covalent bond

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Related to Covalent bonds: Covalent Compounds, Polar covalent bonds


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 ?
Exposing the protein/aptamer complex to ultraviolet light induces covalent bond formation between the photoaptamer and cognate protein.
When mechanical stress is applied to the material, the weaker covalent bond would fail promptly.
Together these functionalities bridge interfaces, forming covalent bonds between organic polymers and mineral surfaces (e.g., pigments, fillers and glass and metal substrates), resulting in improvement in adhesion, water, chemical, abrasion and UV resistance, flow, and pigment and filler dispersion.
The important statement to remember is that covalent bonds are broken causing a conversion of a functional group from one category to a higher one.
We are currently tweaking the covalent bonds within the polymer itself to get these materials ready for real-world applications."
The double bonds coming from V-POSS or M-POSS had the ability to react with double bonds coming from MMA, so the covalent bonds and cross-linking structure were obtained between POSS and PMMA, which were expected to be beneficial to the outstanding improvement of mechanical and thermal properties of the hybrid materials.
First, the silane coupling agent would change the nature of the chemical bonding at the interface, in which the interfacial hydrogen bonds could be changed to stronger covalent bonds.
Currently, all polymers used as base ingredients for structural plastics have backbones based on covalent bonds. These bonds lack the ability to reform once broken; hence, to make polymers self-healing, it is necessary to include reversible chemical bonds.
Since carbon tends to form covalent bonds, which contain paired electrons, it seems an unlikely candidate to be magnetized.
Moreover, the covalent bonds that were formed between the vinyl groups on the modified silica and PNIPA acted as cross-linking points to decrease the swelling of the hydrogels.
Crosslinking usually connects chain backbones with covalent bonds. Often this involves converting one of the side groups to a carbon-carbon bond.
The scientists anchored one end of the sugar chain to either a glass or a gold surface by means of covalent bonds, in which two atoms share electrons.