Search results for "Photosystem"
showing 10 items of 103 documents
Single amino acids in the lumenal loop domain influence the stability of the major light-harvesting chlorophyll a/b complex.
2004
The major light-harvesting complex of photosystem II (LHCIIb) is one of the most abundant integral membrane proteins. It greatly enhances the efficiency of photosynthesis in green plants by binding a large number of accessory pigments that absorb light energy and conduct it toward the photosynthetic reaction centers. Most of these pigments are associated with the three transmembrane and one amphiphilic alpha helices of the protein. Less is known about the significance of the loop domains connecting the alpha helices for pigment binding. Therefore, we randomly exchanged single amino acids in the lumenal loop domain of the bacterially expressed apoprotein Lhcb1 and then reconstituted the muta…
Picosecond time-resolved study on the nature of high-energy-state quenching in isolated pea thylakoids different localization of zeaxanthin dependent…
1996
Abstract The influence of the transthylakoid proton gradient on the kinetics of picosecond fluorescence decay was examined using isolated pea thylakoids having high or low zeaxanthin contents. Fluorescence lifetime measurements were performed with open (Fo) and closed (Fm) PS II reaction centers. Zeaxanthin formation in membrane energized isolated thylakoids led to a marked decrease of the average fluorescence lifetime at both Fm and Fo. In contrast, when zeaxanthin synthesis was blocked by the inhibitor DTT, the fluorescence lifetime decrease was less pronounced in the Fm state and totally missing in the Fo state. Samples containing the uncoupler ammonium chloride did not exhinit any zeaxa…
Development of the photosynthetic apparatus during light-dependent greening of a mutant of Chlorella fusca.
1977
The formation of chlorophyll, cytochrome f, P-700, ribulose bisphosphate carboxylase as well as photosynthesis and Hill reaction activities were tested during the light-dependent greening process of the Chlorella fusca mutant G 10. Neither chlorophyll nor protochlorophyllide was detected in the darkgrown cells. When transferred to light the mutant cells developed chlorophyll and established its photosynthetic capacity after a short lag phase. In the in vivo absorption spectra a spectral shift of the red absorption peak position from 674 to 680 nm was indicated during the first 3 h of greening. Cytochrome f was already present in the dark-grown cells, but during the greening phase a threefol…
Acclimation Potential to High Irradiance of Two Cultivars of Watermelon
2000
The acclimation potential to high irradiance of two cultivars of watermelon, Reina de Corazones and Toro, calculated as the ratio of sun vs. shade activities of O2− and H2O2 scavenging enzymes and non-radiative energy dissipation, was similar. However, Reina de Corazones exhibited a higher capacity in absolute terms for photoprotection (harmless dissipation of absorbed light energy at PS 2 and ascorbate and O2− and H2O2 scavenging enzymes) suggesting a larger resistance of this cultivar to high irradiance. This could be seen as smaller decreases in fruit productivity and in lower oxidative injury as probed by malondialdehyde content in sun plants of Reina de Corazones than in Toro plants. A…
Quantum dots functionalised artificial peptides bioinspired to the D1 protein from the Photosystem II of Chlamydomonas reinhardtii for endocrine disr…
2021
Herein we describe the design and synthesis of novel artificial peptides mimicking the plastoquinone binding niche of the D1 protein from the green photosynthetic alga Chlamydomonas reinhardtii, also able to bind herbicides. In particular, molecular dynamics (MD) simulations were performed to model in silico the behaviour of three peptides, D1Pep70-H, D1Pep70-S264K and D1Pep70-S268C, as genetic variants with different affinity towards the photosynthetic herbicide atrazine. Then the photosynthetic peptides were functionalised with quantum dots for the development of a hybrid optosensor for the detection of atrazine, one of the most employed herbicides for weed control in agriculture as well …
Thylakoid Membrane Maturation and PSII Activation Are Linked in Greening Synechocystis sp. PCC 6803 Cells
2013
Abstract Thylakoid membranes are typical and essential features of both chloroplasts and cyanobacteria. While they are crucial for phototrophic growth of cyanobacterial cells, biogenesis of thylakoid membranes is not well understood yet. Dark-grown Synechocystis sp. PCC 6803 cells contain only rudimentary thylakoid membranes but still a relatively high amount of phycobilisomes, inactive photosystem II and active photosystem I centers. After shifting dark-grown Synechocystis sp. PCC 6803 cells into the light, “greening” of Synechocystis sp. PCC 6803 cells, i.e. thylakoid membrane formation and recovery of photosynthetic electron transport reactions, was monitored. Complete restoration of a t…
Acceleration of the through space S1 energy transfer rates in cofacial bisporphyrin bio-inspired models by virtue of substituents effect on the Först…
2011
The singlet k(ET) for cofacial β-octaalkylporphyrin/bis(meso-aryl)porphyrin dyads increases linearly with the gap between the donor-acceptor 0-0 fluorescence peaks at 77 K.
THE LIGHT-HARVESTING SYSTEM OF THE UNICELLULAR ALGA Mantoniella squamata (PRASINOPHYCEAE): EVIDENCE FOR THE LACK OF A PHOTOSYSTEM I-SPECIFIC ANTENNA …
1993
The light-harvesting complexes (LHC) were isolated from the unicellular alga Mantoniella squamata (Prasinophyceae) by sucrose-density centrifugation. Beside the major LHC (II), a photosystem I complex was obtained that could be dissociated into a photosystem I core complex and an associated LHC I. In contrast to other chlorophyll b-containing antennae, both LHC II as well as LHC I were observed to be identical with respect to the following features: the molecular weights, the isoelectric points and the retention behavior on anion-exchange chromatography of the apoproteins, the pigment content and the absorption and fluorescence spectra
Isolation and characterization of a photosystem I-associated antenna (LHC I) and a photosystem I—core complex from the chlorophyll c-containing alga …
1993
Abstract A photosystem (PS) I holocomplex was isolated from Pleurochloris meiringensis Vischer (Xanthophyceae) using sucrose density centrifugation. This complex exhibited a fluorescence emission maximum at 715 nm, which is in accordance with the long wavelength emission of whole cells. The complex was further dissociated into a core complex and a light-harvesting protein (LHC I). The core protein contains mainly Chl a and β-carotene, is 8.25 times enriched in P700 and has its main emission maximum at 715 nm. Therefore, the longest wavelength emission of P. meiringensis is due to the PS I core, which is in contrast to higher plants. The LHC I differs from LHC II with regard to its polypepti…
Identification of N- and C-terminal Amino Acids of Lhca1 and Lhca4 Required for Formation of the Heterodimeric Peripheral Photosystem I Antenna LHCI-…
2002
Apoproteins of higher plant light-harvesting complexes (LHC) share considerable amino acid sequence identity/similarity. Despite this fact, they occur in different oligomeric states (i.e., monomeric, dimeric, and trimeric). As a step toward understanding the underlying structure requirements for different oligomerization behavior, we analyzed whether amino acids at the N- and C-termini of Lhca1 and Lhca4 are involved in the formation of the heterodimeric LHCI-730. Using altered proteins produced by deletion or site-directed mutagenesis for reconstitution, we were able to identify amino acids required for the assembly of LHCI-730. At the N-terminus of Lhca1, W4 is involved in heterodimerizat…