Infrared spectroscopy of photodissociated carboxymyoglobin at low temperatures.
- 1 June 1982
- journal article
- research article
- Published by Proceedings of the National Academy of Sciences in Proceedings of the National Academy of Sciences
- Vol. 79 (12), 3744-3748
- https://doi.org/10.1073/pnas.79.12.3744
Abstract
The IR spectra of the bound and photodissociated states of [sperm whale] Mb-12CO and Mb-13CO from 5.2 to 300 K were studied. The absorbance peaks seen between 1800 and 2200 cm-1 correspond to CO stretching vibrations. In the bound state of Mb-12CO, the known lines A0 at 1969, A1 at 1945, and A2 at 1927 cm-1 have center frequencies, widths and absorbances that are independent of temperature between 5.2 and 160 K. Above 160 K, A2 gradually shifts to 1933 cm-1. The low-temperature photodissociated state (Mb*) shows 3 lines (B0, B1, B2) at 2144, 2131, and 2119 cm-1 for 12CO. The absorbances of the 3 lines depend on temperature. B0 is tentatively assigned to free CO in the heme pocket and B1 and B2, to CO weakly bound to the heme or heme pocket wall. The data are consistent with a model in which photodissociation of MbCO leads to B1 and B2. B2 decays thermally to B1 above 13 K; rebinding to A occurs from B1. The barriers between B2 and B1 and between B1 and A are described by activation enthalpy spectra. Heme and the central metal atom in state Mb* have near-IR, EPR and Mossbauer spectra that differ slightly from those of deoxyMb. The observation of essentially free CO in state B implies that the difference between Mb* and deoxyMb is not due to an interaction of the flashed-off ligand with the protein but is caused by an incomplete relaxation of the protein structure at low temperatures.Keywords
This publication has 13 references indexed in Scilit:
- Solvent viscosity and protein dynamicsBiochemistry, 1980
- Chemical reactivity of metalloproteins in conformationally out-of-equilibrium statesBiochimica et Biophysica Acta (BBA) - Reviews on Bioenergetics, 1979
- Temperature-dependent X-ray diffraction as a probe of protein structural dynamicsNature, 1979
- The physical aspects of energy transduction in biological systemsQuarterly Reviews of Biophysics, 1978
- Tunneling in Ligand Binding to Heme ProteinsScience, 1976
- Low temperature photodissociation studies of ferrous hemoglobin and myoglobin complexes by Mössbauer spectroscopyBiochimica et Biophysica Acta (BBA) - General Subjects, 1976
- Dynamics of ligand binding to myoglobinBiochemistry, 1975
- Neutron Diffraction Analysis of Myoglobin: Structure of the Carbon Monoxide DerivativeScience, 1975
- Low temperature photodissociation of hemoproteins: Carbon monoxide complex of myoglobin and hemoglobinBiochimica et Biophysica Acta (BBA) - Protein Structure, 1974
- Low temperature photodissociation of hemoproteins: Oxygenated cobalt-myoglobin and hemoglobinBiochimica et Biophysica Acta (BBA) - Protein Structure, 1974