In controlled drying experiments with dilute isotropic DNA solutions, a number of liquid crystalline states are observed as the DNA and salt concentrations are increased by evaporation of the solvent (water). In areas where the DNA concentration range falls between 250 and 350 milligrams per milliliter, batonnets spontaneously emerge as the first step in the transition to a higher density liquid crystalline phase. The image above depicts an unusually beautiful batonnet that has formed in the cholesteric mesophase. The DNA concentration in this experiment is approximately 300 milligrams per milliliter, and the photomicrograph magnification is approximately 400x. Originally recorded on Fujichrome 64T transparency film using a Nikon Optiphot-Pol microscope with crossed polarized illumination, the image was digitized using a Nikon CoolScan transparency film scanner. Exposures were recorded about 3 f-steps under the recommended value given by an in-camera photomultiplier and were push-processed approximately 1.75 f-steps in the first E-6 developer. |
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