Related topics: cells · protein · atoms · cancer cells · cancer

Tracing the evolution of vision in fruit flies

The function of the visual photopigment rhodopsin and its action in the retina to facilitate vision is well understood. However, there remain questions about other biological functions of this family of proteins (opsins) ...

Uranium 'breaks the rules again'

Work led by the research group of Professor Steve Liddle and published in the prestigious journal Nature Chemistry has reported a uranium dinitrogen molecule that, according to basic chemical theory, should not exist. The ...

New cyclization reactions for synthesizing macrocyclic drug leads

Scientists at EPFL have developed a new method to synthesize and screen thousands of macrocyclic compounds, a family of chemicals that are of great interest in the pharmaceutical industry. The study is published in Science ...

MEG3 kissing loops essential for tumor suppression

A team of researchers in the Marcia group at EMBL Grenoble have discovered that the tumor suppressor MEG3 adopts a complex three-dimensional structure to fulfill its function. Furthermore, they were able to fine-tune its ...

Plant protection: Researchers develop new modular vaccination kit

It could become significantly easier to vaccinate plants against viruses in the future. Scientists at Martin Luther University Halle-Wittenberg (MLU), the Leibniz Institute of Plant Biochemistry (IPB) and the National Research ...

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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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