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Videodensitometric analysis of electron spectroscopic micrographs — a tool for detection of biologically relevant elements with high resolution
Author(s) -
DOOR R.,
BREITIG D.,
MARTIN R.
Publication year - 1997
Publication title -
journal of microscopy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.569
H-Index - 111
eISSN - 1365-2818
pISSN - 0022-2720
DOI - 10.1046/j.1365-2818.1997.2310791.x
Subject(s) - neurofilament , resolution (logic) , electron microscope , biological specimen , chemistry , materials science , nuclear magnetic resonance , analytical chemistry (journal) , optics , physics , artificial intelligence , biology , chromatography , computer science , immunohistochemistry , immunology
Electron energy‐loss spectroscopic imaging (ESI) yields high‐resolution, element‐sensitive images. However, ESI suffers from difficulties in distinguishing element‐specific and background contributions. New methods have therefore been introduced which use grey‐level measurements in micrographic images for a more accurate detection of element distributions. A videodensitometric method allowed the detection of low phosphorus levels in axoplasmic neurofilaments of squid giant axons. Here we further verify these results by investigating the relationship of videodensitometry and electron energy‐loss spectroscopy (EELS), particularly considering the peculiarities of these methods in terms of automatic background correction and representation of the results. Six biological specimens and two nonbiological specimens were examined both by EELS and by videodensitometry. In all cases comparable results were obtained. The overlapping P L2,3 and S L2,3 ionization edges could clearly be recognized individually by both methods, and controls showed that mass density variations within the specimens did not impair elemental analysis. Additional evidence supporting the detection of phosphorylation sites in squid neurofilaments was obtained in both EELS and videodensitometric measurements of neurofilament‐enriched pellets and of aggregated axoplasmic particles. Thus, videodensitometry appears to be a useful tool for an improved exploration of the full imaging capabilities of energy filtering electron microscopy.