X-ray laser microscopy of rat sperm nuclei

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The development of high brightness and short pulse width (<200 picoseconds) x-ray lasers now offers biologists the possibility of high-resolution imaging of specimens in an aqueous environment without the blurring effects associated with natural motions and chemical erosion. As a step toward developing the capabilities of this type of x-ray microscopy, a tantalum x-ray laser at 44.83 angstrom wavelength was used together with an x-ray zone plate lens to image both unlabeled and selectively gold-labeled dried rat sperm nuclei. The observed images show ∼500 angstrom features, illustrate the importance of x-ray microscopy in determining chemical composition, and provide information about the uniformity of sperm chromatin organization and the extent of sperm chromatin hydration.