Biological Soft X-Ray Tomography at the Advanced Light Source
Authors:
Carolyn A. Larabell1,2* ([email protected], PI), Valentina Loconte1,2, Jian-Hua Chen1,2, Mark Le Gros1,2
Institutions:
1University of California–San Francisco; 2Lawrence Berkeley National Laboratory
Abstract
Soft X-ray tomography (SXT) visualizes and quantifies the structural organization of biological organisms up to 20 micrometers in diameter. Specimens are imaged in the near-native state—rapidly frozen in their normal growth conditions—at a resolution up to 35 nanometers. Large numbers of cells can be imaged since it takes only five to 10 minutes to go from the frozen specimen to a reconstructed tomogram. Imaging is based primarily on the absorption of carbon, a common element of all known life. At the same time, water (ice) is virtually invisible so that high-contrast images are obtained based solely on the inherent properties of the structures examined. This is accomplished by imaging with X-ray photons in the ‘water window’ (between 284 to 543 electron volts), where X-ray photons are absorbed an order of magnitude more strongly by carbon- and nitrogen-containing organic material than by water. The absorption of soft X-rays adheres to the Beer-Lambert Law and is, therefore, a function of the chemical composition and concentration of organic material, yielding unique quantitative Linear Absorption Coefficient measurements for specimen components. The team has used this label-free imaging technology to image and quantify a wide variety of structures, including bacteria, yeast, spores, algae, larger mammalian cells and isolated organic particles. This poster will present examples of SXT data that enabled biological findings that couldn’t be obtained with other technologies, including the simultaneous visualization and quantification of carbon, effects of altered environments on cell structures, and novel findings about N2 cycling in an endosymbiotic organism.
Funding Information
This research was supported by the DOE Office of Science, BER program, under contract DE-AC025CH11231.