Friday, July 13, 2012

word of the day: lyotropic

The word of the day is lyotropic:

Etymology:  lyotrop- (in lyotrope adj.) + -ic suffix: see -tropic comb. form.
Physical Chem.  1. Associated with the change of internal pressure of a solution from that of the solvent which is caused by the solute. lyotropic series, a series in which ions are arranged in order of their lytropic effects, esp. their ability to cause precipitation of a lyophilic sol.   
2. Of a mesophase: having its phase transitions readily effected by a change of concentration. Also applied to the mesomorphism exhibited by such a mesophase. (OED)

Perhaps this definition from Case Western is a little more helpful:

"Liquid crystals come in two basic classifications: thermotropic and lyotropic . The phase transitions of thermotropic liquid crystals depend on temperature, while those of lyotropic liquid crystals depend on both temperature and concentration."

"The gangliosides, which are part of the lipid bilayer of the membranes differ in their lyotropic behaviour from the phospholipids and cholesterol which constitute the main components of the membrane.  The membrane phospholipids have two long hydrophobic chains, an interface region and a relatively small inogenic head group.  They are classified as 'non-soluble swelling amphipaths, implying that they do not form micelles but disperse spontaneously in water, forming bilyaered multilamellar large liposomes (MLV) or, upon ultrasonic irradiation small unilamellar vesicles (SUV).  In contrast, the gangliosides are 'soluble amphipaths' which form micelles in water.  The fact that, in spite of their two long hydrophobic chains the gangliosides are classified as 'soluble' amphipaths is explained by their large and highly negatively charged polar head group."

 - Barenholz et al., "Characterization of micellar and liposomal dispersions of gangliosides and phospholipids", Advances in Experimental Medicine and Biology 125:105 (1980).

I'm pretty sure they meant "ionogenic" instead of "inogenic".

I also have an irrepressible desire to look up the authors and mail them each a copy of Lynne Truss's Eats, Shoots, & Leaves.

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