One way of fluorescently tagging a protein is to express it as a fusion with a fluorescent protein. Only few fluorescent proteins are available with far red emission spectra. One resource to search for red fusion proteins matching the Dianthus Filter set is FPbase. The fluorescent protein fluorescence may sometimes have a lower quantum yield and show stronger photobleaching than chemical Fluorophores but has the advantage of being attached to the Target protein at a known position. We recommend performing a Control Experiment, using just the fluorescent protein as target without the fused protein of interest.