| ambident ligand | <chemistry> A ligand that can donate electrons through two or more atoms on their molecule. (05 Feb 1998) |
|---|---|
| cyanocobalamin beta-ligand transferase | <enzyme> Cytosolic enzyme utilizing fad, NADPH and reduced glutathione; forms glutathionylcobalamin from cyanocobalamin Registry number: EC 2.5.1.- Synonym: ccbl transferase (26 Jun 1999) |
| ELAM-1 ligand fucosyltransferase | <enzyme> Directs the expression of an elam-1 ligand; an alpha(1,3) fucosyltransferase Registry number: EC 2.4.1.- Synonym: elft protein, elft gene product (26 Jun 1999) |
| ligand | <chemistry, immunology> Any molecule that binds to another, in normal usage a soluble molecule such as a hormone or neurotransmitter, that binds to a receptor. The decision as to which is the ligand and which the receptor is often a little arbitrary when the broader sense of receptor is used (where there is no implication of transduction of signal). In these cases it is probably a good rule to consider the ligand to be the smaller of the two thus in a lectin sugar interaction, the sugar would be the ligand (even though it is attached to a much larger molecule, recognition is of the saccharide). (18 Nov 1997) |
| ligand binding site | The site on a protein's surface that binds a ligand; equivalent to the active site if the ligand is the substrate of an enzyme. (05 Mar 2000) |
| ligand-gated channel | A class of ion channel's whose ionic permeability is regulated by cell membrane receptors that respond to specific extracellular chemical signals. (05 Mar 2000) |
| ligand gated ion channel | A transmembrane ion channel whose permeability is increased by the binding of a specific ligand, typically a neurotransmitter at a chemical synapse. The permeability change is often drastic, such channels let through effectively no ions when shut, but allow passage at up to 10exp7 ions sexp 1 when a ligand is bound. Recently, the receptors for both acetylcholine and GABA have been found to share considerable sequence homology, implying that there may be a family of structurally related ligand gated ion channels. (18 Nov 1997) |
| ligand induced endocytosis | The formation of coated pits and then coated vesicles as a consequence of the interaction of ligand with receptors, which then interact with clathrin and associated proteins (coatomers) on the cytoplasmic face of the plasma membrane and come together to form a pit. Not all coated vesicle uptake of receptors requires receptor occupancy. (18 Nov 1997) |
| auditory field | The space included within the limits of hearing of a definite sound, as of a tuning fork. (05 Mar 2000) |
| bright field illumination | <microscopy> The method of lighting the specimen with a solid cone of rays. Transmitted bright field illumination is performed by a substage condenser. Reflected bright field illumination is performed by a vertical illuminator. Compare: dark field illumination (05 Aug 1998) |
| bright field imaging | <microscopy> An imaging mode in a transmission electron microscopy that uses only unscattered Electrons to form the image. Contrast in such an image is due entirely to mass-thickness variations in amorphous samples, and may include diffraction contrast in crystalline samples. (05 Aug 1998) |
| bright field microscopy | <technique> Optical microscopy, in which absorption to a great extent and diffraction to a minor extent give rise to the image, as opposed to phase contrast or interference methods of microscopy. (18 Nov 1997) |
| Broca's field | The posterior part of the inferior frontal gyrus of the left or dominant hemisphere, corresponding approximately to Brodmann's area 44; Broca identified this region as an essential component of the motor mechanisms governing articulated speech. Synonym: Broca's area, Broca's field, motor speech centre. (05 Mar 2000) |
| cardioid dark field condenser | <microscopy> A condenser designed with two reflecting surfaces, the first, a spherical surface which reflects the rays to a second, cardioid (heart-shaped) surface. The virtue in such an arrangement is that, if the cardioid surface is of true figure, the lens is both achromatic and aplanatic. It has a limiting numerical aperture of about 1.0. Thus objectives of a greater numerical aperture cannot be used successfully with it. A true cardioid figure is the trace of a point on the circumference of a circle rolling around an equal, fixed circle. (05 Aug 1998) |
| magnetic field | The sphere of influence of a magnet. (05 Mar 2000) |