Synaptic vesicles studied by dynamic light scattering.

Area of Science:

• Neuroscience
• Biophysics
• Biochemistry

Background:

• Synaptic vesicles (SVs) are crucial for neurotransmission.
• Accurate characterization of SV size and fusion dynamics is essential for understanding neuronal function.
• Existing methods may be limited in resolving SV polydispersity and fusion events.

Purpose of the Study:

• To characterize the size polydispersity distribution of synaptic vesicles (SVs) using dynamic light scattering (DLS).
• To quantify and reduce contaminant structures in SV fractions.
• To characterize SV fusion with proteoliposomes using DLS.

Main Methods:

• Dynamic Light Scattering (DLS) for size distribution analysis.
• Asymmetric-flow field-flow (AFFF) fractionation for contaminant removal.
• Analysis of intensity autocorrelation functions using constrained regularization and direct modeling.
• Vesicle fusion assays with syntaxin 1 and SNAP-25A.

Main Results:

• DLS accurately determined SV size polydispersity under quasi-physiological conditions.
• AFFF fractionation effectively reduced larger contaminant structures in SV preparations.
• DLS results quantitatively agreed with cryogenic electron microscopy data.
• DLS successfully quantified size increases in proteoliposomes due to SNARE-dependent SV fusion.

Conclusions:

• DLS is a robust method for characterizing SV size polydispersity and fusion.
• Contaminant structures in SV preparations can be identified and reduced.
• SNARE-mediated fusion leads to quantifiable changes in vesicle size detectable by DLS.