Visible Absorption Spectrum of Chlorophyll a, b, and β-Carotene Molecules mixed in Monolayers at a Water–Air Interface

Abstract

IN a previous communication¹, visible absorption spectra of chlorophyll a or b in monolayers were compared with those taken in several organic solvents. The red and blue absorption peaks of the chlorophylls in monolayers at water–air and water–oil interfaces were found to be shifted towards longer wavelengths as compared with their solution peaks. This shift was postulated to be possibly due to a physical condensed state of the molecules in monomolecular layers, stressing the possibility that the chlorophylls in green plants in vivo are in films adsorbed at liquid interfaces. The results to be presented here not only confirm the above possibility, but also show that the three major pigments of the lamellar structure of the chloroplast could account for almost all the contribution in absorbance. The incorporation of β-carotene in mixed films of chlorophyll a and b became possible after it was found that β-carotene could be used in films².