Structural model of HP35 showing residues labeled with CNPhe and 2D IR spectra of CNPhe in folded (upper panels) and guanidium-denatured (lower panels) HP35 at different waiting times. Structural model: Reprinted with permission from Chung et al. The Journal of Physical Chemistry B, 2012, 116, 11024 – 11031. Copyright © 2012 American Chemical Society. 2D IR spectra: Reprinted with permission from Chung et al. Proceedings of the National Academy of Sciences of the United States of America, 2011, 108, 3578 – 3583.