Modification of a mathematical model for survival curves in photobiology.

A modification of the Haynes' mathematical model (1966) can be suggested as a result of bacterial UV-survival experiments carried out. A new equation is proposed: lnS = Fi(x), + Fr(x), wherein x is the radiation dose, Fi(x) = -- kox describes how radiation damage is produced on the cell and Fr(x) = (krec + kc)x + Re(x) describes how repair systems act. ko is the relative inactivation efficiency of radiation on each cell. krec is the recombination recovery system efficiency. kc gives the additional repair increasing per cell when excision and recombination systems act simultaneously. Re(x) = a(1-e-bs) describes solely the excision repair process. The asymptote of non-exponential curves intercepts the survival fraction axis on the ordinate so (extrapolated point). In the modified model a=lnSo instead of a=So (Haynes' model).