Preserve the mirror for the main molecules of life

The unique feature of biological molecules is that they have hands. The normal particles in mixtures are approximately equal to those of the right and left types. This means that molecules can have the same atoms and shapes, but they cannot be stacked. Instead, they are a mirror image of each other, like our left and right hands.

(This is hard to imagine, which is why doctors spend so much time playing with them before organic chemistry. Molecular models are balls and sticks.)

Natural molecules and biological molecules are all one-sided. Our nucleic acids are all left-handed (called dexter D in Latin) and proteins are all left-handed (L for laevus). This is a unique trait of biological molecules that SETI uses as a token when searching for life. This aberration was first noticed by Louis Pasteur in 1848, and scientists have been speculating about mirror life ever since. Now, they are one step closer to creating it.

One Left, One Step Right

The Ting F Zhou Laboratory of Tsinghua University in Beijing combines all the components necessary for the central dogma of an inverted image. The researchers used synthetic chemical methods to synthesize short regions of L-DNA and L-RNA with a mirror image. But it is much more efficient to make nucleic acids using enzymes called polymerase-proteins. But the natural proteins we use for this only work with D-DNA.

So the lab used synthetic chemistry to make reversible D-protein DNA polymerases and used it to amplify the short L-DNA strands. . In other words, a mirror image of a typical protein can replicate a mirror image of normal DNA. Separately, the researchers modified the DNA polymerases of RNA proteins into RNA polymerases so that they could transcribe the short L-DNA strands into L-RNA. These polymers were a surprising proof of concept, but were ineffective and error-prone and could only produce short fragments of L nucleic acids. Zhou Lab is now a mirror image of an enzyme commonly used for polymerase chain reaction reactions called Pfu DNA polymerase. This enzyme is heat resistant and has a very high precision. But that's twice the size of the polymers the researchers had previously made. Scientists had to combine it into two parts and then connect them. . The gene they chose encodes ribosomal RNA, so when they can transcribe it, they will have a portion of the ribosome in mirror image. Once they have all the ingredients, they will no longer have to rely on massive synthetic methods to make reversed D proteins. Longevity

One possible use of the L-DNA mirror image is that, like its natural counterpart, D-DNA, it can be used as a compact device. Trust is used to store information. But unlike their natural counterpart, enzymes can't break them down, because no one has yet created D-DNases with an inverted image that can destroy them. To illustrate one application, Zhou generated DNA barcodes for surrounding water samples - you can imagine the barcodes using base sequences to represent things like "Lotus Pond, Beijing". When he tried to amplify the normal D-DNA code from the pond sample the day after it was added, he couldn't find it. The degraded L-DNA barcode was still recognized with a mirror image a year later. They made the main DNA molecule, half D and half L. Their semi-normal and semi-inverse image, as a reference text, is encoded in paragraph 1860 Pasteur, who speculated about mirror life, in D-DNA. If the key is read using normal DNA polymerase, it will give an error message when decrypting with the Pasteur script. But if it is read with L-DNA polymerase, it gives a hidden message from mirror DNA.

Zhou's team is apparently currently planning to make mirror image ribosomes to turn mirror image mRNAs into mirrors. Picture proteins are no small feat — ribosomes are very complex and contain dozens of proteins and many RNA molecules — but researchers are still making rapid progress. Of course, they also plan to make D-DNases in reverse "to remove the L-DNA molecules that store information after they are used as an environmental protection strategy." Nature Biotechnology, 2021 DOI: 10.1038 / s41587 -021-00969-6