The prebiotic role of Liquid Crystal self-assembly of DNA oligomers

Molecular crowding has a crucial role in tuning the hierarchical self-assembly of complex macromolecular structures and in boosting chemical reactions, allowing the proximity of reactants. It has been recently shown that at high concentration (> 200 mg/ml) short DNA oligomers (4-20 bases) associated in double helices may order into Liquid Crystal (LC) phases despite their nearly globular shape [1]. In these systems the formation of LC is mediated by the end-to-end aggregation of DNA duplexes into columns of chemically distinct but physically continuous duplexes. LC ordering of DNA oligomers appears to be a robust phenomenon even in crowded molecular mixtures. Indeed LC phases are found in concentrated solution of random sequence DNA oligomers [2], and in systems in which double stranded DNA is mixed with DNA single strands or with poly-(ethylene glycol) (PEG) chains [3]. In these systems the formation of LC domains is associated with phase separations providing a mechanism of self-selection and compartmentalization of DNA in water, otherwise unusual without the presence of vesicle membrane (see cartoons in Fig.). Moreover we found that DNA-PEG phase separation influences the quality and the yield of non-enzymatic ligation of DNA duplexes, catalyzing the formation of longer strands (graph in Fig.). 1) M. Nakata et al.,Science, 318, 1276 (2007). 2) T. Bellini et al., PNAS, 109, 1110 (2012). 3) G. Zanchetta, M. Nakata, M. Buscaglia, T. Bellini, N.A. Clark, PNAS, 105, 1111 (2008).