title: The measurement of water distribution in frozen specimens.
abstract: 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.
authors.affiliation: Institute of Pathology, Charite, Berlin, Germany.
authors.forename: T
authors.initials: T
authors.lastname: von Zglinicki
mesh_terms: D000818:Animals; D005612:Freeze Drying; D005629:Frozen Sections; D008854:Microscopy, Electron; D014867:Water / Q000032:analysis*
chemical_list: D014867:Water