CONSTRUCTION AND X-RAY REFLECTIVITY STUDY OF SELF-ASSEMBLED LYSOZYME POLYION MULTILAYERS/

The process of multilayer assembly via layer-by-layer deposition of li near polyions anti lysozyme have been studied. The films were fabricat ed on glass slides by alternate electrostatic adsorption of anionic po ly(styrenesulfonate) (PSS), cationic poly(allylamine) (PAA) polyions a nd hen egg-white lysozyme. The multilayer build-up was monitored by th e small-angle X-ray diffraction method. X-ray reflectivity curves from the films measured at different steps of the assembly reveal Kiessig fringes. From their periodicity the film thickness was calculated. The growth step for a PSS/PAA bilayer equals 37 Angstrom. The thickness o f the lysozyme layer equals 45 Angstrom, which is close to dimensions of the lysozyme molecule determined by X-ray crystallography. An analy sis of surface charges of the lysozyme molecule shows some preferentia lly positive charged regions, which are the most probable sites of int eractions with negatively charged PSS.