Effect of buffer composition on the shape of reassembled particles. When the VLPs had been dissociated, the sample (now containing free pentamers) was dialyzed again against buffers with different concentrations of a monovalent salt, NaCl (0.0 to 1.0 M), pH (7.0 to 7.8), and a divalent ion, Ca2+ (0.0 to 100.0 mM). Square: buffer conditions when less then 30% of the reassembled particles had a T=1 symmetry. Triangle: buffer conditions when more then 80% of the reassembled particles had a T=1 symmetry. All experiments were done at room temperature and overnight.