Xenonucleic acids
HNA is no worse than DNA
Artificial repositories of genetic information have been created –
alternatives to natural DNA and RNA
Grigory Kolpakov, Newspaper.
An alternative to natural carriers of genetic information, RNA and DNA – xenonucleic acids, capable of transmitting genetic information, have been synthesized in the laboratory. They can be transformed into various biologically useful forms with the help of "directed evolution" and used as biosensors.
An international group of researchers from the USA, Great Britain, Belgium and Denmark published in the latest issue of the journal Science a report on the molecules synthesized by them that can act as alternatives to natural carriers of genetic information – RNA and DNA (Pinheiro et al., Synthetic Genetic Polymers Capable of Heredity and Evolution).
The question of whether such alternatives can exist has long been the subject of much research and fierce debate in the scientific community. John Chapat, a biochemist from the Institute of Biosynthesis at the University of Southern Arizona, also took a direct part in them.
Recently, he suggested that one of such alternatives could be threose nucleic acid (threose is one of the simplest sugars with the formula C 4 H 8 O 4). Now he continued the development of his research as part of a European group engaged in a more general issue – xenonucleic acids (XNA), that is, foreign nucleic acids, molecules that do not exist in nature, but just like RNA and DNA, capable of storing and transmitting genetic information. Today, for the first time, this group demonstrated a set of six such "unnatural" nucleic acid polymers created by it.
The creation of xenosubstantial beings based on them, which first occurs to journalists, is still too fantastic and unrealistic, and its researchers, of course, have not even considered it. They had enough of what can be done with XNA at the moment. It turned out that one of them can be transformed into various biologically useful forms with the help of "directed evolution".
So, in the laboratory, the so-called aptamers of nucleic acids, peculiar chemical sensors, receptors that react to the appearance of a certain chemical compound were also created. In conventional genetics, they are used, in particular, to search for damage in DNA or react to the appearance of a compound to which they are tuned by turning off the corresponding gene. The xeno-aptamers created by the group are not only capable of participating in such genetic processes, they can work on the principle of antibodies, finding and binding the corresponding molecules with high efficiency.
John Chapat claims that XNA can be used to create new types of diagnostics and new xeno-biosensors that can work even more successfully than natural ones, since natural enzymes-guards set up to destroy other people's DNA and RNA, they simply will not be seen.
Experimental xenobiology, a new science, the beginning of which was laid by this work, according to Chapet, will allow in the future to create previously unseen therapeutic methods. This work on xenonucleic acids provides a possible answer to another question that has been tormenting geneticists for decades: how DNA and RNA appeared on Earth.
At the end of the last century, scientists found out that DNA most likely appeared after less complex RNA, but they did not understand how RNA, also the most complex molecule, could be synthesized in nature. Academician Alexander Spirin, one of the world's leading experts on RNA, once claimed that he spent two years of his life on this question, and found out that random synthesis of RNA could occur in a time much longer than the lifetime of the Universe. The probability of such an event is much less than the probability that a monkey, slapping the keys, will write "War and Peace".
According to one hypothesis, RNA molecules were preceded by simpler molecules – pre-RNA, but it had a lot of inconsistencies, which are perfectly removed if we assume that the intermediary between pre-RNA and RNA was some kind of xenogenetic compound - xeno–nucleic acid.
Such an intermediary, according to Chapet, could well be his favorite nucleic acid threose (TNK). Having the ability to work with four nucleotides, four letters that make up the genetic alphabet – A, C, T and G – according to the laws established by Watson and Crick, who discovered the double helix of DNA, this TNC could play the role of a simultaneous interpreter who transmitted information from the world of pre-RNA to the world of RNA.
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20.04.2012