8 - Some Properties of Chlorophyll Monolayers and Crystalline Chlorophyll

Abstract

This chapter explores some of the properties of chlorophyll monolayers and crystalline chlorophyll. The concepts of chlorophyll aggregation in vivo have led many investigators to simulate the functional structure of the photosynthetic apparatus with close-packed monomolecular layers of chlorophyll molecules, possibly oriented in some way, and to study their physical and chemical properties. The state and properties of a monolayer are governed by the molecular structure of the material forming the layer, the temperature, the lateral pressure within the monolayer, and the composition of the sub-phase. Among the more important parameters for characterizing chlorophyll monolayers are the surface pressure vs. area (F-A) isotherms, surface potential, film viscosity, absorption spectrum, and fluorescence spectrum. The F-A isotherms of chlorophyll b monolayers are similar to those of Chl a, but occasionally, the Chl b monolayer isotherms reach a much higher plateau pressure. Compression and decompression of chlorophyll films spread from benzene indicate that benzene can remain trapped in the film and may be squeezed out after the first compression. It is, therefore, recommended that films spread from benzene should always be precompressed before the actual measurement is made.