Fluorescent and cross-linked proteins of human erythrocyte ghosts formed by reaction with hydroperoxylinoleic acid, malonaldehyde and monofunctional aldehydes.

Abstract

Human erythrocyte ghosts modified with 13-hydroperoxylinoleic acid (LOOH) and the secondary degradation products of peroxidized lipids, i.e. malonaldehyde (MDA) and monofunctional aldehydes, were analyzed for fluorescence formation and protein cross-linking. Reaction of ghosts with LOOH produced fluorescent ghost proteins with an excitation maximum at 357 nm and an emission maximum at 438 nm. The MDA-modified ghost proteins exhibited fluorescence spectra with a longer maximum wavelength, an excitation maximum at 398 nm and an emission maximum at 467 nm, whereas the fluorescence spectra of the ghost proteins modified with 1-heptanal and 2, 4-decadienal were indistinguishable from those observed for LOOH-modified ghost proteins. Similar results were obtained for lipid extracts of the modified ghosts. Like LOOH and MDA, the monofunctional aldehydes such as 1-hexanal, 1-heptanal and 2, 4-decadienal were capable of cross-linking the ghost proteins as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The importance of MDA in the formation of fluorescence and cross-links may have been exaggerated in earlier reports.