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Abstract
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Radioprotective effects of vitamin C and vitamin E as a water-soluble and a lipid-soluble
agent, respectively, were investigated at the molecular level during the imposition of gamma
radiation-induced structural changes to bovine serum albumin (BSA) at the therapeutic dose of
3 Gy. Secondary and tertiary structural changes of control and irradiated BSA samples were investigated
using circular dichroism and fluorescence spectroscopy. The preirradiation tests showed
nonspecific and reversible binding of vitamins C and E to BSA. Secondary and tertiary structures of
irradiated BSA considerably changed in the absence of the vitamins. Upon irradiation, -helices of
BSA transitioned to beta motifs and random coils, and the fluorescence emission intensity decreased
relative to nonirradiated BSA. In the presence of the vitamins C or E, however, the irradiated BSA was
protected from these structural changes caused by reactive oxygen species (ROS). The two vitamins
exhibited different patterns of attachment to the protein surface, as inspected by blind docking,
and their mechanisms of protection were different. The hydrophilicity of vitamin C resulted in the
predominant scavenging of ROS in the solvent, whereas hydrophobic vitamin E localized on the
nonpolar patches of the BSA surface, where it did not only form a barrier for diffusing ROS but
also encountered them as an antioxidant and neutralized them thanks to the moderate BSA binding
constant. Very low concentrations of vitamins C or E (0.005 mg/mL) appear to be sufficient to prevent
the oxidative damage of BSA.
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