Xeno nucleic acid
For example, peptide nucleic acids, where the backbone is made up of repeating aminoethylglycine units, are extremely stable and resistant to degradation by nucleases because they are not recognised.
[3] As of 2011[update], at least six types of synthetic sugars have been shown to form nucleic acid backbones that can store and retrieve genetic information.
The "X" in XNA stands for "xeno-", meaning strange or alien, indicating the difference in the molecular structure as compared to DNA or RNA.
[5] More recently, synthetic biologists Philipp Holliger and Alexander Taylor succeeded in creating XNAzymes, the XNA equivalent of a ribozyme, enzymes made of RNA.
This demonstrates that XNAs not only store hereditary information but can also serve as enzymes, raising the possibility that life elsewhere could have begun with something other than RNA or DNA.
A nucleotide is made up of three chemical components: a phosphate, a five-carbon sugar group (this can be either a deoxyribose sugar—which gives us the "D" in DNA—or a ribose sugar—the "R" in RNA), and one of five standard bases (adenine, guanine, cytosine, thymine or uracil).
Most work has focused on different chemical structures in place of the ribose, including:[3] HNA could potentially be used as a drug that can recognize and bind to specified sequences.
Typically, for sugar-based XNAs, to synthesize the xeno nucleoside, the 5 carbon sugar analog is chemically synthesised first then, the nucelobase is attached.
[5] Investigations into XNAs will allow researchers to assess whether DNA and RNA are the most efficient and desirable building blocks of life, or if these two molecules emerged randomly after evolving from a larger class of chemical ancestors.
Because XNA is foreign and because it is believed that humans have not yet evolved the enzymes to break them down, XNAs may be able to serve as a more durable counterpart to the DNA and RNA-based treatment methodologies that are currently in use.
[19] Experiments with XNA have already allowed for the replacement and enlargement of this genetic alphabet, and XNAs have shown complementarity with DNA and RNA nucleotides, suggesting potential for its transcription and recombination.
One experiment conducted at the University of Florida led to the production of an XNA aptamer by the AEGIS-SELEX (artificially expanded genetic information system - systematic evolution of ligands by exponential enrichment) method, followed by successful binding to a line of breast cancer cells.
[3] One of the key questions here is whether XNA in an in vivo setting would intermix with DNA and RNA in its natural environment, thereby rendering scientists unable to control or predict its implications in genetic mutation.
This research may be used in determining whether DNA and RNA's role in life emerged through natural selection processes or if it was simply a coincidental occurrence.
[22] XNA may be employed as molecular clamps in quantitative real-time polymerase chain reactions (qPCR) by hybridizing with target DNA sequences.
