Twist grain-boundary mesophase

It is likely that the other more complex hyperbolic mesophases are also to be found in chiral systems twisted grain boundary and blue phases (whose twist numbers are less than and greater than unity respectively, cf. section 4.14), are also prevalent in proteinaceous matter. (Note that a blue phase of DNA in water has recently been reported [11]). 

There is a wide range of other chiral mesophases that are somewhat unconventional in terms of their structure and many of these are rather recent developments. Blue phases are cubic mesophases that have a double twist stracture. They are exhibited by highly chiral materials and appear at temperatures above the chiral nematic phase. These phases give characteristic platelet type textures that are often blue (hence the name) but they can also appear green, yellow and red. The twist grain boundary (TGBA ) phase also has a fmstrated complex helical stmcture. In this case the normal lamellar stmcture is... 

---