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Poster Presentations

Faculty/Scientist Poster Presentation

FPP01

Negative Entropy and Photosynthesis

Harvey J.M. Hou* and Felesia Dukes

Department of Physical/Forensic Sciences, Alabama State University, Montgomery, Alabama 36104. *Email: hhou@alasu.edu

Entropy is a measure of energy dispersal at a specific temperature. The Second Law of Thermodynamics requires that the total entropy of an isolated system cannot decrease. Life is able to decrease or maintain its entropy by importing the negative entropy (Schrodinger 1944). The driving force of  a chemical reaction, the Gibbs free energy (DG), is composed of two parts, the enthalpy term (DH) and the negative entropy term (-TDS), as given by DG=DH-TDS. Photosynthesis can capture and convert the solar energy into chemical energy in higher plants, algae and cyanobacteria. We have previously reported the thermodynamic parameters of electron transfer in Synechocystis (Hou et al 2001, Hou et al 2006, Hou et al 2010). In this work we investigated and analyzed that thermodynamic behaviors of PS I mutants with two different quinone cofactors via engineering the menA, menB, and menG genes in Synechocystis sp. PCC 6803. The enthalpy and volume changes of the electron transfer in these mutants were obtained. The data showed that the electron transfer from the quinone acceptor to iron sulfur cluster step in the mutants are similar and entropy driven, which supports the critical roles of the proteins in photosynthetic process. As previously pointed out by Schrodinger that entropy is essential in life, we proposed that entropy may play an important role in photosynthesis (Figure 1). Following the primary electron transfer steps, entropy may be deposited into the photosynthetic reaction centers and consumed by the following photosynthetic reactions.

Figure 1. Entropy is important in life, which is able to capture the negative entropy from environment, and photosynthesis, which is able to store entropy in the photosynthetic membrane proteins by using solar energy

Schrödinger E (1944) What is Life – the Physical Aspect of the Living Cell. Cambridge University Press

Hou JM, Boichenko VA, Wang YC, Chitnis PR, Mauzerall D (2001) A photoacoustic study revealed a similarity to bacterial reaction centers on electron transfer in photosystem I in both volume change and entropy, Biochemistry, 40, 7109-7116

Hou HJM and Mauzerall D (2006) The A- to FA/B step in Synechocystis 6803 photosystem I is entropy driven, J. Am. Chem. Soc., 128, 1580-1586

Hou HJM and Sakmar TP (2010) Methodology of pulsed photoacoustics and its application to probe photosystems and receptors, Sensors, 10, 5642-5667