Probing beta amyloid aggregation using fluorescence anisotropy: experiments and simulation.

Area of Science:

• Biochemistry
• Biophysics
• Computational Biology

Background:

• Beta amyloid (Ab) protein aggregation is a key pathological feature of Alzheimer's disease.
• Understanding the molecular mechanisms of Ab aggregation is crucial for developing therapeutic strategies.

Purpose of the Study:

• To investigate the dynamics of beta amyloid (Ab) protein aggregation using fluorescence anisotropy.
• To elucidate the role of tyrosine (Tyr) side chain dynamics during Ab aggregation through experimental and computational approaches.

Main Methods:

• Fluorescence anisotropy measurements to monitor Ab aggregation.
• Monte Carlo (MC) simulations for coarse-grained analysis of Tyr side chain movement.
• All-atom Molecular Dynamics (MD) simulations for high-resolution molecular insights.

Main Results:

• Experimental fluorescence anisotropy revealed two distinct rotational timescales associated with Ab aggregation.
• MC simulations indicated that restricted Tyr side chain movement is necessary to replicate experimental anisotropy.
• MD simulations confirmed that Ab aggregation leads to restricted Tyr side chain dynamics, consistent with experimental findings.

Conclusions:

• The combined experimental and simulation approach provides a unique molecular-level understanding of Ab aggregation.
• Restricted tyrosine side chain dynamics are a significant feature of the Ab aggregation process.
• This integrated methodology can be applied to study other protein aggregation systems relevant to disease.