Interaction between an Anionic Amphiphilic Sequential Polypeptide and Anionic Bilayer Membrane

Abstract

ABSTRACT:The interaction between an anionic amphiphilic sequential polypeptide and an anionic bilayer membrane composed of sodium dilaurylphosphate (DLPNa) was investigated and compared with hydrophobic polypeptide-DLPNa bilayer membrane and anionic polypeptide-DLPNa bilayer membrane interactions. A hydrophobic polypeptide, poly(y-methyl L-glutamate) (PMG, M,=4400), was incorporated into the DLPNa bilayer membrane due to their hydrophobic interaction. The incorporation of PMG, however, did not effectively increase sodium ion permeability across the DLPNa bilayer membrane. There was no appreciable interaction between an anionic polypeptide, poly(L-glutamic acid) (PGA, M,=9200), and anionic DLPNa bilayer membrane because of Coulombic repulsion. On the other hand, an anionic amphiphilic sequential polypeptide, poly(y-methyl L-glutamate-co-L-glutamic acid) (am.-MG/GA), of molecular weight 4300 whose a-helix was anionic on one face consisting of L-glutamic acid and hydrophobic on the opposite face comprising of y-methyl L-glutamate was easily incorporated into the anionic DLPNa membrane and remarkably increased sodium ion permeability based on a transmembrane bundle consisting of amphiphilic helical rods. It was shown, moreover, that lithium ion apparently decreased the sodium ion permeation through the DLPNa bilayer membrane containing where MG and GA denoted 1 1-methyl Lglutamate and L-glutamic acid residue, respectively. A solid condensed monolayer of poly-(y-methyl L-glutamate) (PMG) at an airwater interface was first formed. The PMG side chains hydrated in the aqueous phase were selectively saponified, keeping the remaining side chains oriented away from the aqueous phase unreacted (Figure 1). As a result, the * To whom correspondence should be addressed.

Photoinduced Structural and Functional Changes of an Azobenzene Containing Amphiphilic Sequential Polypeptide

“…We have already reported that several amphiphilic sequential polypeptides associate to form high-order micellar aggregates in aqueous solution4 and transmembrane bundles in bilayer membranes. 5,6 Here we demonstrate a photoinduced structural control of aggregates composed of photoresponsive amphiphilic sequential polypeptides, am aqueous solution containing 0.1 M KC1 at pH 6.9 (-• -), and a DPPC vesicle (-).…”

“…In a previous study, we reported a preparation of an amphiphilic sequential polypeptide by a monolayer reaction method4 and a bundle arrangement of the polypeptides in bilayer membranes. [5][6][7] The polypeptides formed an amphiphilic a-helix that is hydrophilic on one face (which consists of L-glutamic acid side chains) and hydrophobic on the opposite face (which comprises '/-methyl L-glutamate side chains). The amphiphilic a-helices were incorporated into the bilayer membrane to form the transmembrane bundle with a hydrophilic inner pore surrounded by hydrophilic Lglutamic acid side chains and a hydrophobic exterior, composed of hydrophobic /-methyl L-glutamate, in contact with the hydrocarbon region of the membrane.…”

Photocontrol of Molecular Orientation of a Photoresponsive Amphiphilic α-Helix in a Lipid Monolayer

“…The polypeptides formed amphiphilic α-helices that are hydrophilic on one face (which consists of l -glutamic acid side chains) and hydrophobic on the opposite face (which comprised γ-methyl l -glutamate side chains). The amphiphilic α-helices were incorporated into a vesicular membrane and provided an ion permeable pore through the membrane. − Furthermore, we prepared a photoresponsive amphiphilic sequential polypeptide composed of two amphiphilic α-helices joined by azobenzene (am.-MAzoM, Scheme ) . The am.-MAzoM was also incorporated into the vesicular membrane and formed ionic pores in the dark.…”

“…The amphiphilic R-helices were incorporated into a vesicular membrane and provided an ion permeable pore through the membrane. [8][9][10] Furthermore, we prepared a photo-responsive amphiphilic sequential polypeptide composed of two amphiphilic R-helices joined by azobenzene (am.-MAzoM, Scheme 1). 11 The am.-MAzoM was also incorporated into the vesicular membrane and formed ionic pores in the dark.…”