Alteration of water structure by peptide clusters revealed by neutron scattering in the small-angle region (below 1 Å(-1))

Solution scattering of neutrons and x-rays can provide direct information on local interactions of importance for biomolecular folding and structure. Here, neutron scattering experiments are combined with molecular-dynamics simulation to interpret the scattering signal of a series of dipeptides with varying degrees of hydrophobicity (GlyAla, GlyPro, and AlaPro) in concentrated aqueous solution (1:20 solute/water ratio) in which the peptides form large segregates (up to 50-60 amino acids). Two main results are found: 1), the shift to lower Q of the so-called water-ring peak (Q ≈ 2 Å(-1)) arises mainly from an overlap of water-peptide and peptide-peptide correlations in the region of 1.3