0000000000083111
AUTHOR
Clara Fronticelli
Properties of Human Hemoglobins with Increased Polarity in the α- or β-Heme Pocket
The spectroscopic, conformational, and functional properties of mutant carbonmonoxy hemoglobins in which either the β-globin Val67(E11) or the α-globin Val62(E11) is replaced by threonine have been investigated. The thermal evolution of the Soret absorption band and the stretching frequency of the bound CO were used to probe the stereodynamic properties of the heme pocket. The functional properties were investigated by kinetic measurements. The spectroscopic and functional data were related to the conformational properties through molecular analysis. The effects of this nonpolar-to-polar isosteric mutation are: (i) increase of heme pocket anharmonic motions, (ii) stabilization of the A 0 co…
Dynamic properties of some β-chain mutant hemoglobins
The thermal behavior of the Soret band relative to the carbonmonoxy derivatives of some beta-chain mutant hemoglobins is studied in the temperature range 300-10 K and compared to that of wild-type carbonmonoxy hemoglobin. The band profile at various temperatures is modeled as a Voigt function that accounts for homogeneous broadening and for the coupling with high- and low-frequency vibrational modes, while inhomogeneous broadening is taken into account with a gaussian distribution of purely electronic transition frequencies. The various contributions to the over-all bandwidth are singled out with this analysis and their temperature dependence, in turn, gives information on structural and dy…
Active site conformation in the αH87G mutant hemoglobin: An optical absorption and FTIR study
We have studied the active site conformation in the carbonmonoxy derivative of the αH87G mutant hemoglobin by means of optical absorption and FTIR spectroscopies. A red shift (≈30 cm−1) of the Soret band peak frequency, together with a concomitant red shift (≈2 cm−1) of the bound CO stretching frequency has been observed for the mutant protein. This indicates an altered electrostatic environment of the heme group in the mutated subunits. In view of the FTIR data showing that the bound CO molecule experiences an increased positive electrostatic field, we attribute the observed effects to a closer interaction of the CO ligand with the partially positively charged imidazole side chain of the p…