title: Experiments on Hemoglobin in Single Crystals and Silica Gels Distinguish among Allosteric Models.
abstract: Trapping quaternary structures of hemoglobin in single crystals or by encapsulation in silica gels has provided a demanding set of data to test statistical mechanical models of allostery. In this work, we compare the results of those experiments with predictions of the four major allosteric models for hemoglobin: the quaternary two-state model of Monod, Wyman, and Changeux; the tertiary two-state model of Henry et al., which is the simplest extension of the Monod-Wyman-Changeux model to include pre-equilibria of tertiary as well as quaternary conformations; the structure-based model of Szabo and Karplus; and the modification of the latter model by Lee and Karplus. We show that only the tertiary two-state model can provide a near quantitative explanation of the single-crystal and gel experimental results.
authors.affiliation: Laboratory of Chemical Physics, NIDDK, National Institutes of Health, Bethesda, Maryland.
authors.forename: Eric R
authors.initials: ER
authors.lastname: Henry
authors.affiliation: Institute of Biophysics, CNR, Pisa, Italy; Department of Pharmacy, University of Parma, Parma, Italy.
authors.forename: Andrea
authors.initials: A
authors.lastname: Mozzarelli
authors.affiliation: Department of Physics and Earth Sciences, University of Parma, Parma, Italy; NEST, Nanoscience Institute, CNR, Pisa, Italy.
authors.forename: Cristiano
authors.initials: C
authors.lastname: Viappiani
authors.affiliation: NEST, Nanoscience Institute, CNR, Pisa, Italy; Department of Life Sciences, University of Parma, Parma, Italy.
authors.forename: Stefania
authors.initials: S
authors.lastname: Abbruzzetti
authors.affiliation: Department of Neurosciences, University of Parma, Parma, Italy.
authors.forename: Stefano
authors.initials: S
authors.lastname: Bettati
authors.affiliation: Department of Neurosciences, University of Parma, Parma, Italy.
authors.forename: Luca
authors.initials: L
authors.lastname: Ronda
authors.affiliation: Institute of Biophysics, CNR, Pisa, Italy.
authors.forename: Stefano
authors.initials: S
authors.lastname: Bruno
authors.affiliation: Laboratory of Chemical Physics, NIDDK, National Institutes of Health, Bethesda, Maryland. Electronic address: eaton@helix.nih.gov.
authors.forename: William A
authors.initials: WA
authors.lastname: Eaton
mesh_terms: D000494:Allosteric Regulation; D006454:Hemoglobins / Q000737:chemistry* / Q000378:metabolism*; D006801:Humans; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008958:Models, Molecular; D010100:Oxygen / Q000737:chemistry; D020836:Protein Structure, Quaternary; D058428:Silica Gel / Q000737:chemistry*; D012996:Solutions; D013696:Temperature
chemical_list: D006454:Hemoglobins; D012996:Solutions; D058428:Silica Gel; D010100:Oxygen