Ergodicity, configurational entropy and free energy in pigment solutions and plant photosystems: influence of excited state lifetime.
We examine ergodicity and configurational entropy for a dilute pigment solution and for a suspension of plant photosystem particles in which both ground and excited state pigments are present. It is concluded that the pigment solution, due to the extreme brevity of the excited state lifetime, is non-ergodic and the configurational entropy approaches zero. Conversely, due to the rapid energy transfer among pigments, each photosystem is ergodic and the configurational entropy is positive. This decreases the free energy of the single photosystem pigment array by a small amount. On the other hand, the suspension of photosystems is non-ergodic and the configurational entropy approaches zero. The overall configurational entropy which, in principle, includes contributions from both the single excited photosystems and the suspension which contains excited photosystems, also approaches zero. Thus the configurational entropy upon photon absorption by either a pigment solution or a suspension of photosystem particles is approximately zero.
Consiglio Nazionale delle Ricerche, Istituto di Biofisica, sede di Milano, via Giovanni Celoria 26, 20133 Milano, Italy; Dipartimento di Bioscienze, Università degli Studi di Milano, via Giovanni Celoria 26, 20133 Milano, Italy. Electronic address: robert.jennings@unimi.it.
Robert C
RC
Jennings
Consiglio Nazionale delle Ricerche, Istituto di Biofisica, sede di Milano, via Giovanni Celoria 26, 20133 Milano, Italy; Dipartimento di Bioscienze, Università degli Studi di Milano, via Giovanni Celoria 26, 20133 Milano, Italy.
Giuseppe
G
Zucchelli
D019277:Entropy; D045322:Photosynthetic Reaction Center Complex Proteins / Q000737:chemistry* / Q000378:metabolism; D010860:Pigments, Biological / Q000737:chemistry*; D010944:Plants / Q000737:chemistry* / Q000378:metabolism; D011789:Quantum Theory; D012996:Solutions
D045322:Photosynthetic Reaction Center Complex Proteins; D010860:Pigments, Biological; D012996:Solutions
Configurational entropy; Nonergodic state; Photosynthesis; Photosystem