Subcellular mass determination by 4 He + energy-loss micro-spectrometry

Share Embed


Descripción

Anal Bioanal Chem (2002) 374 : 390–394 DOI 10.1007/s00216-002-1511-8

S H O RT C O M M U N I C AT I O N

Guillaume Devès · Richard Ortega

Subcellular mass determination by 4He+ energy-loss micro-spectrometry

Received: 17 May 2002 / Revised: 18 July 2002 / Accepted: 23 July 2002 / Published online: 11 September 2002 © Springer-Verlag 2002

Abstract The scanning transmission ion microscope (STIM) has been used to determine the intracellular mass of human cultured cells. A 4He+ microbeam of 2.0 MeV energy was chosen to obtain enhanced ion-energy-loss sensitivity through the micron-thick freeze-dried cells. Local sample mass calculation, based on energy-loss conversion by use of appropriate matrix stopping powers, was performed by use of dedicated software. The method was validated with epoxy resin sections and polymer foil as analogues of biological samples in the range of (intra)cellular thickness, 150 to 3000 nm. STIM analysis resulted in less than 5% error in mass determination. 4He+ energy-loss micro-spectrometry was performed on freezedried human ovarian cancer cells, the mean areal mass obtained was 120 µg cm–2 (200 µg cm–2 in the nucleus and 250 µg cm–2 in nucleoli). This method is particularly useful for mass normalization of X-ray fluorescence yields resulting from particle-induced X-ray emission microanalysis (micro-PIXE). When performed successively these two ion-beam micro-analytical methods enable the mapping of true element concentrations within single cells. Keywords Chemical imaging · Scanning transmission ion microscopy · Cellular mass · Microanalysis · Ion-beam analysis

Introduction The manner in which elements are distributed in cells and intracellular compartments, which is critical for cell function, is highly organized and regulated by the genome [1]. Imaging and quantification of the distribution of chemical

G. Devès · R. Ortega (✉) Chimie Nucléaire Analytrique et Bioenvironnementale CNRS UMRS084, Université de Bordeaux 1, BP 120 Le Haut-Vigneau, 33175 Gradignan cedex, France e-mail: [email protected]

elements in human cells, especially inorganic elements, is a major challenge for analytical chemistry in the postgenomic era. Analytical techniques that can provide chemical information in the form of a spatially resolved image are required in this purpose. Electron probe X-ray microanalysis (EPMA) is a well established technique for element analysis in cells but suffers from a relative lack of sensitivity when applied to the determination of trace elements (
Lihat lebih banyak...

Comentarios

Copyright © 2017 DATOSPDF Inc.