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Interfacial Tension Kinetics of Nisin and β-Casein at on Oil - Water Interface
Lee, Woo Kul,Ahmad, Bani Jaber,McGuire, Joseph,Daeschel, Mark A .,Jung, Il Hyun 한국화학공학회 2000 Korean Journal of Chemical Engineering Vol.17 No.2
The concentration- and time-dependence of interfacial pressure of raisin and β-casein at an n-hexadecane-water interface were evaluated by using DuNou¨y tensiometry. The two emulsifiers attained interfacial saturation at a bulk concentration of about 0.1 mg/ml, the reduction of the interfacial tension by nisin at that concentration being about equivalent to that of β-casein. The time dependence of interfacial tension recorded for each protein was described by using two kinetic models. In the first, the reduction of interfacial tension with time was considered to be a result of molecular penetration into the interface followed by rearrangement. Nisin exhibited more rapid penetration and rearrangement at the interface than did β-casein. In the second, the model allowed for the parallel, irreversible adsorption of protein into each of two states from solution, where state 2 molecules occupy a greater interfacial area and are more tightly bound than state 1 molecules. The extent of adsorption in state 1 and state 2 was determined to be highly concentration dependent for each protein; adsorption occurs mostly in state 1 at high concentration and mostly in state 2 at low concentrations.
Characterization of Low-Crystalline Calcium Phosphate Thin Films Formed on Silica Glass Surface
Mo, Man Jin,Shin, Hyun Young,Jung, Il Hyun,Ko, Jea Seung,McGuire, Joseph,Lee, Woo-Kul 한국공업화학회 2005 Journal of Industrial and Engineering Chemistry Vol.11 No.2
Low-crystalline calcium phosphate (CaP) thin films were formed on silica glass surfaces by using quasi-saturated calcium and phosphate ionic solutions at 37℃. The silica glass surfaces were incubated at 37℃ for different periods of time to synthesize different types of CaP crystal films. An investigation on the effects that incubation time have on the chemical and physical properties of the synthesized CaP films was performed. The surface morphology of the synthesized CaP films displayed it to be highly porous. The surface roughness of the CaP films varied with incubation time, showing that the surface roughness increased rapidly during the initial stage of incubation but remained stationary during the later periods. X-Ray photoelectron spectroscopic analysis confirmed that the film consists of calcium and phosphorus and provided detailed information on the chemical composition of the CaP films. With an increase of the incubation time. the relative amounts of calcium and phosphorus (Ca/P ratio) increased, implying that the film thickness increased. The nature of the CaP film represented by the Ca/P ratio appeared to be similar to that of octacalcium phosphate at the initial stages of formation. During the later stages of incubation, the Ca/P ratio of the film decreased to create calcium-deficient nonstoichiometric CaP crystals. These results demonstrate that the properties of CaP films can be modulated by adjusting the incubation time. Because the prepared CaP film possessed a highly porous structure, the surface area is expected to increase, which may provide more chances for adhesion molecules to adsorb onto the CaP film.