title: Oxygen penetration and diffusion into myoglobin revealed by quenching of zincprotoporphyrin IX fluorescence.
abstract: Oxygen quenching experiments were carried out on zincprotoporphyrin IX reconstituted myoglobin (MbFe-->Zn) at different temperatures and two solvent viscosities. The data were fit to a dynamic model for quenching of fluorophores in protein interiors previously presented (Biophysical J., 45 (1984) 789-794). The parameters associated with the oxygen entry rate (k+), exit rate (k-), and migration rate (chi) in the protein were obtained at six temperatures and two viscosities (1 and 8 cp), along with the activation enthalpies associated with the above rates (k+ and k-). The partition coefficient (alpha) was calculated at each temperature along with the free energy, delta G0, associated with this partition. The rate parameters (k+, k-, chi) and the partition coefficient (alpha) have also been determined for the sample in 40% sucrose (8 cp), to evaluate the effect of bulk solvent viscosities on these values. The steady-state Stern-Volmer quenching plot was calculated using the rate parameters obtained from the analysis (of the dynamic model). Comparison of the Stern-Volmer points obtained using the dynamic model and those obtained experimentally showed excellent agreement.
authors.affiliation: Department of Physics, University of Illinois at Urbana-Champaign 61801-3080, USA.
authors.forename: J
authors.initials: J
authors.lastname: Carrero
authors.forename: D M
authors.initials: DM
authors.lastname: Jameson
authors.forename: E
authors.initials: E
authors.lastname: Gratton
mesh_terms: D055598:Chemical Phenomena; D002627:Chemistry, Physical; D004058:Diffusion; D005453:Fluorescence; D007700:Kinetics; D008432:Mathematical Computing; D008956:Models, Chemical; D009211:Myoglobin / Q000737:chemistry* / Q000378:metabolism; D010100:Oxygen / Q000737:chemistry* / Q000378:metabolism; D011524:Protoporphyrins / Q000737:chemistry*; D012997:Solvents / Q000737:chemistry; D013696:Temperature; D013816:Thermodynamics; D014783:Viscosity
chemical_list: D009211:Myoglobin; D011524:Protoporphyrins; D012997:Solvents; C017803:zinc protoporphyrin; D010100:Oxygen