Molecularly Flat Films of Linear Polyions and Proteins Obtained by the Alternate Adsorption Method

Abstract

Alternately assembled films of poly(ethyleneimine) (PEI) and poly(styrenesulfonate) (PSS), as examined by non-contact atomic force microscopy (AFM), provided molecularly flat surfaces with height difference of several Å. Similar observations on alternate protein films of PEI-glucose oxidase, PEI-ferritin and PSS-peroxidase showed that films with outermost protein layers gave well-packed island structures and that the size of the island and the film roughness were related to the size of proteins used. Subsequent adsorption of a polyion layer decreased the surface roughness of protein layers significantly probably due to bridging of protein molecules by polyion chains.