Effect of trehalose on the phase properties of hydrated and lyophilized dipalmitoylphosphatidylcholine multilayers

The structure and thermal behavior of hydrated and lyophilized dipalmitoylphosphatidylcholine (DPPC) multilayers in the presence of trehalose were investigated by differential scanning calorimetry and X-ray diffraction methods. Trehalose enters the aqueous space between hydrated bilayers and increases the interbilayer separation (from 0.36 to 1.37 nm in the different DPPC phases at 1 M trehalose). It does not affect the lipid chain packing and also the slow isothermal conversion at 4 degrees C of the metastable L beta' phase into the equilibrium crystalline Lc phase. Addition of trehalose leads to a slight upward shift (about 1 degrees C at 1 M trehalose) of the three phase transitions (sub-, pre-, and main transition) in fully hydrated DPPC while their other properties (enthalpy, excess specific heat, and transition width) remain unchanged. The effect of trehalose on the thermal behavior of DPPC multilayers freeze-dried from an initially completely hydrated state is qualitatively similar to that of water. These data support the "water replacement" hypothesis about trehalose action. It is suggested that trehalose prevents the formation of direct interbilayer hydrogen bonds in states of low hydration.     

2-(Phenylethyl)ammonium hydrogensquarate hemihydrate: crystal structure,solid-state IR-spectroscopic and theoretical characterization

The title compound, 2-(phenylethyl)ammonium hydrogensquarate hemihydrate, was synthesized and structurally and spectroscopically characterized by a single crystal X-ray diffraction and solid-state polarized IR spectroscopy of oriented colloids in a nematic host. The crystal structure consists of two crystallographically independent 2-(phenylethyl)ammonium cations, joined in a 2D hydrogen-bonded network with hydrogensquarate anions and solvent water molecules. Surprisingly, the crystallographically non-equivalent cations exhibit differing pseudo T and G trans configurations.     

Trapping of the quenched conformation associated with non-photochemical quenching of chlorophyll fluorescence at low temperature

The kinetics of non-photochemical quenching (NPQ) of chlorophyll fluorescence was studied in pea leaves at different temperatures between 5 and 25°C and during rapid jumps of the leaf temperature. At 5°C, NPQ relaxed very slowly in the dark and was sustained for up to 30 min. This was independent of the temperature at which quenching was induced. Upon raising the temperature to 25°C, the quenched state relaxed within 1 min, characteristic for qE, the energy-dependent component of NPQ. Measurements of the membrane permeability (ΔA₅₁₅) in dark-adapted and preilluminated leaves and NPQ in the presence of dithiothreitol strongly suggest that the effect of low temperature on NPQ was not because of limitation by the lumenal pH or the de-epoxidation state of the xanthophylls. These data are consistent with the notion that the transition from the quenched to the unquenched state and vice versa involves a structural reorganization in the photosynthetic apparatus. An eight-state reaction scheme for NPQ is proposed, extending the model of Horton and co-workers (FEBS Lett 579:4201–4206, 2005), and a hypothesis is put forward concerning the nature of conformational changes associated with qE. Electronic supplementary material The online version of this article (doi: ) contains supplementary material, which is available to authorized users.     

Effects of Cd2+ on the physiological state and photosynthetic activity of young barley plants

Barley plants (Hordeum vulgare L. cv. Obzor) were grown as a water culture in a climatic room. One part of them was subjected to a long-term Cd²⁺ stress - 12 d with 5.4×10^?5 M Cd. The Cd²⁺ stress inhibited formation of the photosynthetic apparatus and its capacity for ¹⁴C photoassimilation, decreased the content of soluble proteins, increased the dark respiration rate and the free amino acids content, disturbed plant water relations, as well as the distribution of ¹⁴C within primary photoproducts of the treated barley plants.

     

Effect of cytokinins on the photosynthetic apparatus in water-stressed and rehydrated bean plants

Effects of the cytokinins 6-benzylaminopurine (BAP) and N-2-chloro-4-pyridyl-N′-phenylurea (4-PU-30) on the photochemical activity, oxygen flash yields, and thermoluminescence in bean plants under a water stress were studied. The cytokinins increased the photochemical (Hill reaction) activity and thermoluminescence "B"-band in control as well as in stressed and rehydrated plants, while the oxygen flash yields were affected only in the stressed and rehydrated plants. This revised version was published online in June 2006 with corrections to the Cover Date.     

Dependence of trehalose protective action on the initial phase state of dipalmitoylphosphatidylcholine bilayers

Dipalmitoylphosphatidylcholine (DPPC) bilayers hydrated in the presence of trehalose were equilibrated at various temperatures (4, 20, and 60 degrees C) corresponding to the crystalline Lc, gel L beta', and liquid-crystalline L alpha phases, respectively, and then desiccated at these temperatures or freeze-dried at -80 degrees C to ca. DPPC dihydrate. The thermotropic behavior of the resulting DPPC/trehalose mixtures was investigated by differential scanning calorimetry and found to be dependent not only on the trehalose concentration but also on the phase state of the hydrated bilayers prior to their drying. Trehalose was most effective when the desiccation was carried out from the L alpha phase at 60 degrees C. In this case, one trehalose molecule per two DPPC molecules was sufficient to depress the melting temperature from values typical of DPPC dihydrate to 45 degrees C. Trehalose's influence decreased when dried from the L beta' phase and was significantly less pronounced when dried from the Lc phase. These data show that trehalose's protective influence depends on the initial phase state of the lipid bilayer and reaches its maximum in the liquid-crystalline state. The possible role of this effect in anhydrobiosis is pointed out.     

Short-term effect of elevated CO2 concentration and high irradiance on the antioxidant enzymes in bean plants

The effect of short-term exposure to elevated CO₂ concentration and high irradiance on the activity of superoxide dismutase (SOD), ascorbate peroxidase (APX), guaiacol peroxidases (GPX) and catalase (CAT), and on the extent of the lipid peroxidation was studied in bean (Phaseolus vulgaris L.) plants. Plants were exposed for 4 d (8 h a day) to irradiance of 100 (LI) or 1000 (HI) μmol m⁻² s⁻¹ at ambient (CA, 350 μmol mol⁻¹) or elevated (CE, 1300 μmol mol⁻¹) CO₂ concentration. Four-day exposure to CE increased the leaf dry mass in HI plants and RuBPC activity and chlorophyll content in LI plants. Total soluble protein content, leaf dry matter and RuBPC activity were higher in HI than in LI plants, although the HI and CE increased the contents of malonyldialdehyde and H₂O₂. Under CA, exposure to HI increased the activity of APX and decreased the total SOD activity. Under CE, HI treatment also activated APX and led to reduction of both, SOD and GPX, enzymes activities. CE considerably reduced the CAT activity at both irradiances, possibly due to suppressed rate of photorespiration under CE conditions.     

Synthesis,spectroscopic and structural elucidation of sympathomimetic amine,tyraminium dihydrogenphosphate

The synthesis, isolation, spectroscopic and structural elucidation of sympathomimetic amine, tyramine dihydrogenphosphate are of interest due to its biological activity and the establishing correlation between spectroscopic properties and structure. The complex approach for investigation included single crystal X-ray diffraction, new technique in linear-polarized IR-spectroscopy in solid state and quantum chemical calculations with a view to predict the electronic structure and vibrational data of interacting species in entitled compound, the correlation structure–spectroscopic properties as well as the influence of intermolecular interaction on IR-characteristic bands are carried out.     

Polarized spectroscopic elucidation of N-acetyl-l-cysteine, l-cysteine, l-cystine, l-ascorbic acid and a tool for their determination in solid mixtures

Method of linear polarized vibrational (both IR- and Raman) spectroscopy of oriented colloids in nematic host is applied on N-acetyl-l-cysteine, l-cysteine, l-cystine and l-ascorbic acid with a view to obtain experimental bands assignment and local structural elucidation in solid-state. Structural results are compared with available crystallographic data for all of the systems studied. Scopes and limitations of the polarized method are shown. Discussion on the correlation between polarized spectroscopic data and the space group type as well as the number of the molecules in the unit cell (Z) is performed. Compounds with monoclinic space group P2₁, containing Z = 1 (N-acetyl-l-cysteine) and 2 (l-cysteine and l-ascorbic acid) are elucidated. One of the rare for organic molecules, hexagonal P6₁22 space group and Z = 6 (l-cystine) is also elucidated. Experimental assignment of the characteristics frequencies is obtained, explaining the typical for the crystals Fermi-resonance, Fermy–Davydov and Davydov splitting effects. For first time in the literature we are reported the orientation of the solid-mixture in nematic host, using the trade product ACC (Hexal, Germany), containing mainly N-acetyl-l-cysteine and l-ascorbic acid. Quantitative IR-spectroscopic approach for determination of solid mixtures is presented as well. The intensity ratio between 1,716 cm^?1 (characteristic for N-acetyl-l-cysteine) and 990 cm^?1, (attributed N-acethyl-cysteine and vitamin C) is used. Linear regression analysis between content and the peak ratio data for ten solid-binary mixtures, leads to straight-line plot y = 1.08₂ (±0.04₉) + (?0.11₄ ± 0.01₁)x, where x = 1/X _i . Factor r of 0.9641 and a reliability of 98.85% are obtained. The analysis of ACC 200 (Hexal, Germany) show that the IR measurements leads to standard deviation of 0.010 and 0.011 at P about 0.0500 for the systems and a confidence of >98.77₁%.     

Plant Responses to Drought,Acclimation, and Stress Tolerance

At the whole plant level, the effect of stress is usually perceived as a decrease in photosynthesis and growth. That is why this review is focused mainly on the effect of drought on photosynthesis, its injury, and mechanisms of adaptation. The analysed literature shows that plants have evolved a number of adaptive mechanisms that allow the photochemical and biochemical systems to cope with negative changes in environment, including increased water deficit. In addition, the acquisition of tolerance to drought includes both phenotypic and genotypic changes. The approaches were made to identify those metabolic steps that are most sensitive to drought. Some studies also examined the mechanisms controlling gene expression and putative regulatory pathways.