Biological & Soft Matter Seminar: On the Liquid Crystal Ordering of Nucleic Acids and its Intimate Connection to Watson-Crick Pairing

Abstarct:

A decade of experiments has unveiled that the formation of Liquid Crystal (LC) ordering is a universal motif of self-organization in concentrated suspension of Nucleic Acids (NA - DNA or RNA) oligomers, which we have observed and characterized by optical microscopy and spectroscopy, and x-ray diffractometry in a wide variety of NA solutions. Ordering is obtained by a hierarchical self-assembly process, in which base pairing and duplex formation is followed by the formation of linear aggregates of duplexes stabilized by the stacking between terminal nucleobases, in turn yielding long range molecular ordering. We find that the whole process, resulting from a fine balance of attractive and repulsive interactions, is quite sensitive to the variety of NA duplex structure and terminals, resulting in a variety of LC phase boundaries [1].

Watson-Crick pairing, the basic rule for the hybridization of NA chains of some length, has also been observed to be the elemental assembly step for the formation of LC ordering in solutions of single NA bases [2], in which A-T and C-G arrange in columns of paired bases, a geometry that closely resembles the double helical structure. This indicates that LC molecular packing is a sufficient constraint to promote Watson-Crick selectivity and suggests that such packing could have played a role in the selection and linear polymerization of prebiotic molecules [3,4]. Indeed, the finding that the key information-carrying biological molecules are capable of such a fine-tuned hierarchical assembly is evocative of an enthralling primordial natural history.

1 – F. Fontana et al., Macromolecules, 55, 5946 (2022)

2 - G. Smith et al. Proc. Nat. Acad. Sci. USA, 115, E7658 (2018) 

3 - T.P. Fraccia et al Nat. Commun. 6, 6424 (2015)

4 - M. Todisco et al. ACS Nano, 12, 9750 (2018)