Source of Electrofreezing of Supercooled Water by Polar Crystals.

Polar crystals, which display pyroelectricity, have a propensity to elevate, in a heterogeneous nucleation, without epitaxy, the freezing temperature of supercooled water (SCW). Upon cooling, such crystals accumulate an electric charge at their surfaces, which creates weak electric fields,

The dynamic nature of amyloid beta (1-40) aggregation.

In this paper, we characterize the dynamic nature of the full amyloid beta (1-40) (Aß (1-40)) aggregates. We labeled the peptide with either 5-carboxytetramethylrhodamine (TAMRA) or with fluorescein-isothiocyanate (FITC). The labeled peptides were mixed after separate fibrillization, and the dynamic changes in the structure of the fibrils were imaged using confocal microscopy. Fluorescence resonance energy transfer (FRET) measurements showed that the Aß (1-40) peptides detach from and reattach to the fibrils in a biologically relevant timescale (days). With time, the two peptides mix at the molecular level. This process is concentration dependent and occurs primarily in the external parts of the aggregates with a half time between 4 and 7 days. This study shows that the combination of confocal microscopy and FRET analysis is a facile method for studying dynamic processes in supra-molecular aggregates.