A tendril perversion in a helical oligomer: trapping and characterizing a mobile screw-sense reversal

Abstract

Inducing opposite screw senses at the two ends of a helix traps a helix reversal, allowing it to be characterised spectroscopically.

Ambidextrous α,γ‐Hybrid Peptide Foldamers

“…This type of opposite screw sense is a subject of interest, and the co‐existence of left‐ and right‐handed helical screw sense is rather unusual in peptide foldamers. Recently, Clayden and colleagues have demonstrated the tendril perversion at molecular level by introducing amino acids opposite chirality at the N ‐ and C ‐terminus of a helix composed of achiralAib oligomers . The crystal structure analysis of P1 reveals three interesting features; the two N ‐t erm inus residues adopted a left‐handed helix screw sense, while the middle five residues adopted a right‐handed helix screw sense, and finally the C‐terminal Adb ester adopted a left‐handed conformation with reversal of helix directionality.…”

“…Interestingly, Adb4 NH is not participating in the canonical H‐bonding, and this type of non H‐bonding partners have been observed at the junction of left‐ and right‐handed helical fusion . The right‐handed helix observed from the residues Aib3 to Aib7 is stabilized by 12‐membered H‐bonds (12‐helix) between the residues i and i+3 , which is the most stable helix conformation observed in the α,γ‐hybrid peptides composed of γ 4 ‐amino acids .…”

A Temperature‐Driven, Reversible, Helical‐Handedness Inversion in Peptaibol Analogues Tuned by the C‐Terminal Capping Moiety

“…Considering the short peptide length, a temperature‐dependent total reversal of screw sense can be hypothesized, although we cannot rule out the possibility of an incomplete screw‐sense inversion, involving only a portion of the sequence. In this context, a recent paper showed that screw‐sense inversions could be accommodated in the middle of a helical peptide chain with ambivalent chirality …”

Sequence Engineering to Control the Helix Handedness of Peptide Foldamers

“…Interestingly,t he uniform helix handedness of Aib-based sequences can be perturbed by compellingt he amide oligomer to adopt ar ight-handed conformation at one end and al efthandedc onformation at the other. [45] This leads to the local inversion of the screw sense. The observed reversal of the handedness is not localizeda taspecific locationb ut migrates acrossanumber of molecules in solution.…”

“…Interestingly, the uniform helix handedness of Aib‐based sequences can be perturbed by compelling the amide oligomer to adopt a right‐handed conformation at one end and a left‐handed conformation at the other . This leads to the local inversion of the screw sense.…”