Optical fusion assay based on membrane-coated spheres in a 2D assembly

Area of Science:

• Membrane biophysics
• Cell biology
• Virology

Background:

• Understanding membrane fusion is crucial for neurophysiology and enveloped virus research.
• Current assays face challenges in reliably identifying fusion stages with minimal labeling.
• Lipid and protein composition significantly influences membrane fusion dynamics.

Purpose of the Study:

• To develop a fast and reliable optical assay for quantifying membrane fusion and its inhibition.
• To enable the identification of distinct membrane-membrane interaction stages, from docking to merging.
• To overcome limitations of existing methods, such as aggregation and extensive labeling.

Main Methods:

• Introduction of a two-dimensional fusion assay utilizing monodisperse membrane-coated microspheres.
• Employing a hard-sphere fluid model to capture and quantify fusion events.
• Validation using a model system of coiled-coil heterodimers on opposing microspheres.

Main Results:

• The assay unequivocally assigns docking and membrane fusion events.
• It quantifies fusion stages without interference from aggregation, liposome rupture, or light scattering.
• Demonstrated feasibility with a coiled-coil heterodimer model system.

Conclusions:

• The developed optical microsphere assay provides a robust platform for studying membrane fusion.
• This method facilitates research in neurophysiology and enveloped virus biology by offering precise fusion stage analysis.
• The assay minimizes the need for extensive fluorescent or radioactive labeling.