Unwinding in Cholesteric Mesophases

Unwinding in Cholesteric Mesophases

Unwinding of the cholesteric mesophase occurs during controlled drying experiments with liquid crystalline DNA. The photomicrograph above illustrates progressive unwinding as the DNA concentration is increased. Smooth blue textures of cholesteric liquid crystalline DNA slowly acquire darker tints as the mesophase unwinds and the DNA molecules reorient themselves. The DNA concentration for this specimen was initially 100 milligrams per millimeter, but this changes as the solvent evaporates. The magnification is approximately 90x. Originally recorded on Fujichrome 64T transparency film using a Nikon Optiphot-Pol microscope with crossed polarized illumination, the image above was digitized using a Nikon CoolScan transparency film scanner. Exposures were recorded about 2.5 f-steps under the recommended value given by an in-camera photomultiplier and were push-processed approximately 1.5 f-steps in the first E-6 developer.

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