The discovery and application of new types of helical peptidic foldamers have been an attractive endeavor to enable the development of new materials, catalysts and biological molecules. To maximize their application potential through structure-based design, it is imperative to control their helical handedness based on their molecular scaffold. Herein we first demonstrate the generalizability of the solid-state right-handed helical propensity of the 4₁₃-helix of L-α/L-sulfono-γ-AA peptides that as short as 11-mer, using the high-resolution X-ray single crystallography. The atomic level folding conformation of the foldamers was also elucidated by 2D NMR and circular dichroism under various conditions. Subsequently, we show that the helical handedness of this class of foldamer is controlled by the chirality of their chiral side chains, as demonstrated by the left-handed 4₁₃-helix comprising 1:1 D-α/D-sulfono-γ-AA peptide. In addition, a heterochiral coiled-coil-like structure was also revealed for the first time, unambiguously supporting the impact of chirality on their helical handedness. Our findings enable the structure-based design of unique folding biopolymers and materials with the exclusive handedness or the racemic form of the foldamers in the future.

The blue-green fungal pigment xylindein, extracted from species of the Chlorociboria genus, has a long history of use in the arts and is of growing interest to material scientists as a component in photovoltaic cells, textile dyes, and semiconductors. Although there is a plethora of fundamental research on xylindein, commercial scale-up of pigment production has not yet occurred, and the methodology for reliable batch culture growth is still evolving. To help aid in eventual commercial batch culturing and processing of xylindein, this research explored additional mechanical processing methods and solvent combinations. None of the physical processing steps (ultrasonication, centrifugation, and drying) produced significantly more xylindein than any other. However, all solvent combinations that contained benzyl alcohol extracted a visually significant amount of yellow color—a compound that was determined to be xylindein as well. Specifically, solvent combinations of dicholormethane (DCM) and benzyl alcohol (BA), methylethylketone (MEK) and BA, and tetrahydrofuran (THF) and MEK showed a significantly greater color shift toward the yellow spectrum. The results of this research, while unexpected, allow for control over the relative blue–yellow balance in xylindein pigment and for a reliable yellow pigment production from xylindein.