title: Antenna entropy in plant photosystems does not reduce the free energy for primary charge separation.
abstract: We have investigated the concept of the so-called "antenna entropy" of higher plant photosystems. Several interesting points emerge: 1. In the case of a photosystemwhich harbours an excited state, the “antenna entropy” is equivalent to the configurational (mixing) entropy of a thermodynamic canonical ensemble. The energy associated with this parameter has been calculated for a hypothetical isoenergetic photosystem, photosystem I and photosystem II, and comes out in the range of 3.5 - 8% of the photon energy considering 680 nm. 2. The “antenna entropy” seems to be a rather unique thermodynamic phenomenon, in as much as it does not modify the free energy available for primary photochemistry, as has been previously suggested. 3. It is underlined that this configurational (mixing) entropy, unlike heat dispersal in a thermal system, does not involve energy dilution. This points out an important difference between thermal and electronic energy dispersal.
authors.affiliation: Consiglio Nazionale delle Ricerche, Istituto di Biofisica, sede di Milano, via Giovanni Celoria 26, 20133 Milan, Italy; Dipartimento di Bioscienze, Università degli Studi di Milano, via Giovanni Celoria 26, 20133 Milan, Italy. Electronic address: robert.jennings@unimi.it.
authors.forename: Robert C
authors.initials: RC
authors.lastname: Jennings
authors.affiliation: Consiglio Nazionale delle Ricerche, Istituto di Biofisica, sede di Milano, via Giovanni Celoria 26, 20133 Milan, Italy; Dipartimento di Bioscienze, Università degli Studi di Milano, via Giovanni Celoria 26, 20133 Milan, Italy.
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Zucchelli
mesh_terms: D019277:Entropy; D055668:Photochemical Processes; D010788:Photosynthesis; D045331:Photosystem I Protein Complex / Q000737:chemistry* / Q000378:metabolism; D045332:Photosystem II Protein Complex / Q000737:chemistry* / Q000378:metabolism; D010944:Plants / Q000378:metabolism*
chemical_list: D045331:Photosystem I Protein Complex; D045332:Photosystem II Protein Complex
keywords: Antenna entropy; Configurational entropy; Energy spreading without dilution; Free energy; Plant photosystems