This is the 'spot' where you put the ink in your 3D atom printer.
Life had used its entire 'ANSI-code' for its own purposes, (naturally (literally)). But if we want to insert our own stuff, we need a place to put it. So these guys refactored the entire code of e. Coli to avoid one of the lesser used characters, which can then be used as an escape character for any new code you want to use. Basically, refactoring an old ASCII program (e. Coli (20 amino acids)) to allow compatibility with UTF-8 (modern chemistry (~unlimited amino acids)) by shifting all uses of one of the letters to a compatible, but not identical case. And now you can use that letter for anything you like (when designing proteins).
You get to use new amino acids in building your proteins. The current amino acids have been evolutionarily defined by being metabolically creatable, useful, etc. and are restricted in number. Some get modified after the fact, but in general, there are only a limited number of amino acids used to build proteins. (Protein = biological machine)
If you have an 'escape character' in your DNA, you can insert any amino acid you want into that protein by registering it in that empty spot. This can include introducing amino acids you created chemically in a lab. So now your new organism can start to use amino acids in its proteins that are impossible to build in nature. Creativity gets opened wide. Right-handed amino acids are the obvious choice to start with - biologically 'inert' (immune system doesn't recognize them), but functionally identical. Theoretically you could start to use non-organic atoms. New biologically orthogonal reactive groups. Or entirely new structural features.
You can now incorporate non-natural chemical moieties with atomic resolution.
In addition to the applications mentioned by toufka, one would be data storage.
There has been some work[1] done on using DNA as a medium of high-density self-replicating storage for digital data, and it would be exciting to have another couple bases to work with.
What would be exciting is if the bases had properties that made them amenable to easy read operations using non biological means. Currently it takes 1 - 3 days fort a DNA sequencer to read what is effectively a few gigabytes of data in a human DNA sequence. That is painfully slow for any practical use. However if we had DNA bases that had atomic properties that could interact with some sort of electronic device, we might be able to engineer a sequencer that is quite easy and cheap. In fact, we might even be able to design an enzyme that translates regular DNA into a synthetic form for easy sequencing (similar to how RNA polymerase turns DNA to RNA)
Life had used its entire 'ANSI-code' for its own purposes, (naturally (literally)). But if we want to insert our own stuff, we need a place to put it. So these guys refactored the entire code of e. Coli to avoid one of the lesser used characters, which can then be used as an escape character for any new code you want to use. Basically, refactoring an old ASCII program (e. Coli (20 amino acids)) to allow compatibility with UTF-8 (modern chemistry (~unlimited amino acids)) by shifting all uses of one of the letters to a compatible, but not identical case. And now you can use that letter for anything you like (when designing proteins).
You get to use new amino acids in building your proteins. The current amino acids have been evolutionarily defined by being metabolically creatable, useful, etc. and are restricted in number. Some get modified after the fact, but in general, there are only a limited number of amino acids used to build proteins. (Protein = biological machine)
If you have an 'escape character' in your DNA, you can insert any amino acid you want into that protein by registering it in that empty spot. This can include introducing amino acids you created chemically in a lab. So now your new organism can start to use amino acids in its proteins that are impossible to build in nature. Creativity gets opened wide. Right-handed amino acids are the obvious choice to start with - biologically 'inert' (immune system doesn't recognize them), but functionally identical. Theoretically you could start to use non-organic atoms. New biologically orthogonal reactive groups. Or entirely new structural features.
You can now incorporate non-natural chemical moieties with atomic resolution.