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Circular dichroism reveals conformational distinctions between S and RS peptides
Comparative solution phase CD studies (Supplementary Fig. 2b) revealed that ACT-132577 each peptide had a characteristic spectrum showing strong (?) maxima at 207 and 222 nm. The ratios of the 207:222 nm intensities were 1.26 and 1.33 for S and RS peptides, respectively. It is well known that in α helices, intensities of the two (?) maxima at 206 and 222 nm are very close while in 310 helices the 222 nm transition has a reduced intensity with respect to the 207 nm intensity [20] and [21]. It appears that while both S and RS peptides have propensity for a helical fold, the preponderance of 310 helix may be higher in the RS than in the S peptide.
NMR studies indicate different structures for S and RS peptides
Fig. 1.
NMR measurements on S and RS peptides: (A) 1D proton NMR spectra of S and RS peptides (solvent: trifluoroethanol:H2O biggrin 20::70:25:5). (B) A section of NOESY spectrum showing NH–NH cross-peaks for S and RS peptides. Note the differences in the pattern of cross-peaks indicating that the two peptides have different structures.