Improvement of Permeability of Low Molecular Weight Substances through Poly(L-leucine-co-γ-benzyl L-glutamate) by Addition of Hydrophilic Property

Abstract

A homogeneous membrane which is mainly conformed in an a-helical structure was obtained from a copolymer of L-leucine and γ-benzyl L-glutamate (copoly(LL-BLG)), an apparent mole ratio of 2: 1. The permeability of gases through this membrane, as can be expected from much more composition of L-leucine residue, was very large compared with poly(γ-benzyl L-glutamate) (PBLG). The copoly(LL-BLG) membrane is quite hydrophobic from the view point of oxygen permeability. In other words no effect of water to the oxygen permeability was found. Taking the advantage of the chemically inert isobutyl group of copoly(LL-BLG), only γ-benzyl L-glutamate residue was reacted into N-(3-hydroxypropy1)glutamine residue by 3-amino-1-propanol or r-glutamic acid residue by a mixed solution of 1 mol/l NaOH and methanol. The membranes thus obtained became highly water-swallen. Copoly(LL-HPG) membrane with N'-(3-hydroxypropyl)glutamine residue contains water about 230% and copoly(LL-GA) membrane with glutamic acid residue contains water about 690%. The oxygen permeability through these membranes was extremely high and similar to that through cornea.
The transport properties of NaCl, KCl, urea, creatinine and uric acid for copoly(LL-HPG)and copoly(LL-GA) membranes were determined. Except for uric acid, the permeability coefficients and diffusion coefficients depended on the water content. The small permeability of uric acid through copoly(LL-HPG) membrane was attributable to the extremely small diffusivity.