Ultrafast Heme Dynamics of Ferric Cytochromeâ
c in Different Environments: Electronic, Vibrational, and Conformational Relaxation.
Chemphyschem
; 16(18): 3974-83, 2015 Dec 21.
Article
em En
| MEDLINE
| ID: mdl-26416435
ABSTRACT
The excited-state dynamics of ferric cytochromeâ
c (Cytâ
c), an important electron-transfer heme protein, in acidic to alkaline medium and in its unfolded form are investigated by using femtosecond pump-probe spectroscopy, exciting the heme and Tryptophan (Trp) to understand the electronic, vibrational, and conformational relaxation of the heme. At 390â
nm excitation, the electronic relaxation of heme is found to be ≈150â
fs at different pH values, increasing to 480â
fs in the unfolded form. Multistep vibrational relaxation dynamics of the heme, including fast and slow processes, are observed at pHâ
7. However, in the unfolded form and at pHâ
2 and 11, fast phases of vibrational relaxation dominate, revealing the energy dissipation occurring through the covalent bond interaction between the heme and the nearest amino acids. A significant shortening of the excited-state lifetime of Trp is observed at various pH values at 280â
nm excitation due to resonance energy transfer to the heme. The longer time constant (25â
ps) observed in the unfolded form is attributed to a complete global conformational relaxation of Cytâ
c.
Palavras-chave
Texto completo:
1
Base de dados:
MEDLINE
Assunto principal:
Citocromos c
/
Heme
Limite:
Animals
Idioma:
En
Ano de publicação:
2015
Tipo de documento:
Article