Etude de différentes méthodes de biofonctionnalisation pour la ...

III. Etudes du film Lan gmuir-Blodgett enzymatique
thread to a surface tension
sensor (NMA type PS4). The output signal was fed into the port of a
computer across an interface lu (NIMA) and recorded.
The subphase temperature was held constant and equal to 22 ± 0.1°C during the experiments.
Before each experiment, the surface of the subphase was cleaned by aspiration. The surface was
considered as cleaned when the change in surface pressure of the clean subphase upon compression
of the area was less than 0.2 mN mc'.
22. Surface pressure-surface area measurements
ODA (C18NH2) or stearic acid (C21 H43COOH) (1 mg mí1) was spread from chloroform solution (22
pl) onto an aqueous subphase by using a microsyringe of 100 j.il. The spreading was achieved at the
same distance above the subphase in all the experiments. After spreading, the monolayers were left
for 10 min to allow the solvent to evaporate, after which compression was initiated at a rate of about
10 cm2 minuntil a desired surface pressure was reached. The moving rates of the compression
barrier were controlled automatically by a mini-motor. The subphase was constituted of pure water,
buffer solution or enzyme aqueous solution of 2 mg r1, 4 mg
1
or 8 mg 1 In the case of the mixed
monolayers, the enzyme was first atlowed to adsorb from the unstirred subphase to the air-water
interface. The change in surface pressure was recorded until a constant value was obtained. The time
to get the adsorption equilibrium was about 3 hours.
3. Results
3.1. Adsorption of enzyme at the air-water interface
The surface pressure vs time (71-t) curves presented in figure 1 were measured for the adsorption
of pure enzyme at two different concentrations and for two mixed films: ODAlprotein and SAc/protein.
Concerning the ODAlprotein system, three different enzyme concentrations were tested: 2, 4, 8 mg [.
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