title: Effects of temperature, pH, and salt concentration on beta-lactoglobulin deposition kinetics studied by optical waveguide lightmode spectroscopy.
abstract: Deposition kinetics of beta-lactoglobulin at a solid-liquid interface was studied with optical waveguide lightmode spectroscopy (OWLS) over a range of temperatures between 61 and 83 degrees C. A new temperature-controlled cell for OWLS measurements allows fast, on-line monitoring of the deposit formation at elevated temperatures. Primary protein layers were deposited at 25 degrees C in order to precondition and stabilize the waveguide surface. Sustained deposition lasting from a few minutes (around 80 degrees C) to hours (below 70 degrees C) resulted in multilayer deposits up to several tens of nanometers thick. The measured deposition rates were strongly influenced by temperature, pH, and NaCl concentration. Deposition rates decreased with increasing pH from 5.5. to 7.4, in a trend similar to that for noncovalent aggregation of beta-lactoglobulin in solution. Activation energies for deposition rates decreased with increasing pH, from 340 kJ/mol at pH 5.5 to 230 kJ/mol at pH 7.4 and were similar to the activation energies for denaturation of beta-lactoglobulin in solution.
authors.affiliation: Institut für Chemie- und Bioinginieurwissenschaften, ETH Zürich, 8093 Zürich, Switzerland.
authors.forename: Marek
authors.initials: M
authors.lastname: Kroslak
authors.forename: Jan
authors.initials: J
authors.lastname: Sefcik
authors.forename: Massimo
authors.initials: M
authors.lastname: Morbidelli
mesh_terms: D000818:Animals; D002021:Buffers; D002417:Cattle; D004305:Dose-Response Relationship, Drug; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D007782:Lactoglobulins / Q000737:chemistry*; D015233:Models, Statistical; D011817:Rabbits; D012492:Salts / Q000494:pharmacology*; D012822:Silicon Dioxide / Q000737:chemistry; D013053:Spectrophotometry / Q000379:methods; D013696:Temperature; D013997:Time Factors; D014025:Titanium / Q000737:chemistry
chemical_list: D002021:Buffers; D007782:Lactoglobulins; D012492:Salts; C009495:titanium dioxide; D012822:Silicon Dioxide; D014025:Titanium