Dresden 2006 – wissenschaftliches Programm
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CPP: Chemische Physik und Polymerphysik
CPP 6: Electronic Structure and Spectroscopy I
CPP 6.2: Vortrag
Montag, 27. März 2006, 14:45–15:00, ZEU 114
Femtosecond spectroscopic study of carminic acid-DNA interactions — •Radu Comanici1, Bianca Gabel1, Thomas Gustavsson2, Rusu Catalin1, and Kryschi Carola1 — 1Institute of Physical Chemistry I, FAU, D-91058 Erlangen — 2CEA/Saclay, DSM/DRECAM/SCM, F-91191 Gif-sur-Yvette
Photo-excited carminic acid and carminic acid-DNA associates have been examined using a variety of spectroscopy techniques, e.g. the femtosecond resolved fluorescence up-conversion and transient absorption spectroscopy. The observation of dual fluorescence emission, one peaks at 470 and the other 570 nm, shows that carminic acid undergoes an excited-state (S1) intramolecular proton transfer (ESIPT). Transient absorption spectroscopy measurements of carminic acid in BPES yielded four lifetimes of the excited state (S1): 8 ps, 15 ps, 33 ps and 46 ps. On the other hand, only two lifetimes, 34 ps annd 47 ps, were observed by fluorescence up-conversion. The four S1 lifetimes were ascribed to the coexistence of respectively two tautomer (normal and tautomer) forms of carminic acid, in the undissociated state (CAH) and in the deprotonated state (CA-). Fluorescence up-conversion measurements of carminic acid-DNA associates showed that the coupling to DNA is associated with the prolongation of the fluorescence lifetimes. This effect is taken as evidence for the formation of intercalation complexes between the carminic acid and the DNA. The intercalative binding of the carminic acid to DNA is confirmed by the fluorescence titration experiments.