Behavior of 尾-Amyloid 1鈭?6 at the Air鈭扺ater Interface at Varying pH by Nonlinear Spectroscopy and Molecular Dynamics Simulations

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• 作者：Abigail E. Miller ; Poul B. Petersen ; Christopher W. Hollars ; Richard J. Saykally ; Jan Heyda ; Pavel Jungwirth
• 刊名：Journal of Physical Chemistry A
• 出版年：2011
• 出版时间：June 16, 2011
• 年：2011
• 卷：115
• 期：23
• 页码：5873-5880
• 全文大小：1061K
• 年卷期：v.115,no.23(June 16, 2011)
• ISSN：1520-5215

文摘

The adsorption and aggregation of 尾-amyloid (1鈭?6) fragment at the air鈭抴ater interface was investigated by the combination of second harmonic generation (SHG) spectroscopy, Brewster angle microscopy (BAM), and molecular dynamics simulations (MD). The Gibbs free energy of surface adsorption was measured to be 鈭?0.3 kcal/mol for bulk pHs of 7.4 and 3, but no adsorption was observed for pH 10鈭?1. The 1鈭?6 fragment is believed not to be involved in fibril formation of the 尾-amyloid protein, but it exhibits interesting behavior at the air鈭抴ater interface, as manifested in two time scales for the observed SHG response. The shorter time scale (minutes) reflects the surface adsorption, and the longer time scale (hours) reflects rearrangement and aggregation of the peptide at the air鈭抴ater interface. Both of these processes are also evidenced by BAM measurements. MD simulations confirm the pH dependence of surface behavior of the 尾-amyloid, with largest surface affinity found at pH = 7. It also follows from the simulations that phenylalanine is the most surface exposed residue, followed by tyrosine and histidine in their neutral form.