Polymer-Modified Single-Walled Carbon Nanotubes Affect Photosystem II Photochemistry, Intersystem Electron Transport Carriers and Photosystem I End Acceptors in Pea Plants

Single-walled carbon nanotubes (SWCNT) have recently been attracting the attention of plant biologists as a prospective tool for modulation of photosynthesis in higher plants. However, the exact mode of action of SWCNT on the photosynthetic electron transport chain remains unknown. In this work, we examined the effect of foliar application of polymer-grafted SWCNT on the donor side of photosystem II, the intersystem electron transfer chain and the acceptor side of photosystem I. Analysis of the induction curves of chlorophyll fluorescence via JIP test and construction of differential curves revealed that SWCNT concentrations up to 100 mg/L did not affect the photosynthetic electron transport chain. SWCNT concentration of 300 mg/L had no effect on the photosystem II donor side but provoked inactivation of photosystem II reaction centres and slowed down the reduction of the plastoquinone pool and the photosystem I end acceptors. Changes in the modulated reflection at 820 nm, too, indicated slower re-reduction of photosystem I reaction centres in SWCNT-treated leaves. We conclude that SWCNT are likely to be able to divert electrons from the photosynthetic electron transport chain at the level of photosystem I end acceptors and plastoquinone pool in vivo. Further research is needed to unequivocally prove if the observed effects are due to specific interaction between SWCNT and the photosynthetic apparatus

Surprising Structural and Functional Properties of Favism Erythrocytes Are Linked to Special Metabolic Regulation: A Cell Aging Study

Favism uniquely arises from a genetic defect of the Glucose-6 Phosphate Dehydrogenase (G6PD) enzyme and results in a severe reduction of erythrocytes’ (RBCs) reducing power that impairs the cells’ ability to respond to oxidative stresses. After exposure to fava beans or a few other drugs, the patients experience acute hemolytic anemia due to RBCs’ lysis both intra and extra-vascularly. In the present paper, we compared selected biochemical, biophysical, and ultra-morphological properties of normal RBCs and cells from favism patients measured along cellular aging. Along the aging path, the cells’ characteristics change, and their structural and functional properties degrade for both samples, but with different patterns and effectors that have been characterized in biophysical and biochemical terms. In particular, the analysis revealed distinct metabolic regulation in G6DP-deficient cells that determines important peculiarities in the cell properties during aging. Remarkably, the initial higher fragility and occurrence of structural/morphological alterations of favism cells develop, with longer aging times, into a stronger resistance to external stresses and higher general resilience. This surprisingly higher endurance against cell aging has been related to a special mechanism of metabolic regulation that permits lower energy consumption in environmental stress conditions. Our results provided a direct and coherent link between the RBCs’ metabolic regulation and the cell properties that would not have been possible to establish without an investigation performed during aging. The consequences of this new knowledge, in particular, can be discussed in a more general context, such as understanding the role of the present findings in determining the characteristics of the favism pathology as a whole

Fluorescence lifetime imaging microscopy of synechocystis WT cells — variation in photosynthetic performance of individual cells in various strains of sp. PCC 6803

The FLIM (fluorescence lifetime imaging microscopy) technique allows picosecond fluorescence measurements at the level of the individual cell. Using this technique we were able to observe heterogeneity of cyanobacterial cells in a culture grown under controlled conditions and we were able to resolve structural variations within individual cells. It can be concluded that on the one hand the inhomogeneous distribution of photosynthetic pigments within the cell leads to variation of the fluorescence intensity, whereas on the other hand it is impossible to detect variation in the relative amounts of photosystem I and II throughout the cell. Different Synechocystis sp. PCC 6803 strain lines were compared to each other and differences were observed in the average fluorescence lifetimes obtained for individual cells of the various cell lines. The differences can be traced back to variable efficiency of excitation energy transfer from the phycobilisome antenna to the photosystems. We could successfully demonstrate that there is heterogeneity inside individual cells, within individual cultures, and between various wild-type cell lines

Relations between photosynthetic performance and polyphenolics productivity of Artemisia alba Turra in in vitro tissue cultures

Establishing optimal growth conditions for secondary metabolites production in vitro is vital for the biotechnological development of medicinal plants. In the present work we investigate the relations between the supplementation of plant growth regulators (benzyl adenine and indole-3-butyric acid) to in vitro shoot cultures of the medicinal plant Artemisia alba Turra, the productivity of antioxidant polyphenolic compounds and the structural and functional characteristics of the photosynthetic apparatus. We assayed the structural characteristics of isolated thylakoid membranes from the aerial parts by means of circular dichroism spectroscopy and atomic force microscopy, and the photosynthetic performance by pulse amplitude fluorescence modulated imaging. Although a complex relationship between benzyl adenine and indole-3-butyric acid supplementation, the polyphenolic levels and the architecture and functionality of the photosynthetic thylakoid membranes was revealed, a clear correlation was established between the concentration of the produced polyphenolic compounds and the quantum yield of photosystem II. Our data demonstrate that there is an optimal combination of the applied plant growth regulators that triggers efficient photosynthesis and high phenolics production

Blood Plasma Thermograms Dataset Analysisby Means of InterCriteria and Correlation Analyses for the Case of Colorectal Cancer

The approaches of InterCriteria Analysis and Correlation Analysis are applied to a dataset of calorimetric and statistical parameters obtained from blood plasma proteome thermograms of colorectal cancer patients. The analysis was performed for four individual predefined subsets of calorimetric profiles. Specific interrelations between the studied criteria were identified that were found to differ among the different calorimetric subsets. For three of the subsets the enthalpy of the thermal profiles was in strong consonance with the excess heat capacity of the immunoglobulins assigned thermal transition. For the calorimetric subsets that differed most from the control healthy set a strong interrelation between the excess heat capacities of the main plasma proteins (albumin and immunoglobulins) was additionally evident. Our results demonstrate that these mathematical approaches can complement the analysis of calorimetric datasets generated for a variety of diseases

Effects of enhanced brassinosteroid perception on photosynthesis in Arabidopsis thaliana line BRIOE

The relation between brassinosteroid signalling and photosynthesis in A Arabidopsis thaliana is studied by comparing the photosynthetic performance of wild-type plants and BRIOE line with increased level of the brassinosteroid receptor BRI1 The data reveal that enhanced brassinosteroid perception does not influence the net photosynthetic rate but leads to lower stomatal conductance and transpiration rate. Furthermore, the results presented demonstrate that BRIOE plants are characterized by lower oxygen evolution yield and alterations of the energy coupling of photosystem II core complex. While the photochemistry of photosystem II in BRIDE is not modified, the photochemical efficiency of photosystem I is reduced

Structural integrity of Synechocystis sp. PCC 6803 phycobilisomes evaluated by means of differential scanning calorimetry

Phycobilisomes (PBSs) are supramolecular pigment-protein complexes that serve as light-harvesting antennae in cyanobacteria. They are built up by phycobiliproteins assembled into allophycocyanin core cylinders (ensuring the physical interaction with the photosystems) and phycocyanin rods (protruding from the cores and having light-harvesting function), the whole PBSs structure being maintained by linker proteins. PBSs play major role in light-harvesting optimization in cyanobacteria; therefore, the characterization of their structural integrity in intact cells is of great importance. The present study utilizes differential scanning calorimetry and spectroscopy techniques to explore for the first time, the thermodynamic stability of PBSs in intact Synechocystis sp. PCC 6803 cells and to probe its alteration as a result of mutations or under different growth conditions. As a first step, we characterize the thermodynamic behavior of intact and dismantled PBSs isolated from wild-type cells (having fully assembled PBSs) and from CK mutant cells (that lack phycocyanin rods and contain only allophycocyanin cores), and identified the thermal transitions of phycocyanin and allophycocyanin units in vitro. Next, we demonstrate that in intact cells PBSs exhibit sharp, high amplitude thermal transition at about 63 degrees C that strongly depends on the structural integrity of the PBSs supercomplex. Our findings implicate that calorimetry could offer a valuable approach for the assessment of the influence of variety of factors affecting the stability and structural organization of phycobilisomes in intact cyanobacterial cells

Seed Priming with Single-Walled Carbon Nanotubes Grafted with Pluronic P85 Preserves the Functional and Structural Characteristics of Pea Plants

The engineering of carbon nanotubes in the last decades resulted in a variety of applications in electronics, electrochemistry, and biomedicine. A number of reports also evidenced their valuable application in agriculture as plant growth regulators and nanocarriers. In this work, we explored the effect of seed priming with single-walled carbon nanotubes grafted with Pluronic P85 polymer (denoted P85-SWCNT) on Pisum sativum (var. RAN-1) seed germination, early stages of plant development, leaf anatomy, and photosynthetic efficiency. We evaluated the observed effects in relation to hydro- (control) and P85-primed seeds. Our data clearly revealed that seed priming with P85-SWCNT is safe for the plant since it does not impair the seed germination, plant development, leaf anatomy, biomass, and photosynthetic activity, and even increases the amount of photochemically active photosystem II centers in a concentration-dependent manner. Only 300 mg/L concentration exerts an adverse effect on those parameters. The P85 polymer, however, was found to exhibit a number of negative effects on plant growth (i.e., root length, leaf anatomy, biomass accumulation and photoprotection capability), most probably related to the unfavorable interaction of P85 unimers with plant membranes. Our findings substantiate the future exploration and exploitation of P85-SWCNT as nanocarriers of specific substances promoting not only plant growth at optimal conditions but also better plant performance under a variety of environmental stresses

Thermal stability and binding energetics of thymidylate synthase ThyX

International audienceThe bacterial thymidylate synthase ThyX is a multisubstrate flavoenzyme that takes part in the de novo synthesis of thymidylate in a variety of microorganisms. Herein we study the effect of FAD and dUMP binding on the thermal stability of wild type (WT) ThyX from the mesophilic Paramecium bursaria chlorella virus-1 (PBCV-1) and from the thermophilic bacterium Thermotoga maritima (TmThyX), and from two variants of TmThyX, Y91F and S88W, using differential scanning calorimetry. The energetics underlying these processes was characterized by isothermal titration calorimetry. The PBCV-1 protein is significantly less stable against the thermal challenge than the TmThyX WT. FAD exerted stabilizing effect greater for PBCV-1 than for TmThyX and for both mutants, whereas binding of dUMP to FAD-loaded proteins stabilized further only TmThyX. Different thermodynamic signatures describe the FAD binding to the WT ThyX proteins. While TmThyX binds FAD with a low μM binding affinity in a process characterized by a favorable entropy change, the assembly of PBCV-1 with FAD is governed by a large enthalpy change opposed by an unfavorable entropy change resulting in a relatively strong nM binding. An enthalpy-driven formation of a high affinity ternary ThyX/FAD/dUMP complex was observed only for TmThyX