In the spirit of the Monty Python Yorkshire exaggerator sketch: Eee by gum, in tha good ol' days we used t' drench our cells in p32, use lead underwear and turn off tha Geiger counters. Ask a grad student today to find out which amino acids are labelled and they dive into a catalogue. Luxury! Pah, nowt beats a good PAA, antibodies are fer wimps. Jim