Ubiquinones: Stereochemistry and Biological Implications

Abstract

Proton NMR and ¹³C-NMR studies on the configuration of CoQ_n homologues show that the polyisoprenoid side-chain is in the all-trans configuration and confers a higher degree of ridigity to the quinones with respect to the acyl-chains of the phospholipids within the membrane bilayer.

The quinonoid ring appears to be specifically involved in the redox function of the coenzyme while the side-chain length only affects the lipophilicity of the molecule.

LIS data show that the ring strongly interacts with metals as a consequence of the high π-electron density on the carbonyls that is somewhat larger on the carbonyl oxygen in α to the isoprenoid chain.

Key Words:

• Coenzyme Q configuration
• Proton NMR ¹³C-NMR
• LIS