We have prepared a polyampholyte (P(SA)₉₁) composed of anionic sodium 2-acrylamido-2-methylpropanesulfonate (AMPS, S) and cationic 3-acrylamidopropyl trimethylammonium chloride (APTAC, A) via reversible addition-fragmentation chain transfer (RAFT) radical polymerization. The subscript in P(SA)₉₁ indicates degree of polymerization (DP). P(SA)₉₁ can dissolve in pure water to form small inter-polymer aggregates. In aqueous solutions of NaCl, P(SA)₉₁ can dissolve in the unimer state. When protein and polyelectrolytes were mixed in phosphate buffered saline (PBS), the hydrodynamic radius (R_h) and light-scattering intensity (LSI) increased. There was no interaction between P(SA)₉₁ and protein, because corresponding increases could not be observed. Furthermore, AMPS was polymerized using P(SA)₉₁ macro-chain transfer agent (CTA) to prepare an anionic diblock copolymer (P(SA)₉₁S₆₇). APTAC was also polymerized using P(SA)₉₁ macro-CTA to prepare a cationic diblock copolymer (P(SA)₉₁A₈₈). The DP values were estimated with a quantitative ¹³C NMR technique. Charge neutralized mixture of aqueous solutions of P(SA)₉₁S₆₇ and P(SA)₉₁A₈₈ formed water-soluble polyion complex (PIC) micelles comprising a PIC core and P(SA)₉₁ shells (Figure 1). Interactions between the PIC micelles and protein in PBS were evaluated by changing R_h and LSI. Increases in R_h and LSI cannot be observed for the mixture of PIC micelle and protein in PBS. This observation suggests that there is no interaction between the PIC micelles and proteins, because the surface of the PIC micelles was covered with polyampholyte shells.

Dr. Shin Yusa

Associate Professor, University of Hyogo

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