beinvolved in long-term memory.  NO is synthesized in vivo from the amino acid L-arginine, which is catalysed by the haem-containing NO synthase (NOS) enzymes. There are three forms of NO synthases: neuronal NOS (nNOS), inducible NOS (iNOS) and endothelial NOS (eNOS). Inducible NOS (iNOS) is a high-output enzyme and its activity does not depend on the presence of Ca2+ ions whereas the isoformsnNOS and eNOS depend on Ca2+ for their activity. It has been shown that eNOS and nNOS synthesize NO in response to intracellular Ca2+ levels and the effectiveness of NOS isoforms depends on their binding with calmodulin[12]. L-arginine is converted to L-citrulline and NO, in a two-step reaction, involving a 5-electron oxidation process, which requires oxygen in addition to the cofactor NADPH.   NHNHNH2NH2COOHNHNH2ONH2COOHL-Arginine L-Citrulline+ + +NO 2NADP 2H2ONO synthase2 NADPH; 2 O2  Figure 2. Synthesis of NO through the conversion of L-arginine to L-citrulline  NO has been linked with some non-human activities, for example, when the blood-sucking insectRhodniusprolixus attacks a victim. Once its saliva is injected into its victim NO causes the blood vessels to expand and inhibiting blood clotting, making the victim an effective blood donor. The victim now releases histamine to aid healing of the wound but this favors the attacking  4296                              International Journal of Information Research and Review, Vol. 04, Issue, 07, pp.4294-4298, July, 2017 insect[4,13]. NO activities have been implicated in plant physiological and biochemical processes, which has led to its classification as a phytohormone[14,15,16,17]. NO in plants is thought to be generated through enzymatic and non-enzymatic pathways. The enzymatic pathway seems to be catalysed by cytosolic nitrate reductase (cNR), NOS or NOS-like enzymes and nitrite:NO reductase (N:NOR). Non-enzymatic pathway is nitrite dismutation to NO and nitrate at acidic pH values[18,19,20,21,22]. Even though NOS-like activity has been detected in plants, animal-type NOS has not been found. NO has been found to have significant effect on seed dormancy, growth, senescence, nitrate reductase activity, respiration, stomatal movement, chlorophyll content, photosynthesis and antioxidant system[21]. NO is also related to the function of the well-known anti-impotence drug Viagra® (sildenafil), which works by affecting the concentration of cyclic guanosine monophosphate (cGMP) in the body. On sexual stimulation, NO is released in the body and this leads to the production of cGMP. cGMP triggers relaxation of smooth muscle and an increase in blood flow in the penis, which causes and erection. However an enzyme CGMP phosphodiesterase type5 (PDE5) destroys cGMP and this causes loss of erection. Viagra® inhibits PDE5, thereby maintaining the concentration of cGMP in the body and duration of erection.  SNNONNHNNOOONHNNNOOOPOOHONH2OHSexual stimulationNOcGMPGMPPDE5an erectionViagra inhibits PDE5no erectionViagra (sildenafil)cGMP Figure 3. Role of Viagra® in erectile dysfunction; note that both Viagra and cGMP have similar heterocyclic rings [4]  Conclusion  Nitric oxide has been shown to play a remarkable role in living systems, as it is involved in blood pressure regulation and blood clotting, neurotransmission. With its involvement in this biochemical and physiological processes in both humans and plants, NO, a small inorganic substance deserves the attention it received which led to the award of the Nobel Prize and the attention it continues to receive. However, the mechanism of its action in plants still requires attention as NO-like protein has not been identified.  REFERENCES  Anderson JF.Structure and Mechanism in salivary proteins from blood-feeding arthropods, Toxicon2010, 56, 1120– 1129 doi.org/10.1016/j.toxicon.2009.11.002 Besson-Bard A, Pugin A and Wendehenne D. New insights into Nitrix oxide signaling in plants, Ann Rev Plant Biol, 2008, 59, 21 – 39 DOI:10.1146/annurev.arplant.59.032607.092830 Chemical and Engineering News: The surprising life of nitric oxide Small, reactive and containing no carbon atoms, nitric oxide is nevertheless emerging as a biochemical of major importance, 1993, 71(51) 26 – 38 DOI: 10.1021/cen-v071no051.p026 Chemistry3 Introducing Inorganic, Organic and Physical Chemistry, 2nd Edition, Burrow A, Holman J, Parsons A, Pilling G and Price G. Oxford University Press, 2013: Oxford Clark J What is nitric oxide and how does it work? (assessed 17 April 2017) http://www.nutritionexpress.com/ showarticle.aspx?articleid=286 Furchgott RF.Endothelium-Derived Relaxing Factor: Discovery, Early Studies, and Identifcation as Nitric Oxide, Angew. Chem. Int. Ed. 1999, 38, 1870 – 1880 Graziano Mand Lamattina L. Nitric oxide and iron in plants: an emerging and converging story, Trends Plant Sci, 2005, 10, 4 – 8 doi.org/10.1016.j.tplants.2004.12.004 Greenwood NN and Earnshaw A. Chemistry of the Elements, Pergamon Press, Oxford, 1989 Hayat S, Hasan SA, Mori M, Fariduddin Qand Ahmad A. Nitric oxide: Chemistry, biosynthesis and physiological role, in Nitric oxide in plant physiology, Ed. S Hayat, M Mori, J Pichtel and A Ahmad, Wiley-VCH Verlag GmbH & Co, KGaAWeinhelm, 2010: pp 1 – 16 Housecroft CE and Sharpe AG. Inorganic Chemistry, 4th Edition, Pearson: 2012 London  4297                                  Adebola P. Okedere et al. Some chemicaland physiological properties of nitric oxide: A mini review  Ignarro LJ. Nitric Oxide: A Unique Endogenous Signaling Molecule in Vascular Biology, Angew. Chem. Int. Ed. 1999, 38, 1882 – 1892 Jones L and Atkins P. Chemistry Molecules, Matter and Change, 4th Edition, WH Freeman and Company, New York, 1999 KotzJC and Treichel P, Jr. Chemistry and Chemical Reactivity, 4th Edition, Saunders Golden Sunburst Series, Saunders College Publishing, Harcourt Brace College Publishers, Forth Worth, 1999 Lamattina L, Garcia-Mata C, Graziano Mand Pagnussat GC.Nitric oxide: The versatility of an extensive signal molecule, Annu Rev Plant Biol2003, 54 109 – 136 DOI:10.1146/annurev.arplant.54.031902.134752 Leshem YY. Nitric oxide in plants, in occurrence, Function and Use, 2000, Kluwer Academic Publishers, Dordrecht, The Netherlands Murad F. Discovery of Some of the Biological Effects of Nitric Oxide and Its Role in Cell Signaling, Angew. Chem. Int. Ed. 1999, 38, 1856 – 1868 Neill SJ, Desikan R and Hancock JT. Nitric oxide signaling in plants, New Phytol 2003, 159, 11 – 35 DOI:10.1046.j.1469-8137.2003.00804.x Omer N, Rohilla A, Rohilla S and Kushnoor A. Nitric oxide: role in human biology. Int J Pharm Sci Drug Res, 2012, 4(2), 105 – 109. Pagnussat GC, Simontacchi M, Puntarulo Sand Lamattina, L. Nitric Oxide Is Required for Root Organogenesis. Plant Physiology, 2002, 129, 954 – 956 doi.10.1104/pp.004036 Stohr C and Ullrich WR.Generation and possible roles of nitric oxide in plant and roots and their apoplastic space, J Exp Bot 2002, 53, 2293 – 2303 DOI.org/10.1093.jxb/erf110 Stohr Cand Stremlau S.Formation and possible roles of nitric oxide in plant roots, J Exp Bot, 2006, 57, 463 – 470 doi.org/10.1093/jxb/erj058 Weller M, Overton T, Burke J, and Armstrong F.Inorganic Chemistry, 6th Edition, Oxford University Press: 2010 Oxford  *******  4298                              International Journal of Information Research and Review, Vol. 04, Issue, 07, pp.4294-4298, July, 2017 

SOME CHEMICALAND PHYSIOLOGICAL PROPERTIES OF NITRIC OXIDE: A MINI REVIEW

http://eprints.covenantuniversity.edu.ng/9875/1/IJIRR%20-%202085%20-%20SOME%20CHEMICAL%20AND%20PHYSIOLOGICAL%20PROPERTIES%20OF%20NO.pdf

SOME CHEMICAL AND PHYSIOLOGICAL PROPERTIES OF NITRIC OXIDE: A MINI REVIEW

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