title: Coil leads to helix transition in polyadenylic acid induced by the binding of epinephrine, norepinephrine, and isoproterenol: circular dichroism study.
abstract: A circular dichroism spectropolarimetric study on the conformation of polyadenylic acid (poly A) in neutral solutions demonstrated a coil leads to helix transition induced by intercalative binding of critical amounts of epinephrine, norepinephrine, and isoproterenol relative to poly A. Theoretical treatment of the experimental data indicated a first-order kinetic transition in poly A. It was possible to measure transition rate constants of the epinephrine-poly A and norepinephrine-poly A systems and to calculate the activation energies. The results indicate a high level of temperature dependence of the rate constants. The effects can be reversed by increasing ionic strength, indicating the significance of the electrostatic interactions. The importance of the results is discussed in terms of the possible role of the catecholamines as control mechanisms for the poly A-regulated translation of the genetic code on mRNA.
mesh_terms: D002942:Circular Dichroism / Q000379:methods; D004837:Epinephrine / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D007545:Isoproterenol / Q000378:metabolism*; D007700:Kinetics; D008968:Molecular Conformation; D009638:Norepinephrine / Q000378:metabolism*; D011061:Poly A / Q000378:metabolism*; D013696:Temperature
chemical_list: D011061:Poly A; D007545:Isoproterenol; D009638:Norepinephrine; D004837:Epinephrine