Probing lipid peroxidation by using linoleic acid and benzophenone.

Area of Science:

• Photochemistry
• Organic Chemistry
• Biophysical Chemistry

Background:

• Benzophenone (BZP) is a photosensitizer.
• 1,4-dienes are susceptible to radical reactions.
• Understanding photoreactions is crucial for biological processes like oxidative stress.

Purpose of the Study:

• To elucidate the reaction mechanisms between benzophenone (BZP) and various 1,4-dienes.
• To investigate the formation and reactivity of radicals, particularly linoleyl radical (LA(.)).
• To correlate photoreaction pathways with biological phenomena such as oxidative stress.

Main Methods:

• Steady-state photolysis
• Laser flash photolysis (LFP)
• Photochemically induced dynamic nuclear polarization (photo-CIDNP)

Main Results:

• BZP undergoes cross-coupling and hydrogen abstraction with 1,4-dienes.
• Radical intermediates were detected and characterized, including linoleyl radical (LA(.))
• LA(.) was shown to form conjugated isomers on a millisecond timescale.
• Reactivity of model dienes with triplet excited BZP was quantified (k(q) ≈10(8) M(-1)s(-1)).

Conclusions:

• The study provides a detailed mechanistic understanding of BZP-diene photoreactions.
• Experimental evidence for linoleyl radical (LA(.)) formation and its subsequent conversion was established.
• These findings offer insights into the molecular mechanisms underlying oxidative stress and membrane damage.