Abstract
A series of DNA hairpins (AqGn) possessing a tethered anthraquinone (Aq) end-capping group were synthesized in which the distance between the Aq and a guanine-cytosine (G-C) base pair was systematically varied by changing the number (n - 1) of adenine-thymine (A-T) base pairs between them. The photophysics and photochemistry of these hairpins were investigated using nanosecond transient absorption and time-resolved electron paramagnetic resonance (TREPR) spectroscopy. Upon photoexcitation, 1*Aq undergoes rapid intersystem crossing to yield 3*Aq, which is capable of oxidizing purine nucleobases resulting in the formation of 3(Aq -•Gn +•). All 3(Aq -•Gn +•) radical ion pairs exhibit asymmetric TREPR spectra with an electron spin polarization phase pattern of absorption and enhanced emission (A/E) due to their different triplet spin sublevel populations, which are derived from the corresponding non-Boltzmann spin sublevel populations of the 3*Aq precursor. The TREPR spectra of the 3(Aq -•Gn +•) radical ion pairs depend strongly on their spin-spin dipolar interaction and weakly on their spin-spin exchange coupling. The anisotropy of 3(Aq -•Gn +•) makes it possible to determine that the π systems of Aq -• and G +• within the radical ion pair are parallel to one another. Charge recombination of the long-lived 3(Aq -•Gn +•) radical ion pair displays an unusual bimodal distance dependence that results from a change in the rate-determining step for charge recombination from radical pair intersystem crossing for n <4 to coherent superexchange for n > 4.
| Original language | English |
|---|---|
| Pages (from-to) | 11251-11260 |
| Number of pages | 10 |
| Journal | Journal of the American Chemical Society |
| Volume | 134 |
| Issue number | 27 |
| DOIs | |
| Publication status | Published - Jul 11 2012 |
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ASJC Scopus subject areas
- Chemistry(all)
- Catalysis
- Biochemistry
- Colloid and Surface Chemistry
Cite this
Structure and dynamics of photogenerated triplet radical ion pairs in DNA hairpin conjugates with anthraquinone end caps. / Carmieli, Raanan; Smeigh, Amanda L.; Mickley Conron, Sarah M.; Thazhathveetil, Arun K.; Fuki, Masaaki; Kobori, Yasuhiro; Lewis, Frederick D.; Wasielewski, Michael R.
In: Journal of the American Chemical Society, Vol. 134, No. 27, 11.07.2012, p. 11251-11260.Research output: Contribution to journal › Article
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TY - JOUR
T1 - Structure and dynamics of photogenerated triplet radical ion pairs in DNA hairpin conjugates with anthraquinone end caps
AU - Carmieli, Raanan
AU - Smeigh, Amanda L.
AU - Mickley Conron, Sarah M.
AU - Thazhathveetil, Arun K.
AU - Fuki, Masaaki
AU - Kobori, Yasuhiro
AU - Lewis, Frederick D.
AU - Wasielewski, Michael R
PY - 2012/7/11
Y1 - 2012/7/11
N2 - A series of DNA hairpins (AqGn) possessing a tethered anthraquinone (Aq) end-capping group were synthesized in which the distance between the Aq and a guanine-cytosine (G-C) base pair was systematically varied by changing the number (n - 1) of adenine-thymine (A-T) base pairs between them. The photophysics and photochemistry of these hairpins were investigated using nanosecond transient absorption and time-resolved electron paramagnetic resonance (TREPR) spectroscopy. Upon photoexcitation, 1*Aq undergoes rapid intersystem crossing to yield 3*Aq, which is capable of oxidizing purine nucleobases resulting in the formation of 3(Aq -•Gn +•). All 3(Aq -•Gn +•) radical ion pairs exhibit asymmetric TREPR spectra with an electron spin polarization phase pattern of absorption and enhanced emission (A/E) due to their different triplet spin sublevel populations, which are derived from the corresponding non-Boltzmann spin sublevel populations of the 3*Aq precursor. The TREPR spectra of the 3(Aq -•Gn +•) radical ion pairs depend strongly on their spin-spin dipolar interaction and weakly on their spin-spin exchange coupling. The anisotropy of 3(Aq -•Gn +•) makes it possible to determine that the π systems of Aq -• and G +• within the radical ion pair are parallel to one another. Charge recombination of the long-lived 3(Aq -•Gn +•) radical ion pair displays an unusual bimodal distance dependence that results from a change in the rate-determining step for charge recombination from radical pair intersystem crossing for n <4 to coherent superexchange for n > 4.
AB - A series of DNA hairpins (AqGn) possessing a tethered anthraquinone (Aq) end-capping group were synthesized in which the distance between the Aq and a guanine-cytosine (G-C) base pair was systematically varied by changing the number (n - 1) of adenine-thymine (A-T) base pairs between them. The photophysics and photochemistry of these hairpins were investigated using nanosecond transient absorption and time-resolved electron paramagnetic resonance (TREPR) spectroscopy. Upon photoexcitation, 1*Aq undergoes rapid intersystem crossing to yield 3*Aq, which is capable of oxidizing purine nucleobases resulting in the formation of 3(Aq -•Gn +•). All 3(Aq -•Gn +•) radical ion pairs exhibit asymmetric TREPR spectra with an electron spin polarization phase pattern of absorption and enhanced emission (A/E) due to their different triplet spin sublevel populations, which are derived from the corresponding non-Boltzmann spin sublevel populations of the 3*Aq precursor. The TREPR spectra of the 3(Aq -•Gn +•) radical ion pairs depend strongly on their spin-spin dipolar interaction and weakly on their spin-spin exchange coupling. The anisotropy of 3(Aq -•Gn +•) makes it possible to determine that the π systems of Aq -• and G +• within the radical ion pair are parallel to one another. Charge recombination of the long-lived 3(Aq -•Gn +•) radical ion pair displays an unusual bimodal distance dependence that results from a change in the rate-determining step for charge recombination from radical pair intersystem crossing for n <4 to coherent superexchange for n > 4.
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U2 - 10.1021/ja303721j
DO - 10.1021/ja303721j
M3 - Article
VL - 134
SP - 11251
EP - 11260
JO - Journal of the American Chemical Society
JF - Journal of the American Chemical Society
SN - 0002-7863
IS - 27
ER -