Water-soluble polypeptides with elongated, charged side chains adopt ultrastable helical conformations

A study was conducted to demonstrate the design and synthesis of a water-soluble α-helical polypeptide electrolytes (αHPE), (poly(γ-(4-aminoethylthiopropoxyl)benzyl-L-glutamate) (PAOBLG-AET) with side chain charge situated 17 σ-bonds away from the peptide backbone. The ring-opening polymerizations (ROPs) of γ-(4-Allyloxylbenzyl)-L-glutamate N-carboxyanhydride (AOB-LGlu-NCA) initiated by hexamethyldisilazane (HMDS) yielded PAOBLGs with controlled molecular weights (MWs) and narrow molecular-weight distributions (MWDs) that were determined by gel permeation chromatography (GPC). The MW and MWD of PAOBLG₁₀ obtained by matrix-assisted laser desorption ionization mass spectrometry (MALDI-TOF MS agreed well with the values obtained by GPC. 1,5,7-triazabicyclo[4.4.0]dec-5-ene (TBD) was also used as a cocatalyst to accelerate the polymerization of AOB-L-Glu-NCA and synthesize higher MW PAOBLGs.