Chlorophyll a auto-aggregation in water rich region

Visible absorption and fluorescence spectroscopy, togheter with circular dichroism were employed to investigate the equilibrating chlorophyll a species formed in solution at different water/acetonitrile content and different pigment concentrations. Changes in chlorophyll a auto-aggregation occurring in water containing acetonitrile in the range 0.1-33% (v/v) were observed and related to the bulk properties of the medium. A 713 nm absorbing species, occurring in solution for water concentrations exceeding 99% was characterized. The influence of the ionic strength of the solution was also subject of the present study, together with the time evolution of the different aggregates