The decription of β-Amyloid (1-16)

The fragment adsorption and aggregation of β-amyloid (1-16) at the air-water interface was studied by the combination of second-harmonic generation (SHG) spectroscopy, Brewster angle microscopy (BAM), and molecular dynamics (MD). The Gibbs free energy of surface adsorption was measured at -10.3 kcal / mol for bulk pH of 7.4 and 3, but no adsorption was observed for pH 10-11. The fragment 1-16 is estimated not to be involved in fibril formation of β-amyloid protein, but it presents an interesting behavior at the air-water interface, as manifested in the two time scales for SHG response observed. The shorter time scale (minutes) reflects the adsorption surface, and the longer time scale (hours) reflects a rearrangement and aggregation of the peptide to the air-water interface. These two processes are also highlighted by BAM measurements. Molecular dynamics simulations confirm the pH dependence of behavior of the surface of the β-amyloid, with an affinity greater surface area is at pH = 7. It also follows from the simulations phenylalanine residue is the most exposed surface, followed by tyrosine and histidine in their neutral form.
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