Lyotropic Liquid Crystalline State of Biopolymers

Biopolymers such as proteins have a sequence of amino acid residues in the polymer chain. Due to bonding between -CO and -NH groups they may form a and P strucfures or double helix. 

Linear viruses are known to form liquid crystalline structures since tobacco mosaic virus (TMV) was foimd to form nemafic liquid crystalline phase. This inspired Onsager to write his seminal paper about the isotropic-nematic transition in hard rods. According to his theory (see Chapter 3), the isotropic phase becomes unstable with respect to the nematic arrangement when. 

Viruses are charged therefore, in addition to the steric repulsion of the hard rods, a long-range soft repulsion, due to electrostatic interactions, is present. 

In this case the condition to the isotropic nematic transition will be changed so that the diameter D will be replaced by which can be rigorously calculated, 

TMVs are rigid hollow cylinders with lengths of 300 nm and diameter of 18 nm. They are formed by 2130 protein subimits arranged in a single helix aroimd the central hole of radius about 2 nm. In solutions of near neutral pH, each protein subunit has a fixed charge of about -6e, which is practically offset by strongly bound coimterions.  

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