Very few examples of reversible transitions between a 3_(10)-helix (in solvents of low polarity, particularly at low temperatures) and an α-helix (in solvents of low polarity at high temperatures or, better, in polar solvents) have been already published, namely for N~α-acetylated Aib- and L-(αMe)Val- rich co-oligopeptides of different main-chain length (from an hexapeptide ester to a pentadecapeptide amide) [1-3]. X-Ray diffraction analyses of crystals of two peptides grown from solvent mixtures of low polarity confirmed the overwhelming population of 3_(10)-helical molecules in those environments.
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