Complexity of excited-state dynamics in DNA

Excited state interactions between flurbiprofen and tryptophan in drug–protein complexes and in model dyads. Fluorescence studies from the femtosecond to the nanosecond time domains

“…For HSA, an initial value of 75 about 0.18 was observed, the same as for isolated Trp. Thus, the Beyond a few picoseconds, the decays of the two FBP/HSA complexes became slightly more rapid than that of free FBP 45 ( Figure 4B). This behaviour can be explained in terms of a FBP dynamic quenching when bound to the protein, which is clearly configuration-dependent.…”

“…Monoexponential fitting gave a characteristic time of 0.44 ± 0.03 ns for (S)-FBP/HSA and 0.62 ± 0.07 ns for (R)-FBP/HSA. The difference in lifetimes can be related to the orientation of the drug within the protein, which 10 may restrict the degrees of freedom for conformational relaxation 45 Trp. 38 While this explanation remains a possibility, it can neither be confirmed nor discarded by the present time-resolved experiments.…”

“…11 Optical spectroscopy has proven to be particularly useful in the study of drug-protein binding. 12,13 The observed excited state 45 dynamics may be interpreted in terms of fundamental processes drug-protein binding. Characterisation of the excited states provides a better understanding of the molecular recognition governing the drug transport.…”

“…In particular, femtosecond emission [28][29][30][31][32] indole to act as an electron donor. 36 In view of the complexity of the FBP/HSA system and the potential difficulties to interpret the fluorescence properties, complementary information is necessary in order to investigate 20 45 nanosecond time-resolved measurements, the fluorescence lifetimes at em = 340 nm were much shorter in the dyads (F < 1 ns) than in (S)-TrpMe, indicating a dynamic quenching. However, these F values were judged inaccurate, due to the limitations of the equipment.…”

Fluorescence of the DNA Double Helix (dA)20·(dT)20 Studied by Femtosecond SpectroscopyEffect of the Duplex Size on the Properties of the Excited States

“…On the one hand, the damage induced by intense femtosecond pulses to DNA duplexes, either by direct photon absorption or by electrophilic attack from the generated solvated electrons, imposes the use of specific experimental protocols. 8 In this respect, the much higher cost of DNA duplexes compared to the monomeric chromophores is a serious limiting factor. On the other hand, the complexity of such systems makes the interpretation of the experimental results difficult.…”