THE X-MODEL - A MODIFIED VERSION OF THE COMPETITION THEORY

In 1985, Edgren et al. proposed a modified version of the competition theory to explain the interaction of sensitizers and protectors with t arget molecules damaged by radiation, which was designated the 'X' mod el. This model incorporates concepts which have been considered previo usly, namely that a type of radiation damage exists which cannot be ch emically repaired, and that cells may contain a naturally occurring se nsitizer. The model leads to testable predictions, such as, e.g. the c rossing of 'K curves' when the level of protection is varied. It can o nly be applied to the immediate effects of radiation, i.e. before enzy matic reactions play a part. The present paper is a summary of work ca rried out since 1985 to test the predictions of the 'X' model and an e xposition of the related algebra.