NONOate

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NONOate, in chemistry is a compound having the chemical formula R¹R³N-(NO^-)-N=O. One example for this is the 1,1-diethyl-2-hydroxy-2-nitrosohydrazine or diethylamine dinitric oxide. These compounds are unusual as they have three sequential nitrogen atoms i.e. having amine functional group, a bridging NO^- group and a terminal nitrosyl functional group. In contact with water this compounds releases NO (nitric oxide).

pH dependent decomposition of NONOates.

Most NONOates are stable in alkaline solution above pH 8.0 (e.g. 10 mM NaOH) and can be stored at -20 ^oC in this way for the short term. In order to generate NO from NONOates the pH must be lowered accordingly. Typically a dilution of the stock NONOate solution is made in phosphate buffer (pH7.4, Tris buffers can also be used) and incubated at room temperature for the desired time to allow NO to accumulate in solution. This is often visible as bubbles at high NONOate concentrations. Incubation time is important since the different nonoates have different half lives (t1/2) in phosphate buffer at pH 7.4. For example, the halflife of MAHMA NONOate under these conditions is ~3.5 minutes, whilst the t1/2 of DPTA NONOate is 300 minutes. This is often useful in biological systems where a combination of different NONOates can be used to give a sustained release of nitric oxide. It should be noted that at pH 5.0, most NONOates are considered to decompose almost instantaneously.

References

• L. A. Sheffler, D. A. Wink, G. Melillo, G. W. Cox (1995). "Characterization of nitric oxide-stimulated ADP-ribosylation of various proteins from the mouse macrophage cell line ANA-1 using sodium nitroprusside and the novel nitric oxide-donating compound diethylamine dinitric oxide". Journal of Leukocyte Biology 57 (1): 152 - 159.
• Joseph A. Hrabie, John R. Klose, David A. Wink, Larry K. Keefer (1993). "New nitric oxide-releasing zwitterions derived from polyamines". J. Org. Chem. 58 (6): 1472-1476. doi:10.1021/jo00058a030.