Sensor surface for surface plasmon resonance assays

A method for preparing a sensor surface for a surface plasmon resonance (SPR) instrument, comprising forming a self assembled monolayer (SAM) on a surface by reacting said surface with one or more thiol C10-C30 alkane reagent(s) having at least one type of functional groups, wherein one or more protein resistant compound(s) is/are coupled to a first fraction of said functional group(s), wherein the one or more protein resistant compound(s) comprise polyethylene glycol (PEG) or a derivative thereof;

• and wherein one or more capturing molecule(s) is/are coupled directly or via a linker which is not said protein resistant compound(s) to a second fraction of said functional group(s) on said surface, wherein no capturing molecule(s) is/are coupled to the protein resistant compound(s), wherein the second fraction of said functional group(s) comprises a portion of the at least one type of functional groups not coupled to the one or more protein resistant compound(s) after the coupling of the protein resistant compound(s) via the first fraction of the functional group(s), and wherein the first and second fraction of said functional group(s) are of the same or different type.