A new way of using the genetic code, allowing proteins to be made with properties that have never been seen in the natural world has been created by scientists at the University of Cambridge.
According to Jason Chin and his colleagues from the university, the breakthrough could eventually lead to the creation of new or 'improved' life forms incorporating these new materials into their tissue.
In all existing life forms, the four 'letters' of the genetic code, called nucleotides, are read in triplets, so that every three nucleotides encode a single amino acid.
Chin and colleagues have now redesigned the cell's machinery so that it reads the genetic code in quadruplets.
In the genetic code that life has used up to now, there are 64 possible triplet combinations of the four-nucleotide letters; these genetic "words" are called codons.
Each codon either codes for an amino acid or tells the cell to stop making a protein chain.
Now Chin's team has created 256 blank four-letter codons that can be assigned to amino acids that don't even exist yet.
To achieve this, the team had to redesign three pieces of the cellular machinery that make proteins.
The researchers went on to prove their new genetic code works by assigning two "unnatural" amino acids to their quadruplet codons, and incorporated them into a protein chain.
"It's the beginning of a parallel genetic code," New Scientist quoted Chin as saying.
They've also shown that these amino acids can react with each other to form a different kind of chemical bond to those, which usually hold proteins together in their three-dimensional shape.
The normal kind of bonds - disulphide bonds - can be broken by changes in heat and acidity, causing proteins to lose their 3D structure.
However, the bonds created between Chin's new amino acids are stronger - and so could allow proteins to work in a much wider range of environments.
For instance, this could help make drugs that can be taken orally without being destroyed by the acids in the digestive tract.
The study appears in the Journal Nature.