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

Thèse : Mécanique : Faculté des sciences de Paris : 1831. Thèse : Astronomie : Faculté des sciences de Paris : 1831. / Titre provenant de l'écran-titre.

Thèse : Mécanique : Faculté des sciences de Paris : 1855. Thèse : Géométrie : Faculté des sciences de Paris : 1855. / Titre provenant de l'écran-titre.

Reproduction de : Thèse de doctorat : Physique : Lyon 1 : 2006. / Titre provenant de l'écran titre. Bibliogr. p.201-207.

Thesis (doctoral)--Westfälischen Wilhelms-Universität zu Münster, 1911. / Cover title. Vita. Includes bibliographical references.

published_or_final_version / Mechanical Engineering / Master / Master of Philosophy

Theoretical studies on the wetting of cylindrical solid surfaces with axisymmetric rugosities explicitly showed the presence of contact angle hysteresis, non-equilibrium jumps during contact line motion and the formation of composite surfaces. For physically rough surfaces with unidirectional randomness it was shown that hysteresis increases with decreasing roughness dimensions and with increasing standard deviation in the solid surface slope distribution. / The wetting of solid surfaces by liquids was investigated by a new tensiometric technique called capillarography. At large roughness wavelengths ((TURN)100 (mu)m) the contribution of concentric sawtooth-shaped regular roughness was found to be close to the values calculated theoretically. At smaller roughness wavelengths ((TURN)1 (mu)m) the wetting is complicated by intrinsic roughness and chemical heterogeneity. / High energy surfaces such as platinum and quartz exhibit a regular stick-jump behavior when wetted with water above a very low critical contact line velocity. This is caused by minute amounts of surface active impurities in the system. From the experimental data it can be deduced that surface active molecules diffuse onto and over the solid surface. / A relaxation of the contact angle was observed when an initially slow moving contact line was brought to a full stop. This is attributed to the slow establishment of a new equilibrium, possibly by surface capillary waves, involving metastable contact line positions separated by energy barriers. For receding contact angles, the main cause of the relaxation seems to be a stabilization of a liquid film left behind a receding contact line. / The observations made in this study contribute to a better understanding of the complicated nature of the wetting of solids.

Thesis (Ph. D.)--University of Hong Kong, 2008. / Includes bibliographical references (p. 159-170) Also available in print.

Thesis (Ph. D.)--Oregon State University, 2010. / Printout. Includes bibliographical references (leaves 136-139). Also available on the World Wide Web.

Thesis (doctoral)--Rheinische Friedrich-Wilhelms-Universität Bonn, 1999. / Includes bibliographical references (p. 77-79).