Japanese Cartoons in Biology

Remember Sonic Hedgehog protein?  Well, how about the Raichu probe?

Raichu stands for Ras interacting chimeric unit, where someone has attached a CFP to Raf to make a chimera protein (fusion protein).  Then, this Raf-CFP can can interact with Ras engineered with YFP.  Normally, Raf only binds to Ras-GTP, not Ras-GDP.  Bioengineers invented Raichu to be able to detect and localize Ras-GTP in action, using FRET.  When they use fluorescence to zap the cell with CFP's excitation wavelength, CFP is excited and sends out light at the CFP emission wavelength.  Conveniently, CFP's emission wavelength is YFP's excitation wavelength, so if Ras-CFP has a GTP and binds Raf-YFP, then your initial light excites CFP which excites YFP so you will see the color of YFP's emission, not CFP's emission. If you see that, that means Ras is bound very closely to Raf.

Raichu actually stands for Ras interacting protein chimeric unit, but it's not surprising they left out the "p" when making the acronym.  :P