High protective action against gamma radiation damage, by a tryptophan-ethanol mixture.

Between a group of non sulphydryl radioprotectors (methanol, formaldehyde, acetaldehyde, formiate, acetate, ethanol and tryptophan) ; ethanol and tryptophan were selected because its high protector action on irradiated purine and pyrimidine bases. At molarities of the order of 10~4 for tryptophan-ethanol and bases and DNA the respective DRF values were: for guanine: 20.58; for adenine: 3.75; for thymine: 4.94; for cytosine: 5.52; for uracil: 5.43; and for DNA: 18.95. For irradiated seeds protected with tryptophan-ethanol ( 1 . 5 X 1 0 ~ 3 M ; 2.6 X 1 0 2 M) the DRF value was of 3.33 and radiation damage becames evident only after a total dose of 2 x 104 rads. A partial different mechanisms for radioprotection with ethanol and tryptophan is postulated; this is supported by the fact that when tryptophan molarities attains that of protected DNA, there are a rapid increase in its values of DRF, crossing up the ethanol protection curve. Actually tryptophan could act not only as a radical scavenger, but also, as localized radical quenchor and/or energy trapper.