Ultrafast dissociation dynamics studied

Abstract

Researchers at Harvard University have obtained femtosecond infrared spectra of carbon monoxide dissociating from the heme prosthetic group in myoglobin, a protein that serves as a reserve oxygen source in muscle. The study pushes the sensitivity and time-resolution limits of IR spectroscopy and provides answers to long-standing questions about the mechanism of CO dissociation under physiological conditions. The work, carried out by graduate students Manho Lim and Timothy A. Jackson and chemistry professor Philip A. Anfinrud, reveals two detailed routes by which CO can dissociate from heme and shows the role played by myoglobin conformational changes in the process. Myoglobin's normal physiological function is to bind oxygen, but it is capable of binding other ligands, such as CO. Anfinrud and coworkers used a laser to photodissociate CO from myoglobin, and then obtained timeresolved IR spectra of the departing ligand. The researchers found that, upon dissociation of CO from its heme binding site, the lig...