Arp2/3 filament nucleation images
Here are some stills from the Arp2/3 model movies (the movies themselves are on this page).
Filament Nucleation
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The Arp2/3 nucleation reaction: Components: Mother filament, Arp2/3 complex, VCA, and an actin monomer

The Arp2/3 nucleation reaction: Arp2/3 docks onto the mother filament
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The Arp2/3 nucleation reaction: VCA delivers an actin monomer to the Arp2/3 complex

The Arp2/3 nucleation reaction: VCA docks the actin monomer onto the Arp2/3 complex

The Arp2/3 nucleation reaction: Actin polymerizes from the completed nucleus, VCA released
Filament Capping
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Arp2/3 about to cap an actin filament

Arp2/3 capping an actin filament