A robust hybrid peptide crystal formed with weak hydrogen bonds

Karle, Isabella L. ; Venkateshwarlu, P. ; Ranganathan, S. (2006) A robust hybrid peptide crystal formed with weak hydrogen bonds Peptide Science, 84 (5). pp. 502-507.

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Official URL: http://onlinelibrary.wiley.com/doi/10.1002/bip.205...

Related URL: http://dx.doi.org/10.1002/bip.20535


In the course of our work relating to the design of a bihelical structure (I) from diphenic anhydride by tethering with cystine di-OMe, stable, hard, and rigid crystals, mp 215-218°C were isolated in low yields (?2%). The crystal structure established that it was a bis amide (II) arising from diphenic acid and cystine di-OMe [(II), C22H22N2O6S2 (a = 9.897 (1) Å, b = 12.210 (1) Å, c=18.192 (1) Å, sp. gr. P212121)]. An authentic sample of (II) was subsequently prepared in 47% yields by condensation of diphenic acid dichloride with cystine di-OMe. A most surprising feature of II was, despite its high density, rigidity, and hardness, it did not exhibit any normal hydrogen bonds. The nearest approximation to a "usual" hydrogen bond was the single NH···OC linkage that occurred between molecules along a twofold screw axis. In this linkage, N···O=3.265 Å and H···O=2.43 Å, values that are at least 10% longer than those usually observed in peptides. The rigidity of the crystals appears to depend upon many weak hydrogen bonds of the type CH···O, CH···π, CH···S, and NH···S working in concert. Even these attractions have separations that are at the high end of the range of previously observed values, although some of the weak hydrogen bonds have been rarely reported and have poorly defined ranges. The attractive effect of each of these weak bonds may be enhanced by the occurrence of a number of them in a parallel fashion like rungs in a ladder.

Item Type:Article
Source:Copyright of this article belongs to John Wiley and Sons.
Keywords:Crystal Structure; Disulfide Bonds; Lack of Strong Hydrogen Bonds; Weak Hydrogen Bonds in Enhancing Ensembles
ID Code:76840
Deposited On:07 Jan 2012 08:47
Last Modified:07 Jan 2012 08:47

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