Premium
The measurement of water distribution in frozen specimens
Author(s) -
Zglinicki Thomas
Publication year - 1991
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 - 10.1111/j.1365-2818.1991.tb03079.x
Subject(s) - analytical chemistry (journal) , radiation , chemistry , scattering , resolution (logic) , materials science , optics , chromatography , physics , artificial intelligence , computer science
SUMMARY There are three techniques to measure local water fractions in the cryomicroscope. First, water content may be measured by a direct analysis of oxygen in bulk samples using a windowless detector. Secondly, mass thickness may be estimated in frozen‐hydrated, then frozen‐dried sections. This technique offers unrivalled spatial resolution, especially if the radiation dose in the frozen‐hydrated state is kept low by the use of electron scattering techniques instead of an X‐ray microanalytical background determination. External water content standards can be used instead of frozen‐hydrated sections and the whole analysis can even be performed exclusively on frozen‐dried sections at room temperature. Thirdly, local water fractions can be evaluated from X‐ray microanalytical measurements of element concentrations per mass in the frozen‐hydrated and frozen‐dried state. Corrections necessary for the other techniques cancel out. However, the high radiation dose required for a fully quantitative analysis excludes the use of these methods in thin or ultrathin sections.