Localization of hydrophobic N-diazeniumdiolates in aqueous micellar solution.

The interaction of phenyl-substituted zwitterionic N-diazeniumdiolates PhCH(2)N[N(O)NO](-)(CH(2))(2)NH(3)(+) (1) and PhCH(2)N[N(O)NO](-)(CH(2))(2)NH(2)(+)CH(2)Ph (2) with aqueous micellar solutions of prototypal surfactants was investigated by means of UV/vis and (1)H NMR spectroscopy in order to establish the localization of hydrophobic N-diazeniumdiolates in micelles as a model for the binding of the NO donors in biological membranes. In the presence of sodium dodecyl sulfate (SDS), significant shifts of the apparent pK(a) values of 1 and 2 were observed, suggesting strong electrostatic interaction between the diazeniumdiolates and the negatively charged SDS micelles. No effect on both pK(a) and rate of NO release was found in the presence of Triton X-100.

Hydrophobic N-diazeniumdiolates and the aqueous interface of sodium dodecyl sulfate (SDS) micelles.

Zwitterionic diazeniumdiolates of the form RN[N(O)NO(-)](CH(2))(2)NH(2) (+)R, where R=CH(3) (1), (CH(2))(3)CH(3) (2), (CH(2))(5)CH(3) (3), and (CH(2))(7)CH(3) (4) were synthesized by reaction of the corresponding diamines with nitric oxide. Spectrophotometrically determined pK(a)(O) values, attributed to protonation at the terminal oxygen of the diazeniumdiolate group, show shifts to higher values in dependence of the chain lengths of R. The pH dependence of the decomposition of NO donors 1-3 was studied in buffered solution between pH 5 and 8 at 22 degrees C, from which pK(a)(N) values for protonation at the amino nitrogen, leading to release of NO, were estimated.