The urea-dipeptides show stronger H-bonding propensity to nucleate β-sheetlike assembly than natural sequence

In this article, we report the distinct solution behavior of a set of urea-dipeptides to that of natural sequence. The urea-dipeptides adopt beta-folding conformations and form into beta-sheetlike assembly in chloroform. Most surprisedly, the urea-dipeptides tend to form interpeptide H-bonding interactions even at a concentration of as low as 0 1 mM, while the natural sequence shows H-bonding propensity at a concentration of about 7 mM, indicating that the urea-dipeptides Show Much stronger H-bonding propensity to nucleate formation of beta-sheetlike assembly than the natural sequence CD spectra reveal that the investigated urea-dipeptides have two negative CD bands, respectively, around 217 nm and 224 nm, supporting the beta-folding conformations and in turn formation of beta-sheetlike assembly. The beta-sheetlike assembly is also confirmed by the XRD reflections, which give two typical d-spacings of 12 7 and 4 8 angstrom, respectively, corresponding to stacking periodicity of the beta-sheets and the spacing between peptide backbones running orthogonal to the beta-sheet axis. (C) 2009 Elsevier Ltd All rights reserved