Repair of DNA Double-Strand Breaks: Errors Encountered in the Determination of Half-Life Times in Pulsed-Field Gel Electrophoresis and Neutral Filter Elution

For theoretical reasons, it is incorrect to define experimentally the half-life times of DNA double-strand breaks (DSBs) as the half-life time of an amount of DNA. This is illustrated by one example of human DNA, where the half-life for first-order kinetics of the disappearance of DSBs has been assumed to be 10 min. Experimental sources of errors and their influence on experimental results are analyzed. Some experimental situations may lead to serious misinterpretation of data. The differential decreases in fractions released (amounts of DNA) as often followed in pulsed-field gel electrophoresis depend on run conditions, background and level of DSB induction and are a function of time itself-a time function that is unrelated to the half-life of DSBs. It is shown that, using the decrease of a measured amount of DNA, one may obtain practically any value for the half-life time.