The interaction between a water-soluble anionic Ga(III) corrole [Ga(tpfc)(SO3Na)(2)] andcalf thymus DNA (ct-DNA) has been investigated by using femtosecond transient absorption Spectroscopy. A significant broadening from 570 to 585 nrn of positive absorption band of the blend Of Ga(tpfc)(SO3Na)(2) and ct-DNA (Ga(tpfc)(SO3Na)(2)-ctDNA) has been observed from 0.15 to 0.50 ps after photoexcitation of Ga(tpfc) (SO3Na)(2) into the Soret band. The control experiment has been performed On the model DNA ([poly(dG-dC)](2)) rich in guanine bases, which exhibits a similar Spectral broadening, whereas it is absent for [poly(dA-dT)](2) without guanine bases. The molecular orbital calculation shows that HOMO of Ga(tpfc)(SO3Na)(2) is lower than that of guanine bases: The results of the electrochemical experiment show the reversible electron transfer (ET) between Ga(tpfc) (SO3Na)(2) and guanine bases, of ct-DNA is thermodynamically favorable. The dynamical analysis of the transient absorption spectra reveals that an ultrafast forward ET from the guanine bases to Ga(tpfc)(SO3Na)(2) occurs within the pulse duration (156 fs), leading to the formation of an intermediate state. The following back ET to the ground state of Ga(tpfc)(SO3Na)(2) may be accomplished in 520 fs.