X-ray contact microscopy system for spectromicroscopy of biological specimens

Abstract

An X-ray contact microscopy system has been developed for the study of molecular and elemental distributions in biological specimens based on X-ray absorption characteristics. The system consists of a chamber for measuring XANES (X-ray absorption near-edge structure) of biomolecules, and a contact microscopy system for dried specimens with an electronic zooming tube. With this system the elemental distribution of carbon, nitrogen, oxygen, Ca and Fe in an HeLa cell has been studied, and the DNA-related image using a peak from the XANES pro®le of the DNA at the Kabsorption edge of phosphorus has been obtained.

Application of XANES profiles to X-ray spectromicroscopy for biomedical specimens: Part II. Mapping oxidation state of cysteine in human hair

“…At the spectroscopy section upstream of the system, XANES spectra are measured for thin films of biomolecules. By removing the sample and a detector in the spectroscopy section from the X-ray path, X-rays are introduced to the imaging section, where the dried hair specimens were observed with contact microscopy [13].…”

Applications of Synchrotron-Based X-ray Microprobes

“…In another study, it was demonstrated that freeze-drying similar chromosomes by three different procedures all introduced significant structural artifacts when compared to a wet unsectioned chromosome. Several subsequent investigations 51,56,97,229,233,242 demonstrated the ability of chemical contrast STXM to map proteins, DNA, and inorganic constituents in various specimens, including fibroblasts, sperm, , and human HeLa cells ).…”

“…223 As a result of both superior spatial resolution and the ability to examine lighter elements, soft X-ray microscopy has been utilized in studies of biological specimens and tissues to a far greater extent than hard X-ray microprobes and the applications have expanded dramatically over the past five years. 29,32,50,56,72,77,82,83,96,97,210,212,[226][227][228][229][230][231][232][233][234][235][236][237][238][239][240][241][242][243][244][245][246][247][248] It is not possible to review the voluminous literature in detail herein. Rather, we will select a range of examples that illustrate the versatility and power of soft X-ray microscopy and spectromicroscopy as a tool for examining biological specimens, tissues, and molecules.…”

“…Several subsequent investigations 51,56,97,229,233,242 demonstrated the ability of chemical contrast STXM to map proteins, DNA, and inorganic constituents in various specimens, including fibroblasts, 56 sperm, 97,235 and human HeLa cells. 238 The images were generated by exploiting specific spectral features in the C K-edge XANES spectra based on relative concentrations and chemical environment of CdC, CdN, and CdO bonds that give rise to different π* resonance intensities and energies (Figure 14). An example of STXM images of individual bull sperm cells along with DNA and protein distribution maps based on features in the C K-edge XANES spectra are illustrated in Figure 15.…”

X-ray spectroscopy and X-ray diffraction at wavelengths near theK-absorption edge of phosphorus

“…Structural studies on macromolecules have to rely on phosphorus as such. Examples are the soft X-ray contact microscopy techniques developed by Ito et al (1998Ito et al ( , 2003, allowing analysis of localization and chemical status of minor elements (Ca, S, P etc.) in biological specimens at relatively spatial resolution compared with X-ray diffraction.…”