Dark‐field electron microscopy of unstained biological materials embedded in Nanoplast

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Abstract
Extremely thin sections of unstained materials (beef liver catalase, double‐stranded calf thymus DNA, horse spleen ferritin and mammalian skeletal muscle), embedded in the water‐soluble melamine resin Nanoplast FB101, were studied by dark‐field electron microscopy and electron spectroscopic imaging.While ferritin molecules so recorded show 04 and 09 nm lattice fringes within the crystalline iron core, double‐stranded DNA shows a helical repeat with a spacing of 34 nm.The gain in resolution of structural detail reported here is probably due mainly to the reduced section thickness as compared to traditional thin‐sectioning techniques. As we reported earlier (Frösch & Westphal, 1984), melamine resins can be sectioned extremely thinly (<10 nm) and observed without a supporting film, making them especially suitable for dark‐field electron microscopy.