R. Bortolini et al., P-31 NMR-STUDIES ON THE INTERACTION OF MORPHOLINYL ANTHRACYCLINES ANDRELATED-COMPOUNDS WITH D(CGTACG)2 - THERMODYNAMIC AND KINETIC-PARAMETERS, Applied magnetic resonance, 7(1), 1994, pp. 71-87
Citations number
27
Categorie Soggetti
Spectroscopy,"Physics, Atomic, Molecular & Chemical
P-31 NMR spectroscopy has been used to study the intercalation of the
anthracyclines doxorubicin 1, daunorubicin 2, 4-demethoxydaunorubicin
3, morpholinodoxorubicin 4, methoxymorpholinodoxorubicin 5 and 9-deoxy
daunorubicin 6 with the DNA fragment d(CGTACG)2. The individual phosph
ate resonances of the oligonucleotide were assigned in the free as wel
l as in the intercalated species. The P-31 chemical shift variations a
llowed us to identify the intercalation sites, which resulted to be th
e same for all compounds i.e. between the terminal CG base-pairs of th
e helix (two molecules of drug per duplex). The binding constants, the
dissociation rate constants and DELTAG# values have been determined i
n different conditions of ionic strength and temperature. The kinetic
constant (k(off)) of the slow step of the anthracycline/duplex interca
lation process has been directly measured by NOE exchange techniques.
Binding constants depend on the ionic strength and on the self-associa
tion process so greatly, that their use to study by NMR anthracycline/
DNA interactions is questionable. On the contrary, the k(off) are not
affected by these phenomena and present an interesting trend for 1-6,
thus showing that the average life-time of the drug in the intercalati
on site appears to be important for determining the cytotoxicity and t
he antimitotic activity.