Analysis of localization and chemical status of minor elements in a mammalian cell using soft X-ray contact microscopy

Abstract

We have developed computer-assisted procedures for mapping minor light elements and their chemical bond information from a set of soft X-ray transmission images of biological specimens. Minor light elements such as Ca, S and P play an important role in the biological function and structure in a cell. Contact X-ray microscopy with an electric zooming tube covering wide wavelength range from the K absorption edge of S to the L absorption edge of P is applied to elemental mapping. The procedure of elemental mapping depends basically on the subtraction of the contribution of major elements such as C, O and N in intracellular absorption spectra to find the presence of the absorption edges of minor elements. The results of simulation experiments were presented. Chemical bond imaging utilizes a XANES spectrum corresponding to a specific chemical bond. Since the intensity is relatively low for minor elements, the ratio between absorption at the peak and at the bottom, which represents the chemical bond distribution, becomes small. We developed the computer program for the enhancement of very small ratio value. This procedure was applied to the S-S and S-C bond imaging at the S-K absorption edge.