As a molecule that carries the genetic information of an organism, DNA plays a crucial role in the construction of cells and proteins. Vast amounts of information in DNA in sequences of molecules called bases.
The conventional model of DNA used today was proposed by James Watson and Francis Crick in 1953 following the suggestion that the structure should be able to store information and undergo Darwinian evolution. Watson and Crick (WC) developed a model where the four bases are made of molecules adenine (A), thymine (T), cytosine (C), and guanine (G), which come in pair to form the double helix structure.
Watson-Crick DNA versus Synthetic DNA
The WC model of DNA successfully shows DNA's ability to carry the genetic information of all life on Earth. However, it fails to answer why DNA bases are limited to four and why they are made of specific molecules.
In situations where active DNA is not possible or not preferred, laboratory-made or synthetic DNA is used by researchers. They are designed and controlled using computer-aided design software. The process involves advanced DNA sequencing to simulate reactions in the human body. It provides the key to advancements in various industries in medicine and biotechnology, such as vaccination and gene therapy.
Synthetic DNA allows the engineering of fresh genes or the improvement of existing ones. As it encodes and sustains Darwinian evolution, it opens the doors to a deeper understanding of genetic systems. Recent advances in synthetic biology also reveal that WC bases are not the only molecules that can sustain life and that evolution can be made possible by a set of alternative bases.
In 2020, a type of synthetic DNA was proposed by Shuichi Hoshika and his colleagues, which they called the hachimoji DNA. Unlike the WC model, the hachimoji DNA contains eight bases, allowing increased information density since more pairs can be formed.
Developed as a synthetic nucleic acid extension of DNA, hachimoji DNA contains four additional bases labeled Z, P, S, and B. This synthetic DNA is not yet found in natural living organisms, but experts believe it can be potentially observed on exoplanets and contribute to the genetic material of alternative life forms.
The Impact of Proton Transfers on Hachimoji DNA
A group of quantum biologists from the University of Surrey investigated the properties of hachimoji DNA. The team, led by Harry Warman, studied the possible transfer of protons between the bases of this DNA.
The research presented a proton transfer mechanism for hachimoji DNA, then calculated proton transfer rates using density functional theory. Other components, such as tunneling factors and the kinetic isotope effect in this synthetic DNA, were also measured.
Warman and his team found out that with sufficiently low reaction barriers, proton transfer is possible to happen even at biological temperatures. They also discovered that the proton transfer rates of hachimoji DNA are faster than in conventional DNA Watson and Crick due to the lower barrier for Z-P and S-B. As proton transfer occurs more frequently, hachimoji DNA has the potential to initiate mutation at a higher rate.
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