Aggregation studies in crystals of apolar helical peptides: Boc-Aib-Val-Ala-Leu-Aib-Val-Ala-Leu-Aib-OMe.
In the crystal, the backbone of Boc-(Aib-Val-Ala-Leu)2-Aib-OMe adopts a helical form with four alpha-type hydrogen bonds in the middle, flanked by 3(10)-type hydrogen bonds at either end. The helical molecules stack in columns with head-to-tail hydrogen bonds, either directly between NH and CO, or bridged by solvent molecules. The packing of the helices is parallel, even in space group P2(1). Cell parameters are a = 9.837(2) A, b = 15.565(3) A, c = 20.087(5) A, beta = 96.42(2) degrees, dcalc = 1.091 g/cm3 for C46H83N9O12.1.5H2O.0.67CH3OH. There appears to be some hydration of the backbone in this apolar helix.
Karle
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IL
Laboratory for the Structure of Matter, Naval Research Laboratory, Washington, D.C.
Flippen-Anderson
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JL
Uma
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Balaram
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D055598:Chemical Phenomena; D002621:Chemistry; D003460:Crystallization; D006860:Hydrogen Bonding; D008958:Models, Molecular; D009842:Oligopeptides / Q000138:chemical synthesis; D011487:Protein Conformation
D009842:Oligopeptides