Instability in the photosynthetic system and its relevance to biodevices

The photosynthetic apparatus is a naturally occurring energy conversion and energy transmission system. However, one of the greatest defects of an isolated system in vitro is its instability. Hence an adequate knowledge of stability is essential for the effective application of the working principles of the photosystem in making a biodevice. The instability of a system can be characterized with the help of thermodynamic parameters such as activation energy, frequency factor, entropy and free energy. These parameters can be obtained by analysing thermoluminescence (TL) glow peaks obtained from photosynthetic material. To study the instability of the system, TL glow curves were obtained from untreated chloroplast samples and those treated with a chemical modifying agent, 8-hydroxyquinoline (8-HQ). The above-mentioned parameters were obtained by using a mathematical model based on general order kinetics. Further studies in this direction would help in the design of a molecular electronic device such as a molecular photodiode modelled after the mechanism of photosynthesis.