Membrane Potentials in Photosynthesis

Junge, Wolfgang

doi:10.1146/annurev.pp.28.060177.002443

Cited by 189 publications

(60 citation statements)

References 72 publications

(99 reference statements)

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“…The large electrochromic absorbance changes of carotenoids in chloroplast thylakoid membranes as well as in photosynthetic bacteria originate from an almost homogeneous shift of the absorption bands of the so-called field-indicating pigment molecules; the magnitude of the shift, a few Ångstroms, when measured in energy units is linearly proportional to the field strength [15,16]. Hence, the resulting light-induced electrochromic absorbance transient spectra are composed of the first derivatives of the absorbance bands of the participating electronic transitions.…”

Section: Resultsmentioning

confidence: 99%

“…Recently we used "in vivo Stark spectroscopy", flash-induced electrochromic absorbance transients, to identify the field-indicating pigment molecules [13] that exhibit large static dipoles [14][15][16]. We found that Phaeodactylum tricornutum cells exhibit strong electrochromic signals between 470 and 570 nm, and observed an intense band peaking at an unusually long wavelength position, at 564 nm, and a somewhat weaker band at around 510 nm, which were assigned to originate from two different Fx transitions [13].…”

Section: Introductionmentioning

confidence: 99%

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Functional heterogeneity of the fucoxanthins and fucoxanthin-chlorophyll proteins in diatom cells revealed by their electrochromic response and fluorescence and linear dichroism spectra

Szabó¹,

Premvardhan²,

Lepetit³

et al. 2010

Chemical Physics

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In this work, by analyzing the electrochromic transient spectra, the 77 K fluorescence emission and excitation, as well as the linear dichroism (LD) and circular dichroism (CD) spectra of low-light (LL) and high-light (HL) grown Phaeodactylum tricornutum cells, we show that the fucoxanthins (Fx) and fucoxanthin-chlorophyll proteins (FCP) exhibit marked functional heterogeneity. Electrochromic transients reveal that LL and HL cells differ substantially in their relative contents of two Fx forms, which absorb at 501 and 550 nm; they exhibit distinct LD signals but are CD silent. Fluorescence emission and excitation spectra at 77K reveal that although both forms efficiently transfer excitation energy to Chl a, the red form feeds somewhat more energy to photosystem II than to photosystem I. Similar data obtained in Cyclotella meneghiniana cells suggest that the heterogeneity of the FCP pool, with different Fx, forms plays a role in the regulation of energy utilization in FCP-containing organisms.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Functional heterogeneity of the fucoxanthins and fucoxanthin-chlorophyll proteins in diatom cells revealed by their electrochromic response and fluorescence and linear dichroism spectra

Szabó¹,

Premvardhan²,

Lepetit³

et al. 2010

Chemical Physics

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“…1, inset (31). The preference of the negatively charged ferricyanide anion to accept electrons from PSI rather than PSII under these conditions may reflect a difference in the electrical surface charge properties in the immediate vicinities of the two photosystems (11,12). On the other hand, DCIP photoreduction was affected less by the addition of cholesteryl hemisuccinate, with the maximum inhibition for the concentration range of cholesteryl hemisuccinate examined being 10%o.…”

Section: Methodsmentioning

confidence: 95%

Relationship between Thylakoid Membrane Fluidity and the Functioning of Pea Chloroplasts

Yamamoto¹,

Ford²,

Barber³

1981

Plant Physiol.

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Cholesteryl hemisuccinate has been incorporated into pea chloroplast thylakoids to investigate the relationship between fluidity and functioning of this membrane system. Levels of sterol which increased the apparent viscosity of the membrane, estimated by fluorescence polarization measurements using the lppboilic probe, 1,6-diphenyl-1,3,5 hexatriene, affected several photosynthetic processes. A decrease in fluidity was accompanied by an inhibition of dark limiting steps associated with electron transfer between photosystems two and one (PSII and PSI) as observed by the oxidation of the primary acceptor of PSII and by electron flow to ferricyanide. Also, treatment with cholesteryl hemisuccinate inhibited the saltinduced rise in chlorophyli fluorescence and changed the ionic conductivity of the membrane as judged by measurements of the decay of the lightinduced proton gradient. The results are discussed in terms of the effect of fluidity changes on the lateral dfffusion of plastoquinone and chlorophyli protein complexes in the lipid matrix of the membrane.There is increasing evidence that the fluidity of the chloroplast thylakoid membrane may play an important role in controlling the light reactions of photosynthesis (4, 24). The fluidity of biological membranes is determined mainly by the length and the degree of saturation of alkyl chains in fatty acids of the constituent lipids. Thylakoid membranes of higher plants contain galactolipids with highly unsaturated fatty acids and a small portion of phospho-and sulfolipids (1,5,15). Thus, a relatively low viscosity may be expected for the thylakoid membrane at room temperature (2). However, the membrane fluidity can be changed by varying the temperature of the chloroplast suspension and a great deal of evidence has accumulated suggesting effects of temperature on function ofchloroplasts, including electron transport, fluorescence changes, and other related reactions (6,9,13,14,16,19,20,22,29,30,33,34 thylakoid lipid phase on the functioning of various photosynthetic processes such as electron transport, ionic conductivity of the membrane, and cation-induced Chl fluorescence changes. Although this sterol occurs only at low levels in higher plants its effect on the physical properties of biological membranes in general is well documented. Thus, we have simply used this compound, added as the hemisuccinate, in an attempt to artificialy manipulate the fluidity of the thylakoid membrane. MATERIALS AND METHODSPea chloroplasts were prepared according to Nakatani and Barber (21), and then osmotically disrupted, washed once, and suspended in 0.33 M sorbitol and 1 mm Tris-HCl solution (pH 7.5). Cholesteryl hemisuccinate was added to thylakoid membranes by the method of Shinitzky et al. (28); 3.5% (w/w) of polyvinyl pyrrolidone (PVP, Mr 40,000, Sigma) was incubated with 25 mm Tris-HCl buffer (pH 7.5) for at least 30 min and cholesteryl hemisuccinate (Tris-salt), dissolved in a small amount of tetrahydrofuran, was added to give the required concentration. The cholestery...

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“…Electrochromic absorbance changes at 515 nm (DA 515 ) are used to monitor ion permeability of membranes (Junge, 1977;Witt, 1979;Peters et al, 1984) because of the effect on the electrical potential across the thylakoid membranes. In particular, the decay kinetics of the absorbance changes are proportional to the ion flux across the thylakoid membranes and are sensitive indicators of thylakoid membrane intactness (Peters et al, 1984), i.e.…”

Section: Electrochromic Shift and Membrane Conductancementioning

confidence: 99%

Increased Thermostability of Thylakoid Membranes in Isoprene-Emitting Leaves Probed with Three Biophysical Techniques

et al. 2011

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Three biophysical approaches were used to get insight into increased thermostability of thylakoid membranes in isoprene-emittingplants.Arabidopsis (Arabidopsis thaliana) plants genetically modified to make isoprene and Platanus orientalis leaves, in which isoprene emission was chemically inhibited, were used. First, in the circular dichroism spectrum the transition temperature of the main band at 694 nm was higher in the presence of isoprene, indicating that the heat stability of chiral macrodomains of chloroplast membranes, and specifically the stability of ordered arrays of light-harvesting complex IIphotosystem II in the stacked region of the thylakoid grana, was improved in the presence of isoprene. Second, the decay of electrochromic absorbance changes resulting from the electric field component of the proton motive force (DA 515 ) was evaluated following single-turnover saturating flashes. The decay of DA 515 was faster in the absence of isoprene when leaves of Arabidopsis and Platanus were exposed to high temperature, indicating that isoprene protects the thylakoid membranes against leakiness at elevated temperature. Finally, thermoluminescence measurements revealed that S 2 Q B 2 charge recombination was shifted to higher temperature in Arabidopsis and Platanus plants in the presence of isoprene, indicating higher activation energy for S 2 Q B 2 redox pair, which enables isoprene-emitting plants to perform efficient primary photochemistry of photosystem II even at higher temperatures. The data provide biophysical evidence that isoprene improves the integrity and functionality of the thylakoid membranes at high temperature. These results contribute to our understanding of isoprene mechanism of action in plant protection against environmental stresses.

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Membrane Potentials in Photosynthesis

Cited by 189 publications

References 72 publications

Functional heterogeneity of the fucoxanthins and fucoxanthin-chlorophyll proteins in diatom cells revealed by their electrochromic response and fluorescence and linear dichroism spectra

Functional heterogeneity of the fucoxanthins and fucoxanthin-chlorophyll proteins in diatom cells revealed by their electrochromic response and fluorescence and linear dichroism spectra

Relationship between Thylakoid Membrane Fluidity and the Functioning of Pea Chloroplasts

Increased Thermostability of Thylakoid Membranes in Isoprene-Emitting Leaves Probed with Three Biophysical Techniques

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