Excited state complex formation between 3-aminophthalhydrazide and DNA: a fluorescence quenching reaction

Fluorescence quenching reaction of 3-aminophthalhyrdazide (luminol) due to the interaction with short DNA fragments has been studied employing steady- state and time correlated single photon counting techniques. The interactio n of luminol with DNA in the excited state has also been analysed using Ste rn-Volmer (S-V) mechanism. A very weak ground state interaction is proposed to explain the higher values of the quenching rate constant and is consist ent with positive curvatures in the S-V plots. A plausible explanation of t he quenching mechanism has been discussed on the basis of hydrogen bonding interaction between luminol and DNA fragment. It is proposed that the phosp hate backbone present in DNA is responsible for the interaction with lumino l. (C) 1999 Elsevier Science B.V. All rights reserved.