Polymalic Acid Tritryptophan Copolymer Interacts with Lipid Membrane Resulting in Membrane Solubilization

Figure 6

Hypothetic process of membrane solubilization by P/WWW in three steps. (a) P/WWW molecules first bind to lipid membrane in a carpet-like mode with strong affinity of the tryptophan side chains to the lipid layer. However, the carboxylates of the copolymer interact unfavorably with the charged lipid head group of the outer bilayer surface. (b) Under physical agitation, the latent instability induces a reorganization of the primary P/WWW-lipid complex whereby the copolymer chain starts to move into positions where the carboxylate groups locate between the two layers of charged head groups thereby minimizing the free energy. (c) The transition into the new configuration involves the cooperation of several P/WWW chains and the physical agitation. Multiple P/WWW molecules assume a finally stable configuration in which several polymer molecules constitute belts around single lipid packages. The packages are detached from the original membrane in a process observed as the dissolution of the membrane.

(a)

(b)

(c)