Poster Presentation 21st International Conference on Biological Inorganic Chemistry 2025

Thiol Mediated NO Generation from Nitrate at Heme Models. Detection of intermediates in the solvent/water free environment. (#409)

Garik G Martirosyan 1 , Astghik A Hovhannisyan 1 , Lusine S Harutyunyan 1 , Alexei V Iretskii 2 , Peter C. Ford 3
  1. The Scientific Technological Centre of Organic and Pharmaceutical Chemistry NAS RA,, Yerevan, NONE SELECTED, Armenia
  2. Department of Chemistry , Lake Superior State University, Sault Ste. Marie, MICHIGAN, United States
  3. Department of Chemistry and Biochemistry, University of California,, Santa Barbara, California, United States

 

Nitric oxide (NO) is a vital signaling molecule in mammalian physiology produced in vivo by nitric oxide synthases [1]. The inorganic nitrate (NO3-) and nitrite (NO2-) are also found in humans as the products of a particular diet or different oxidative processes [2]. Over the past decade, it has been established that an alternative source of NO exists through the reduction of nitrite by a variety of enzymatic and nonenzymatic pathways [3]. The availability of thiols in the biological milieu has stimulated studies of their role in the conversion of  nitrite to nitric oxide. While thiol/H2S mediated reduction of nitrite at heme model has been studied in details [4], analogous reactivity of heme iron nitrate was only recently communicated [5].

Here we present the low-temperature FT-IR and Uv-Vis spectroscopic results of the H2S/thiol reaction with solid sublimed layers containing the FeTTP(NO3) and FeTTP(NO2) complexes (TTP - meso-tetratolylporphyrin 2-). The eventual product of these reactions in all cases are the nitrosyl complex Fe(TTP)(NO), water and respective disulfides. Mechanism of the reactions that accounts for all spectroscopic observations using the 15N and 18O labeled nitrate is proposed to proceed through the two consecutive oxygen atom transfer reactions: initial rate limiting reduction of coordinated nitate to nitrite followed by fast conversion of the coordinated nitrite to NO. Transient intermediates detected upon monitoring the reaction from 77 K to room temperature and final products, analyzed by mass spectrometry are discussed.

 

Acknowledgements: The financial support from SCS of the Republic of Armenia (Project 21AG-1D040) is gratefully acknowledged.

 

 

 

 

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