Chemical identification of the amyloid peptide aggregation-prone Al(III)-peptide complexes by resonance Raman signatures: A computational study

The aggregation of amyloid peptides as fibril-like β-sheet conformers is of vital importance in the development of Alzheimer's disease. It has been experimentally shown that Al(III) ions are aggregation-prone for amyloid peptides. Recently, it was proposed that Al(III) can directly bond to the peptide backbone and forming a ring structure. This ring structure drastically alters the secondary structure of the amyloid fibrils and induces irreversible denaturation. However, the kinetics and dynamics of Al(III)-peptide binding is still not well understood, which requires the detailed knowledge of the geometric and electronic structures of the binding intermediates and the products. In the present work, based on simple molecular models, we performed ab initio calculations for the spontaneous resonance Raman (RR) spectroscopic signals. The Raman characteristics of the complexes are distinct enough for chemical identification. All these features can be related to the vibronic coupling between the vibrational fingerprints and the specific electronic transitions. The rich structural information contained in the RR signals enables us to identify and characterize the Al(III)-peptide complexes at low concentrations typically in life sciences.