Abstract
Short distance interactions of chlorophyll
a with violaxanthin (Viol) were studied in monolayers at the air-water interface and in Langmuir-Blodgett films. The surface pressure–area (
π–
A) isotherms for Chl
a, Viol, and Chl
a–Viol mixtures clearly indicate the formation of two types of complexes between Chl
a and Viol with the stoichiometric ratios of 2:1 and 1:1. The complexes formed between Chl
a and Viol are reflected by the changes in molecular organization of Viol in monolayers. As the fluorescence properties of Chl
a molecules are known to be strongly dependent on changes in the degree of its aggregation, we followed the changes in fluorescence at different molar ratios. The molecular aggregations are noticed by the changes in band intensities at 683 and 730 nm in fluorescence emission spectra and an increase in the relative intensity of fluorescence short lifetime component of Chl
a. Chl
a–Viol interactions in monolayers were also made clear by the analysis of the shortwave region of the photoacoustic spectra explaining very efficient singlet-singlet excitation energy transfer from caratenoid to Chl
a. Further, Chl
a–Viol interactions and modeling of the formation of the complexes were also discussed based on the FTIR spectra of pure components as well as mixed systems.
