Protein adsorption to material surfaces causes problems in numerous medical applications. A favoured approach in order to preventprotein adsoprtion is to decorate surfaces with brushes of terminally anchored, neutral water soluble polymers (NWSP). But despitethe great importance of NWSP-functionalization, the interaction of proteins with NWSP is not fully understood.In particular, little is known about the role of specific protein adsorption in the regularly observed "brush failure", where proteinadsorption occurs despite NWSP functionalization. Here, we propose a systematic investigation of this phenomenon on a detailedstructural level. Anti-PEG proteins specifically binding to the terminus od PEG polymers will be localized using neutron reflectometry (NR) with contrast variation. The results will provide a valuable basis forthe "rational design" of protein-repellent surface functionalization.