KD: The region of protein G that makes up the peptide used by Mu?oz et al. is shown in Ball and Stick display while the rest of the protein is shown as wireframe. Furthermore, the hydrophobic cluster that W43 is buried in when the hairpin is in its native state is shown in Shapely coloring: W43 is shown in red, V54 in blue, and F52 is shown in green.

AG: The b-hairpin studied by Mu?oz et al. is displayed in cartoon representation. The two sidechains of the short turn that connects the 2 b-strands are displayed in white, the sidechain of D47 is shown in red and the sidechain K50 is blue. The figure illustrates how the orientation of the sidechains in this short hairpin element is maximizing an electrostatic interaction between D47 and K50. No other possible folding scheme in this region would satisfy this interaction. Besides the hydrophobic cluster in the center of the b-sheet, this electrostatic interaction could also account for the unusual property of this short peptide to function as an independently folding unit.

PH: The b-hairpin region is shown in cartoon view. The rest of the protein is shown in strands display. A single tryptophan (W43), which provides an intrinsic probe for both equilibrium and kinetic experiment. Formation of the b-hairpin is accompanied by an increase in W43 fluoresence because of its consolidation into a hydrophobic cluster with F52, V54 and Y45, W43 is shown in red in stick view. F52, V54 and Y45 are shown in Ball and Stick view and in yellow. Hydrogen bonds are shown in dotted line with distances in � units.
In Mu?oz et al., dansylated lysine is added to the C-terminus. Dansyl group serves as the quencher (acceptor) of W43.

WL: The hydrophobic cluster is highlighted in blue with the tryptophan used as a donor in the fluorescence experiments highlighted in yellow and spacefill.

GZ: When examining the hydrophobic pocket that the Trp43 sits in, I noticed something slightly odd. While most of the residues near the Trp were hydrophobic, there is a basic lysine poised close to the Trp (within about 6 �). This is unexpected as lysine's positive charge would normally disrupt hydrophobic interactions. However, note that the third and fourth carbons of the lysine hydrocarbon chain point directly toward the Trp, while the positive terminal amino group faces away from the Trp. In this way, even a polar residue can promote a hydrophobic environment for the Trp.
In this picture, acidic amino acids are red, basic amino acids are blue, hydrophobic amino acids are white and polar uncharged amino acids are green. Trp43 and Lys31 have been given a modest spacefill value to accentuated them.