LATERAL DIFFUSION OF AMPHIPHILES AND MACROMOLECULES AT THE AIR-WATER-INTERFACE

We report a lateral diffusion study on the air water interface of a surface-active protein, bacterial lipase from Pseudomonas fluorescens, and a vinyl poly(tert-butyl methacrylate), with the technique of fluorescence recovery after photobleaching. For the validation of implementing the technique and the calibration of our instrument, we relied on a phospholipid system that Peters and Beck have used earlier and found that our results were in accord with theirs within 20% in absolute magnitude. For both the phospholipid and lipase, we analyzed the lateral diffusion data in terms of the free area model of Sackmann and Trauble. We conclude that the results of lipase could be interpreted by invoking a conformational change induced by lateral compression in the monolayer state and those of the polymer, by postulating the quenching of the diffusion process when its concentration crosses over from the dilute regime to the semidilute regime.