Mechanism of exciplex formation between Cu-porphyrin and calf-thymus DNA as revealed by saturation resonance Raman spectroscopy

Shvedko, A. G.; Kruglik, Sergei G.; Ermolenkov, Vladimir V.; Орлович, В. А.; Turpin, Pierre‐Yves; Greve, Jan; Otto, Cornelis

doi:10.1002/(sici)1097-4555(199908)30:8<677::aid-jrs440>3.0.co;2-9

Cited by 7 publications

(5 citation statements)

References 22 publications

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“…The excited-state difference TR 3 spectra ( d ) are well consistent with the exciplex features previously observed in transient ns-RR spectra of photoexcited CuP bound to AT or T residues containing nucleic acids. − The intensities of the most prominent exciplex bands at ∼1345 cm -1 (ν 4 *) and ∼1551 cm -1 (ν 2 *) decrease in the following order: poly(dA-dT) 2 > DNA ≈ poly(dT) > poly(dA-dC)·poly(dG-dT) > 32-mer.…”

Section: Resultssupporting

confidence: 83%

“…Since the discovery of Fiel et al that water-soluble porphyrins can intercalate into B-form DNA, numerous studies on porphyrin complexes with DNA, RNA, and their model compounds have been performed, − with the aim to exploit the great potential of medical, biological, and photophysical applications of porphyrins, on the basis of a good knowledge of their physicochemical properties. Cationic meso-substituted (metallo)porphyrins are proved to be of interest in many areas, for example, as probes of the local nucleic acid structure and dynamics, as artificial nucleases, and as possible DNA photosensitizers to be used in photodynamic therapy (see reviews, refs −5).…”

Section: Introductionmentioning

confidence: 99%

“…In the recent past, Cu(T4MPyP) attracted a particular interest because, in addition to the steady-state interaction with DNA, a specific photoinduced reaction involving the porphyrin excited states had been discovered 15 and then further studied. − In resonance Raman (RR) under cw irradiation, Cu(T4MPyP) mixed with nucleic acids yields prominent vibrational bands around 1570 (ν 2 ) and 1366 (ν 4 ) cm -1 which originate from the ground electronic state . Under pulsed, high power excitation, extra Raman bands appear around 1550 (ν 2 *) and 1346 (ν 4 *) cm -1 , pairing their ground-state counterparts and corresponding to a porphyrin exciplex state, i.e., a CuP−DNA complex formed in the porphyrin excited state .…”

Section: Introductionmentioning

confidence: 99%

“…Consequently, the previous hypothesis 15-18 that the exciplex is formed during the action of a laser pulse has been confirmed. Moreover, the estimated time range of exciplex formation has decreased from less than 8 ns 17 to less than 50 ps . In using a rate equations approach, simulations of the measured Raman saturation dependencies have been performed for two models .…”

Section: Introductionmentioning

confidence: 99%

“…Moreover, the estimated time range of exciplex formation has decreased from less than 8 ns 17 to less than 50 ps . In using a rate equations approach, simulations of the measured Raman saturation dependencies have been performed for two models . The first one, assuming a preferential CuP intercalation followed by a photoinduced translocation, failed to describe the saturation Raman dependencies.…”

Section: Introductionmentioning

confidence: 99%

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Time-Resolved Resonance Raman Study of the Exciplex Formed between Excited Cu−Porphyrin and DNA

et al. 2001

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The photoinduced reversible process of exciplex formation and decay between the water-soluble cationic metalloporphyrin 5,10,15,20-tetrakis[4-(N-methylpyridyl)]porphyrin (Cu(T4MPyP)) and calf-thymus DNA has been studied by a picosecond time-resolved resonance Raman (ps-TR3) technique. For a detailed analysis of the exciplex properties, the following model compounds have also been investigated: double-stranded polynucleotides poly(dA-dT)2, poly(dG-dC)2, and poly(dA-dC)·poly(dG-dT), single-stranded poly(dT), and the 32-mer d[(GC)7ATAT(GC)7]2. Additional Raman measurements have also been done in using cw and 20-ns laser sources. It is shown that this reversible exciplex is formed, with a yield depending on the nucleic base sequence, in less than 2 ps after photoexcitation, between photoexcited Cu(T4MPyP) and CO groups of thymine residues in all thymine-containing sequences of nucleic acids. Such a rapid exciplex building process implies that it involves porphyrin molecules initially located, in the steady state of this interaction, at AT sites of the nucleic acids. This has two main consequences, which contradict previously reported assumptions (Strahan et al., J. Phys. Chem. 1992, 96, 6450): (i) although the binding mode of the porphyrin actually depends on the base sequence, there is no preferential binding of Cu(T4MPyP) to the various sites of DNA, and (ii) there is no photoinduced ultrafast porphyrin translocation from GC to AT sites of DNA. In addition, it is shown that with surrounding water molecules an exciplex can also be formed in ∼1 ps, whose spectral characteristics are not distinguishable from those formed with thymine residues. However, these two exciplex species can be distinguished from each other by their relaxation kinetics: the lifetime of the exciplex formed with water lies in the 3−12 ps range, while that of the exciplex formed with nucleic acids lies in the nanosecond time domain (1−3 ns). A set of possible routes is discussed for each of the exciplex building/decay processes.

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