M. Enescu et al., INTERACTION OF THE ANTITUMORAL DRUG PAZELLIPTINE WITH POLYNUCLEOTIDES- A SUBPICOSECOND TRANSIENT ABSORPTION STUDY, JOURNAL OF PHYSICAL CHEMISTRY B, 102(18), 1998, pp. 3631-3636
The flat heterocyclic antitumoral drug pazelliptine (PZE) strongly int
eracts with nucleic acids. The transient absorption spectra of PZE/pol
ynucleotide complexes have been investigated with subpicosecond time r
esolution on a large spectral range, 400-850 nm. The relaxation dynami
cs are found to vary widely depending upon the type of polynucleotide
in which PZE has been inserted. For fully protonated PZE and for PZE c
omplexed to poly(dA-dT)-poly(dA-dT), a similar fast spectral relaxatio
n was detected and assigned to a deprotonation of the excited singlet
state of the drug. In the case of the PZE/poly(dG-dC)-poly(dG-dC) comp
lex, the evolution of the transient absorption spectra suggests that t
here are at least two different drug binding sites. The kinetics of th
e differential absorption reveals the activation of a radiationless tr
ansition S-1-->S-0 upon PZE association to poly(dG-dC)-poly(dG-dC). Th
e possible mechanism of this fast molecular process is discussed in co
nnection with previously reported results on heterocycle-nucleotide in
teractions.