Twisted fibrous arrangements

Nucleic acids, proteins and glycoproteins are the main components of the twisted fibrous arrangements. For many of them, biochemical studies are rare or absent. 

Nucleic acids. The DNA of the Dinoflagellate chromosomes forms a cholesteric network which is very similar to that often observed in the bacterial nucleus (6,9,18). Similar structures have been observed in mitochondrial DNA in certain Trypanosomes, after a treatment with certain drugs (review in. DNA in concentrated aqueous solutions can form cholesteric mesophases (4,18, 24). Remarkable cholesteric spherulites have been observed in concentrated ribosomal RNA (first considered as t-RNA, 33-35).  

Proteins. Synthetic polypeptides can form cholesteric solutions in several organic solvents (24-26,29). Twisted arrangements of collagen fibrils are common in sponges (Carrie.re, pers. comm.), in Holothurians (Echinoderms, 6,14, see fig. 1) and in flat worms (j6).  

Microtubular haemoglobin has been observed in erythrocytes in sickle cell anaemia. After deoxygenation and addition of thermal energy, the mutant molecules of haemoglobin (HbS) stack to form monomolecular filaments. Six strands assemble into a heli-coidal microtubule showing six helices of long pitch (review in 19). These microtubules form a cholesteric packing (6). 

Superb twisted arrangements have been observed in larval haemocytes (oenocytoid) of the silkworm, forming regular and concentric series of arcs (2). 

---

Bouligand, Y. (1972). Twisted fibrous arrangements in biological materials and cholesteric mesophases. Tissue and Cell, 4, 189-217. 

---