<title>Soft X-Ray Imaging Of Hydrated Biological Specimens</title>

Abstract

Soft x-ray microscopy was proposed as an exciting new technique almost two decades ago. However, it is only recently with the advent of high resolution recording substrates such as polymethyl methacrylate and the development of synchrotron and pulsed x-ray sources (that can deliver a tuneable x-ray dose in nanoseconds or minutes) that soft x-ray contact microscopy has developed into a significant biological research tool. X-ray photos between the carbon and nitrogen absorption edges (3.1 - 4.4nm) penetrate short airpaths, water and thick specimens without significant diffraction or scattering effects and at dosages and exposure times that produce significantly less damage than charged particle imaging methods. Because the x-ray contact replica is formed by the differential absorption of soft x-rays by the biological specimen itself, small intracellular structures (such as membranes and intracellular organelles) can be clearly imaged at spatial resolutions approaching those of conventional scanning and transmission electron microscopy. This paper presents results obtained from the imaging of hydrated biological subcellular structures (isolated macromolecules found in the ground substance of cartilage and isolated muscle filaments) using soft x-rays from a stationary target and pulsed plasma x-ray source.