Effect of NH2 rotation on the fluorescence of 2-aminopurine in solution

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4 Citations (Scopus)

Abstract

Since the introduction of 2-aminopurine (2AP) in 1969 as a fluorescent analogue of adenine, its intense fluorescence in aqueous solution and the subsequent reduction of this intensity in DNA has been a powerful tool for studies of structural changes in DNA. Herein, we show that the unusual intense fluorescence of 2AP in water is attributed to the formation of a closed complex between one water molecule and 2AP in the excited state. This configuration restricts the rotation of the 2-NH2 group which subsequently lowers the nonradiative decay rate. We supported this finding by attaching heavy masses to the amino group, dimethyl (2-(N(Me)2)) and diethyl (2-(N(Et) 2)). By examining the fluorescence behavior in dioxane (an apolar, aprotic solvent), the lighter NH2 group can rotate in the excited state more freely which enhances the nonradiative loss of fluorescence. On the other hand, this rotation slows down sharply in the two heavy-group derivatives, leading to a restoration of the fluorescence intensity and lifetime very close to that of 2AP in water. Depletion of fluorescence was observed in the 2AP derivatives in water and is attributed to the population of a twisted intramolecular charge transfer (TICT) state due to the strong electron donating power of the NR2 groups, an effect that is absent for the parent 2AP.

Original languageEnglish
Pages (from-to)1-6
Number of pages6
JournalJournal of Photochemistry and Photobiology A: Chemistry
Volume261
DOIs
Publication statusPublished - Jun 1 2013

Fingerprint

2-Aminopurine
Fluorescence
fluorescence
Water
Excited states
water
DNA
deoxyribonucleic acid
Derivatives
adenines
Adenine
restoration
Restoration
decay rates
excitation
Charge transfer
depletion
charge transfer
analogs
aqueous solutions

Keywords

  • 2-Aminopurine
  • DNA base analogue
  • Fluorescence
  • Hydrogen bond
  • Internal rotation
  • Lifetime

ASJC Scopus subject areas

  • Chemistry(all)
  • Chemical Engineering(all)
  • Physics and Astronomy(all)

Cite this

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title = "Effect of NH2 rotation on the fluorescence of 2-aminopurine in solution",
abstract = "Since the introduction of 2-aminopurine (2AP) in 1969 as a fluorescent analogue of adenine, its intense fluorescence in aqueous solution and the subsequent reduction of this intensity in DNA has been a powerful tool for studies of structural changes in DNA. Herein, we show that the unusual intense fluorescence of 2AP in water is attributed to the formation of a closed complex between one water molecule and 2AP in the excited state. This configuration restricts the rotation of the 2-NH2 group which subsequently lowers the nonradiative decay rate. We supported this finding by attaching heavy masses to the amino group, dimethyl (2-(N(Me)2)) and diethyl (2-(N(Et) 2)). By examining the fluorescence behavior in dioxane (an apolar, aprotic solvent), the lighter NH2 group can rotate in the excited state more freely which enhances the nonradiative loss of fluorescence. On the other hand, this rotation slows down sharply in the two heavy-group derivatives, leading to a restoration of the fluorescence intensity and lifetime very close to that of 2AP in water. Depletion of fluorescence was observed in the 2AP derivatives in water and is attributed to the population of a twisted intramolecular charge transfer (TICT) state due to the strong electron donating power of the NR2 groups, an effect that is absent for the parent 2AP.",
keywords = "2-Aminopurine, DNA base analogue, Fluorescence, Hydrogen bond, Internal rotation, Lifetime",
author = "Abou-Zied, {Osama K.}",
year = "2013",
month = "6",
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doi = "10.1016/j.jphotochem.2013.03.007",
language = "English",
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journal = "Journal of Photochemistry and Photobiology A: Chemistry",
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T1 - Effect of NH2 rotation on the fluorescence of 2-aminopurine in solution

AU - Abou-Zied, Osama K.

PY - 2013/6/1

Y1 - 2013/6/1

N2 - Since the introduction of 2-aminopurine (2AP) in 1969 as a fluorescent analogue of adenine, its intense fluorescence in aqueous solution and the subsequent reduction of this intensity in DNA has been a powerful tool for studies of structural changes in DNA. Herein, we show that the unusual intense fluorescence of 2AP in water is attributed to the formation of a closed complex between one water molecule and 2AP in the excited state. This configuration restricts the rotation of the 2-NH2 group which subsequently lowers the nonradiative decay rate. We supported this finding by attaching heavy masses to the amino group, dimethyl (2-(N(Me)2)) and diethyl (2-(N(Et) 2)). By examining the fluorescence behavior in dioxane (an apolar, aprotic solvent), the lighter NH2 group can rotate in the excited state more freely which enhances the nonradiative loss of fluorescence. On the other hand, this rotation slows down sharply in the two heavy-group derivatives, leading to a restoration of the fluorescence intensity and lifetime very close to that of 2AP in water. Depletion of fluorescence was observed in the 2AP derivatives in water and is attributed to the population of a twisted intramolecular charge transfer (TICT) state due to the strong electron donating power of the NR2 groups, an effect that is absent for the parent 2AP.

AB - Since the introduction of 2-aminopurine (2AP) in 1969 as a fluorescent analogue of adenine, its intense fluorescence in aqueous solution and the subsequent reduction of this intensity in DNA has been a powerful tool for studies of structural changes in DNA. Herein, we show that the unusual intense fluorescence of 2AP in water is attributed to the formation of a closed complex between one water molecule and 2AP in the excited state. This configuration restricts the rotation of the 2-NH2 group which subsequently lowers the nonradiative decay rate. We supported this finding by attaching heavy masses to the amino group, dimethyl (2-(N(Me)2)) and diethyl (2-(N(Et) 2)). By examining the fluorescence behavior in dioxane (an apolar, aprotic solvent), the lighter NH2 group can rotate in the excited state more freely which enhances the nonradiative loss of fluorescence. On the other hand, this rotation slows down sharply in the two heavy-group derivatives, leading to a restoration of the fluorescence intensity and lifetime very close to that of 2AP in water. Depletion of fluorescence was observed in the 2AP derivatives in water and is attributed to the population of a twisted intramolecular charge transfer (TICT) state due to the strong electron donating power of the NR2 groups, an effect that is absent for the parent 2AP.

KW - 2-Aminopurine

KW - DNA base analogue

KW - Fluorescence

KW - Hydrogen bond

KW - Internal rotation

KW - Lifetime

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