STUDIES ON ENZYMES AND YEAST CELLS WITH 

 ACCELERATED HEAVY IONS 



CORNELIUS A. TOBIAS, TOR BRUSTADt AND THOMAS MANNEY 

 Donner Laboratory, University of California, Berkeley, California, U.S.A. 



SUMMARY 



The action of heavy accelerated ions, with short-range but very high hnear 

 energy transfer, on enzyme molecules, such as trypsin, in the dry state can be 

 modified by the jsresence of the protective substances, dextran, lactose and 

 ribose. The inactivation cross-sections obtained are discussed in the light of 

 current theories. 



Heavy ions produce mutations in irradiated yeast cells and inliibition of cell 

 division and colony formation. The effects produced depend upon the post- 

 irradiation physical environment and the physiological state of the cells. 



INTRODUCTION 

 For the past several years my collaborators and I have been inter- 

 ested in the effects of heavy accelerated ions on living cells and mole- 

 cules of biological importance. Over the past three years, nshig the 

 Berkeley heavy ion linear accelerator (HILAC) machine strong pulsed 

 beams of protons, alpha-particles, Boron-10, Carbon-12, Nitrogen-14, 

 Oxygen-16, Neon-20 and Argon were available (Born et al., 1959). 

 These particles have short range but very heavy Imear energy transfer 

 (LET). Figure 1 shows that irradiations of cells and thin layers of 

 molecules is jjossible by the track segment method up to LET of IQio 

 eV/g cm-2. The radiobiological use of such particles is essential primarily 

 because they help us to understand the primary action of radiation and 

 the mechanisms of molecular energy transfer. The presence of heavy 

 ions in the primary cosmic radiation in outer space makes their study 

 even more interesting. If man should fly in space he will be exposed to 

 some rather penetrating heavy particles. It is further assumed that 

 heavy cosmic ray primaries bombard the surfaces of planets where 

 generation of organic matter might still be in process. On planets with 

 low atmospheric pressure the heavy ions penetrate to the surface so 

 that life, if it exists must continually go on in their presence. 



t On leave of absence from the Norwegian State Cancer Research Laboratory. 



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