[Structure of illexine I2 and its complexes with DNA]

Conformational peculiarities of illexine I2 both in the solution and in the complexes with DNA were studied by circular dichroism, UV-spectroscopy and spectrophotometric melting. IIlexine I2 is shown to have an extended left-handed helical conformation of poly-L-proline II type, that are stable in a wide range of experimental conditions. Upon interaction of illexine I2 with DNA, the parameters of conformation are somewhat distorted but the main peculiarities remain. The DNA double helix changes from B- to the divection of C-form at its interaction with illexine I2. The interaction of illexine I2 with DNA at low ionic strength is non-cooperative and is characterized by some specificity to A--T sequences of DNA. Illexine I2 strongly affects the DNA stability by increasing the melting temperature of DNA.