Fig. 1: Design of single α-helices stabilized by Gln side chain to main chain hydrogen bonds.
From: A glutamine-based single α-helix scaffold to target globular proteins
a Sequences and representation as helical projections of the peptides used to investigate cooperativity, where pink arrows indicate putative Gln side chain to main chain interactions. b Selected region of the 2D 1H13,C HSQC spectra of the peptides at 278 K, where the shaded area corresponds to that of peptide P3-7, which has the highest helical propensity. c Sequence and representation as helical projections of peptides (P3-7)2 and (P3-7)3, as in a. d Top: CD spectra of peptides (P3-7)2, (P3-7)3, and (P3-7)3 Ctrl at the indicated temperatures. Bottom: residue-specific helical propensities as obtained from the C’, Cα, NH, and HN NMR chemical shifts by using CheSPI65,66. e Left: CD spectra of peptide (P3-7)3 at temperatures between 278 K (blue) and 368 K (red) in steps of 10 K; the spectrum obtained at 278 K after refolding is shown in black. Right: superimposition of a selected region of the 13C-detected 2D CACO NMR spectra of peptide (P3-7)3 recorded at 278 K (blue) and 310 K (red), with indications as colored shades of amino acid-specific regions. f Thermal denaturation of peptides (P3-7)3 and (P3-7)3 Ctrl monitored by measuring the mean residue ellipticity at 222 nm.
