Our main interests are centered in the study of the factors
controlling long- range electron transfer (ET) in metalloproteins and photoinduced ET in inorganic
layered systems. The current experimental test protein for the metalloprotein studies is the monomeric hemoglobin
(HbI) from the bacteria-harboring gill of the tropical clam Lucina pectinata. L. pectinata lives
in symbiosis with intracellular chemoautotrophic bacteria that supply organic carbon to the clam.
HbI is a unique protein because its functional state is the ferric-sulfide form. In addition, physiological
function is sulfide transport and release to the symbiont bacteria, which is coupled to an ET step.
Furthermore, instead of a distal histidine HbI has a Gln64(E11), an unusual Phe29(B10) residue and the
unique Phe68(E11) residue. HbI also has an array of nearly-parallel aromatic residues near the heme (Fig.1).
Our group studies how this unique heme pocket microenvironment affects
the ligand binding and electron transfer properties of HbI. The group also studies the redox properties
of HbI using electrochemical methods, UV-Vis spectrophotometry, luminescence steady-state spectroscopy, luminescence
lifetime measurements, transient-absorption spectroscopy, and stopped-flow methods. Surface amino acids are
modified with luminescent metal complexes for long-range ET experiments. Ligand binding properties are analyzed
through IR, Raman, NMR, ESI-MS and time-resolved methods. HbI is a small heme protein that may prove
to be an interesting system to modify and try to design and construct an artificial enzyme. Site-directed
mutagenesis studies will allow pursuing this objective.
We are also interested in the conversion and storage of solar energy using photoinduced ET reactions. To meet this goal, the energy-releasing back reaction must be suppressed. Our group uses the heterogeneous microenvironment provided by zirconium phosphates in a strategy for suppressing the back reaction and enhancing charge separation efficiency. Zirconium phosphates are acidic, inorganic, ion-exchange materials with layered structures (Fig. 2). Detailed, fundamental studies of the photophysics and photochemistry of luminescent metal complexes exchanged into organic derivatives of zirconium phosphates are being conducted. Photocatalytic studies of these materials should help point out new strategies for designing devices to harvest solar energy.
Recent publications:
Mitk El B. Santiago, Meredith M. Velez, Solmarie Borrero, Agustin Diaz,
Craig A. Casillas, Cristina Hofmann, Ana R. Guadalupe and Jorge
L. Colon, NADH electrooxidation
using bis (1,10-phenanthroline-5,6-dione) (2,2'-bipyridine)ruthenium(II)-exchanged
zirconium phosphate modified carbon paste electrodes, Electroanalysis, 18, 559-572 (2006).
Ricardo A. Bermudez, Rafael Arce and Jorge
L. Colon, Photolysis of 1-pyrenemethylamine ion-exchanged into a zirconium phosphate framework, J. Photochem. Photobiol., A, 175, 201-206 (2005).
Ricardo A. Bermudez, Yaitza Colon, Genaro A. Tejada and Jorge
L. Colon, Intercalation and Photophysical Characterization of 1-Pyrenemethylamine in Zirconium Phosphate Layered Materials, Langmuir, 21, 890-895 (2005).
Angel A. Marti, Gellert Mezei, Lorena Maldonado, Giovanni Paralitici, Raphael G. Raptis and Jorge
L. Colon, Structural and photophysical characterisation of fac-[tricarbonyl(chloro)(5,6-epoxy-1,10-phenanthroline)rhenium(I)], Eur. J. Inorg. Chem., 118-124 (2005).
“Structural and Photophysical Characterization
of fac-Tricarbonylchloro-1,10-phenanthroline(5,6) epoxiderhenium(I)” Martí,
A. A.; Mezei G.; Maldonado, L.; Paralitici, G.; Raptis. R.G., Colón,
J. L. Eur.J. Inorg. Chem, 2005, 118-124.
“Intercalation and Photophysical Characterization of 1-Pyrenemethylamine in Zirconium Phosphate Layered Materials”, Bermúdez, R. A.; Colón, Y.; Tejada, G. A.; Colón, J. L. Langmuir,2005,21, 890-895.
“Photolysis of 1-Pyrenemethylamine Ion-Exchanged into a Zirconium Phosphate Framework”. Bermúdez, R. A.; Arce, R.; Colón, J. L., J. Photochem. Photobiol. A: Chem.,2005, in press.
back
|
