Efficient trapping of HNO by deoxymyoglobin

Area of Science:

• Biochemistry
• Inorganic Chemistry
• Chemical Biology

Background:

• Nitrosyl hydride (HNO), also known as nitroxyl, is a reactive species implicated in nitric oxide (NO) biological functions.
• HNO is a transient molecule, making its study and direct trapping challenging.

Purpose of the Study:

• To report the first successful generation and characterization of a stable HNO-metal complex.
• To investigate the reaction of HNO with deoxymyoglobin (Mb-Fe(II)) as a trapping mechanism.
• To elucidate the potential biological relevance of HNO-heme protein interactions.

Main Methods:

• Direct trapping of HNO, generated from MSHA or Angeli's salt, using deoxymyoglobin in aqueous solutions (pH 7-10).
• Characterization of the HNO-deoxymyoglobin adduct (Mb-HNO) using 1H NMR, UV-vis, and EPR spectroscopies.
• Kinetic analysis of Mb-HNO generation and byproduct formation.

Main Results:

• Formation of a stable Mb-Fe(II)-HNO adduct (Mb-HNO) was confirmed by a unique 1H NMR signal at 14.8 ppm.
• Maximum Mb-HNO yields ranged from 60-80%, with side reactions and adduct reactivity limiting efficiency.
• The bimolecular rate constant for HNO trapping by deoxymyoglobin was determined to be at least 1.4 x 10(4) M(-1) s(-1).

Conclusions:

• The rapid and irreversible binding of HNO to deoxymyoglobin demonstrates a viable method for HNO stabilization.
• These findings suggest that the biological activity of nitroxyl may involve its interaction with ferrous heme proteins like myoglobin and hemoglobin.
• This work provides a foundation for further research into HNO's biological roles and therapeutic potential.