Conformational transitions in a Pro-Pro peptide on dissolution of single crystals |
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Authors: | Hemalatha Balaram B.V.Venkataram Prasad P. Balaram |
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Affiliation: | Molecular Biophysics Unit, Indian Institute of Science, Bangalore 560 012, India |
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Abstract: | The peptide t-butyloxycarbonyl-α-aminoisobutyryl-L-prolyl-L-prolyl-N-methylamide has been shown to adopt an extended structure in the solid state. The Pro-Pro segment occurs in the poly-proline II conformation. On dissolution of single crystals at ~ 233°K, a single species corresponding to the all peptide backbone is observed by 270 MHz 1H NMR. On warming, to isomerization about the Pro-Pro bond is facilitated. Both (ψ ~?50°) and (ψ ~ 130°) rotamers about the Pro3 CαCO bond are detectable in the Pro-Pro conformer, at low temperature. These observations demonstrate unambiguously the large differences in the solid state and solution conformations of a Pro-Pro sequence. |
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