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NO Generation from Nitrite at Zinc(II): Role of Thiol Persulfidation in the Presence of Sulfane Sulfur.
Sahana, Tuhin; Valappil, Adwaith K; Amma, Anaswar S P R; Kundu, Subrata.
Affiliation
  • Sahana T; School of Chemistry, Indian Institute of Science Education and Research Thiruvananthapuram (IISER-TVM), Thiruvananthapuram 695551, India.
  • Valappil AK; School of Chemistry, Indian Institute of Science Education and Research Thiruvananthapuram (IISER-TVM), Thiruvananthapuram 695551, India.
  • Amma ASPR; School of Chemistry, Indian Institute of Science Education and Research Thiruvananthapuram (IISER-TVM), Thiruvananthapuram 695551, India.
  • Kundu S; School of Chemistry, Indian Institute of Science Education and Research Thiruvananthapuram (IISER-TVM), Thiruvananthapuram 695551, India.
ACS Org Inorg Au ; 3(5): 246-253, 2023 Oct 04.
Article in En | MEDLINE | ID: mdl-37810413
Nitrite-to-NO transformation is of prime importance due to its relevance in mammalian physiology. Although such a one-electron reductive transformation at various redox-active metal sites (e.g., Cu and Fe) has been illustrated previously, the reaction at the [ZnII] site in the presence of a sacrificial reductant like thiol has been reported to be sluggish and poorly understood. Reactivity of [(Bn3Tren)ZnII-ONO](ClO4) (1), a nitrite-bound model of the tripodal active site of carbonic anhydrase (CA), toward various organic probes, such as 4-tert-butylbenzylthiol (tBuBnSH), 2,4-di-tert-butylphenol (2,4-DTBP), and 1-fluoro-2,4-dinitrobenzene (F-DNB), reveals that the ONO-moiety in the [ZnII]-nitrite coordination motif of complex 1 acts as a mild electrophile. tBuBnSH reacts mildly with nitrite at a [ZnII] site to provide S-nitrosothiol tBuBnSNO prior to the release of NO in 10% yield, whereas the phenolic substrate 2,4-DTBP does not yield the analogous O-nitrite compound (ArONO). The presence of sulfane sulfur (S0) species such as elemental sulfur (S8) and organic polysulfides (tBuBnSnBntBu) during the reaction of tBuBnSH and [ZnII]-nitrite (1) assists the nitrite-to-NO conversion to provide NO yields of 65% (for S8) and 76% (for tBuBnSnBntBu). High-resolution mass spectrometry (HRMS) analyses on the reaction of [ZnII]-nitrite (1), tBuBnSH, and S8 depict the formation of zinc(II)-persulfide species [(Bn3Tren)ZnII-Sn-BntBu]+ (where n = 2, 3, 4, 5, and 6). Trapping of the persulfide species (tBuBnSS-) with 1-fluoro-2,4-dinitrobenzene (F-DNB) confirms its intermediacy. The significantly higher nucleophilicity of persulfide species (relative to thiol/thiolate) is proposed to facilitate the reaction with the mildly electrophilic [ZnII]-nitrite (1) complex. Complementary analyses, including multinuclear NMR, electrospray ionization-MS, UV-vis, and trapping of reactive S-species, provide mechanistic insights into the sulfane sulfur-assisted reactions between thiol and nitrite at the tripodal [ZnII]-site. These findings suggest the critical influential roles of various reactive sulfur species, such as sulfane sulfur and persulfides, in the nitrite-to-NO conversion.

Full text: 1 Collection: 01-internacional Database: MEDLINE Type of study: Prognostic_studies Language: En Journal: ACS Org Inorg Au Year: 2023 Document type: Article Affiliation country: India Country of publication: United States

Full text: 1 Collection: 01-internacional Database: MEDLINE Type of study: Prognostic_studies Language: En Journal: ACS Org Inorg Au Year: 2023 Document type: Article Affiliation country: India Country of publication: United States