Join us from 2-3 p.m. in Beckman 3269 or on Zoom for QCB Seminar featuring Carolyn Larabell, University of California San Francisco and Lawrence Berkeley National Lab. Refreshments prior outside Beckman 3151.
Title: Quantitative 3D Imaging of Whole Cells Using Soft X-ray Tomography
Abstract: Soft x-ray tomography (SXT) visualizes and quantifies the structural organization ofbiological organisms up to 20 um diameter. Specimens are imaged in the near-nativestate - rapidly frozen in their normal growth conditions - at a resolution up to 35 nm.Large numbers of cells can be imaged since it takes only 5-10 min to go from the frozenspecimen to a reconstructed tomogram. Imaging is based primarily on the absorption ofCarbon, a common element of all known life. At the same time, water (ice) is virtuallyinvisible so that high-contrast images are obtained based solely on the inherentproperties of the structures examined. This is accomplished by imaging with x-rayphotons in the 'water window' (between 284 – 543eV), where x-ray photons areabsorbed an order of magnitude more strongly by carbon- and nitrogen-containingorganic 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 andconcentration of organic material, yielding unique quantitative Linear AbsorptionCoefficient (LAC) measurements for specimen components. We have used this label-free imaging technology to image and quantify a wide variety of structures, includingisolated organic particles, bacteria, yeast, spores, algae, larger mammalian cells andtissue. I will present examples of SXT data that enabled biological findings that couldn’t be obtained with other technologies.