| membrane-bound proton-translocating PPi synthase | <enzyme> From rhodospirillum rubrum; functions as an alternative coupling factor; n,n'-dicyclohexylcarbodiimide-sensitive; catalyses the phosphorylation of pi to ppi, the hydrolysis of ppi and the concomitant translocation of proton across the plasma membrane Registry number: EC 3.6.1.- Synonym: h(+)-ppi synthase (26 Jun 1999) |
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| proton | <physics> An elementary atomic particle with a positive charge and a mass of about 1 amu. (09 Oct 1997) |
| proton acceptor | <chemistry> A base, an anionic substance that acceptsa proton during an acid-basereaction. (09 Oct 1997) |
| proton ATPase | <enzyme> An ion pump that actively transports hydrogen ions across lipid bilayers in exchange for ATP. Major groups are the F-type ATPases, that run in reverse to synthesise ATP in bacterial, mitochondrial and chloroplast membranes (ATP synthase) and the V-type ATPases found in intracellular vesicles with an acidic lumen and on certain epithelial cells (e.g. Kidney intercalated cells). Gastric H/K ATPase is a proton ATPase. (18 Nov 1997) |
| proton donor | <chemistry> An acid, a susbstance that donates protons in an acid-base reduction reaction. (10 Jan 1998) |
| proton-motive force | Energy that is generated by the transfer of protons or electrons across an energy-transducing membrane and that can be used for chemical, osmotic, or mechanical work. Proton-motive force can be generated by a variety of phenomena including the operation of an electron transport chain, illumination of a purple membrane, and the hydrolysis of ATP by a proton atpase. (12 Dec 1998) |
| proton pump | Integral membrane proteins that transport protons across a membrane against a concentration gradient. This transport is driven by hydrolysis of ATP by hydrogen-transporting ATP synthase. (12 Dec 1998) |
| proton pump inhibitor | <pharmacology> A group of anti-ulcer medications which work by binding to H+/K+ ATPase, an enzyme which is found on the secretory surface of parietal cells. It thereby inhibits the final transport of hydrogen ions (via exchange with potasium) into the gastric lumen. Examples of proton pump inhibitors include omeprazole and lansoprazole. (27 Sep 1997) |
| affinity | 1. An inherent likeness or relationship. 2. A special attraction for a specific element, organ or structure. 3. <chemistry> The force that binds atoms in molecules, the tendency of substances to combine by chemical reaction. 4. The strength of noncovalent chemical binding between two substances as measured by the dissociation constant of the complex. 5. <immunology> A thermodynamic expression of the strength of interaction between a single antigen binding site and a single antigenic determinant (and thus of the stereochemical compatibility between them), most accurately applied to interactions among simple, uniform antigenic determinants such as haptens. Expressed as the association constant (K litres mole 1), which, owing to the heterogeneity of affinities in a population of antibody molecules of a given specificity, actually represents an average value (mean intrinsic association constant). 6. <chemistry> The reciprocal of the dissociation constant. Origin: L. Affinitas = relationship (06 Oct 1997) |
| affinity adsorbent | <immunology> A support matrix coated with an affinity antibodies. (06 May 1997) |
| affinity antibody | The measure of the interaction between molecules such as a receptor and its ligand. This interaction is reversible. (05 Mar 2000) |
| affinity chromatography | <investigation> A technique of analytical chemistry used to separate and purify a biological molecule from a mixture, based on the attraction of the molecule of interest to a particular ligand which has been previously attached to a solid, inert substance. The mixture is passed through a column containing the ligand attached to the stationary substance, so that the molecule of interest stays within the column while the rest of the mixture continues through to the end. Then, a different chemical is flushed through the column to detach the molecule from the ligand and bring it out separately from the rest of the mixture. (09 Feb 1998) |
| affinity column | <investigation> A technique of analytical chemistry used to separate and purify a biological molecule from a mixture, based on the attraction of the molecule of interest to a particular ligand which has been previously attached to a solid, inert substance. The mixture is passed through a column containing the ligand attached to the stationary substance, so that the molecule of interest stays within the column while the rest of the mixture continues through to the end. Then, a different chemical is flushed through the column to detach the molecule from the ligand and bring it out separately from the rest of the mixture. (09 Feb 1998) |
| affinity labeling | <technique> A method for tagging molecules, such as enzymes, so that they can be more easily detected and studied. The method works by substituting a synthetic substance which is similar to the substance that the enzyme normally bonds with. (09 Feb 1998) |
| affinity labels | Analogs of those substrates or compounds which bind naturally at the active sites of proteins, enzymes, antibodies, steroids, or physiological receptors. These analogs form a stable covalent bond at the binding site, thereby acting as inhibitors of the proteins or steroids. (12 Dec 1998) |