| HEIS | high-energy ion scattering |
|---|---|
| RHEED | reflection high-energy electron diffraction |
| HCD | health care delivery; heavy-chain disease; high-calorie diet; high-carbohydrate diet; homologous can... |
| HD | Haab-Dimmer [syndrome]; Hajna-Damon [broth]; Hansen disease; hearing distance; heart disease; helix ... |
| HFD | hemorrhagic fever of deer; high-fiber diet; high forceps delivery; hospital field director; human fa... |
| noncovalent bond | Bond in which electrons are not shared between atoms; e.g., electrostatic bond, hydrogen bond. (05 Mar 2000) |
|---|---|
| sulfur-sulfur bond isomerases | <enzyme> Enzymes that catalyze the transposition of a sulfur-sulfur bond. Registry number: EC 5.3.4 (12 Dec 1998) |
| disulfide bond | A single bond between two sulfurs; specifically, the -S-S- link binding two peptide chains (or different parts of one peptide chain); also occurs as part of the molecule of the amino acid, cystine, and is important as a structural determinant in many protein molecules, notably keratin, insulin, and oxytocin. A symmetric disulfide is R-S-S-R; R'-S-S-R is a mixed disulfide. (05 Mar 2000) |
| disulphide bond | <chemistry, molecular biology> The S S linkage. A linkage formed between the SH groups of two cysteine moieties either within or between peptide chains. Each cysteine then becomes a half cystine residue. S S linkages stabilise, but do not determine, secondary structure in proteins. They are easily disrupted by SH groups in an exchange reaction and are not present in cytosolic proteins (cytosol has a high concentration of glutathione that has a free SH residue). (18 Nov 1997) |
| double bond | <chemistry> A covalent bond resulting from the sharing of two pairs of electrons; e.g., H2C==CH2 (ethylene). (05 Mar 2000) |
| isopeptide bond | An amide linkage between a carboxyl group of one amino acid and an amino group of another amino acid in which at least one of these groups is not on the a-carbon of one of the amino acids; for example, the bond between the glutamyl residue and the cysteinyl residue of glutathione. Compare: peptide bond, eupeptide bond. (05 Mar 2000) |
| electrostatic bond | Bond between atoms or groups carrying opposite charges (or, in some cases, partial charges). Synonym: heteropolar bond, salt bridge. (05 Mar 2000) |
| triple bond | A covalent bond resulting from the sharing of three pairs of electrons; e.g., HC≡CH (acetylene). (05 Mar 2000) |
| eupeptide bond | A peptide bond between the alpha-carboxyl group of one amino acid and the alpha-amino group of another amino acid. Compare: peptide bond, isopeptide bond. (05 Mar 2000) |
| activation energy | <chemistry> The amount of energy (expressed in joules) that is needed to convert all the molecules in one mole of a reacting substance from a ground state to the transition state. (06 May 1997) |
| binding energy | <chemistry, radiobiology> The binding energy of a nucleus is the minimum energy required to dissociate it into its component neutrons and protons. Neutron or proton binding energies are those required to remove a neutron or proton, respectively, from a nucleus. Electron binding energy is that required to remove an electron from an atom or a molecule. (16 Dec 1997) |
| bioelectric energy sources | Implantable devices which convert biological energy (chemical energy of the metabolism of continuously regenerating body fluids or mechanical energy of periodic movements) to electrical energy. The sources include biogalvanic cells, biofuel cells, and ionic concentration cells. (12 Dec 1998) |
| biomass energy | See Bioenergy. (05 Dec 1998) |
| radiant energy | Energy contained in light rays or any other form of radiation. (05 Mar 2000) |
| radiography, dual-energy scanned projection | A method of producing a high-quality scan by digitizing and subtracting the images produced by high- and low-energy X-rays. (12 Dec 1998) |