Abstract
Flower pigments, anthocyanins, are localized in vacuoles of colored epidermal cells. The concentration of pigments in the vacuole is ca. 10-2 M, and the anthocyanins are stabilized to develop beautiful colors by various molecular stackings. We are studying the mechanisms of in vivo flower color development. To investigate molecular stackings of anthocyanins in vacuoles, we measured circular dichroism (CD) of living petals and colored cells. The pigment of blue flower of Nemophila menziesii was a metalloanthocyanin composed with anthocyanins, co-pigments, and metal ions, nemophilin. The complex composed from Mg2+ showed purple color, but that of Mg2+ and Fe3+ showed blue color. Visible absorption spectra and CD of the fresh blue petal and colored protoplasts were measured. Both spectra were the same as the complex composed with Mg2+ and Fe3+. The CD showed the characteristic exciton-type negative Cotton effect in the visible region, indicating the chiral molecular stacking of anthocyanidin chromophores.
