| aquo-ion | A hydrated ion; an ion containing one or more water molecules; e.g., Cu(H2O)42+. (05 Mar 2000) |
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| gated ion channel | <physiology> Transmembrane proteins of excitable cells, that allow a flux of ions to pass only under defined circumstances. Channels may be either voltage gated, such as the sodium channel of neurons or ligand gated such as the acetylcholine receptor of cholinergic synapses. Channels tend to be relatively ion specific and allow fluxes of typically 1000 ions to pass in around 1ms, they are thus much faster at moving ions across a membrane than transport ATPases. (05 May 1997) |
| central metal ion | <chemistry> The metal ion to which the ligands are attached at the centre of a coordination complex. (09 Oct 1997) |
| voltage gated ion channel | <physiology> A transmembrane ion channel whose permeability to ions is extremely sensitive to the transmembrane potential difference. These channels are essential for neuronal signal transmission and for intracellular signal transduction. See: sodium channel. (18 Nov 1997) |
| gram-ion | <chemistry> The weight in grams of an ion that is equal to the sum of the atomic weights of the atoms making up the ion. (05 Mar 2000) |
| mobile ion carrier | <chemistry> A molecule that allows ions to cross lipid bilayers. There are two classes: carriers and channels. Carriers, like valinomycin, form cage like structures around specific ions, diffusing freely through the hydrophobic regions of the bilayer. Channels, like gramicidin, form continuous aqueous pores through the bilayer, allowing ions to diffuse through. See: ion channels. (18 Nov 1997) |
| common ion effect | <chemistry> The influence on an equilibrium by the presence of a substance which contains ions that participate in the equilibrium. (09 Oct 1997) |
| complex ion | The colour, texture, and general appearance of the skin of the face. Origin: L. Complexio, a combination, (later) physical condition (05 Mar 2000) Previous: complex carbohydrate, complex closure, complex febrile convulsion, complexinNext: complex ion, complexity, complex learning processescomplex ion <chemistry> An ion formed by the combination of a central metal ion and ligands. (05 Jan 1998) |
| Heavy Ion Beams | <radiobiology> Particle beams using heavy (as opposed to light) ions. These can be used for inertial confinement fusion research. (10 Jan 1998) |
| P with a subscript for the ion | <abbreviation> Permeability constant. (05 Mar 2000) |
| hydride ion | The H- i., transferred to acceptor molecules in some biological oxidations. (05 Mar 2000) |
| hydrogen ion | A hydrogen atom minus its electron and therefore carrying a unit positive charge (i.e., a proton); in water, it combines with a water molecule to form hydronium ion, H3O+. (05 Mar 2000) |
| hydronium ion | <chemistry> A positively charged ion that is water with an additional hydrogen atom (H3O). (09 Oct 1997) |
| spectrometry, mass, secondary ion | A mass-spectrometric technique that is used for microscopic chemical analysis. A beam of primary ions with an energy of 5-20 kiloelectronvolts (kev) bombards a small spot on the surface of the sample under ultra-high vacuum conditions. Positive and negative secondary ions sputtered from the surface are analyzed in a mass spectrometer in regards to their mass-to-charge ratio. (12 Dec 1998) |
| sulfonium ion | A compound in which a sulfur atom has three single covalent bonds and therefore has a positive charge analogous to the nitrogen of an ammonium compound; e.g., S-adenosyl-l-methionine. (05 Mar 2000) |