Molecule
hideA 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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News tagged with molecules
New findings suggest strategy to help generate HIV-neutralizing antibodies
Medicine & Health / HIV & AIDS
Nov 19, 2009 |
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New discoveries about anti-HIV antibodies may bring researchers a step closer to creating an effective HIV vaccine, according to a new paper co-authored by scientists at the Vaccine Research Center of the National Institute ...
New research into the mechanisms of gene regulation
Nov 19, 2009 |
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(PhysOrg.com) -- A team led by Penn State's Ross Hardison, T. Ming Chu Professor of Biochemistry and Molecular Biology, has taken a large step toward unraveling how regulatory proteins control the production ...
Technique finds gene regulatory sites without knowledge of regulators
Nov 19, 2009 |
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A new statistical technique developed by researchers at the University of Illinois allows scientists to scan a genome for specific gene-regulatory regions without requiring prior knowledge of the relevant transcription factors. ...
Researchers find explanation for rapid maturation of neurons at birth
Medicine & Health / Neuroscience
Nov 17, 2009 |
4 / 5 (5) |
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At the moment a newborn switches from amniotic fluid to breathing air, another profound shift occurs: nerve cells in the brain convert from hyperexcitability to a calm frame against which outside signals can be detected.
Scientists guide immune cells with light and microparticles (w/ Video)
Nov 16, 2009 |
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A team led by Yale University scientists has developed a new approach to studying how immune cells chase down bacteria in our bodies. Their findings are described in the November 15 issue of Nature Methods Advanc ...
In touch with molecules
Nov 12, 2009 |
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The performance of modern electronics increases steadily on a fast pace thanks to the ongoing miniaturization of the utilized components. However, se-vere problems arise due to quantum-mechanical phenomena ...
Explained: RNA interference
Nov 12, 2009 |
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Every high school biology student learns the basics of how genes are expressed: DNA, the cell’s master information keeper, is copied into messenger RNA, which carries protein-building instructions to the ribosome, ...
Researchers show how to divide and conquer 'social network' of cells
Nov 09, 2009 |
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On Noah's Ark animals came in twos: male and female. In human bodies trillions of cells are coupled, too, and so are the molecules from which they are composed. Yet these don't come in twos, they are regrouped ...
New Synthetic Molecules Trigger Immune Response to HIV and Prostate Cancer
Nov 05, 2009 |
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(PhysOrg.com) -- Researchers at Yale University have developed synthetic molecules capable of enhancing the body’s immune response to HIV and HIV-infected cells, as well as to prostate cancer cells. Their ...
Toward home-brewed electricity with 'personalized solar energy'
Nov 04, 2009 |
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New scientific discoveries are moving society toward the era of "personalized solar energy," in which the focus of electricity production shifts from huge central generating stations to individuals in their ...
Two-In-One Punch Knocks Out Drug Resistant Cancer Cells
Nanotechnology / Bio & Medicine
Nov 04, 2009 |
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(PhysOrg.com) -- Cancer cells, like bacteria, can develop resistance to drug therapy, leading to relapse of disease. One approach showing promise in overcoming multidrug resistance in tumors is to combine two different anticancer ...
A Mars Rover Named 'Curiosity'
Space & Earth / Space Exploration
Oct 30, 2009 |
4.9 / 5 (18) |
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(PhysOrg.com) -- If you found your grandmother's diary, tattered and dust covered, up in the attic, would you read it? Of course you would. Granny was a pistol! Brush off the dust, open up the little book, ...
Alternatively spliced tissue factor identified as promising new biomarker for aggressive cancers
Oct 26, 2009 |
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A recently discovered form of the protein that triggers blood clotting may play a key role in the molecular mechanisms leading to the growth of certain metastatic cancers, according to new research reported by an international ...
Seeing Previously Invisible Molecules for the First Time
Chemistry / Analytical Chemistry
Oct 23, 2009 |
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(PhysOrg.com) -- A team of Harvard chemists led by X. Sunney Xie has developed a new microscopic technique for seeing, in color, molecules with undetectable fluorescence. The room-temperature technique allows ...
Scientists first to see RNA network in live bacterial cells
Oct 22, 2009 |
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Scientists who study RNA have faced a formidable roadblock: trying to examine RNA's movements in a living cell when they can't see the RNA. Now, a new technology has given scientists the first look ever at RNA in a live ...
