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Amorphous hydroxyaluminium silicates formed under physiological saline conditions, and in CaCo3-buffered solutions. Stability and significance for Alzheimer plaque precipitates

Published online by Cambridge University Press:  09 July 2018

V. C. Farmer ,
F. Palmieri ,
A. Violante  and
P. Violante
V. C. Farmer
Affiliation:
Macaulay Land Use Research Institute, Craigiebuckler, Aberdeen, AB9 2QJ, UK
F. Palmieri
Affiliation:
Dipartimento di Scienze Chimico-Agrarie, Universita di Napoli, 80055, Portici, Italy
A. Violante
Affiliation:
Dipartimento di Scienze Chimico-Agrarie, Universita di Napoli, 80055, Portici, Italy
P. Violante
Affiliation:
Dipartimento di Scienze Chimico-Agrarie, Universita di Napoli, 80055, Portici, Italy
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Abstract

In an attempt to determine the nature and conditions of formation of the aluminium silicate precipitates present at the core of senile plaque in the brains of patients with Alzheimer's disease, aluminosilicate precipitates have been prepared and equilibrated for up to one year in physiological saline conditions at 40°C and a pH near 7·4. The structure and composition of these precipitates, and the associated concentrations of free silicic acid, were similar to those found in systems buffered with CaCO3 at 20–25°C. Imogolite-like products with Si : Al ratios near 0·5 were obtained at silicic acid concentrations <100 µm, and hydrous feldspathoid products with ratios ≥1·0 became dominant at silicic acid concentrations greater than ∼150 µm. These products do not match senile plaque precipitates, which have Si : Al ratios ≥1·0, but form in an environment with <100 µm Si. The relative stability of aluminium hydroxides, proto-imogolite allophane and hydrous feldspathoids are estimated from equilibrated silicic acid concentrations.

Type
Research Article
Information
Clay Minerals , Volume 26 , Issue 2 , June 1991 , pp. 281 - 287
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1991

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