covalent bond

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the linkage between atoms or radicals of a chemical compound, or the symbol representing this linkage and indicating the number and attachment of the valencies of an atom in constitutional formulas, represented by a pair of dots or a line between atoms, e.g., H—O—H, H—C≡C—H or H:O:H, H:C:::C:H.
coordinate covalent bond a covalent bond in which one of the bonded atoms furnishes both of the shared electrons.
covalent bond a chemical bond between two atoms or radicals formed by the sharing of a pair (single bond), two pairs (double bond), or three pairs of electrons (triple bond).
disulfide bond a strong covalent bond, —S—S—, important in linking polypeptide chains in proteins, the linkage arising as a result of the oxidation of the sulfhydryl (SH) groups of two molecules of cysteine.
high-energy phosphate bond an energy-rich phosphate linkage present in adenosine triphosphate (ATP), phosphocreatine, and certain other biological molecules. On hydrolysis at pH 7 it yields about 8000 calories per mole, in contrast to the 3000 calories yielded by phosphate esters. The bond stores energy that is used to drive biochemical processes, such as the synthesis of macromolecules, contraction of muscles, and the production of the electrical potentials for nerve conduction.
high-energy sulfur bond an energy-rich sulfur linkage, the most important of which occurs in the acetyl-CoA molecule, the main source of energy in fatty acid biosynthesis.
hydrogen bond a weak, primarily electrostatic, bond between a hydrogen atom bound to a highly electronegative element (such as oxygen or nitrogen) in a given molecule, or part of a molecule, and a second highly electronegative atom in another molecule or in a different part of the same molecule.
ionic bond a chemical bond in which electrons are transferred from one atom to another so that one bears a positive and the other a negative charge, the attraction between these opposite charges forming the bond.
peptide bond the —CO—NH— linkage formed between the carboxyl group of one amino acid and the amino group of another; it is an amide linkage joining amino acids to form peptides.
Miller-Keane Encyclopedia and Dictionary of Medicine, Nursing, and Allied Health, Seventh Edition. © 2003 by Saunders, an imprint of Elsevier, Inc. All rights reserved.
References in periodicals archive ?
Studies show that a constant joining velocity of the horn during welding produces a more homogeneous molecular bond and a more robust weld.
It can quantify the surface abundance of a specific molecular bond with a sensitivity as small as 5% for one monolayer.
It's union with ionised hydrogen was fragile, and did not persist for very long, replaced by progressively more robust and complex molecular bonds.
Different binders have selective affinities for various toxins based on their net charge and molecular bonds. The following are some of the most commonly used binders and the substrates to which they bind:
Scientists have known for decades that broad-spectrum UVC light, which has a wavelength of between 200 to 400 nanometers, or nm), is highly effective at killing bacteria and viruses by destroying the molecular bonds that hold their DNA together.
It is formulated with a pure base oil with stronger molecular bonds, delivering superior protection in extreme engine temperatures for long lasting engine performance.
Mussels cling to solid surfaces with the aid of an adhesive protein and plastic-like fibers that can repair themselves if molecular bonds are broken.
Who would possibly believe that a low-energy source of electrons could break the molecular bonds of C[O.sub.2] to release carbon and oxygen --perhaps only plants, which have been doing this forever, whilst seemingly releasing electrons into the ground.
The research, published in Nature Communications, outlines how the new process rearranges the structure of glass on a molecular level, improving the angle at which molecular bonds occur to make the material stronger.
UV energy at short wavelengths is most severe toward polymeric materials, and can break the covalent molecular bonds forming the polymer backbone.
SDS-BIONIC coatings not only use covalent and ionic molecular bonds to link together the nano particles used in the surface coatings themselves but also to link the coatings to the substrate.
Thermogenic gas, in contrast, is formed at greater depths through thermal cracking of decomposed organic matter or oil into gas -- where molecular bonds are broken due to high heat and temperature -- suggesting higher costs in drilling and extraction.

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