I just had a look at the presentation of O-Biolink, a company based in Denmark, on their systems and protocol to amplify a signal coming from two close antibodies, to detect protein-protein interaction, protein phosphorylation, as well as amplification of DNA without PCR using rolling circle amplification, that works also in fixed tissues.
The file is itneresting, I do not have any conflict of interest or sponsorship for advertising, and it can be viewed by typing this link and launching a media player
mms://www.olink.se/images/webinar_1.wmv

it could be interesting to get a feedback also from the people networking in the protein interactions group, if you get to read this topic, chec kit out!