PROTEIN PACKING IN ADSORBED LAYERS STUDIED BY EXCITATION-ENERGY TRANSFER

Excitation energy transfer (EET) from fluorescein donors attached to a bovine serum albumin molecule to tetramethylrhodamine acceptors attached to another albumin molecule in protein assemblies adsorbed on hydrophobized silica was measured by the total internal reflection fluorescence method as a quantity reflecting the arrangement of adsorbed proteins. There was no evidence of albumin aggregation during the growth of albumin-adsorbed layers. Layers obtained by adsorption from mixed albumin and immunoglobulin (IgG) solutions showed a random distribution of the protein molecules on the surface. A higher EET was observed if albumin was adsorbed from 1 mg/ml solution on a clean surface than if the surface was preexposed to low concentrated solutions before the 1 mg/ml solution was applied. The results suggested that at low solution concentrations the surface was saturated with a metastable, less packed albumin layer. © 1990.