Biomaterial Database

Order of free energy couplings between ligand binding and protein subunit association in hemoglobin. 1984

G Weber

The number of protein subunits that must be liganded to effect changes in subunit interaction may be characterized by defining an order for the free energy couplings between these two processes. From available data on the chemical equilibrium of stripped hemoglobin A with oxygen, I show that couplings are unequivocally of first order. The two-state model of cooperative binding is shown to be incompatible with the results of this analysis, as the Monod-Wyman-Changeux parameters derived from the same experimental data demand free energy couplings of an order higher than the second.

UI	MeSH Term	Description	Entries
D008024	Ligands	A molecule that binds to another molecule, used especially to refer to a small molecule that binds specifically to a larger molecule, e.g., an antigen binding to an antibody, a hormone or neurotransmitter binding to a receptor, or a substrate or allosteric effector binding to an enzyme. Ligands are also molecules that donate or accept a pair of electrons to form a coordinate covalent bond with the central metal atom of a coordination complex. (From Dorland, 27th ed)	Ligand
D008954	Models, Biological	Theoretical representations that simulate the behavior or activity of biological processes or diseases. For disease models in living animals, DISEASE MODELS, ANIMAL is available. Biological models include the use of mathematical equations, computers, and other electronic equipment.	Biological Model,Biological Models,Model, Biological,Models, Biologic,Biologic Model,Biologic Models,Model, Biologic
D009038	Motion	Physical motion, i.e., a change in position of a body or subject as a result of an external force. It is distinguished from MOVEMENT, a process resulting from biological activity.	Motions
D011487	Protein Conformation	The characteristic 3-dimensional shape of a protein, including the secondary, supersecondary (motifs), tertiary (domains) and quaternary structure of the peptide chain. PROTEIN STRUCTURE, QUATERNARY describes the conformation assumed by multimeric proteins (aggregates of more than one polypeptide chain).	Conformation, Protein,Conformations, Protein,Protein Conformations
D006441	Hemoglobin A	Normal adult human hemoglobin. The globin moiety consists of two alpha and two beta chains.
D006801	Humans	Members of the species Homo sapiens.	Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
D000494	Allosteric Regulation	The modification of the reactivity of ENZYMES by the binding of effectors to sites (ALLOSTERIC SITES) on the enzymes other than the substrate BINDING SITES.	Regulation, Allosteric,Allosteric Regulations,Regulations, Allosteric
D013816	Thermodynamics	A rigorously mathematical analysis of energy relationships (heat, work, temperature, and equilibrium). It describes systems whose states are determined by thermal parameters, such as temperature, in addition to mechanical and electromagnetic parameters. (From Hawley's Condensed Chemical Dictionary, 12th ed)	Thermodynamic
D046911	Macromolecular Substances	Compounds and molecular complexes that consist of very large numbers of atoms and are generally over 500 kDa in size. In biological systems macromolecular substances usually can be visualized using ELECTRON MICROSCOPY and are distinguished from ORGANELLES by the lack of a membrane structure.	Macromolecular Complexes,Macromolecular Compounds,Macromolecular Compounds and Complexes,Complexes, Macromolecular,Compounds, Macromolecular,Substances, Macromolecular