Fosforotioaattilinkit

Fosforotioaattilinkit, often translated as phosphorothioate linkages, are a chemical modification of the phosphate backbone in nucleic acids, such as DNA and RNA. In a standard phosphodiester bond, a non-bridging oxygen atom is attached to the phosphorus atom. In a phosphorothioate linkage, this oxygen atom is replaced by a sulfur atom. This substitution results in a chiral center at the phosphorus atom, meaning that phosphorothioate linkages can exist as two different stereoisomers, R and S.

This modification has significant implications for the properties and behavior of nucleic acids. The sulfur atom is less electronegative than oxygen, which alters the charge distribution and stability of the linkage. Phosphorothioate linkages are generally more resistant to degradation by nucleases, enzymes that break down nucleic acids. This increased stability makes them valuable in therapeutic applications.

The most common application of phosphorothioate linkages is in antisense oligonucleotides (ASOs). ASOs are short, synthetic strands of DNA or RNA designed to bind to specific messenger RNA (mRNA) molecules. By binding to mRNA, ASOs can block protein synthesis, thereby modulating gene expression. The nuclease resistance conferred by phosphorothioate linkages allows ASOs to survive in the body long enough to exert their therapeutic effect. They are used in the treatment of various diseases, including genetic disorders and viral infections. The synthesis of these modified nucleic acids requires specialized chemical techniques to incorporate the sulfur atom correctly into the phosphate backbone.