Karle, I. L. ; Flippen-Anderson, J. L. ; Uma, K. ; Balaram, P. (1989) Solvated helical backbones: X-ray diffraction study of Boc-Ala-Leu-Aib-Ala-Leu-Aib-OMe · H2O Biopolymers, 28 (3). pp. 773-781. ISSN 0006-3525
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Official URL: http://www3.interscience.wiley.com/journal/1075888...
Related URL: http://dx.doi.org/10.1002/bip.360280307
Abstract
A second example of insertion of a water molecule into the helical backbone of an apolar peptide is presented here and compared to a similar occurrence in a longer peptide with the same type of sequence of residues, i.e., Boc-Aib-(Ala-Leu-Aib)3-OMe. The backbone of the title compound assumes an approximate 310-helical form with three 4 → 1 hydrogen bonds. In the place of a fourth 4 →1 hydrogen bond, a water molecule is inserted between O(1) and N(4), and acts as a bridge by forming hydrogen bonds N(4) W(1) (2.95 Å) and W(1) O(1) (2.81Å). The water molecule participates in a third hydrogen bond with a neighboring peptide molecule, W(1) O(4) (2.91 Å). The insertion of the water molecule causes the apolar peptide to mimic an amphiphilic helix. Crystals grown from ethyl acetate/petroleum ether (reported here) or from methanol/water solution are in space group P212121 with a = 12.024(4) Å, b = 15.714(6) Å, c = 21.411(7) Å, Z = 4 and dcalc = 1.124 g/cm3 for C32H58N6O9 · H2O. The overall agreement factor R is 6.3% for 2707 reflections observed with intensities > 3σ(F) and the resolution is 0.90 Å.
Item Type: | Article |
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Source: | Copyright of this article belongs to John Wiley and Sons, Inc. |
ID Code: | 4602 |
Deposited On: | 18 Oct 2010 07:23 |
Last Modified: | 16 May 2016 15:13 |
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