Nitration activates tyrosine toward reaction with the hydrated electron

Area of Science:

• Biochemistry
• Chemical Kinetics
• Oxidative Stress Research

Background:

• 3-Nitrotyrosine is a recognized biomarker for oxidative stress, implicated in various diseases.
• Understanding the reactivity of 3-nitrotyrosine with biological species is crucial for disease mechanism elucidation.

Purpose of the Study:

• To investigate the reaction kinetics and spectral properties of hydrated electrons with 3-nitrotyrosine and its derivatives.
• To elucidate the reaction mechanisms and the influence of the nitro group on tyrosine reactivity.

Main Methods:

• Transient UV-visible absorption spectroscopy was employed to study the reaction kinetics.
• The reaction of hydrated electrons (e(aq)(-)) with 3-nitrotyrosine and derivatives was analyzed across different pH levels.

Main Results:

• The reaction rate constants for 3-nitrotyrosine derivatives with hydrated electrons approach the diffusion-control limit, significantly exceeding those of tyrosine.
• Spectra indicate the formation of aromatic nitro anion radicals, with estimated absorptivity at 300 nm.
• pH-dependent studies suggest deprotonation of the amino group influences the reaction pathway, potentially leading to deamination.

Conclusions:

• The nitro group markedly activates tyrosine and its derivatives towards reaction with hydrated electrons.
• This activation influences the redox chemistry of biomolecules, particularly under conditions of oxidative stress.