Electronic transition moments of 2-aminopurine
Journal article, 1997

The electronic spectrum of the unnatural nucleic acid base 2-aminopurine is important in order to understand the spectroscopy and photophysics of the normal DNA bases. Knowledge of transition moment directions and effective absorption components is also a prerequisite for the interpretation of emission spectra of 2-aminopurine incorporated into DNA as a probe of nucleic acid base motion or excitation energy transfer processes. Using linear dichroism, fluorescence anisotropy, and ordinary and magnetic circular dichroism techniques, the near-UV spectrum of 2-aminopurine is resolved into contributions from five electronic transitions. Four moderately strong pi-->pi* transitions (I, III, IV, and V) are observed, polarized at +53 degrees (I), -72 degrees (III), -77 degrees (IV), and +57 degrees or -67 degrees (V) relative to the short molecular axis. In addition, one weak n --> pi* transition (II) polarized perpendicular to the molecular plane has been identified. Semiempirical INDO/S calculations support these assignments.


differential-overlap technique

linear dichroism measurements

base pair

polarization spectra




metal complexes

intermediate neglect

stretched polymer sheets


Anders Holmén

Department of Physical Chemistry

Bengt Nordén

Department of Physical Chemistry

Bo Albinsson

Department of Physical Chemistry

Journal of the American Chemical Society

0002-7863 (ISSN) 1520-5126 (eISSN)

Vol. 119 13 3114-3121

Subject Categories

Chemical Sciences



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