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Encyclopedia > Noncovalent

Noncovalent bonding refers to a variety of interactions, that are not covalent in nature, between molecules or parts of molecules that provide force to hold the molecules or parts of molecules together usually in a specific orientation or conformation. These non-covalent interactions can be broken down more specifically into: ionic bonds, hydrophobic interactions, hydrogen bonds, Van der Waals forces (aka London dispersion forces), Dipole-dipole bonds. Covalent bonding is a form of chemical bonding characterized by the sharing of one or more pairs of electrons between atoms, in order to produce a mutual attraction, which holds the resultant molecule together. ... An ionic bond can be formed after two or more atoms give up (or gain) electrons, so as to become ions. ... Hydrophobe (from the Greek (hydros) water and (phobos) fear) in chemistry refers to the physical property of a molecule that is repelled by water. ... http://www. ... In chemistry, the term Van der Waals force originally referred to all forms of intermolecular forces; however, in modern usage it tends to refer to intermolecular forces that deal with forces due to the polarization of molecules. ... Intermolecular forces are electromagnetic forces which act between molecules or between widely separated regions of a macromolecule. ...


"Noncovalent bonding", "Noncovalent interactions" and "Noncovalent forces" all refer to these forces as a whole without specifying or distinguishing which specific forces are involved because noncovalent interactions often involve several of these forces working in concert. Noncovalent bonds are weak by nature and must therefore work together to have a significant effect. In addition, the combined bond strength is greater than the sum of the individual bonds. This is because the free energy of multiple bonds between two molecules is greater than the sum of the enthalpies of each bond due to entropic effects. In thermodynamics, free energy is a measure of the amount of work that can be extracted from a system. ... Enthalpy (symbolized H, also called heat content) is the sum of the internal energy of matter and the product of its volume multiplied by the pressure. ... The thermodynamic entropy S, often simply called the entropy in the context of thermodynamics, is a measure of the amount of energy in a physical system that cannot be used to do work. ...

Contents


Examples

Protein Structure

Main article: Protein structure Proteins are amino acid chains, made up from 20 different L-α-amino acids, also referred to as residues, that fold into unique three-dimensional protein structures. ...


Intramolecular noncolvalent intreractions are largely responsible secondary and tertiary structure of proteins and therefore the protein's function in the mechanisms of life. Intermolecular noncovalent interactions are responsible for protein complexes (quaternary structure) where two or more proteins function in a coherent mechanism. A representation of the 3D structure of myoglobin, showing coloured alpha helices. ...


Pharmaceuticals

Most drugs work through interacting with biomolecules, such as proteins or RNA, noncovalently. Relatively few drugs actually form covalent bonds with the biomolecules they interact with. Instead they interfere with or activate some biological mechanism through noncovalently interacting in very specific locations on specific biomolecules which present the perfect combination of noncovalent binding partners in just the right geometry. A representation of the 3D structure of myoglobin, showing coloured alpha helices. ... Ribonucleic acid (RNA) is a nucleic acid consisting of a string of covalently-bound nucleotides. ...


See also

ionic bonds, hydrophobic interactions, hydrogen bonds, Van der Waals forces (aka London dispersion forces) An ionic bond can be formed after two or more atoms give up (or gain) electrons, so as to become ions. ... Hydrophobe (from the Greek (hydros) water and (phobos) fear) in chemistry refers to the physical property of a molecule that is repelled by water. ... http://www. ... In chemistry, the term Van der Waals force originally referred to all forms of intermolecular forces; however, in modern usage it tends to refer to intermolecular forces that deal with forces due to the polarization of molecules. ...


  Results from FactBites:
 
3.5.1 (1214 words)
Noncovalent bonds are largely responsible for the secondary and higher order structure of macromolecules.
However, the possibility of combining within a limited area a great number of noncovalent bonds having complementary elements allows the formation of a large specific association whose affinity may be of the same order of magnitude as a covalent bond.
Hydrogen Bond -- A second important noncovalent interaction is the hydrogen bond, a dipole formed when a hydrogen atom covalently bonded to an electronegative atom is shared with a second electronegative atom (typically an oxygen, nitrogen or fluorine atom), such that the proton may be approached very closely by an unshared pair of electrons.
Noncovalent interactions (908 words)
Noncovalent or van der Waals interactions were first recognized by J. van der Waals in the nineteenth century [3].
In noncovalent interactions, in turn, no overlapping is necessary because the attraction comes from the electrical properties of the building blocks.
Noncovalent interactions comprise interactions between permanent multipoles, between a permanent multipole and an induced multipole, and between a time–variable multipole and an induced multipole.
  More results at FactBites »

 
 

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