Scientific Results

Carbon Monoxide Recombination Dynamics in Truncated Hemoglobins Studied with Visible-Pump MidIR-Probe Spectroscopy

Year: 2012

Authors: Lapini A., Di Donato M., Patrizi B., Marcelli A., Lima M., Righini R., Foggi P., Sciamanna N., Boffi A.

Autors Affiliation: LENS European Lab Nonlinear Spectroscopy, I-50019 Sesto Fiorentino, FI, Italy; INO Ist Nazl Ott, I-50125 Florence, Italy; Univ Perugia, Dipartimento Chim, I-06123 Perugia, Italy; Univ Roma La Sapienza, Dipartimento Sci Biochim, Fdn Cenci Bolognetti, Ist Pasteur, I-00185 Rome, Italy

Abstract: Carbon monoxide recombination dynamics upon photodissociation with visible light has been characterized by means of ultrafast visible-pump/MidIR probe spectroscopy for the truncated hemoglobins from Thermobifida fusca and Bacillus subtilis. Photodissociation has been induced by exciting the sample at two different wavelengths: 400 nm, corresponding to the heme absorption in the B-band, and 550 nm, in the Q-bands. The bleached iron-CO coordination band located at 1850-1950 cm(-1) and the free CO absorption band in the region 2050-2200 cm(-1) have been observed by probe pulses tuned in the appropriate infrared region. The kinetic traces measured at 1850-1950 cm(-1) reveal naultiexponential subnanosecond dynamics that have been interpreted as arising from fast geminate recombination of the photolyzed CO. A compared analysis of the crystal structure of the two proteins reveals a similar structure of their distal heme pocket, which contains conserved polar and aromatic amino acid residues closely interacting with the iron ligand. Although fast geminate recombination is observed in both proteins, several kinetic differences can be evidenced, which can be interpreted in terms of a different structural flexibility of the corresponding heme distal pockets. The analysis of the free CO band-shape and of its dynamic evolution brings out novel features about the nature of the docking site inside the protein cavity.

Journal/Review: JOURNAL OF PHYSICAL CHEMISTRY B

Volume: 116 (30)      Pages from: 8753  to: 8761

More Information: The authors acknowledge the Italian Ministero dell\’Istruzione dell\’Universita e della Ricerca (PRIN 2008, 2008BFJ34R) and Istituto Pasteur Fondazione Cenci Bolognetti. A.L. and A.M. acknowledge the financial support of the Regione Toscana through the found POR FSE 2007-2013 obiettivo 2 asse IV, project EPHODS. The financial support of the Cassa di Risparmio di Firenze is also gratefully acknowledged.
KeyWords: Amino acids; Carbon monoxide; Chemical reactions; Crystal structure; Hemoglobin; Photodissociation; Porphyrins; Proteins, Aromatic amino acid; Bacillus Subtilis; Distal pocket; Docking sites; Dynamic evolution; Geminate recombination; Heme pockets; Infrared regions; Iron ligand; Kinetic traces; Probe pulse; Probe spectroscopy; Protein cavity; Q-bands; Recombination dynamics; Structural flexibilities; Subnanosecond; Thermobifida fusca; Truncated hemoglobins; Two different wavelengths; Ultra-fast; Visible light, Dynamics
DOI: 10.1021/jp3019149

Citations: 5
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English