Hem
Till vänster bakterien Pseudomonas aeruginosa. Till höger en petriskål, som ofta används vid bakterieodling. (TT)

Forskare varnar: Spegelvända bakterier kan döda allt

Forskare varnar för att den konstgjorda utvecklingen av ”spegelvända” mikroorganismer kan hota allt liv på planeten, skriver Time.

Många molekyler förekommer naturligt vända åt både höger och vänster, medan andra bara förekommer i den ena vändningen. Att spegelvända en struktur på konstgjord väg tros kunna ha stora fördelar: Det kan till exempel handla om insulin som stannar längre i kroppen eftersom de enzymer som bryter ner molekylerna inte passar in i den spegelvända versionen.

I förlängningen undersöker vissa forskare också att skapa hela mikroorganismer där alla enskilda molekyler är spegelvända. Det skulle kunna innebära katastrof av apokalyptiska mått, varnar andra.

Precis som enzymet inte skulle klara av att bryta ner insulinet, skulle nämligen inga antikroppar vara verksamma på en spegelvänd mikroorganism.

– När den stötte på människor eller djur eller växter skulle den vara i stort sett osårbar för våra immunsystem. Vi skulle sannolikt dö, säger mikrobiologen David Relman vid Stanford.

Flera forskare kräver nu att utvecklingen av spegelvända molekyler och organismer förbjuds helt.

bakgrund
 
Kiralitet: Höger- och vänsterhänta molekyler
Wikipedia (en)
In chemistry, a molecule or ion is called chiral () if it cannot be superposed on its mirror image by any combination of rotations, translations, and some conformational changes. This geometric property is called chirality (). The terms are derived from Ancient Greek χείρ (cheir) 'hand'; which is the canonical example of an object with this property. A chiral molecule or ion exists in two stereoisomers that are mirror images of each other, called enantiomers; they are often distinguished as either "right-handed" or "left-handed" by their absolute configuration or some other criterion. The two enantiomers have the same chemical properties, except when reacting with other chiral compounds. They also have the same physical properties, except that they often have opposite optical activities. A homogeneous mixture of the two enantiomers in equal parts is said to be racemic, and it usually differs chemically and physically from the pure enantiomers. Chiral molecules will usually have a stereogenic element from which chirality arises. The most common type of stereogenic element is a stereogenic center, or stereocenter. In the case of organic compounds, stereocenters most frequently take the form of a carbon atom with four distinct (different) groups attached to it in a tetrahedral geometry. Less commonly, other atoms like N, P, S, and Si can also serve as stereocenters, provided they have four distinct substituents (including lone pair electrons) attached to them. A given stereocenter has two possible configurations (R and S), which give rise to stereoisomers (diastereomers and enantiomers) in molecules with one or more stereocenter. For a chiral molecule with one or more stereocenter, the enantiomer corresponds to the stereoisomer in which every stereocenter has the opposite configuration. An organic compound with only one stereogenic carbon is always chiral. On the other hand, an organic compound with multiple stereogenic carbons is typically, but not always, chiral. In particular, if the stereocenters are configured in such a way that the molecule can take a conformation having a plane of symmetry or an inversion point, then the molecule is achiral and is known as a meso compound. Molecules with chirality arising from one or more stereocenters are classified as possessing central chirality. There are two other types of stereogenic elements that can give rise to chirality, a stereogenic axis (axial chirality) and a stereogenic plane (planar chirality). Finally, the inherent curvature of a molecule can also give rise to chirality (inherent chirality). These types of chirality are far less common than central chirality. BINOL is a typical example of an axially chiral molecule, while trans-cyclooctene is a commonly cited example of a planar chiral molecule. Finally, helicene possesses helical chirality, which is one type of inherent chirality. Chirality is an important concept for stereochemistry and biochemistry. Most substances relevant to biology are chiral, such as carbohydrates (sugars, starch, and cellulose), all but one of the amino acids that are the building blocks of proteins, and the nucleic acids. Naturally occurring triglycerides are often chiral, but not always. In living organisms, one typically finds only one of the two enantiomers of a chiral compound. For that reason, organisms that consume a chiral compound usually can metabolize only one of its enantiomers. For the same reason, the two enantiomers of a chiral pharmaceutical usually have vastly different potencies or effects.
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