Helix–coil transition of poly(α,L‐glutamic acid) at an interface: Correlation with static and dynamic membrane properties

Abstract

SynopsisWhen adsorbed from an aqueous dilute solution at high pH into the pores of an inert cellulose acetate filter, poly(a,L-glutamic acid) remains strongly anchored to the pore walls. The existence of the helix-coil transition for the adsorbed polypeptide in a certain pH range is evidenced by static and dynamic membrane properties displayed by the "activated" filter, such as excess cation uptake, membrane potential, and hydraulic permeability. In particular, the variations of the hydrodynamic thickness present a sigmoidal shape characteristic of the helix-coil transition at the interface, a transition apparently less sharp than in solution.

Swelling and biocompatibility of sodium alginate/poly(γ‐glutamic acid) hydrogels

“…At acidic pH, the conformation of γ ‐PGA is α ‐helix which is more hydrophobic. At higher pH, the conformation of γ ‐PGA becomes random coil and is more hydrophilic, thus increasing the swelling ratio 44. Because the p K a of PGA is about 4.8, the swelling ratio increased further in higher pH due to charge repulsion.…”

Preparation and characterization of Poly(γ-glutamic acid) hydrogels as potential tissue engineering scaffolds

“…The -PGA has the helix conformation and the intermolecular interaction of hydrogen bond exists. The protonation/de-protonation of carboxyl groups can cause the formation or dissociation of inter-carboxyl hydrogen bonding [30] , which would facilitate the helix-coil transition and affect the conformational state of the polymer in aqueous [3133] . When the carboxyl groups are protonated, the inter-carboxyl hydrogen bonding would make the polymer chain more compact and less hydrated; once the carboxyl groups are deprotonated, the electro-repulsion forces between the negatively charged side groups would make the polymer chain less compact and highly hydrated with a random-coil conformation.…”

A polyelectrolyte brush theory

“…As the second step, one varies the position of the free end of a chain, p¡, while the conformation of the chain satisfies eq 4. dAF(pi,r¡(n)) dpi Pi = r,(0) (5) Thus, at equilibrium eq 5 (implying minimum free energy of system) will be satisfied subject to eq 4 (describing the conformation of the chains).…”