Abstract: The present application relates to assays and systems for the detection of analyte molecules in a liquid sample, preferably a biological sample. In particular the invention relates to a method for determining the presence of a target analyte in a liquid sample, comprising contacting and incubating the sample with a first proximity probe comprising an analyte-binding domain having specificity for the target analyte, wherein the first proximity probe is tethered to a solid support by a polymeric or biopolymeric tether molecule which alters the observed properties.