S-Nitroso-N-acetyl-D,L-penicillamine (SNAP) is a synthetic S-nitrosothiol compound, serving as a stable and widely used nitric oxide (NO) donor. It is a racemic mixture of the D- and L-isomers of N-acetylpenicillamine that has been S-nitrosylated. SNAP spontaneously decomposes in solution to release nitric oxide, a crucial signaling molecule in biological systems. Its primary application is in life science research as a tool compound to study the physiological and pathological roles of nitric oxide. Researchers utilize SNAP to induce vasodilation, modulate neurotransmission, investigate immune responses, and explore cellular signaling pathways involving cGMP. It is particularly valued for its relative stability compared to gaseous NO, allowing for controlled delivery in experimental settings. SNAP is also employed in the development of NO-releasing materials and in studies related to cardiovascular biology, neuroscience, and inflammation. Due to its ability to release NO, it requires careful handling and storage, typically at low temperatures and protected from light to prevent premature decomposition.