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Home >> Dictionary of Bioinformatics, Biochemistry, Biotechnology >> Low Molecular Weight Protein LMP Lundh Test
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Looped domain (looped solenoid) A highly compact structure observed during mitosis and meiosis. At the highest level of organisation, the 30nm fibre assumes a looped domain structure. Each loop of the solenoid consists of 20-100kb DNA anchored to an nuclear scaffold containing several proteins including histone H1 and topo-isomerase ll.
Attachment of DNA Loops to the Nuclear Scaffold
| 1. DNA Loops |
2. 0.25 nm |
3. Nuclear Scaffold |
Loss of heterozygosity (LOH) See Knudsons two-hit hypothesis.
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Lovastatin A HMG CoA reductase inhibitor that effectively lowers LDL cholesterol levels by upregulation of LDL receptors. It causes regression of ischemic heart disease and has minimum side effects.
Low complexity region (LCR) A subsequence of a protein or nucleic acid in which a small number of monomer types predominate. The SEG programme is used to mask or filter LCRs in amino acid queries, while DUST is used to mask or filter LCRs in nucleic acid queries.
Low density lipoproteins (LDL) Also called b-lipoproteins based on their electrophoretic mobility. A lipoprotein comprising a single protein molecule and many molecules of cholesterol ester together with other lipids. These are formed from the catabolism of very low density lipoproteins (VLDL). LDL is involved in the transport of cholesterol into cells. Three subtypes of LDL-LDL l, LDL ll and LDL lll have been recognised.
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Low-energy phosphate compound A phosphorylated compound that has a relatively small standard free energy of hydrolysis.
Low molecular weight protein (LMP) A subunit of the proteasome, where processing of endogenous proteins occurs.
Low threshold substances Substances that are not reabsorbed or reabsorbed only slightly (urea, uric acid).
LPS See lipopolysaccharide.
LTP See Long-term potentiation.
LTR See long terminal repeat.
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Lucifer yellow A fluorescent dye used as a tracer to visualise living cells.
Luciferase An enzyme isolated from fireflies that catalyses the decarboxylation of the substrate luciferyl adenylate to generate light. This reaction is used as a nonradioactive method for labeling molecules.
Luciferin The substrate for luciferase. The enzyme acts of luciferin, a chemiluminescent compound to form oxyluciferin in presence of ATP that can be measured by luminometry.
Lumen The interior of a compartment bounded by membranes such as in an organelle (mitochondrion, endoplasmic reticulum) or an organ (stomach, intestine).
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Luminescence The emission of light from a chemical reaction below the temperature of incandescence. The phenomenon is usually due to oxidative reactions taking place in solutions producing molecules in an excited state. While some of these reactions release energy in the form of heat, others release it in the form of photons. Examples of luminescent compounds include luciferin and luminal.
Luminal The most popular chemiluminescent compound used as a marker in chemiluminescent assays. It is oxidised by hydrogen peroxide at pH 10-11 to release photons with maximal intensity at 430 nm.
Luminometer An instrument for measuring emitted light used as an analytical tool for estimating the cellular content of ATP and other high-energy compounds by utilising biochemical reactions that emit light.
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Lundh test A test meal of corn oil, skimmed milk powder and dextrose is given to stimulate pancreatic secretion. The duodenal secretion is aspirated for 2 h and the active of trypsin estimated. In chronic pancreatic insufficiency, the activity of trypsin is lowered.
Luria, Salvador (1912-1999) A geneticist who worked on bacterial and bacteriophage mutants that led to the elucidation of gene structure. He was awarded the Nobel Prize in Medicine in 1969 together with Max Delbruck and Alfred Hershey for the discovery of replication mechanism and the genetic structure of viruses.
Luteinising hormone A hormone secreted by the anterior pituitary. In females, the hormone induces growth of the yellow body of the ovary (corpus luteum) and in males, it stimulates activity of the interstitial cells of the testis.
Lux (lx) The unit for the measurement of the amount of illumination that impinges upon a surface. 1lx is the illuminance impinging upon a surface of 1m2, each point of which is at a distance of 1 m away from a uniform point source of light of 1 cd (candela). This supersedes the foot-candle. See photon.
Luxury consumption Absorption of nutrients by an organism in excess of that required for optimum growth and productivity.
Luxury genes Genes that code for specialised functions. These are found in large amounts in particular cell types.
Lyase Enzymes that catalyse either the cleavage of a double bond and the addition of new groups to a substrate, or the formation of a double bond.
Lycopene A 40-carbon aliphatic, highly unsaturated molecule containing eleven conjugated and two unconjugated double bonds. The red colour of tomatoes is due to the presence of lycopene. Lycopene is a more stable and potent singlet oxygen quenching agent compared to other carotenoids. In addition to its antioxidant properties, lycopene shows an array of biological effects including cardioprotective, anti-inflammatory, antimutagenic and anticarcinogenic activities. The mechanisms underlying the anticancer effects of lycopene could involve scavenging of reactive oxygen species, upregulation of detoxification systems, interference with cell proliferation, induction of gap-junctional communication, inhibition of cell cycle progression and modulation of signal transduction pathways.
Lycopene Structure
Lymph The colourless fluid that is formed by filtration of blood through the capillary walls. It carries they lymphocytes in a special system of ducts and vessels, termed the lymphatic system.
Lymph node A collection of lymphoid tissue distributed throughout the body, and connected by lymphatics to the circulatory system.
Lymphadenopathy Disease of the lymph nodes.
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