Inchemistry, aNONOate, also called adiazeniumdiolate,[1] is a compound having thechemical formula R1R2N−(NO−)−N=O, where R1 and R2 arealkyl groups. These compounds are unusual in having three sequentialnitrogen atoms: anaminefunctional group, a bridging NO− group, and a terminalnitrosyl group.[2][3] Almost all known examples form with the oxygen atomscis to the double bond, which is also the more thermodynamically stable configuration.[1]
NONOates form reversibly when a puresecondary amine is exposed tonitric oxide:[1]
In contact withwater, these compounds release NO (nitric oxide).[2][3]
Most NONOates are stable inalkaline solution abovepH 8.0 (e. g. 10 mMNaOH) and can be stored at −20 °C in this way for the short term. To generate NO from NONOates, the pH is lowered accordingly. Typically, adilution of the stock NONOate solution is made in aphosphate buffer (pH 7.4;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 NONOateconcentrations. Incubation time is important, since the different NONOates have differenthalf-lives (t1/2) in phosphate buffer at pH 7.4. For example, the half-life of MAHMA NONOate under these conditions is ~3.5 minutes, whilst thet1/2 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. At pH 5.0, most NONOates are considered todecompose almost instantaneously.