Preparation and Properties of Phospholipid-Modified Polypeptide

Abstract

Poly(sodium glutamate) (DP = 160) was modified by sheep brain l-α-phosphatidylethanolamine with about 65% substitution in side chains via the active ester method. The structure of the modified polypeptide was characterized by its IR and 1H NMR spectral data and elemental analysis. The π−A isotherms of the modified polypeptide at different temperatures and pH were measured. Reproducible Y-type deposition, with a deposition ratio of 0.9 Y-type Langmuir−Blodgett films (30 layers) of the modified polypeptide were also prepared, and lamellar structure, together with an average 32 Å thick monolayer was observed by transmission electron microscopy. The formation of β-structure but no α-helix structure for cast film of the modified polypeptide was observed by circular dichroism spectroscopy. A wide-angle X-ray diffraction pattern investigation for the cast film showed a small peak at 2θ = 5.7° and a big peak at 2θ = 20.1°, corresponding to d spacing of 15.5 and 4.4 Å, respectively. In addition, investigation of Na+ ion and K+ ion transport behavior for cast film of the modified polypeptide showed that Na+ ion permeating through the cast film was easier than K+ ion, and both Na+ ion and K+ ion permeated through the film easier under acidic conditions (pH 4) than that under neutral conditions (pH 7).

Facile synthesis of pH‐responsive glycopolypeptides with adjustable sugar density

“…However, the sugar density can only be adjusted by copolymerization with other monomers, because an incompletely functionalized homopolymer bears the remaining reactive groups. Another post‐polymerization strategy is the functionalization of poly(α, l ‐glutamic acid) (PGA) precursors with amines using amide coupling reactions . The great advantage of this approach is that the grafting density can be adjusted after the polymerization.…”