Journal of Physical Chemistry B, Vol.103, No.16, 3070-3072, 1999
Stark-effect spectroscopy of the heme charge-transfer bands of deoxymyoglobin
We report the Stark spectra of the Soret, Q, and charge-transfer bands of deoxymyoglobin. The data show that band In: has charge-transfer character but that the magnitude of the charge displacement is significantly smaller than expected or than what is observed for band I or even the Soret or Q bands. The data also show that Symmetry breaking of iron-protoporphyrin LX in myoglobin produces a larger difference dipole moment in the Soret transition when compared to the dimethyl-ester of protoporphyrin IX. The results lend further credence to the hypothesis that the electrostatic environment of the heme pocket in myoglobin is important in modifying the properties of the heme transitions, and they provide a basis for quantitative analysis of the static and time-dependent band shifts observed in response to environmental electrostatic perturbations and ligand binding dynamics.
Keywords:CARBONMONOXY-MYOGLOBIN;PROTEINS;HEMOGLOBIN;DYNAMICS;PHOTODISSOCIATION;ABSORPTION;RELAXATION;BINDING