Protein adsorption to material surfaces causes problems in numerous medical applications. A favoured approach in order to prevent protein adsoprtion is to decorate surfaces with brushes of terminally anchored, neutral water soluble polymers (NWSP). But despite the 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 protein adsorption occurs despite NWSP functionalization. Here, we propose a systematic investigation of this phenomenon on a detailed structural level. Anti-PEG proteins specifically binding to the backbone of PEG polymers will be localized using neutron reflectometry (NR) with contrast variation. The results will provide a valuable basis for the "rational design" of protein-repellent surface functionalization.