[Mono- and Binuclear Dinitrosyl Iron Complexes with Thiol-containing Ligands in Various Biosystems]

Area of Science:

• Biochemistry
• Bioinorganic Chemistry

Background:

• Dinitrosyl iron complexes (DNICs) with thiol ligands are found in biological systems.
• These complexes are often EPR-silent binuclear forms when associated with proteins like bovine serum albumin.
• Nitric oxide (NO) plays a crucial role as a biological regulator.

Purpose of the Study:

• To investigate the forms and transformations of DNICs in biological contexts.
• To elucidate the role of DNICs as a potential storage or transport form of NO.

Main Methods:

• Electron Paramagnetic Resonance (EPR) spectroscopy to detect and characterize iron-nitrosyl complexes.
• Studies in biological systems like baker's yeast and animal tissues.
• Chemical manipulation of pH and addition of specific reagents like dithiocarbamates.

Main Results:

• DNICs with thiol ligands predominantly exist as EPR-silent binuclear species in biological environments.
• These binuclear forms can be converted to EPR-active mononuclear forms under specific conditions (e.g., increased pH, bielectronic reduction, or dithiocarbamate treatment).
• Dithiocarbamates transform DNICs into EPR-active mononitrosyl iron complexes.

Conclusions:

• Endogenous binuclear DNICs with thiol ligands are proposed as the functional
• ,
• working form
• of endogenous nitric oxide.
• The biological activity of these DNICs is similar to endogenous NO systems, supporting their regulatory role.