Gt. Taylor et al., PROTEIN ADSORPTION FROM SEAWATER ONTO SOLID SUBSTRATA .1. INFLUENCES OF SUBSTRATUM SURFACE-PROPERTIES AND PROTEIN-CONCENTRATION, Marine chemistry, 45(1-2), 1994, pp. 15-30
To model non-specific protein adsorption in seawater, partitioning of
the plant enzyme, ribulose-1,5-bisphosphate carboxylase-oxygenase (RuB
isCO), from seawater onto a variety of materials (Ti, Cu, Fe, PTFE [Te
flon], Polycarbonate, Pyrex) was examined as functions of time and bul
k concentration. Protein film thicknesses on titanium and copper varie
d temporally over 24 h in a laminar flow regime, increasing rapidly in
the first hour on both metals and continuing to increase slowly on Ti
but decreasing on Cu in the subsequent 15-23 h. Films also varied spa
tially from 0 to 28 nm on Ti and from 20 to 160 nm on Cu. Desorption k
inetics of protein monolayers bound to Ti oxide surfaces were twice as
rapid as those bound to Cu oxides. Proteins in overlying layer(s) of
multilayered films, bound only to other proteins, desorbed more rapidl
y than molecules bound to metal oxide surfaces, irrespective of the ty
pe of substratum. Isothermic adsorption studies of H-3-RuBisCO indicat
ed that surface concentrations were best described as a first-order fu
nction (GAMMA = KC01/n) of bulk protein concentration, C0, which was v
aried from 0.001 to 1050 mug cm-3. Surface films varied in thickness f
rom submono- to multilayer coverage. Each substratum material exhibite
d significantly different binding capacities (K) and adsorption intens
ities (1/n) and at moderate bulk protein concentrations (10 mug cm-3)
yielded an overall ranking of adsorption equilibria as follows: Pyrex<
PTFE < Ti < PC < Cu <Fe. While the chemical composition of the substr
atum surfaces varied widely among the six materials tested, the initia
l critical surface tensions (CST) of these surfaces accounted for 87%
of the variance observed in adsorption intensity, 1/n, (excluding Pyre
x). In seawater, bulk concentration and substratum CST were shown to b
e critical in determining rates of non-specific protein adsorption and
desorption as well as partitioning equilibria. Results illustrate the
complexity of protein adsorption in seawater indicative of multilayer
ed, heterogeneous adsorption at the surface.