Conformation of poly-l-glutamate is independent of ionic strength

CD and UV resonance Raman measurements surprisingly find that the charge screening of even 2 M concentrations of NaCl and KCl does not alter the unfolded PPII and 2.51-helix conformations of poly-l-glutamate. These salts appear to be excluded from the region between the side chain charges and the peptide backbone. Furthermore, no direct ion pairing occurs between these salts and the side chain carboxylates.

Graphic abstractHighlights► Poly-l-glutamate adopts unfolded PPII and 2.51-helix conformations in pure water. ► Charge screening of 2 M salts does not alter the conformation of poly-l-glutamate. ► Salts are excluded from the region between side chain charges and peptide backbone. ► No direct ion pairing occurs between salts and the side chain carboxylates.