Precholesteric to Cholesteric Phase Transition

Precholesteric to Cholesteric Phase Transition

Transition of the dilute precholesteric to cholesteric phase is occurring in this photomicrograph of liquid crystalline calf thymus DNA. Domains with a light blue background represent those areas of the specimen that have undergone the transition from precholesteric to cholesteric. Areas with a darker background and having a lesser degree of birefringence are precholesteric. The DNA concentration for this specimen was initially 100 milligrams per millimeter, but this changes as the solvent evaporates. The magnification is approximately 150x. 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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