TY - JOUR
T1 - Optical properties of guanine nanowires
T2 - Experimental and theoretical study
AU - Changenet-Barret, Pascale
AU - Emanuele, Emanuela
AU - Gustavsson, Thomas
AU - Improta, Roberto
AU - Kotlyar, Alexander
AU - Markovitsi, Dimitra
AU - Vayá, Ignacio
AU - Zakrzewska, Krystyna
AU - Zikich, Dragoslav
PY - 2010/9/2
Y1 - 2010/9/2
N2 - Long nanowires formed by ca. 800 guanine tetrads (G4-wires) are studied in phosphate buffer containing sodium cations. Their room temperature optical properties are compared to those of the monomeric chromophore 2-deoxyguanine monophosphate (dGMP). When going from dGMP to G4-wires, both the absorption and the fluorescence spectra change. Moreover, the fluorescence quantum yield increases by a factor of 7.3 whereas the average fluorescence lifetime increases by more than 2 orders of magnitude, indicating emission associated with weakly allowed transitions. The behavior of G4-wires is interpreted in the light of a theoretical study performed in the frame of the exciton theory combining data from molecular dynamics and quantum chemistry. These calculations, carried out for a quadruplex composed of three tetrads, reveal the existence of various exciton states having different energies and oscillator strengths. The degree of delocalization of the quadruplex Franck-Condon excited states is larger than those found for longer duplexes following the same methodology. The slower excited-state relaxation in G4-wires compared to dGMP is explained by emission from exciton states, possibly limited on individual tetrads, whose coherence is preserved by the reduced mobility of guanines due to multiple Hoogsteen hydrogen bonds.
AB - Long nanowires formed by ca. 800 guanine tetrads (G4-wires) are studied in phosphate buffer containing sodium cations. Their room temperature optical properties are compared to those of the monomeric chromophore 2-deoxyguanine monophosphate (dGMP). When going from dGMP to G4-wires, both the absorption and the fluorescence spectra change. Moreover, the fluorescence quantum yield increases by a factor of 7.3 whereas the average fluorescence lifetime increases by more than 2 orders of magnitude, indicating emission associated with weakly allowed transitions. The behavior of G4-wires is interpreted in the light of a theoretical study performed in the frame of the exciton theory combining data from molecular dynamics and quantum chemistry. These calculations, carried out for a quadruplex composed of three tetrads, reveal the existence of various exciton states having different energies and oscillator strengths. The degree of delocalization of the quadruplex Franck-Condon excited states is larger than those found for longer duplexes following the same methodology. The slower excited-state relaxation in G4-wires compared to dGMP is explained by emission from exciton states, possibly limited on individual tetrads, whose coherence is preserved by the reduced mobility of guanines due to multiple Hoogsteen hydrogen bonds.
UR - http://www.scopus.com/inward/record.url?scp=77956166006&partnerID=8YFLogxK
U2 - 10.1021/jp102106d
DO - 10.1021/jp102106d
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AN - SCOPUS:77956166006
SN - 1932-7447
VL - 114
SP - 14339
EP - 14346
JO - Journal of Physical Chemistry C
JF - Journal of Physical Chemistry C
IS - 34
ER -