Gt. Taylor et al., PROTEIN ADSORPTION FROM SEAWATER ONTO SOLID SUBSTRATA .2. BEHAVIOR OFBOUND PROTEIN AND ITS INFLUENCE ON INTERFACIAL PROPERTIES, Marine chemistry, 47(1), 1994, pp. 21-39
Modification of solid surfaces (e.g. minerals, biogenic debris, engine
ered materials, etc.) and exchanges across their interfaces in seawate
r can be influenced by the composition and behavior of adsorbed solute
s, such as proteins. The present study illustrates that the degrees to
which extracellular proteins adsorb from seawater solutions, denature
in the bound state, alter the wettability of the interface, and imped
e dissolution and oxidation of the substratum strongly depend on prote
in concentration and substratum type. For all variables measured, a tr
ansition in state of the interface is evident within the surface conce
ntration range required to establish a monomolecular layer. The plant
enzyme, ribulose-1,5-bisphosphate carboxylase-oxygenase (RuBisCO), was
used to examine the behavior of protein adsorbed to well-defined tita
nium and copper surfaces in seawater. Secondary structure of proteins
in thin films on Ti were most altered while those in thicker films and
in Cu-bound films more closely resembled native protein as indicated
by relative intensities of amide II and I, vibrational frequency shift
s, and amide III features in spectra obtained by Fourier Transform Inf
rared Reflectance-Absorbance Spectrometry (FT-IRAS). Critical surface
tension (CST) of Ti oxides was significantly reduced in the presence o
f very thin films, but was enhanced on coated Cu oxide surfaces. Diffe
rences in interfacial CST reflect a higher degree of denaturation upon
adsorption onto Ti oxides than onto Cu oxides, i.e. greater exposure
of hydrophobic protein residues on less wettable substrata. Potential
substratum oxidation rates and surface oxide accumulation derived from
Electrochemical Impedance Spectroscopy (EIS) and ellipsometric measur
ements, respectively, were inversely related to protein surface concen
tration. Results consistently illustrate that substratum composition a
nd protein concentration control film organization, protein denaturati
on and interfacial attributes which are manifested as interfaces with
varying wetting properties and as solid phases with varying susceptibi
lity to oxidation and dissolution.