ENERGY TRANSFER FROM CHLOROPHYLL b TO CHLOROPHYLL a IN A HYDROPHOBIC MODEL SYSTEM

Abstract— Chlorophyll a and chlorophyll b purified by high-performance liquid chromatography (HPLC) were subsequently adsorbed on the surface of a pellicular reverse phase packing normally used in HPLC. The granule surface is reacted with octadecyl groups and furnishes an hydrophobic substrate for pigment adsorption. Reflectance spectra of chlorophyll a and chlorophyll b , each adsorbed at average spacings of about 11 nm² per molecule, had red region maxima at 664 and 643nm respectively. Fluorescence excitation spectra for 740nm emission from these surfaces peaked at about 420nm for chlorophyll a and 460nm for chlorophyll b. Adsorbed pigments excited at either of the two wave lengths had a single fluorescence emission peak at 683nm for chlorophyll a and at 664nm for chlorophyll b. A surface having both pigments adsorbed in approximately equal amounts with an overall average spacing of about 5.6nm² per molecule also had peaks at 420 and 460nm in the excitation spectrum. However, excitation of adsorbed molecules on this (latter) surface, at either 420 or 460nm, produced emission with the single chlorophyll a peak at 683nm. It is concluded that, under the conditions of our experiment, exciting adsorbed chlorophyll b contributes strongly to emission from adsorbed chlorophyll a.