Upon agonist binding, FPR1 internalises following activation of G protein subunits, resulting in receptor desensitisation. To determine whether Probe-TAMRA exhibited similar behaviour to and to assess its potential for FPR1 imaging, we incubated HEK293T cells transfected with FPR1 with 10 nM probe-TAMRA in glass-well culture dishes on ice for 30 mins and imaged these by confocal microscopy following washing. Clear fluorescent signal was observed on the membrane of transfected cells with low background in non-transfected controls (Figure ). Upon heating to 37 °C, fluorescent material was observed to transfer into the cytosol (Figure ), suggesting receptor internalisation similar to observations made with peptide formyl-Nle-Leu-Phe-Nle-Tyr-Lys(TAMRA)-OH in previous studies. This shows that probe-TAMRA binds to FPR1 on the surface and likely acts as an agonist to trigger receptor internalisation.