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Consistent helicities from CD and template t/c data for N-templated polyalanines: progress toward resolution of the alanine helicity problem.

Robert J Kennedy·Kwok-Yin Tsang·Daniel S Kemp
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Abstract

The helicity reporting parameters t/c and [theta](222) have been measured at 2, 25, and 60 degrees C in water for the solubilized polyalanine series Ac-Hel-A(n)-(t)LInp(2)K(4)W-NH(2) of length 4 < or = n < or = 14 that bears the helix-initiating and monitoring N-cap Ac-Hel and the spaced solubilizer (t)LInp(2)K(4)W-NH(2) as a C-cap. Correlation of t/c with length shows that the helical propensity for n < or = 6 is ca. 1.0, consistent with our early reports, but that a dramatic increase in temperature dependence and helical propensity occurs for n > or = 8. A model based on hydrogen-bonding cooperativity is proposed to explain this finding, and both t/c and [theta](222) are modeled successfully by length-dependent alanine propensities at 2 degrees C of 1.03 for n = 6, 1.15, for 7 < or = n < or = 9 and 1.26 for n > or = 10. The implications of these results for the energetics of helix formation by alanine-rich peptide sequences are discussed.

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AlanineAlgorithmsCircular DichroismModels, ChemicalOligopeptidesPeptidesProtein ConformationSolutionsTemplates, GeneticWaterJournal Article

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Robert J Kennedy, Kwok-Yin Tsang, Daniel S Kemp. 2002-02-13. Consistent helicities from CD and template t/c data for N-templated polyalanines: progress toward resolution of the alanine helicity problem.. https://doi.org/10.1021/ja016285c

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