Intermolecular association and molecular weight of aggregates of a monodisperse homohexapeptide, Nps‐[Glu(OBzl)]₆‐NHEt, in solution

Light scattering from the solutions of Nps‐[Glu(OBzl)] 6 ‐NHEt in dioxane or ethylene dichloride has been measured at different concentrations, and a critical concentration of intermolecular association is found to exist, which is equal to the critical concentration of β‐form formation. The Debye plot of light scattering leads to the molecular weight of aggregates at the critical concentration, which corresponds to an aggregation number 15 in dioxane and 53 in ethylene dichloride. In the latter solvent the aggregates further associate into a larger aggregate consisting of 330 molecules when the concentration is increased beyond the critical concentration. The content of β‐form, which is a measure of number of hydrogen bonds, is derived from the ir data previously obtained. The results on the modes of intermolecular association and hydrogen bonding lead to possible structures of aggregates formed by both hydrogen bonds and other nonbonding side‐chain interactions.