Helix promotion in polypeptides by polyols

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Abstract
The helix content of [L-Lys(Me3)]n · ClO4, and [L-Lys(Me3)50, L-Ala50]n · ClO4 in water is markedly increased by the presence of sucrose and glycerol. For [L-Lys(Me3)]n · ClO4 the ellipticity at 222 nm changes from +2 × 103 deg cm2 dmole−1 in water to −44 × 103 in 50% glycerol. Sucrose does not promote helix formation in melittin at pH 7.2, but glycerol does. At pH 5.5 sucrose and, more so, glycerol, induce helix in melittin. Glycerol induces some helix in methylated melittin, but less than in melittin. The results are discussed in relation to excluded volume effects, ΔG of transfer of peptide and hydrophobic groups from water to mixed solvents, electrostatic effects, and preferential hydration. © 1993 John Wiley & Sons, Inc.