Cholesteric liquid crystals are ubiquitous in animal and plant kingdoms. We review the advances and open questions in the cholesteric organisation of DNA, chromatin, chitin, collagen, cellulose, viruses, silk fibroin and cholesterol esters. The roles and functions of biological cholesteric liquid crystals include maximisation of packing efficiency, morphogenesis, mechanical stability, optical information, radiation protection and evolution pressure.
Liquid crystals play an important role in biology because the combination of order and mobility is a basic requirement for self-organization and structure formation in living systems. In animal and plant kingdoms, the cholesteric structure is a recurring design, suggesting a convergent evolution to an optimised left-handed helix. In this article, we review the recent advances in the cholesteric organisation of DNA, chromatin, chitin, cellulose, collagen, viruses, silk and cholesterol esters deposition in atherosclerosis. Cholesteric structures can be found in bacteriophages, archaea, eukaryotes, bacteria nucleoids, chromosomes of unicellular algae, sperm nuclei of many vertebrates, cuticles of crustaceans and insects, bone, cornea, fish scales and scutes, cuttlebone and squid pen, plant cell wall, virus suspensions, silk produced by spiders and silkworms, and arterial wall lesions. This article specifically aims at describing the consequences of the cholesteric geometry in living matter, which are far from being fully defined and understood, and discusses various perspectives. The roles and functions of biological cholesterics include maximisation of packing efficiency, morphogenesis, mechanical stability, optical information, radiation protection and evolution pressure.
The following questions were taken into consideration while analysing the recent advances:
Cholesteric liquid crystals in living matter, Michel Mitov, Soft Matter (2017), 13, 4176-4209
Michel MITOV, mitov at cemes.fr