YET another clue has been found which might help unravel the mystery surrounding cancer. Three chemists, working at the University of Oklahoma in Norman, us, have discovered how nitrosamines -- normally inert organic compounds found in cigarette smoke, some processed foods, medicines and cosmetics -- could be activated in the body to exert carcinogenic effects.

Nitrosamines bond to important biomolecules such as haemoglobin and to certain enzymes. George Richter-Addo, Geun-Bae Yi and Masood Khan have found a way to attach a nitrosamine to a synthetic version of the iron-containing haem group, which is at the heart of haemoglobin and the enzyme cytochrome p-450. The chemists claim that this enzyme plays an important role in the metabolism of nitrosamines and haem could be a key to their carcinogenic properties.

To look at how nitrosamines might associate with haem, the researchers reacted their synthetic haem with diethylnitrosamine in an inert nitrogen atmosphere, leading to the formation of reddish-purple crystals, which were later found to be made from units of nitrosamine bonded to the iron atom of the haem molecule. But what other researchers would like to know is whether this process actually takes place in the human body.