G. Fragneto et al., Adsorption of proteins from aqueous solutions on hydrophobic surfaces studied by neutron reflection, PHYS CHEM P, 2(22), 2000, pp. 5214-5221
The two proteins, beta -casein (beta -CN) and beta -lactoglobulin (beta -Lg
), were adsorbed on hydrophobic silicon substrates from buffer solutions at
pH 8, 7, 5 and 3. The structure, in terms of thickness and composition of
the adsorbed species, was determined by means of neutron reflectivity. At p
H 7 beta -CN forms a structure that is described by two layers, a compact l
ayer adjacent to the solid surface and a looser layer protruding into the s
olution. beta -Lg adsorbs as a uniform layer. At lower pH both proteins ads
orb more, with thicker layers, and beta -Lg also adsorbs as a non-uniform l
ayer. The adsorption of both proteins is irreversible. The merits of contra
st variation are discussed and, in particular, the importance for the syste
ms studied of the use of water of scattering length density 4.5x10(-6) Angs
trom (-2) is described. Owing to the large size of the proteins, this contr
ast, intermediate between those of D2O and silicon, allows details masked b
y the higher critical angle of D2O to be revealed.