Interactions between proteins and contact surfaces can have
important implications in the food industry. Such interactions
contribute to the course of fouling of membrane surfaces and they
appear to mediate bacterial and spore adhesion to some degree as
well. In addition to protein and solution properties, interfacial
behavior is strongly influenced by contact surface properties. Among
these, hydrophobicity and the potential to take part in acid-base
interaction have received considerable attention, but in a quantitative
sense we know very little about their respective influences on protein
adsorption. It was the purpose of this research to quantify the
equilibrium adsorptive behavior of the milk protein β-lactoglobulin as
it is influenced by the presence of different contact surface functional
groups.
Monocrystalline and polished silicon surfaces were modified to be
hydrophilic by oxidation and hydrophobic by silanization with dichlorodiethylsilane (DDES), dichlorodimethylsilane (DDMS), and
dichlorodiphenylsilane (DDPS), each used at concentrations of 0.82,
3.3, and 82 mM. Surface hydrophobicities were evaluated with contact
angle methods. Adsorption isotherms were constructed after allowing
each modified silicon surface to independently contact β-lactoglobulin
(0.01 M phosphate buffer, pH 7.0) at concentrations ranging between
200 and 2000 mg/L for eight h at room temperature. Surfaces were
then rinsed and dried. Optical properties of the bare- and
film-covered surfaces, necessary for calculation of adsorbed mass,
were obtained by ellipsometry.
Plots of adsorbed mass as a function of protein concentration
exhibited attainment of plateau values beyond a protein concentration
of about 200 mg/L. At high silane concentration, the plateau values
associated with surfaces exhibiting ethyl groups were observed to be
greatest followed by those exhibiting phenyl, methyl, then hydrophilic
(OH) groups. At the low DDMS and DDES concentrations (0.82 and 3.3
mM), adsorbed mass did not increase beyond that value recorded for
the hydrophilic surface. This is likely due to some critical spacing of
methyl and ethyl groups being required to produce a favorable
hydrophobic effect on adsorption. For surfaces treated with
dichlorodiphenylsilane, adsorbed mass increased with silane
concentration. Apparently, a favorable acid-base interaction effected by
the hydrophilic surface is inhibited by the presence of small amounts
of methyl and ethyl groups, but somewhat less inhibited by the
presence of phenyl groups because the latter have the ability to
undergo acid-base interaction. / Graduation date: 1993
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/27111 |
| Date | 11 August 1992 |
| Creators | Al-Makhlafi, Hamood K. |
| Contributors | McGuire, Joseph |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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