Measurement of the protein-ligand bond energy of carboxymyoglobin by pulsed photoacoustic calorimetry

A photoacoustic calorimetry study of horse carboxymyoglobin on the 10-nanosecond time scale

“…the present and prior The enthalpy change accompanying the formation of the instantaneously produced intermediate species is in accord with the results of Choy and co-workers (Leung et al, 1987), who obtained an enthalpy change following Fe-CO bond cleavage of 13.4 ± 0.5 kcal/mol in 0.1 M phosphate buffer at pH 7. Their method of data analysis differed from ours in that they subtracted the volume change signal obtained at the (3-null temperature from their MbCO waves at higher temperature.…”

The contribution of heme propionate groups to the conformational dynamics associated with CO photodissociation from horse heart myoglobin

“…The enthalpy change associated with water binding to His 64 (DH H 2 O ) was estimated to be $À9 kcal mol À1 using the measured activation energies for water binding and dissociation from deoxyMb [10], and scaling this value by the water occupancy of 0.8. The enthalpy change for CO molecule solvation (DH CO ) was previously determined to be 2.6 kcal mol À1 [65]. The observed enthalpy change can then be expressed as…”

Time Resolved Thermodynamics Associated with Diatomic Ligand Dissociation from Globins

“…Thus the observed thermodynamic parameters reflect the transition between fully ligated (CO) 4 Hb and triple ligated (CO) 3 Hb. Consequently, the observed reaction enthalpy corresponds to the enthalpy change due to the cleavage of the Fe-CO bond (ΔH Fe-CO =17.5 kcal mol -1 (Leung et al, 1987;Miksovska et al, 2005)), the enthalpy change due to the solvation of a CO molecule (ΔH solv = 2.6 kcal mol -1 (Leung et al, 1987)), the enthalpy change of structural relaxation associated with the ligand release from the protein matrix, and enthalpy of the distal pocket hydration. The occupancy of water molecules in the distal pocket of deoxyHb was determined to be significantly lower than that in Mb (~0.64 for the Hb -chain and ~ 0.33 for the Hb -chain (Esquerra et al, 2010)).…”