The missing donut problem

Normal lab work was not quite possible lately, so I turned my work to simulations of latest microscopy techniques and had a closer look at single molecules microscopy. It is quite a feat that we can even see single fluorescent molecules with a light microscope – it’s like detecting a lightbulb from space. A fluorescent molecule is a kind of miniscule radio antenna that emits light instead of radio waves. The emission profile between radio antenna and fluorophore is similar though. You get most signal when standing next to the "pole" and nothing in the direction where the antenna is pointing to. When you look at an antenna that is “pointing at you”, you receive no signal. Similarly, when you look at a fluorophore with a microscope it appears very characteristically to be ‘donut’ shaped - no light on the optical axis. But sometimes, that's where you find most light and the donut is gone... This is where our story starts.