title: The effects of cation-induced and pH-induced membrane stacking on chlorophyll fluorescence decay kinetics.
abstract: We have compared the effects of thylakoid membrane appression by electrostatic screening and by charge neutralization on the room-temperature chlorophyll fluorescence decay kinetics of broken spinach chloroplasts. Monovalent and divalent metal cations induce both a structural differentiation of thylakoid membranes and a lateral segregation of pigment-protein complexes. These phenomena have distinct effects on the F0- and Fmax-level chlorophyll fluorescence decay kinetics at different levels of added cation. We further find specific cation effects, particularly on a 1-2 ns decay component at the Fmax fluorescence level, that are proposed to be related to the effectiveness of electrostatic screening as determined by the hydrated metal ionic radius. Distinct pH-induced effects on chlorophyll fluorescence decay kinetics are associated with the alternative mechanism of electrostatic neutralization to induce membrane stacking. These observations are used to construct a model of chlorophyll fluorescence emission that accounts for the variable kinetics and multiexponential character of the fluorescence decay upon membrane appression.
mesh_terms: D001464:Barium / Q000494:pharmacology; D002118:Calcium / Q000494:pharmacology; D002412:Cations / Q000494:pharmacology*; D002734:Chlorophyll / Q000378:metabolism*; D002736:Chloroplasts / Q000187:drug effects / Q000378:metabolism* / Q000648:ultrastructure; D005453:Fluorescence; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D008094:Lithium / Q000494:pharmacology; D008274:Magnesium / Q000494:pharmacology; D010944:Plants / Q000378:metabolism; D011188:Potassium / Q000494:pharmacology; D012964:Sodium / Q000494:pharmacology
chemical_list: D002412:Cations; D002734:Chlorophyll; D001464:Barium; D008094:Lithium; D012964:Sodium; D008274:Magnesium; D011188:Potassium; D002118:Calcium