(A) Stick representation of loop 1 in the known crystal structure of Pin WW (PDB: 1PIN) (26), rendered in Pymol. Overlaid text shows the amino acids to be perturbed at positions 16 (i), 19 (i+3), and 21 (i+5), which are highlighted in yellow. Dashed lines indicate hydrogen bonds in wild-type Pin WW. (B) Variable temperature circular dichroism data (monitored at 227 nm) for glycoprotein g-WW-F,T (orange circles) and non-glycosylated WW-F,T (open circles). Fits of the data to a two-state folding model (18) are shown in orange and gray lines, respectively.