Well as of January 30, 2008 a press release was issued that Scripps Research Institute of La Jolla, California has suceeded in creating the first artificial base pair that can be consistently replicated by natural enzymes in living organisms that already exist.
Dr. Romesberg wrote:With the help of graduate student Aaron Leconte, the group synthesized and screened 3600 candidates. Two different screening approaches turned up the same pair of molecules, called dSICS and dMMO2.
The molecular pair that worked surprised Romesberg. "We got it and said, 'Wow!' It would have been very difficult to have designed that pair rationally."
But the team still faced a challenge. The dSICS base paired with itself more readily than with its intended partner, so the group made minor chemical tweaks until the new compounds behaved properly.
"We probably made 15 modifications," says Romesberg, "and 14 made it worse." Sticking a carbon atom attached to three hydrogen atoms onto the side of dSICS, changing it to d5SICS, finally solved the problem. "We now have an unnatural base pair that's efficiently replicated and doesn't need an unnatural polymerase," says Romesberg. "It's staring to behave like a real base pair."
The team is now eager to find out just what makes it work. "We still don't have a detailed understanding of how replication happens," says Romesberg. "Now that we have an unnatural base pair, we are continuing experiments to understand it better."
In the near future, Romesberg expects the new base pairs will be used to synthesize DNA with novel and unnatural properties. These might include highly specific primers for DNA amplification; tags for materials, such as explosives, that could be detected without risk of contamination from natural DNA; and building novel DNA-based nanomaterials.
"So what?" you may be asking yourself. Well increasing the number of base pairs from four to six increases the possible number of protien coding combinations from 64 to 216. That means that artificial DNA strings with six base pairs have the potential to supply scores of new amino acid synthesizing combinations. Biotech companies desire this abillity because genetically modified bacteria grown in the cultures are by far the cheapest way to attain synthetic Amino Acids.
Now for the rub, if you are altering a common bacterium to act as your Amino Acid supply source that means the codon's have to be stable and replicable by normal living organisms. That being the case it becomes ever more likely that that bacteria with this artificial DNA could escape into the environment and survive there.