title: Concentration Threshold and Amplification Exhibited by a Helicene Oligomer during Helix-Dimer Formation: A Proposal on How a Cell Senses Concentration Changes of a Chemical.
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.
authors.affiliation: Department of Organic Chemistry, Graduate School of Pharmaceutical Sciences, Tohoku University, Aoba, Sendai, 980-8578 (Japan).
authors.forename: Yo
authors.initials: Y
authors.lastname: Kushida
authors.affiliation: Department of Organic Chemistry, Graduate School of Pharmaceutical Sciences, Tohoku University, Aoba, Sendai, 980-8578 (Japan).
authors.forename: Masanori
authors.initials: M
authors.lastname: Shigeno
authors.affiliation: Department of Organic Chemistry, Graduate School of Pharmaceutical Sciences, Tohoku University, Aoba, Sendai, 980-8578 (Japan). yama@m.tohoku.ac.jp.
authors.forename: Masahiko
authors.initials: M
authors.lastname: Yamaguchi
mesh_terms: D001669:Biochemical Phenomena; D002384:Catalysis; D008958:Models, Molecular; D011083:Polycyclic Compounds / Q000737:chemistry*; D012996:Solutions / Q000737:chemistry*; D013696:Temperature
chemical_list: D011083:Polycyclic Compounds; D012996:Solutions; C031660:helicenes
keywords: concentration amplification; concentration hysteresis; helical structures; self-catalysis; sulfonamides