Figure 5.

Predicted behavior for capsid assembly. (A) Capsid assembly at equilibrium. Very little capsid is observed until the total dimer concentration reaches a pseudocritical concentration of assembly, referred to as K_Dapp, the apparent dissociation constant. Above K_Dapp, almost all additional free dimer assemble into capsid (red), leaving a nearly constant concentration of free dimer (green); a slope of almost zero indicates that assembly is very close to equilibrium (Zlotnick 2007; Katen and Zlotnick 2009). (B) Assembly of large populations of particles displays sigmoidal kinetics (Endres and Zlotnick 2002; Hagan and Chandler 2006; Katen and Zlotnick 2009). The observed lag phase of assembly is proportional to the time to establish a steady state of intermediates. Following the lag phase, capsid particles accumulate (Hagan and Chandler 2006; Katen and Zlotnick 2009). As more free subunits are consumed to form capsids, the reaction slowly approaches equilibrium, plateauing when the pseudocritical concentration is reached (Katen and Zlotnick 2009). Nucleation and intermediate formation occurs throughout the entire assembly reaction.