colocalization by immunostaining true coloc immunostaining The subcellular location of a protein can be demonstrated by treating cells fixed on a microscope slide with an antibody specific for the protein of interest. A secondary antibody conjugated with a reactive enzyme (e.g. horseradish peroxidase) is then added. Following a washing step to remove the unbound secondary ligand, a chromogenic substrate (e.g. 3,3', 5,5' tetramethyl benzidine chromogen [TMB]) is converted to a soluble coloured product by the conjugated enzyme and can then be visualised by standard microscopic techniques. OBSOLETE since combination of Interaction Detection Method and Interaction Type.Consider using the Interaction Detection Method imaging techniques (MI:0428) coupled with Interaction Type colocalisation (MI:0403) and Participant detection immunostaining (MI:0422) instead. MI:0022 Immunostaining PSI-MI Immunofluorescence Staining