We present the results of time-dependent density functional theory calculations of the optical absorption spectra of synthetic nucleobases and of their hydrogen-bonded and stacked base pairs. We focus on sizeexpanded analogues of the natural nucleobases obtained through the insertion of a benzene ring bonded to the planar heterocycles (x-bases), according to the protocol designed and realized by the group of Eric Kool (e.g., see: Gao, J.; Liu, H.; Kool, E.T. Angew. Chem., Int. Ed. 2005, 44, 3118, and references therein). We find that the modifications of the frontier electron orbitais with respect to natural bases, which are induced by the presence of the aromatic ring, also affect the optical response. In particular, the absorption onset is pinned by the benzene component of the HOMO of each x-base (xA, xG, xT, xC). In addition, the main trait of the H-bonding interbase coupling is a conspicuous red shift of spectral peaks in the low-energy range. Finally, the hypochromicity, a well-known fingerprint of stacking, is more pronounced in stacked xG-C and xA-T pairs than that in stacked G-C and A-T pairs, an index of enhanced stacking. © 2007 American Chemical Society.
Ab initio optical absorption spectra of size-expanded xDNA base assemblies / Varsano, Daniele; Anna, Garbesi; Rosa Di, Felice. - In: JOURNAL OF PHYSICAL CHEMISTRY. B, CONDENSED MATTER, MATERIALS, SURFACES, INTERFACES & BIOPHYSICAL. - ISSN 1520-6106. - STAMPA. - 111:50(2007), pp. 14012-14021. [10.1021/jp075711z]
Ab initio optical absorption spectra of size-expanded xDNA base assemblies
VARSANO, DANIELE;
2007
Abstract
We present the results of time-dependent density functional theory calculations of the optical absorption spectra of synthetic nucleobases and of their hydrogen-bonded and stacked base pairs. We focus on sizeexpanded analogues of the natural nucleobases obtained through the insertion of a benzene ring bonded to the planar heterocycles (x-bases), according to the protocol designed and realized by the group of Eric Kool (e.g., see: Gao, J.; Liu, H.; Kool, E.T. Angew. Chem., Int. Ed. 2005, 44, 3118, and references therein). We find that the modifications of the frontier electron orbitais with respect to natural bases, which are induced by the presence of the aromatic ring, also affect the optical response. In particular, the absorption onset is pinned by the benzene component of the HOMO of each x-base (xA, xG, xT, xC). In addition, the main trait of the H-bonding interbase coupling is a conspicuous red shift of spectral peaks in the low-energy range. Finally, the hypochromicity, a well-known fingerprint of stacking, is more pronounced in stacked xG-C and xA-T pairs than that in stacked G-C and A-T pairs, an index of enhanced stacking. © 2007 American Chemical Society.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.