Theory of RBE for Heavy Ion Bombardment of Dry Enzymes and Viruses. Radiation Res. 30, 855-871 (1967).The response of dry enzymes and viruses to heavy ion bombardment may be predicted from their response to y-irradiation (and no further knowledge of their size and structure). The molecules are approximated as point particles whose response to ionization is the same for heavy ion bombardment as for y-rays. From the 8-ray distribution formula and an extrapolated range-energy relation for electrons, the radial distribution of secondary ionization energy may be found. Under this dosage distribution the inactivation probability may be found as a function of radial distance from the ion's path, and then may be integrated over all space to find the inactivation cross section. These essentially geometric theoretical relations between the y-ray D37 values and the inactivation cross section constitute a complete theory of RBE for the heavy ion bombardment of these substances. Theoretical relationships agree with published experimental values to an average deviation of 15 % for the enzymes ,f3-galactosidase and trypsin, and for T-1 and 4X-174 bacteriophages, when bombarded with ions ranging from Z = 1 to 18, at ion speeds of 0.07 c (2.3 MeV/nucleon) and 0.145 c (10 hleV/nucleon).
The product of two empirical relations, for the practical range and the transmission probability of normallyincident electrons through plane sheets of matter, may be differentiated to yield a simple formulation of the energy deposition by electron beams, in agreement with more complex formulations and with experimental data. When combined with the 5-ray distribution formula, these results provide a theory of the spatial distribution of ionization energy about the path of a rapidly moving ion, which is basic to theories of radiation damage and detection.
A new theory of track formation in emulsion accounts for the tracks of charged particles on the basis of a theory developed earlier for the response of biological molecules and NaI(T1) to energetic heavy ions. The pro!~ahility that an emulsion grain nil1 remain undeveloped when exposed to 6 rays depositing a mean energy E is assumed to be e-CIEo, where b o is the dose at which l / e (3773 of the emulsion grains remain undeveloped, as in the one-or-more-hit cumulative Poisson distribution. The parameter LO incorporates variations in einulsion properties and processing conditions. Calculation of the spatial distribution of the ionization energy deposited by 6 rays is combinecl with the assumed emulsion response to yield the spatial distribution of developed grains about the path of the charged particle. Calculations are in agreement with experimental data for grain counts (up to the relativistic rise), blackness profiles, and track width.
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