A neutron reflection study of adsorbed deuterated myoglobin layers on hydrophobic surfaces

The structure of adsorbed globular protein layers on hydrophobic surfaces is elucidated in detail by combining the use of a fully deuterated protein, myoglobin, and the neutron reflectivity technique. The hydrophobic surfaces consist of grafted self-assembled monolayer of octadecyltrichlorosilane (OTS) and polystyrene (PS) layer on silicon substrates. Different protein concentrations ranging from 1 mg/ml to 0.01 mg/ml are used. On the OTS surface and for low protein concentration, the adsorbed protein layer consists of a dense layer of thickness around 13 Å indicating that proteins are denaturated when adsorbed on the hydrophobic interface – myoglobin being a globular protein with an average diameter of about 40 Å. At high protein concentration, an additional layer is observed on the top of this first denaturated layer. The thickness of this layer corresponds roughly to the dimensions of the myoglobin suggesting that additional proteins in their bulk conformation are adsorbed on the top. In the case of PS, the protein is significantly less flattened at the interface, PS being a less hydrophobic surface.

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► Protein adsorbed on hydrophobic surfaces were characterized with neutron reflection.
► Deuterated myoglobin is denaturated on OTS surface while on PS it is less flattened.
► For higher protein concentration a second nondenaturated layer is also observed.
► Combination of deuterated protein and neutron reflection is an ideal technique.