Egg white varnishes on ancient paintings: a molecular connection to amyloid proteins

For about 400 years, egg white was used to coat and protect paintings without detailed understanding of its molecular properties. A molecular basis is provided for its advantageous properties and one of its protective properties is demonstrated with oxygen transport behavior. Compared to the native secondary structure of ovalbumin in solution of circa 33% α-helix and β-sheet, attenuated total reflection-FTIR (ATR-FTIR) spectra showed a 73% decrease of α-helix content and a 44% increase of β-sheet content over eight days. The data suggest that the final coating of dissolved ovalbumin from egg white after long exposure to air, which is hydrophobic, comprises mostly β-sheet content (ca. 50%), which is predicted to be the lowest-energy structure of proteins and close to that found in amyloid fibrils. Coating a synthetic polytetrafluoroethylene membrane with multiple layers of egg white decreased oxygen diffusion by 50% per layer with a total decrease of almost 100% for four layers.