| metals, light | Metals with low specific gravity, typically smaller than 5, characterised by a single valence (1, 2, or 3), a simple spectrum, strong electromotive force (positive), and colourless compounds. (12 Dec 1998) |
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| minimum light | Threshold of visual sensation, the minimal light intensity evoking a visual sensation. Synonym: achromatic threshold, minimum light threshold. (05 Mar 2000) |
| minimum light threshold | Threshold of visual sensation, the minimal light intensity evoking a visual sensation. Synonym: achromatic threshold, minimum light threshold. (05 Mar 2000) |
| cold light | Fluorescent light as opposed to incandescent light. (05 Mar 2000) |
| monochromatic light | <microscopy> Light composed of one wavelength. It may be obtained by the use of a laser or by gaseous discharge tubes in combination with proper filters. An approximation is obtained by interference filters or monochromators. (05 Aug 1998) |
| plane-polarized light | <chemistry> Light which is passed through a filter which blocks out all the light except that which ocillates in one plane. (09 Jan 1998) |
| cone of light | A triangular area at the anterior inferior part of the tympanic membrane, running from the umbo to the periphery, where there is seen a bright reflection of light. Synonym: cone of light, light reflex, Politzer's luminous cone, red reflex, Wilde's triangle. Malacarne's pyramid, a lobule on the undersurface of the cerebellum, the posterior portion of the vermis. (05 Mar 2000) |
| Wood's light | Ultraviolet light produced by Wood's lamp. (05 Mar 2000) |
| consensual light reflex | Contraction of the pupil of the fellow eye in consensus with the pupil of the illuminated eye. Synonym: consensual light reflex, indirect pupillary reaction. (05 Mar 2000) |
| P light chain | <protein> Myosin light chain that can be phosphorylated by myosin light chain kinase, as a result of phosphorylation, the myosin is activated. (18 Nov 1997) |
| polarised light | Light in which, as a result of reflection or transmission through certain media, the vibrations are all in one plane, transverse to the ray, instead of in all planes. (05 Mar 2000) |
| polarized light | <microscopy> Light that is vibrating in one plane (plane-polarized light), light with a rotary vibration (circular polarized light), or light that is vibrating elliptically (elliptically polarized light). Moonlight and skylight are polarized, as is much reflected light, cloud light is polarized under certain conditions. However, naturally polarized light is, on the whole, rather imperfectly polarized. (05 Aug 1998) |
| polarized light microscope | <instrument, microscopy> A microscopical polarizcope, i.e., a compound microscope which is equipped with two polars and a Bertrand lens, chemists and mineralogists are the principal users. (05 Aug 1998) |
| myosin light chain | <protein> The light chains of the muscle protein myosin. Each molecule of myosin is composed of two heavy chains and two pairs of light chains. The light chains have a molecular weight of about 20 kD and there is one dissimilar pair of light chains associated with each heavy chain. The proteins all have sequence homology to calmodulin, but not all with calcium binding activity. Several types are known: regulatory light chains (LC 2, DNTB light chains) probably regulate the ATPase activity of the heavy chain directly (through the binding of calcium) or indirectly (activating when they themselves are phosphorylated by myosin light chain kinase) and essential light chains (LC 1, LC 3, alkali light chains), which have a more subtle and apparently nonessential role. In molluscan muscle the EDTA light chains (similar to LC 2 from vertebrate muscle) confer calcium sensitivity on the myosin itself. The light chains are "calmodulin-like" proteins that bind calcium. Two of them can be removed easily, and two with difficulty. The light chains bind the heavy chains in the vicinity of the head groups of the myosin. (12 Dec 1998) |
| myosin light chain kinase | <enzyme> An enzyme that phosphorylates myosin light chains in the presence of ATP to yield myosin-light chain phosphate and ADP, and requires calcium and calmodulin. The 20-kD light chain is phosphorylated more rapidly than any other acceptor, but light chains from other myosins and myosin itself can act as acceptors. The enzyme plays a central role in the regulation of smooth muscle contraction. Chemical name: ATP:myosin-light-chain O-phosphotransferase Registry number: EC 2.7.1.117 (12 Dec 1998) |