| 1. |
- Ahmadova, Nigar, et al.
(författare)
-
Formation of tyrosine radicals in photosystem II under far-red illumination
- 2018
-
Ingår i: Photosynthesis Research. - : Springer Science and Business Media LLC. - 0166-8595 .- 1573-5079. ; 136:1, s. 93-106
-
Tidskriftsartikel (refereegranskat)abstract
- Photosystem II (PS II) contains two redox-active tyrosine residues on the donor side at symmetrical positions to the primary donor, P680. TyrZ, part of the water-oxidizing complex, is a preferential fast electron donor while TyrD is a slow auxiliary donor to P680 +. We used PS II membranes from spinach which were depleted of the water oxidation complex (Mn-depleted PS II) to study electron donation from both tyrosines by time-resolved EPR spectroscopy under visible and far-red continuous light and laser flash illumination. Our results show that under both illumination regimes, oxidation of TyrD occurs via equilibrium with TyrZ • at pH 4.7 and 6.3. At pH 8.5 direct TyrD oxidation by P680 + occurs in the majority of the PS II centers. Under continuous far-red light illumination these reactions were less effective but still possible. Different photochemical steps were considered to explain the far-red light-induced electron donation from tyrosines and localization of the primary electron hole (P680 +) on the ChlD1 in Mn-depleted PS II after the far-red light-induced charge separation at room temperature is suggested.
|
|
| 2. |
- Allakhverdiev, Suleyman I., et al.
(författare)
-
Vyacheslav (Slava) Klimov (1945-2017) : A scientist par excellence, a great human being, a friend, and a Renaissance man
- 2018
-
Ingår i: Photosynthesis Research. - : Springer. - 0166-8595 .- 1573-5079. ; 136:1, s. 1-16
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Vyacheslav Vasilevich (V.V.) Klimov (or Slava, as most of us called him) was born on January 12, 1945 and passed away on May 9, 2017. He began his scientific career at the Bach Institute of Biochemistry of the USSR Academy of Sciences (Akademy Nauk (AN) SSSR), Moscow, Russia, and then, he was associated with the Institute of Photosynthesis, Pushchino, Moscow Region, for about 50 years. He worked in the field of biochemistry and biophysics of photosynthesis. He is known for his studies on the molecular organization of photosystem II (PSII). He was an eminent scientist in the field of photobiology, a well-respected professor, and, above all, an outstanding researcher. Further, he was one of the founding members of the Institute of Photosynthesis in Pushchino, Russia. To most, Slava Klimov was a great human being. He was one of the pioneers of research on the understanding of the mechanism of light energy conversion and of water oxidation in photosynthesis. Slava had many collaborations all over the world, and he is (and will be) very much missed by the scientific community and friends in Russia as well as around the World. We present here a brief biography and some comments on his research in photosynthesis. We remember him as a friendly and enthusiastic person who had an unflagging curiosity and energy to conduct outstanding research in many aspects of photosynthesis, especially that related to PSII.
|
|
| 3. |
- Beckmann, Katrin, et al.
(författare)
-
On-line mass spectrometry : membrane inlet sampling
- 2009
-
Ingår i: Photosynthesis Research. - : Springer Netherlands. - 0166-8595 .- 1573-5079. ; 102:2-3, s. 511-522
-
Tidskriftsartikel (refereegranskat)abstract
- Significant insights into plant photosynthesis and respiration have been achieved using membrane inlet mass spectrometry (MIMS) for the analysis of stable isotope distribution of gases. The MIMS approach is based on using a gas permeable membrane to enable the entry of gas molecules into the mass spectrometer source. This is a simple yet durable approach for the analysis of volatile gases, particularly atmospheric gases. The MIMS technique strongly lends itself to the study of reaction flux where isotopic labeling is employed to differentiate two competing processes; i.e., O2 evolution versus O2 uptake reactions from PSII or terminal oxidase/rubisco reactions. Such investigations have been used for in vitro studies of whole leaves and isolated cells. The MIMS approach is also able to follow rates of isotopic exchange, which is useful for obtaining chemical exchange rates. These types of measurements have been employed for oxygen ligand exchange in PSII and to discern reaction rates of the carbonic anhydrase reactions. Recent developments have also engaged MIMS for online isotopic fractionation and for the study of reactions in inorganic systems that are capable of water splitting or H2 generation. The simplicity of the sampling approach coupled to the high sensitivity of modern instrumentation is a reason for the growing applicability of this technique for a range of problems in plant photosynthesis and respiration. This review offers some insights into the sampling approaches and the experiments that have been conducted with MIMS.
|
|
| 4. |
|
|
| 5. |
- Björn, Lars Olof, et al.
(författare)
-
A tribute to Per Halldal (1922-1986), a Norwegian photobiologist in Sweden.
- 2007
-
Ingår i: Photosynthesis Research. - : Springer Science and Business Media LLC. - 0166-8595 .- 1573-5079. ; 92:1, s. 7-11
-
Tidskriftsartikel (refereegranskat)abstract
- We present here a tribute to Per Halldal (February 2, 1922-March 26, 1986), a leader, an instrumentalist, an expert on phototaxis in algae, and one whom we remember, even after 20 years of his death, as a person who spread joy, enthusiasm and knowledge wherever he went.
|
|
| 6. |
- Björn, Lars Olof, et al.
(författare)
-
A viewpoint: Why chlorophyll a?
- 2009
-
Ingår i: Photosynthesis Research. - : Springer Science and Business Media LLC. - 0166-8595 .- 1573-5079. ; 99:2, s. 85-98
-
Forskningsöversikt (refereegranskat)abstract
- Chlorophyll a (Chl a) serves a dual role in oxygenic photosynthesis: in light harvesting as well as in converting energy of absorbed photons to chemical energy. No other Chl is as omnipresent in oxygenic photosynthesis as is Chl a, and this is particularly true if we include Chl a2, (=[8-vinyl]-Chl a), which occurs in Prochlorococcus, as a type of Chl a. One exception to this near universal pattern is Chl d, which is found in some cyanobacteria that live in filtered light that is enriched in wavelengths [700 nm. They trap the long wavelength electronic excitation, and convert it into chemical energy. In this Viewpoint, we have traced the possible reasons for the near ubiquity of Chl a for its use in the primary photochemistry of Photosystem II (PS II) that leads to water oxidation and of Photosystem I (PS I) that leads to ferredoxin reduction. Chl a appears to be unique and irreplaceable, particularly if global scale oxygenic photosynthesis is considered. Its uniqueness is determined by its physicochemical properties, but there is more. Other contributing factors include specially tailored protein environments, and functional compatibility with neighboring electron transporting cofactors. Thus, the same molecule, Chl a in vivo, is capable of generating a radical cation at ?1 V or higher (in PS II), a radical anion at -1 V or lower (in PS I), or of being completely redox silent (in antenna holochromes).
|
|
| 7. |
- Björn, Lars Olof, et al.
(författare)
-
Teaching about photosynthesis with simple equipment: analysis of light-induced changes in fluorescence and reflectance of plant leaves
- 2013
-
Ingår i: Photosynthesis Research. - : Springer Science and Business Media LLC. - 0166-8595 .- 1573-5079. ; 116:2-3, s. 349-353
-
Tidskriftsartikel (refereegranskat)abstract
- Solar energy absorbed by plants results in either reflection or absorption. The latter results in photosynthesis, fluorescence, or heat. Measurements of fluorescence changes have been used for monitoring processes associated with photosynthesis. A simple method to follow changes in leaf fluorescence and leaf reflectance associated with nonphotochemical quenching and light acclimation of leaves is described. The main equipment needed consists of a green-light emitting laser pointer, a digital camera, and a personal computer equipped with the camera acquisition software and the programs ImageJ and Excel. Otherwise, only commonly available cheap materials are required.
|
|
| 8. |
- Blomqvist, Lisa A., 1978, et al.
(författare)
-
Proteomic analysis of highly purified prolamellar bodies reveals their significance in chloroplast development
- 2008
-
Ingår i: Photosynthesis Research. - : Springer Science and Business Media LLC. - 0166-8595 .- 1573-5079. ; 96:1, s. 37-50
-
Tidskriftsartikel (refereegranskat)abstract
- The prolamellar body (PLB) proteome of dark-grown wheat leaves was characterized. PLBs are formed not only in etioplasts but also in chloroplasts in young developing leaves during the night, yet their function is not fully understood. Highly purified PLBs were prepared from 7-day-old dark-grown leaves and identified by their spectral properties as revealed by low-temperature fluorescence spectroscopy. The PLB preparation had no contamination of extra-plastidal proteins, and only two envelope proteins were found. The PLB proteome was analysed by a combination of 1-D SDS-PAGE and nano-LC FTICR MS. The identification of chlorophyll synthase in the PLB fraction is the first time this enzyme protein was found in extracts of dark-grown plants. This finding is in agreement with its previous localization to PLBs using activity studies. NADPH:protochlorophyllide oxidoreductase A (PORA), which catalyses the reduction of protochlorophyllide to chlorophyllide, dominates the proteome of PLBs. Besides the identification of the PORA protein, the PORB protein was identified for the first time in dark-grown wheat. Altogether 64 unique proteins, representing pigment biosynthesis, photosynthetic light reaction, Calvin cycle proteins, chaperones and protein synthesis, were identified. The in number of proteins' largest group was the one involved in photosynthetic light reactions. This fact strengthens the assumption that the PLB membranes are precursors to the thylakoids and used for the formation of the photosynthetic membranes during greening. The present work is important to enhance our understanding of the significance of PLBs in chloroplast development.
|
|
| 9. |
- Bossmann, B, et al.
(författare)
-
Screening of chlorina mutants of barley (Hordeum vulgare L.) with antibodies against light-harvesting proteins of PS I and PS II : Absence of specific antenna proteins
- 1997
-
Ingår i: Photosynthesis Research. - 0166-8595 .- 1573-5079. ; 52:2, s. 127-136
-
Tidskriftsartikel (refereegranskat)abstract
- Twenty-three chlorina (clo) mutants from the barley mutant collection of the Carlsberg Laboratory, Copenhagen, were tested for the presence of the four light-harvesting chlorophyll (Chl) a/b-binding proteins (LHC) of Photosystem I (Lhcal-4) and the PS II antenna proteins Lhcb1-3 (LHC II), Lhcb4-6 (CP29, CP26, CP24) and PsbS (CP22) using monospecific and monoclonal antibodies. Mutants allelic to barley mutant clo-f2, impaired in Chi b synthesis, provided evidence that Lhca4, Lhcb1 and Lhcb6 are unstable in the absence of Chi b, and the accumulation of Lhcb2, Lhcb3 and Lhcb4 is also impaired. Mutants at the locus chlorina-a (clo-a(117), clo-a(126) and clo-a(134)) lack or have only trace amounts of Lhca1, Lhca4, Lhcb1 and Lhcb3, whereas a mutant at the locus chlorina-b (clo-b(125)) had reduced amounts of all Lhca proteins. These two mutations could have an effect in protein import or assembly. Evidence is presented that Lhcb5 is the innermost LHC protein of PS II, and that Lhca1 and Lhca4, which have been supposed to be intimately associated in the LHCI-730 complex, can accumulate independently of each other. 77 K fluorescence emission spectra taken from leaves of clo-f2(101), clo-a(126) and clo-b(125) indicate that chlorophyll(s) emitting at 742 nm are coupled to the presence of Lhca4 that is bound to the reaction centre, and those emitting around 730 nm are located on Lhca1.
|
|
| 10. |
- Buapet, Pimchanok, et al.
(författare)
-
The role of O-2 as an electron acceptor alternative to CO2 in photosynthesis of the common marine angiosperm Zostera marina L.
- 2016
-
Ingår i: Photosynthesis Research. - : Springer Science and Business Media LLC. - 0166-8595 .- 1573-5079. ; 129:1, s. 59-69
-
Tidskriftsartikel (refereegranskat)abstract
- This study investigates the role of O-2 as an electron acceptor alternative to CO2 in photosynthesis of the common marine angiosperm Zostera marina L. Electron transport rates (ETRs) and non-photochemical quenching (NPQ) of Z. marina were measured under saturating irradiance in synthetic seawater containing 2.2 mM DIC and no DIC with different O-2 levels (air-equilibrated levels, 3 % of air equilibrium and restored air-equilibrated levels). Lowering O-2 did not affect ETR when DIC was provided, while it caused a decrease in ETR and an increase in NPQ in DIC-free media, indicating that O-2 acted as an alternative electron acceptor under low DIC. The ETR and NPQ as a function of irradiance were subsequently assessed in synthetic seawater containing (1) 2.2 mM DIC, air-equilibrated O-2; (2) saturating CO2, no O-2; and (3) no DIC, air-equilibrated O-2. These treatments were combined with glycolaldehyde pre-incubation. Glycolaldehyde caused a marked decrease in ETR in DIC-free medium, indicating significant electron flow supported by photorespiration. Combining glycolaldehyde with O-2 depletion completely suppressed ETR suggesting the operation of the Mehler reaction, a possibility supported by the photosynthesis-dependent superoxide production. However, no notable effect of suppressing the Mehler reaction on NPQ was observed. It is concluded that during DIC-limiting conditions, such as those frequently occurring in the habitats of Z. marina, captured light energy exceeds what is utilised for the assimilation of available carbon, and photorespiration is a major alternative electron acceptor, while the contribution of the Mehler reaction is minor.
|
|
