Cancer

Stitching together a 'Google Earth' for cancer

In southwest London, on the edge of Bushy Park, is a building whose occupants are responsible for measurements. Precise measurements, to be precise. The building is the gatekeeper of time, the resting place of the kilogram, ...

Medical research

New role for death molecule

Cellular death is vital for health. Without it, we could develop autoimmune diseases or cancers. But a cell's decision to self-destruct is tightly regulated, so that it only happens to serve the best interests of the body. ...

Neuroscience

Simple drug combination creates new neurons from neighboring cells

A simple drug cocktail that converts cells neighboring damaged neurons into functional new neurons could potentially be used to treat stroke, Alzheimer's disease, and brain injuries. A team of researchers at Penn State identified ...

Medical research

Zebrafish useful to model ALS-linked mutations

Scientists from the University of Bath have shown that the zebrafish is a useful model to study a molecule called Rnasel-1, a counterpart to human Angiogenin, a molecule linked to the neurodegenerative disease ALS (Amyotrophic ...

Diseases, Conditions, Syndromes

Molecule effective in killing tuberculosis bacteria

A team of researchers affiliated with several institutions in the U.S. and one in France has found a molecule that is effective against tuberculosis. In their paper published in the journal Science, the group identifies the ...

Diseases, Conditions, Syndromes

Treatment for obesity and fatty liver disease may be in reach

Amiram Goldblum and his team at the Hebrew University of Jerusalem's Institute for Drug Research have discovered 27 new molecules. These molecules all activate a special protein called PPAR-delta and have the potential to ...

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Molecule

A molecule is defined as a sufficiently stable, electrically neutral group of at least two atoms in a definite arrangement held together by very strong (covalent) chemical bonds. Molecules are distinguished from polyatomic ions in this strict sense. In organic chemistry and biochemistry, the term molecule is used less strictly and also is applied to charged organic molecules and biomolecules.

In the kinetic theory of gases the term molecule is often used for any gaseous particle regardless of its composition. According to this definition noble gas atoms are considered molecules despite the fact that they are composed of a single non-bonded atom.

A molecule may consist of atoms of a single chemical element, as with oxygen (O2), or of different elements, as with water (H2O). Atoms and complexes connected by non-covalent bonds such as hydrogen bonds or ionic bonds are generally not considered single molecules.

No typical molecule can be defined for ionic crystals (salts) and covalent crystals (network solids), although these are often composed of repeating unit cells that extend either in a plane (such as in graphene) or three-dimensionally (such as in diamond or sodium chloride). The theme of repeated unit-cellular-structure also holds for most condensed phases with metallic bonding. In glasses (solids that exist in a vitreous disordered state), atoms may also be held together by chemical bonds without any definable molecule, but also without any of the regularity of repeating units that characterises crystals.

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