A method for detecting a protein in a sample, wherein said protein has been separated in an electrophoretic gel or on a blotting membrane, said method comprising: a) providing a said gel or a said membrane containing a said protein from said sample; b) providing a proximity probe pair, each probe comprising a binding moiety with affinity for a different binding site on said protein and a reactive oligonucleotide, coupled thereto; c) binding said proximity probes to their respective binding sites on said protein through the binding moiety; d) adding a splint oligonucleotide and a backbone oligonucleotide which are complementary to the reactive oligonucleotide pair, and allowing them to hybridize to the reactive oligonucleotides, such that when said probes in said proximity probe pair have both bound to said protein the respective ends of the splint oligonucleotide are hybridised directly in contact with the ends of the backbone oligonucleotide; e) ligating, using a DNA ligase, the hybridized backbone and splint oligonucleotides to create a circularized DNA molecule wherein said circularized DNA molecule is formed from the backbone and splint oligonucleotides only when said probes in said proximity probe pair have both bound to said protein; f) elongating one of the reactive oligonucleotides by isothermal amplification using the circularized DNA molecule as template, thereby creating a localized amplification product; and g) detecting the presence and quantity of said protein using a detection oligonucleotide complementary to the amplification product; wherein the binding between the proximity probe pairs and the protein as well as the detection are performed directly in an electrophoretic gel, or wherein the sample containing said protein is first separated using gel electrophoresis and then transferred from the electrophoretic gel onto a suitable blotting membrane, such as a nitrocellulose or PVDF membrane, before binding and detection with the proximity probes. a) providing a said gel or a said membrane containing a said protein from said sample; b) providing a proximity probe pair, each probe comprising a binding moiety with affinity for a different binding site on said protein and a reactive oligonucleotide, coupled thereto; c) binding said proximity probes to their respective binding sites on said protein through the binding moiety; d) adding a splint oligonucleotide and a backbone oligonucleotide which are complementary to the reactive oligonucleotide pair, and allowing them to hybridize to the reactive oligonucleotides, such that when said probes in said proximity probe pair have both bound to said protein the respective ends of the splint oligonucleotide are hybridised directly in contact with the ends of the backbone oligonucleotide; e) ligating, using a DNA ligase, the hybridized backbone and splint oligonucleotides to create a circularized DNA molecule wherein said circularized DNA molecule is formed from the backbone and splint oligonucleotides only when said probes in said proximity probe pair have both bound to said protein; f) elongating one of the reactive oligonucleotides by isothermal amplification using the circularized DNA molecule as template, thereby creating a localized amplification product; and g) detecting the presence and quantity of said protein using a detection oligonucleotide complementary to the amplification product;