The simplest amino acid. Contains a single hydrogen where amino acids normally have an aliphatic or aromatic side chain. Also known as aminoacetic acid.

Formula: C2H5NO2
Molecular Weight: 75.07
Three-letter code: Gly
One-letter code: G
Due to the fact that glycine has a hydrogen in place of the beta-carbon, the alpha-carbon of the backbone is less sterically constrained and has more freedom of bend and rotation. If you plot backbone dihedral angles on phi-psi Ramachandran plot, glycine can occupy parts of phase space that are inaccessible to the other 19 natural amino acids.

As a result, glycine is often found in protein loops - sections of the protein that bridge secondary structure elements. Becuase of the backbone flexibility, then make good turns between rigid units. They are also found preferentially in 'hinge' regions of a protein where a protein undergoes a conformational change. A conserved glycine in a class of proteins is indicative of conserved need for flexibility.

In 1994 a team of astronomers from the University of Illinois, led by Lewis Snyder, claimed that they found the glycine molecules in space. Turned out they didn't... But eight years later, in 2002 Lewis Snyder and Yi-Jehng Kuan from National Taiwan Normal University repeated the finding, this time for real. The evidence that molecules of glycine exist in interstellar space was found when 10 spectrum lines of glycin were identified by radio telescope.

According to computer simulations and lab-based experiments, glycin was probably formed when ices containing simple organic molecules were exposed to ultraviolet light.

Before glycin, more than 130 simpler molecules were found in deep space, including sugars and ethanol. But amino acids, sometimes called building blocks of life, are a much more intersting find.

This does not prove that life exists outside Earth, but certainly make that possibility more likely, proving that amino acids exists in outer space. This also indirectly supports the idea of Panspermia, saying that life was brough to Earth from space.

Source: New Scientist

Update: As of 12.01.2004, anthracene and pyrene have been found in a nebula called the Red Rectangle, 1000 light years from Earth. Scientists hypothesize that hot carbon and hydrogen are blown from the old star and form complex organic molecules in the nebula after cooling.

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