The finding that short alanine peptides possess a high fraction of polyproline II (PII) structure (Phi=-75 degrees, Psi=+145 degrees ) at low temperature has broad implications for unfolded states of proteins. An important question concerns whether or not this structure is locally determined or cooperative. We have monitored the conformation of alanine in a… (More)
Fig. 1. CD spectroscopy of the peptides of this study. (A) Far-UV CD spectra of GGAGG. (B) The transition curve of GGAGG from CD 215 nm absorbance. The fit curve is shown in red. (C) Far-UV CD spectra of GGAAGG. (D) Far-UV CD spectra of GGAAAGG. The Insets in A, C, and D show the difference spectra between 10°C and 90°C.