2-Aminopurine optical spectra: Solvent, pentose ring, and DNA helix melting dependence

Academic Article


  • 2-Aminopurine (2AP) absorption and fluorescence excitation and emission spectra in a series of solvents have been measured to assess effects of solvent polarity. Emission spectra of the free base shift to the red in solvents of a higher dielectric constant, including water but excepting dioxane. Excitation spectra also red-shift, except in water. A change in dipole moment of 2.8 D upon excitation is obtained from a Bilot-Kawski plot which includes data from potentially anomolous solvents such as alcohols but which excludes dioxane and aqueous solvents. Attachment of ribose or 2′-deoxyribose causes 1 to 2-nm shifts in the position of fluorescence excitation and emission spectra of 2AP in water and little change in fluorescence yield. Melting of the DNA duplex d[CTGA(2AP)TTCAG]2 yields a blue shift of the excitation and no shift of the emission spectrum-results consistent with increased exposure to water and formation of 2AP-water H bonds in the ground state. The spectral shift occurs 5°C or more below the helix melting temperature, implying a premelting structural change in the decamer. © 1992 Plenum Publishing Corporation.
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    Digital Object Identifier (doi)

    Author List

  • Evans K; Xu D; Kim Y; Nordlund TM
  • Start Page

  • 209
  • End Page

  • 216
  • Volume

  • 2
  • Issue

  • 4