DEAE-Dextran Induced Increase of Membrane Permeability and Inhibition of Photosynthesis in Dunaliella parva

DEAE-Dextran, Dunaliella, Membrane Permeability, Photosynthesis, Polycations As a prerequisite for studies o f the intracellular distribution o f enzymes o f the glycerol cycle in Dunaliella parva, the effect o f the polycation DEAE-dextran on the permeability o f membranes for various endogenous compounds and on photosynthesis was investigated. DEAE-dextran induces an increase o f the permeability o f membranes for low and high m olecu­ lar weight compounds: U nder the influence o f DEAE-dextran low molecular compounds o f the cells diffuse more rapidly along the chemical concentration gradient into the medium iildi'i iilaCrOmolecules. Furthermore enzymes o f the cytoplasm do occur more rapidly in the outer medium than enzymes o f the chloroplasts. Photosynthetic C 0 2 fixation is inhibited already at low DEAE-dextran concentrations. This in­ direct inhibition is due to an unspecific efflux o f compounds o f low molecular weight, such as inorganic cations, metabolites or nucleotides. At high DEAE-dextran concentrations photo­ synthetic electron transport is directly affected at the level o f the thylakoids: Electron transport is inhibited between plastoquinone and photosystem I. The efflux characteristics o f marker enzymes o f DEAE-dextran treated D. parva cells show that under optimal experimental conditions this technique may be a suitable tool to get information about the intracellular distribution o f enzymes o f unknown localization in the alga.