| molecular structure | The location of the atoms, groups or ions relative to one another in a molecule, as well as the number and location of chemical bonds. (12 Dec 1998) |
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| molecular weight | The sum of the atomic weight's of all the atoms constituting a molecule; the mass of a molecule relative to the mass of a standard atom, now 12C (taken as 12.000). Relative molecular mass (Mr) is the mass relative to the dalton and has no units. See: atomic weight. Synonym: molecular mass, molecular weight ratio, relative molecular mass. (05 Mar 2000) |
| molecular weight ratio | The sum of the atomic weight's of all the atoms constituting a molecule; the mass of a molecule relative to the mass of a standard atom, now 12C (taken as 12.000). Relative molecular mass (Mr) is the mass relative to the dalton and has no units. See: atomic weight. Synonym: molecular mass, molecular weight ratio, relative molecular mass. (05 Mar 2000) |
| heparin, low-molecular-weight | <chemical> Heparin fractions with a molecular weight usually between 4000 and 6000 kD. These low-molecular-weight fractions are effective antithrombotic agents. Their administration reduces the risk of haemorrhage, they have a longer half-life, and their platelet interactions are reduced in comparison to unfractionated heparin. They also provide an effective prophylaxis against postoperative major pulmonary embolism. Pharmacological action: anticoagulant, fibrinolytic agent. (12 Dec 1998) |
| directed molecular evolution | Techniques used to produce molecules exhibiting properties that conform to the demands of the experimenter. (12 Dec 1998) |
| epidemiology, molecular | The application of molecular biology to the answering of epidemiological questions. The examination of patterns of changes in DNA to implicate particular carcinogens and the use of molecular markers to predict which individuals are at highest risk for a disease are common examples. (12 Dec 1998) |
| european molecular biology lab gene bank | <molecular biology> A large database of DNA sequence data in Heidelberg, Germany, compiled from international sources. It is the European equivalent to the Genbank DNA sequence databank in the United States of America. WWW: EMbase. (09 Oct 1997) |
| evolution, molecular | Evolution at the molecular level of DNA sequences and proteins. (rieger et al., glossary of genetics: classical and molecular, 5th ed) (12 Dec 1998) |
| kinetic molecular theory | <chemistry> This theory assumes that molecules must collide in order to react. The more collisions the more likely it is for a reaction to occur. However, depending on the conditions, only a small fraction of the collisions are effective in producing a reaction. There are several constraints. In order for a reaction to occur, bonds initially are broken, which requires energy. This energy depends on the type of the reaction and comes from the kinetic energies that the molecules possess before the collision. It is called the activation energy. Increasing the temperature increases the kinetic energies and more collisions will occur. In adition, at a higher temperature a greater number of the reacting molecules might possess an energy equal to or greater than the activation energy. However the molecules must also collide in a specific orientation, called the steric factor in order for a reaction to occur. A reaction will only be successful, if the collision has enough energy to be either equal to or greater than the activation energy and if the orientation of the collision allows for correct bond formation. These factors are in the Arrhenius equation: k = zp The rate constant k is proportional to the Arrhenius factor A. A is the product of the collision frequency z, and the steric factor p. The fraction of collisions with sufficient energy to produce a reaction are in the term of the equation. (09 Jan 1998) |
| kininogen, high-molecular-weight | A plasma protein, molecular weight of 110 kD, that normally exists in plasma in a 1:1 complex with prekallikrein. Hmwk is split by plasma kallikrein to produce bradykinin. The complex is a cofactor in the activation of coagulation factor xii. The product of this reaction, xiia, in turn activates prekallikrein to kallikrein. (12 Dec 1998) |
| kininogen, low-molecular-weight | A protein, molecular weight 50 kD, located in various normal tissues. Upon cleavage by kallikrein or other kallikreins, it forms kallidin. Kallidin, in turn, is converted into bradykinin. (12 Dec 1998) |
| air | 1. The fluid which we breathe, and which surrounds the earth; the atmosphere. It is invisible, inodourous, insipid, transparent, compressible, elastic, and ponderable. By the ancient philosophers, air was regarded as an element; but modern science has shown that it is essentially a mixture of oxygen and nitrogen, with a small amount of carbon dioxide, the average proportions being, by volume: oxygen.96 per cent.; nitrogen.00 per cent.; carbon dioxide.04 per cent. These proportions are subject to a very slight variability. Air also always contains some vapor of water. 2. Symbolically: Something unsubstantial, light, or volatile. "Charm ache with air." "He was still all air and fire. (Macaulay). [Air and fire being the finer and quicker elements as opposed to earth and water]" 3. A particular state of the atmosphere, as respects heat, cold, moisture, etc, or as affecting the sensations; as, a smoky air, a damp air, the morning air, etc. 4. Any aeriform body; a gas; as, oxygen was formerly called vital air. 5. Air in motion; a light breeze; a gentle wind. "Let vernal airs through trembling osiers play." (Pope) 6. Odouriferous or contaminated air. 7. That which surrounds and influences. "The keen, the wholesome air of poverty." (Wordsworth) 8. Utterance abroad; publicity; vent. "You gave it air before me." (Dryden) 9. Intelligence; information. 10. A musical idea, or motive, rhythmically developed in consecutive single tones, so as to form a symmetrical and balanced whole, which may be sung by a single voice to the stanzas of a hymn or song, or even to plain prose, or played upon an instrument; a melody; a tune; an aria. In harmonised chorals, psalmody, part songs, etc, the part which bears the tune or melody in modern harmony usually the upper part is sometimes called the air. 11. The peculiar look, appearance, and bearing of a person; mien; demeanor; as, the air of a youth; a heavy air; a lofty air. "His very air." 12. Peculiar appearance; apparent character; semblance; manner; style. "It was communicated with the air of a secret." (Pope) 12. An artificial or affected manner; show of pride or vanity; haughtiness; as, it is said of a person, he puts on airs. 14. The representation or reproduction of the effect of the atmospheric medium through which every object in nature is viewed. Carriage; attitude; action; movement; as, the head of that portrait has a good air. 15. The artificial motion or carriage of a horse. 16. To expose to the air for the purpose of cooling, refreshing, or purifying; to ventilate; as, to air a room. "It were good wisdom . . . That the jail were aired." (Bacon) "Were you but riding forth to air yourself." (Shak) 17. To expose for the sake of public notice; to display ostentatiously; as, to air one's opinion. "Airing a snowy hand and signet gem." (Tennyson) 18. To expose to heat, for the purpose of expelling dampness, or of warming; as, to air linen; to air liquors. Air is much used adjectively or as the first part of a compound term. In most cases it might be written indifferently, as a separate limiting word, or as the first element of the compound term, with or without the hyphen; as, air bladder, air-bladder, or airbladder; air cell, air-cell, or aircell; air-pump, or airpump. Air balloon. See Balloon. Air bath. An apparatus for the application of air to the body. An arrangement for drying substances in air of any desired temperature. Air castle. See Castle in the air, under Castle. Air compressor, a machine for compressing air to be used as a motive power. Air crossing, a passage for air in a mine. Air cushion, an air-tight cushion which can be inflated; also, a device for arresting motion without shock by confined air. Air fountain, a contrivance for producing a jet of water by the force of compressed air. Air furnace, a furnace which depends on a natural draft and not on blast. Air line, a straight line; a bee line. Hence Air-line,; as, air-line road. <medicine> Air lock Unsupported and liable to be turned or taken in flank; as, the army had its wing in the air. To take air, to be divulged; to be made public. To take the air, to go abroad; to walk or ride out. Origin: OE. Air, eir, F. Air, L. Aer, fr. Gr, air, mist, for, fr. Root to blow, breathe, probably akin to E. Wind. In sense 10 the French has taking a meaning fr. It. Aria atmosphere, air, fr. The same Latin word; and in senses 11, 12, 13 the French meaning is either fr. L. Aria, or due to confusion with F. Aire, in an older sense of origin, descent. Cf. Ary, Debonair, Malaria, Wind. Source: Websters Dictionary (01 Mar 1998) |
| air ambulances | Fixed-wing aircraft or helicopters equipped for air transport of patients. (12 Dec 1998) |
| air bags | Automotive safety devices consisting of a bag designed to inflate upon collision and prevent passengers from pitching forward. (12 Dec 1998) |
| air bladder | 1. <anatomy> An air sac, sometimes double or variously lobed, in the visceral cavity of many fishes. It originates in the same way as the lungs of air-breathing vertebrates, and in the adult may retain a tubular connection with the pharynx or oesophagus. 2. A sac or bladder full of air in an animal or plant; also an air hole in a casting. Source: Websters Dictionary (01 Mar 1998) |