Interaction of poly-L-lysine with photosynthetic reaction center for the Langmuir–Blodgett film preparation

Abstract

The interaction between poly-L-lysine (PLL) and photosynthetic reaction center (RC) from Rodopseudomonas viridis was studied with special interest for the Langmuir–Blodgett (LB) film preparation. PLL of low concentration (0.5mM) in the subphase of the LB trough as a counterion stabilized the protein at the air/water interface and enhanced the protein deposition efficiency onto the substrate. PLLs of various degree of polymerization (n=1, 5, 10, 15 and 20) were synthesized and the effect of each PLL was examined. Enhancement of the deposition of RC was observed using high n peptide (n=10, 15 and 20) but not using low n one (n=1 and 5). When PLL (n=1, 5, 10, 15 and 20) was added to the RC solution, the protein–protein association and the subsequent precipitation of RC occurred. Highly polymerized PLLs were effective on both RC deposition and RC precipitation suggesting that RCs spread at air/water interface were linked by PLL. The number of PLL molecules which were adsorbed on one RC molecule was 9.0 (±1.5) and 6.6 (±0.5) in the case of n=10 and 20 of PLL, respectively.