The NEXAFS of biological calcium phosphates

Abstract

The absorption cross section of a number of calcium salts has been assessed at the calcium L edge by measuring the total electron yield (TEY) at the NSLS U13UA beamline. TEY was used because of distortions introduced by instrumentation when using a transmission signal. The effect of these distortions has been evaluated and is presented. The TEY signal was normalized to the incident beam using the signal from a new beam monitor which is detailed here. Comparative spectra are presented for some calcium salts associated with osteoarthritis.

Chemical and mechanical analysis of tribofilms from fully formulated oils Part 1 – Films on 52100 steel

“…The intense L 3 (y346?2 eV) and L 2 (y349?6 eV) edges (spin orbit doublets) are easily viewed in Fig. 7 69 The authors have also measured the C K-edge XANES (Fig. 2).…”

“…Unfortunately, differences in Ca chemistry are not easy to identify with XANES, as the changes in the XANES spectra with changes in Ca chemistry are very subtle and it is very difficult to distinguish between CaF . 69 The authors have also measured the C K-edge XANES (Fig. 2).…”

Applications of Synchrotron-Based X-ray Microprobes

“…A series of studies have utilized STXM, Ca L-edge, and C K-edge XANES to examine Ca distribution maps in human cartilage, biological calcium phosphates, and calcified human tendon . It was demonstrated that differences in absorption cross section at Ca L-edge preionization and postionization energies along with differences arising from features in the XANES spectra could be combined with pre- and post-C K-edge images to provide a quantitative method for mapping Ca locations in mineralized tissues with a detection limit of 0.1 μg cm -2 .…”

“…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.…”

X-ray contact microscopy system for spectromicroscopy of biological specimens

“…Imaging with a difference in chemical states of Ca has been performed by Buckley et al (1994) for different distributions of Ca hydroxy apatite in bone and tricalcium phosphate in prostheses. Buckley et al (1995) also compared XANES pro®les of some Ca salts associated with osteoarthritis. Ade et al (1992), followed by Zhang et al (1994), applied XANES peaks at the K-edge of carbon to the molecular mapping of DNA in a chromosome using a difference in the spectrum of the C C bond in DNA from that in bovine serum albumin.…”