title: Activation volumes of processes linked to the phototransformation of protochlorophyllide determined by fluorescence spectroscopy at high pressure.
abstract: The photochemical activity of NADPH:protochlorophyllide oxidoreductase (POR) was studied in etiolated wheat (Triticum aestivum, L., cult. MV17) leaf homogenates. The kinetics of the transformation of protochlorophyllide into chlorophyllide was detected by fluorescence intensity changes at 690 nm (formation of chlorophyllide) and 655 nm (decay of protochlorophyllide) at 20 degrees C, excited at 440 nm while the pressure was varied between 0.1 and 400 MPa. Both kinetics could be fitted by two exponentials and the reaction rates were pressure-dependent. A model was suggested based on the comparison of the two kinetics. Reaction rates of the processes occurring during the prototransformation were determined in function of pressure. The evaluation yielded the activation volume as 1.7 ml mol(-1), which corresponds with the formation of one H-bond/molecule.
authors.affiliation: Department of Plant Anatomy, Eötvös University, Pázmány P. 1/c, Budapest H-1117, Hungary.
authors.forename: Katalin
authors.initials: K
authors.lastname: Solymosi
authors.forename: László
authors.initials: L
authors.lastname: Smeller
authors.forename: Béla
authors.initials: B
authors.lastname: Böddi
authors.forename: Judit
authors.initials: J
authors.lastname: Fidy
mesh_terms: D007700:Kinetics; D010777:Photochemistry; D018515:Plant Leaves / Q000378:metabolism; D011312:Pressure; D011521:Protochlorophyllide / Q000378:metabolism*; D013050:Spectrometry, Fluorescence; D014908:Triticum
chemical_list: D011521:Protochlorophyllide