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Concentration Threshold and Amplification Exhibited by a Helicene Oligomer during Helix-Dimer Formation: A Proposal
Yo Kushida1, Masanori Shigeno1, Masahiko Yamaguchi2
1Department of Organic Chemistry, Graduate School of Pharmaceutical Sciences, Tohoku University, Aoba, Sendai, 980-8578 (Japan).
Abstract:
Sulfonamidohelicene tetramer (M)-1 exhibits a concentration threshold and amplification phenomena in solution during helix-dimer formation from a random-coil. The (M)-tetramer is a random-coil below a threshold concentration, and the concentration of the helix-dimer is irreversibly amplified once the threshold concentration is exceeded. For example, a 15% increase in (M)-tetramer total concentration from 0.6 to 0.7 mM induces an 8-fold increase in the concentration of the helix-dimer, being 8:0.15=53-fold amplification, under temperature oscillation conditions between 47 and 49 °C. Experiments without oscillation also exhibit concentration amplification. The threshold and amplification phenomenon involves concentration hysteresis, being away from equilibrium, and self-catalysis. On the basis of this study, a proposal on how a biological cell senses concentration changes of a chemical substance is provided.
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