Surprisingly, however, research has now shown that a single strand of TNA can indeed bind with both DNA and RNA by Watson-Crick base pairing – a fact of critical importance if TNA truly existed as a transitional molecule capable of sharing information with more familiar nucleic acids that would eventually come to dominate life.
In the current study, Chaput and his group use an approach known as molecular evolution to explore TNA’s potential as a genetic biomolecule.
Extending this technique to TNA requires polymerase enzymes that are capable of translating a library of random DNA sequences into TNA.
They first attempted to demonstrate that TNA nucleotides could attach by complementary base pairing to a random sequence of DNA, forming a hybrid DNA-TNA strand. Many of the random sequences, however, contained repeated sections of the guanine nucleotide, which had the effect of pausing the transcription of DNA into TNA.
Once random DNA libraries were built excluding guanine, a high yield of DNA-TNA hybrid strands was produced.
Chaput’s experiments with the nucleic acid TNA provide an attractive case.
To begin with, TNA uses tetrose sugars, named for the four-carbon ring portion of their structure.Sequences that bound with the target were recovered and amplified through PCR.The DNA portion was removed and used as a template for further amplification, while the TNA molecules displaying high-affinity, high specificity binding properties were retained.Once such a pool of TNA strands has been generated, a process of selection must successfully identify members that can perform a given function, excluding the rest.