Femtosecond dynamics in the lactim tautomer of phycocyanobilin: a long-wavelength absorbing model compound for the phytochrome chromophore.
Chemphyschem
; 15(17): 3824-31, 2014 Dec 01.
Article
em En
| MEDLINE
| ID: mdl-25196062
ABSTRACT
Transient UV/Vis absorption spectroscopy is used to study the primary dynamics of the ring-A methyl imino ether of phycocyanobilin (PCB-AIE), which was shown to mimic the far-red absorbance of the Pfr chromophore in phytochromes (R. Micura, K. Grubmayr, Bioorg. Med. Chem. Lett.- 1994, 4, 2517-2522). After excitation at 615 nm, the excited electronic state is found to decay with τ1 =0.4 ps followed by electronic ground-state relaxation with τ2 =1.2 and τ3 =6.7 ps. Compared with phycocyanobilin (PCB), the initial kinetics of PCB-AIE is much faster. Thus, the lactim structure of PCB-AIE seems to be a suitable model that could not only explain the bathochromic shift in the ground-state absorption but also the short reaction of the Pfr as compared to the Pr chromophore in phytochrome. In addition, the equivalence of ring-A and ring-D lactim tautomers with respect to a red-shifted absorbance relative to the lactam tautomers is demonstrated by semiempirical calculations.
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Coleções:
01-internacional
Base de dados:
MEDLINE
Idioma:
En
Revista:
Chemphyschem
Assunto da revista:
BIOFISICA
/
QUIMICA
Ano de publicação:
2014
Tipo de documento:
Article