Figure 2.

Percentages of peptide NH groups exchanging in native, locally unfolded, and globally unfolded states of procapsid shells (54%, 32%, and 14%, respectively) and expanded shells (47%, 27%, and 25%, respectively). Exchange fractions were calculated from amide III′ band areas in the spectral interval 900-1020 cm⁻¹. Exchange by local unfolding is defined as exchange that occurs at 35°C but not at 10°C. Exchange by global unfolding, which requires shell disassembly and subunit denaturation in 6 M GuDCl, defines peptides of the exchange-protected core.