Thin narrow An stripes suitable for propagating long-range surface plasmon-polaritons were deposited by evaporation and lift-off on a thermal oxide layer on a silicon substrate, and modified by direct adsorption of bovine serum albumin (BSA). Atomic force microscopy (AFM) measurements reveal that BSA adsorbs onto the An stripes from phosphate buffer solutions forming an adlayer having an average thickness of about 2 nm (surface mass density of about 2 ng/mm(2)). Comparisons with a simple adsorption model suggest the side-on adsorption of a single monolayer of BSA followed by denaturation and flattening. The BSA-coated stripes have an increased surface roughness compared to a virgin stripe. (c) 2007 Elsevier B.V. All rights reserved.