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Topic Name: Scientists for the First Time Identify Amino Acetonitrile Near the Centre of Our Milky Way

Category: Chemical

Research persons: Arnaud Belloche

Location: Max Planck Institute for Radio Astronomy (MPIfR) in Bonn, Germany

Details

Researchers from the Max Planck Institute for Radio Astronomy (MPIfR) in Bonn have detected for the first time a molecule closely related to an amino acid: amino acetonitrile. The organic molecule was found with a 30 metre radio telescope in Spain and two radio interferometers in France and Australia in the "Large Molecule Heimat", a giant gas cloud near the galactic centre in the constellation Sagittarius.

The Large Molecule Heimat is a very dense, hot gas clump within the star forming region Sagittarius B2. In this source of only 0,3 light-year diameter, which is heated by a deeply embedded newly formed star, most of the interstellar molecules known to date have been found, including the most complex ones such as ethyl alcohol, formaldehyde, formic acid, acetic acid, glycol aldehyde (a basic sugar), and ethylene glycol.

Starting from 1965, more than 140 molecular species have been detected in space, in interstellar clouds as well as in circumstellar envelopes. A large fraction of these molecules is organic or carbon-based. A lot of attention is given to the quest for so-called "bio"-molecules, especially interstellar amino acids. Amino acids, the building blocks of proteins and therefore key ingredients for the origin of life, have been found in meteorites on Earth, but not yet in interstellar space.

The simplest amino acid, glycine (NH2CH2COOH), has long been searched for in the interstellar medium but has so far not been unambiguously detected. Since the search for glycine has turned out to be extremely difficult, a chemically related molecule was searched for, amino acetonitrile (NH2CH2CN), probably a direct precursor of glycine.

The scientists from the Max Planck Institute for Radioastronomy in Bonn selected the "Large Molecule Heimat", as the source has been named by experts, and investigated a dense forest of 3700 spectral lines from complex molecules with the IRAM 30-metre telescope in Spain. Atoms and molecules emit light at very specific frequencies, which appear as characteristic lines in the radiation spectrum. By analyzing these spectral lines, astronomers can determine the chemical composition of cosmic clouds. The more complex a molecule is, the more possibilities it has to radiate its internal energy. This is the reason why complex molecules emit many spectral lines, which are very weak and therefore difficult to identify in the "line jungle".

"Still, we were finally able to assign 51 very weak lines to the molecule amino acetonitrile" says Arnaud Belloche, scientist at the Max Planck institute and first author of the research paper. This result was confirmed at 10 times higher spatial resolution with two radio telescope arrays, the IRAM Plateau de Bure interferometer in France and the Australia Telescope Compact Array. These observations showed that all the candidate lines were emitted from the same position in the "Large Molecule Heimat", "a strong proof of the reliability of our identification".
"Finding amino acetonitrile has greatly extended our insight into the chemistry of dense, hot star-forming regions. I am sure we will be able to identify in the future many new, even more complex organic molecules in the interstellar gas. We already have several candidates!" says Karl Menten, director at the Max Planck Institute for Radioastronomy and head of the "Millimeter and Submillimeter Astronomy" research group.

Note for Sagittarius B2
Sagittarius B2 (Sgr B2) is a giant molecular cloud of gas and dust that is located about 120 parsecs from the center of the Milky Way. This complex is the largest molecular cloud in the vicinity of the core and one of the largest in the galaxy, spanning a region about 45 parsecs across. The total mass of Sgr B2 is about 3 million times the mass of the Sun. The mean hydrogen density within the cloud is 3000 atoms per cm3, which is about 20–40 times more dense than a typical molecular cloud.

The internal structure of this cloud is complex, with varying densities and temperatures. The cloud is divided into three main cores, designated north (N), middle or main (M) and south (S) respectively. Thus Sgr B2(N) represents the north core. The sites Sgr B2(M) and Sgr B2(N) are sites of massive star formation. The first 10 H II regions discovered were designated A through J. H II regions A-G, I and J lie within Sgr B2(M), while region K is in Sgr B2(N) and region H is in Sgr B2(S). The 5-parsec-wide core of the cloud is a star-forming region that is emitting about 10 million times the luminosity of the Sun.

Temperatures in the cloud vary from 300 K in dense star-forming regions to 40 K in the surrounding envelope. Because the average temperature and pressure in Sgr B2 are low, chemistry based on the direct interaction of atoms is exceedingly slow. However, the Sgr B2 complex contains cold dust grains consisting of a silicon core surrounded by a mantle of water ice and various carbon compounds. The surfaces of these grains allow chemical reactions to occur by accreting molecules that can then interact with neighboring compounds. The resulting compounds can then evaporate from the surface and join the molecular cloud.

The molecular components of this cloud can be readily observed in the 102–103 m range of wavelengths. About half of all the known interstellar molecules were first found near Sgr B2, and nearly every other currently known molecule has since been detected in this feature.

The European Space Agency's gamma-ray observatory INTEGRAL has observed gamma rays interacting with Sgr B2, causing x-ray emission from the molecular cloud. This energy was emitted about 350 years before by the supermassive black hole (SMBH) at the galaxy's core. The total energy from this outburst is an estimated million times stronger than the current output from the SMBH.

Note for Ethylene Glycol
Ethylene glycol (monoethylene glycol (MEG), IUPAC name: ethane-1,2-diol) is an alcohol with two -OH groups (a diol), a chemical compound widely used as an automotive antifreeze. In its pure form, it is an odorless, colorless, syrupy liquid with a sweet taste. Ethylene glycol is toxic, and its ingestion should be considered a medical emergency. Ethylene glycol is produced from ethylene, via the intermediate ethylene oxide.

The major use of ethylene glycol is as an antifreeze in, for example, automobiles and personal computers. Due to its low freezing point, it is also used as a deicing fluid for windshields and aircraft. Ethylene glycol is also commonly used in chilled water air conditioning systems that place either the chiller or air handlers outside, or systems that must cool below the freezing temperature of water.

Ethylene glycol has become increasingly important in the plastics industry for the manufacture of polyester fibers and resins, including polyethylene terephthalate, which is used to make plastic bottles for soft drinks. The antifreeze capabilities of ethylene glycol have made it an important component of vitrification mixtures for low-temperature preservation of biological tissues and organs.

Minor uses of ethylene glycol include the manufacture of capacitors, as a chemical intermediate in the manufacture of 1,4-dioxane and as an additive to prevent corrosion in liquid cooling systems for personal computers.

Ethylene glycol is commonly used in laboratories to precipitate out proteins in solution. This is often an intermediary step in fractionation, purification and/or crystallization. It can be used to protect functional groups from reacting during organic synthesis. To get the functional group back to its original composition, simply add water and acid.

Ethylene glycol is commonly used as a preservative for specimens in schools, frequently during dissection. It is said to be safer than formaldehyde, but the safety is questionable.

Ethylene glycol's high boiling point and affinity for water makes it an ideal desiccant for natural gas production. In the field, excess water vapor is usually removed by glycol dehydration. Ethylene glycol flows down from the top of a tower and meets a rising mixture of water vapor and hydrocarbon gases from the bottom. The glycol chemically removes the water vapor, allowing dry gas to exit from the top of the tower. The glycol and water are separated, and the glycol cycles back through the tower.

Instead of removing water Ethylene glycol can also be used to depress the temperature at which hydrates are formed. The purity of glycol used for hydrate suppression (mono-ethylene glycol) is typically around 80%, whereas the purity of glycol used for dehydration (tri-ethylene glycol) is typically 95-99+%. Moreover, the injection rate for hydrate suppression is much lower than the circulation rate in a glycol dehydration tower.

Ethylene glycol is also used in the manufacture of some vaccines, but it is not itself present in these injections. It is used as a minor (1–2%) ingredient in shoe polish and also in some inks and dyes. Ethylene glycol has seen some use as a rot and fungal treatment for wood, both as a preventative and a treatment after the fact. It has been used in a few cases to treat partially rotted wooden objects to be displayed in museums. It is one of only a few treatments that are successful in dealing with rot in wooden boats, and is relatively cheap.

IRAM, the "Institute for Radio Astronomy at Millimeter wavelengths", is a joint German-French-Spanish radio astronomy venture which runs the 30m radio telescope on Pico Veleta in the Sierra Nevada mountains in southern Spain and also the Plateau de Bure interferometer in the French alps near Grenoble. Both facilities were utilized for the first detection of amino acetonitrile described here.

ATCA, the "Australia Telescope Compact Array", is an array of six 22-m antennas located about 25 km west of the town of Narrabri, about 500 km north-west of Sydney, Australia. It is operated by the Australia Telescope National Facility (ATNF).