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Biomedical subjects

J Wyman

Publications and source records attributed to J Wyman.

At least 37 records · Page 2Linked to original sources
PubMed1987

Nesting: hierarchies of allosteric interactions.

A generalization of the allosteric model is presented that incorporates a hierarchy of conformational equilibria. Such a formulation draws upon structural organization already seen in many large macromolecular systems. The functional binding properties of the macromolecule reflect conformational equilibria at each structural level. Appropriate "nested" models are used to interpret structural features and functional aspects of two hemocyanin systems with a large number (12 and 24) of binding sites.

Allosteric Regulation↗
PubMed1985

Generalized binding phenomena in an allosteric macromolecule.

A general macromolecular partition function is developed in terms of chemical ligand activity, temperature and pressure for systems described by an array of species which are characterized by their state of allosteric conformation and ligand stoichiometry. The effects of chemical ligand binding, enthalpy change, and volume change are treated in a parallel manner. From a broad viewpoint all of these effects can be regarded as specific cases of generalized binding phenomena. This approach provides a general method for analyzing calorimetric and ligand binding experiments. Several applications are given: (1) Thermal scanning data for tRNAphe (P.L. Privalov and V.V. Filimonov, J. Mol. Biol. 122 (1978) 447) are shown to fit a general model with six conformational states. By application of linkage theory it is shown that sodium chloride is expelled as the molecule denatures. (2) The results of calorimetric titrations on the arabinose binding protein (H. Fukada, J.M. Sturtevant and F.A. Quiocho, J. Mol. Biol. 258 (1983) 13193) are shown to fit a simple two-state allosteric model. (3) A thermal binding curve is simulated for an unusual respiratory protein, trout I hemoglobin (B.G. Barisas and S.J. Gill, Biophys. Chem. 9 (1979) 235), in order to illustrate both the similarities and differences between enthalpy and chemical ligand binding processes.

Allosteric Regulation↗
PubMed1985

Unidirectional circulation in a prebiotic photochemical cycle.

In this brief note, we suggest the possibility that a soliton-assisted unidirectional photochemical cycle has played a role in prebiotic evolution. This suggestion is based on a model calculation which is itself based on the detection of Davydov-type soliton overtones in acetanilide.

Journal Article↗
PubMed1984

Soliton-assisted unidirectional circulation in a biochemical cycle.

The unidirectional circulation of an enzyme round a working cycle can be understood in terms of the formation and decay of a soliton that acts as a ligand for the protein and for which the surrounding heat bath serves as a sink. An experimental confirmation of this interpretation is suggested in which the soliton is of the Davidov type and is created by infrared photon absorption as in recent experiments on acetanilide.

Journal Article↗
PubMed1982

Linkage graphs.

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Biopolymers↗
PubMed1981

A plausible two-state model for cytochrome c oxidase.

The catalytic properties of pulsed and resting cytochrome c oxidase (ferrocytochrome c: oxygen oxidoreductase, EC 1.9.3.1), expressed in terms of a minimal kinetic scheme and simulated by numerical computations, were successfully described. A two-state model, in which the relative amounts of the enzyme present in each conformation are regulated by the rates of electron flux and O2 binding on one side and the interconversion rates on the other, accounts for the activation of cytochrome c oxidase during turnover.

Electron Transport Complex IV↗
PubMed1980

Ligand-linked phase changes in a biological system: applications to sickle cell hemoglobin.

Polyphasic linkage is a close analog of the allosteric and polysteric linkages shown by many biological macromolecules. Like them, it gives rise to both homotropic and heterotropic effects. It is governed by a group of linkage potentials applicable to each separate phase and also, subject to certain conditions, by a group of lower order applicable to the whole system, globally. A good example of polyphasic linkage is provided by sickle cell hemoglobin which, under suitable conditions and subject to control by oxygen, precipitates out of solution to form what appear to be microtubules. This is but one instance of the way in which macromolecular assembly and the formation of subcellular structures generally can be regulated by various small molecules acting as ligands.

Chemical Phenomena↗
PubMed1979

On thermal transitions in biological macromolecules.

The thermal transitions shown by macromolecules are to be understood as an allosteric phenomenon. They can be dealt with in terms of the same linkage principles as those governing the binding of a chemical ligand. This provides a basis for analyzing the observed differences between the reversible heat denaturation of proteins and the melting of nucleic acids. It also adds to our understanding of cooperativity and heterotropic linkage.

Journal Article↗