A Laser Temperature Jump Investigation of the Interaction between Proflavine and Calf‐Thymus Deoxyribonucleic Acid at Low and High Ionic Strength Avoiding Electric Field Effects

Abstract

AbstractWe have used our very fast “Iodine‐Laser Temperature‐Jump” technique with a time resolution between 10−10 and 100 s to investigate the intercalation of proflavine into calf thymus DNA. Salt concentrations between 10−2 and 1 M and temperatures from 290 to 320 K were used. The DNA concentration ranged from 10−3 to 10−5 M and was always in large excess of the proflavine concentration to avoid aggregation of the dye in solution as well as on the surface of DNA. Under all experimental conditions only a single relaxation time which varied between 10−4 and 10−3 s could be detected. This result is in contrast to all temperature jump experiments performed so far using “Joule‐heating” equipments. The reason for this behaviour is that our technique is the only one which avoids the electric field effects inevitably associated with the “Joule‐heating” T‐jump arrangements.