Selective Nucleobase Pairing Extends Plausible Prebiotic Conditions to the Solid State

27 June 2019, Version 1
This content is a preprint and has not undergone peer review at the time of posting.


Pairing of complementary nucleobases is the most famous example of molecular recognition. However, it has long been known that except 9-methyladenine (9-mA) and 1-methylthymine (1-mT), all other binary combinations of nucleobases do not form base pairs under plausible prebiotic conditions, e.g., in water or in the solid state. It is surprising that nucleobases would have been incorporated into DNA if they were unable to self-assemble prior to their attachment. Here we show how the formation of an elusive base pair between 9-methylguanine (9-mG) and 1-methylcytosine (1-mC) is possible in the solid state via Watson-Crick hydrogen bonding. Molecular recognition of 9-mG:1-mC as well as 9-mA:1-mT base pairs was observed by X-ray diffraction monitoring during heating their 1:1 solid mixtures, while all other binary mixtures failed to give base pairs. To demonstrate the selectivity of complementary nucleobase pairing, we showed how 9-mA and 1-mT self-assembled in ternary mixture containing also 1-methyluracil (1-mU), and both 9-mA:1-mT and 9-mG:1-mC pairs self-assembled in quaternary mixture. The results presented here indicate the importance that the solid state as a reaction medium might have had as a prebiotic molecular selection tool towards compatibility as found in the DNA.


Solid State
Prebiotic Chemistry
Chemical Evolution
Base pairing

Supplementary materials



Comments are not moderated before they are posted, but they can be removed by the site moderators if they are found to be in contravention of our Commenting Policy [opens in a new tab] - please read this policy before you post. Comments should be used for scholarly discussion of the content in question. You can find more information about how to use the commenting feature here [opens in a new tab] .
This site is protected by reCAPTCHA and the Google Privacy Policy [opens in a new tab] and Terms of Service [opens in a new tab] apply.