(525c) Structural Effects on Adsorption Kinetics of Phosphatidylcholine Vesicles at an Air-Water Interface

The dynamic surface tension of several purified phospholipids onto a clean air-water interface was studied via drop volume tensiometry in order to gain insight into the mechanism of adsorption. Long chain phospholipids spontaneously organize into vesicles when dispersed in water due to their high hydrophobic character. Upon creation of a clean air-water interface, these vesicles will diffuse to a region just below the surface and then kinetically adsorb to the interface. We are able to gain insight into this adsorption process via dynamic surface tension experiments. We have demonstrated that the adsorption of purified phospholipid vesicles to an air-water interface is kinetically limited, rather than diffusion limited for liquid-phase vesicles. The mechanistic process that takes places during the kinetically controlled adsorption step, however, remains unresolved. We have examined the effects of vesicle size, temperature, and chain length on dynamic surface tension as a means of developing an appropriate kinetic model. Dynamic surface tension profiles are then coupled with dynamic light scattering results for comparison to model predictions.