Aqueous Solution Properties of Bacterial Poly-γ-D-glutamate

A preliminary physico-chemical characterization of a bacterial poly-γ-glutamate sample (96% D-glutamic acid content), γ-D-PGA, in dilute aqueous solutions has been carried out by means of potentiometric, viscosimetric, infrared and chiroptical spectroscopic experiments. The biopolymer exhibits properties strikingly dependent on a number of parameters, mainly: polymer concentration, pH, ionic strength, and nature of added salt. In dilute solutions (polymer concentration around 0.1% w/V) and for pH > 7, γ-D-PGA chains assume elongated, stiff conformations while upon protonation (pH < 3) globular states would prevail. Addition of divalent counterions (Ca(II)) also leads to compact γ-D-PGA conformations.