Etude par dichroïsme circulaire de l'acide polyriboinosinique

Summary A systematic study of polyriboinosinic acid, using circular dichroism and U.V. absorption, as a function of ionic strength and temperature, shows the existence of three conformations. At low ionic strength (10 −3 M KF) poly I is a single stranded helix, with smaller stacking than poly A or poly C in similar conformation. At higher ionic strength (5.10 −2 M KF) poly I forms a multistranded structure. At high ionic strength (1 M KF) poly I exists as an aggregated form. Between these values of the ionic strength there is a mixture of these conformations. At low ionic strength samples which have been previously frozen, contain the aggregated conformation. Temperature and concentration of the polymer affect the range of ionic strength where the three conformations exist.