Dynamics of photoinduced processes in adenine and thymine base pairs.
The excited-state dynamics of adenine and thymine dimers and the adenine-thymine base pair were investigated by femtosecond pump-probe ionization spectroscopy with excitation wavelengths of 250-272 nm. The base pairs showed a characteristic ultrafast decay of the initially excited pi pi* state to an n pi* state (lifetime tau(pi pi*) approximately 100 fs) followed by a slower decay of the latter with tau(n pi*) approximately 0.9 ps for (adenine)2, tau(n pi*) = 6-9 ps for (thymine)2, and tau(n pi*) approximately 2.4 ps for the adenine-thymine base pair. In the adenine dimer, a competing decay of the pi pi* state via the pi sigma* state greatly suppressed the n pi* state signals. Similarities of the excited-state decay parameters in the isolated bases and the base pairs suggest an intramonomer relaxation mechanism in the base pairs.
Samoylova
E
E
Max-Born-Institut, Max-Born-Strasse 2a, D-12489 Berlin, Germany.
Lippert
H
H
Ullrich
S
S
Hertel
I V
IV
Radloff
W
W
Schultz
T
T
D000225:Adenine / Q000737:chemistry*; D020029:Base Pairing; D013058:Mass Spectrometry; D010777:Photochemistry; D013816:Thermodynamics; D013941:Thymine / Q000737:chemistry*
D000225:Adenine; D013941:Thymine