Nano-Anatase Relieves the Inhibition of Electron Transport Caused by Linolenic Acid in Chloroplasts of Spinach

Linolenic acid is an inhibitor of electron transport in chloroplasts of higher plants. It has obvious effects on the structure and function of chloroplasts. In the present paper, we investigated the nano-anatase relieving the inhibition of photoreduction activity and oxygen evolution caused by linolenic acid in spinach chloroplasts. The results showed that linolenic acid in various concentrations could obviously reduce the whole chain electron transport and the photoreduction activity of two photosystems, especially on the oxidative reside and reduce reside of photosystem II (PS II). After adding nano-anatase to chloroplasts treated by linolenic acid, the whole chain electron transport rate, the photoreduction activity of two photosystems, and the oxygen evolution rate were increased significantly, indicating that nano-anatase could obviously decrease the inhibition of linolenic acid on the electron transport, photoreduction activity, and oxygen evolution of spinach chloroplasts.     

Effects of Nanoanatase TiO2 on Photosynthesis of Spinach Chloroplasts Under Different Light Illumination

With a photocatalyzed characteristic, nanoanatase TiO₂ under light could cause an oxidation–reduction reaction. Our studies had proved that nano-TiO₂ could promote photosynthesis and greatly improve spinach growth. However, the mechanism of nano-TiO₂ on promoting conversion from light energy to electron energy and from electron energy to active chemistry energy remains largely unclear. In this study, we report that the electron transfer, oxygen evolution, and photophosphorylation of chloroplast (Chl) from nanoanatase-TiO₂-treated spinach were greatly increased under visible light and ultraviolet light illumination. It was demonstrated that nanoanatase TiO₂ could greatly improve whole chain electron transport, photoreduction activity of photosystem II, O₂-evolving and photophosphorylation activity of spinach Chl not only under visible light, but also energy-enriched electron from nanoanatase TiO₂, which entered Chl under ultraviolet light and was transferred in photosynthetic electron transport chain and made NADP⁺ be reduced into NADPH, and coupled to photophosphorylation and made electron energy be transformed to ATP. Moreover, nanoanatase h⁺, which photogenerated electron holes, captured an electron from water, which accelerated water photolysis and O₂ evolution.     

Rubisco Activase mRNA Expression in Spinach: Modulation by Nanoanatase Treatment

Characterized by a photocatalysis property, nanoanatase is closely related to the photosynthesis of spinach. It could not only improve light absorbance, transformation from light energy to electron energy, and active chemical energy, but also promote carbon dioxide (CO₂) assimilation of spinach. However, the molecular mechanism of carbon reaction promoted by nanoanatase remains largely unclear. In this study, we report that the amounts of Rubisco activase (rca) mRNA in the nanoanatase-treated spinach were increased by about 51%, whereas bulk-TiO₂ treatment produced an increase of only 5%. Accordingly, the protein level of Rubisco activase from the nanoanatase-treated spinach was increased by 42% compared with the control; however, bulk-TiO₂ treatment resulted in a 5% improvement. Further analysis indicated that the activity of Rubisco activase in the nanoanatase-treated spinach was significantly higher than the control by up to 2.75 times, and bulk-TiO₂ treatment had no such significant effects. Together, one of the molecular mechanisms of carbon reaction promoted by nanoanatase is that the nanoanatase treatment results in the enhancement of rca mRNA expressions, protein levels, and activities of Rubisco activase, thereby leading to the improvement of Rubisco carboxylation and the high rate of photosynthetic carbon reaction.     

Effects of Nano-anatase TiO<Subscript>2</Subscript> on Absorption,Distribution of Light,and Photoreduction Activities of Chloroplast Membrane of Spinach

The effects of nano-anatase TiO₂ on light absorption, distribution, and conversion, and photoreduction activities of spinach chloroplast were studied by spectroscopy. Several effects of nano-anatase TiO₂ were observed: (1) the absorption peak intensity of the chloroplast was obviously increased in red and blue region, the ratio of the Soret band and Q band was higher than that of the control; (2) the great enhancement of fluorescence quantum yield near 680 nm of the chloroplast was observed, the quantum yield under excitation wavelength of 480 nm was higher than the excitation wavelength of 440 nm; (3) the excitation peak intensity near 440 and 480 nm of the chloroplast significantly rose under emission wavelength of 680 nm, and F ₄₈₀ / F ₄₄₀ ratio was reduced; (4) when emission wavelength was at 720 nm, the excitation peaks near 650 and 680 nm were obviously raised, and F ₆₅₀ / F ₆₈₀ ratio rose; (5) the rate of whole chain electron transport, photochemical activities of PSII DCPIP photoreduction and oxygen evolution were greatly improved, but the photoreduction activities of PSI were a little changed. Together, the studies of the experiments showed that nano-anatase TiO₂ could increase absorption of light on spinach chloroplast and promote excitation energy to be absorbed by LHCII and transferred to PSII and improve excitation energy from PSI to be transferred to PSII, thus, promote the conversion from light energy to electron energy and accelerate electron transport, water photolysis, and oxygen evolution.     

Chloroplast envelopes as affected by light or dark pretreatment of pea plants

Glutaraldehyde fixation in 0.33 M sorbitol without any buffer reveals changes in the staining properties of the envelopes of chloroplasts of pea plants kept in the light or in the dark prior to fixation. After dark pretreatment the outer double membrane of the chloroplast does not adsorb heavy metals, resulting in a white unstained rim instead of the usual membrane. All other membranes of the cell, including chloroplast grana, are not affected and stain normally. Light pretreatment of the plants allows the usual staining of the outer membrane of the chloroplats. Fixation carried out in the medium usually used to isolate intact CO₂ fixing chloroplasts (sorbitol+buffer+ions) reverses the above process and results in unstained envelopes of chloroplasts from preilluminated leaves, while the envelopes of chloroplasts from leaves kept in the dark stain normally. Glutaraldehyde-fixed chloroplats isolated from preilluminated leaves show a very basic isoelectric point during electrofocusing, while fixed chloroplasts from predarkened tissue exhibit an isoelectric point at about pH 7.     

Effects of Chromium Picolinate on Oxidative Damage in Primary Piglet Hepatocytes

A proven photocatalyst, titanium dioxide in the form of nano-anatase, is capable of undergoing electron transfer reactions under light. In previous studies, we had proven that nano-anatase could absorb ultraviolet light (UV-B) and convert light energy to stable chemistry energy finally via electron transport in spinach chloroplasts.The mechanisms by which nano-anatase promotes antioxidant stress in spinach chloroplasts under UV-B radiation are still not clearly understood. In the present paper, we investigate the effects of nano-anatase on the antioxidant stress in spinach chloroplasts under UV-B radiation. The results showed that nano-anatase treatment could significantly decrease accumulation of superoxide radicals, hydrogen peoxide (H₂O₂), and malonyldialdehyde (MDA) content, and increase activities of superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), guaiacol peroxidase (GPX), and elevate evolution oxygen rate in spinach chloroplasts under UV-B radiation. Together, nano-anatase could decrease the oxidative stress to spinach chloroplast caused by UV-B radiation.     

Promotion of Energy Transfer and Oxygen Evolution in Spinach Photosystem II by Nano-anatase TiO<Subscript>2</Subscript>

Being a proven photocatalyst, nano-anatase is capable of undergoing electron transfer reactions under light. In previous studies we had proven that nano-anatase improved photosynthesis and greatly promoted spinach growth. The mechanisms by which nano-anatase promotes energy transfer and the conversion efficiency of the process are still not clearly understood. In the present paper, we report the results obtained with the photosystem II (PSII) isolated from spinach and treated by nano-anatase TiO₂ and studied the effect of nano-anatase TiO₂ on energy transfer in PSII by spectroscopy and on oxygen evolution. The results showed that nano-anatase TiO₂ treatment at a suitable concentration could significantly change PSII microenvironment and increase absorbance for visible light, improve energy transfer among amino acids within PSII protein complex, and accelerate energy transport from tyrosine residue to chlorophyll a. The photochemical activity of PSII (fluorescence quantum yield) and its oxygen-evolving rate were enhanced by nano-anatase TiO₂. This is viewed as evidence that nano-anatase TiO₂ can promote energy transfer and oxygen evolution in PSII of spinach.     

Titanium dioxide nanomaterial doped with trivalent lanthanide ions of Tb, Eu and Sm: Preparation, characterization and potential applications

Mesoporous Ln(III)-TiO₂ (Ln = Tb, Eu, Sm) nanomaterials composites have been successfully synthesized by using sol-gel technique.XRD pattern, FT-IR, Raman spectra, and SEM were used to characterize the Ln(III)-TiO₂ nanomaterials. The prepared lanthanide doped TiO₂ nanomaterials have anatase phase and exhibit Ti-O-Ln bond. The absorption spectra of all prepared samples reflect the increasing photoresponse of doped samples to visible light over pure TiO₂. Surface area is remarkably increased due to lanthanide ion-doping.Two newly prepared Ln(III)-TiO₂ (Ln = Eu, Sm) luminescent nanomaterials exhibit enhanced pure red or orange light emission due to energy transfer from host TiO₂ to guest Eu(III) or Sm(III), respectively.In addition, the commercially available textile dye Remazol Red RB-133 degradation was used as a probe reaction to determine the efficiency of the Ln(III)-TiO₂ photocatalysts. The Ln(III) doping brought about remarkable improvement in the photoactivity over pure TiO₂.     

Chloroplast transfer in Nicotiana based on metabolic complementation between irradiated and iodoacetate treated protoplasts

Protoplasts of a light sensitive plastome mutant of Nicotiana tabacum (2 n=48) were irradiated and fused with iodoacetate-treated Nicotiana plumbaginifolia (2 n=20) protoplasts. Treated parental protoplasts were unable to divide. Metabolic complementation, however, helped the recovery of interspecific fusion products which survived and formed calli. Altogether 40 clones were investigated. N. plumbaginifolia plants were obtained in 15 clones (38%), somatic hybrids in 23 clones, and both types of regenerates were found in 2 clones. Irradiation therefore significantly increased the frequency of segregant formation with the non-irradiated N. plumbaginifolia nuclei (the frequency was 1.4% in the absence of irradiation). Regenerated plants in most cases (31 out of 34) contained chloroplasts from the irradiated parent. In 6 clones plants were obtained with both types of chloroplast. Thus, irradiated N. tabacum chloroplasts had an improved chance of dominating the heterokaryonderived cells, many of which contained N. plumbaginifolia nucleus. The system described should be generally applicable for the transfer of chloroplasts without the use of selectable genetic markers.     

The Improvement of Spinach Growth by Nano-anatase TiO<Subscript>2</Subscript> Treatment Is Related to Nitrogen Photoreduction

The improvement of spinach growth is proved to relate to N₂ fixation by nano-anatase TiO₂ in this study. The results show that all spinach leaves kept green by nano-anatase TiO₂ treatment and all old leaves of control turned yellow white under culture with N-deficient solution. And the fresh weight, dry weight, and contents of total nitrogen, , chlorophyll, and protein of spinach by nano-anatase TiO₂ treatment presented obvious enhancement compared with control. Whereas the improvements of yield of spinach were not as good as nano-anatase TiO₂ treatment under N-deficient condition, confirming that nano-anatase TiO₂ on exposure to sunlight could chemisorb N₂ directly or reduce N₂ to NH₃ in the spinach leaves, transforming into organic nitrogen and improving the growth of spinach. Bulk TiO₂ effect, however, was not as significant as nano-anatase TiO₂. A possible metabolism of the function of nano-anatase TiO₂ reducing N₂ to NH₃ was discussed.     

Photosynthetic metabolism of cyanate by the cyanobacterium Synechococcus UTEX 625

Intact cells of the unicellular cyanobacterium Synechococcus UTEX 625 degraded exogenously supplied cyanate (as KOCN) to CO₂ and NH₃ in a light-dependent reaction. NH₃ release to the medium was as high as 80 mol(mgChl)^-1h^-1 and increased 1.7-fold in the presence of methionine sulfoximine, a glutamine synthetase inhibitor. Cyanate also supporte photosynthetic O₂ evolution to a maximum rate of 188 mol O₂(mgChl)^-1h^-1 at pH 8 and 30°C. Cyanate decomposition in cell-free extracts, measured by mass spectrometry as ¹³CO₂ production from KO¹³CN, occurred in the soluble enzyme fraction, but not in the thylakoid/carboxysome fraction, and was enhanced by HCO₃^– and inhibited by the dianion oxalate. CO₂, rather, than HCO₃^–, was a product of cyanate decomposition. The ability to decompose cyanate was not dependent upon pre-exposure of cells to cyanate to induce activity. The collective results indicate that Synechococcus UTEX 625 possesses a constitutive, cytosolic cyanase (EC 4.3.99.1), similar in mechanism to that found in some species of heterotrophic bacteria. The reaction catalyzed was: OCN+HCO₃+2H⁺2CO₂+NH₃. In intact cells, the CO₂ produced by the action of cyanase on OCN^- was either directly fixed by the Calvin cycle enzyme ribulose-1,5-bisphosphate carboxylase/oxygenase, leading to O₂ evolution, or leaked into the medium where it was returned to the cell by the active CO₂/HCO₃^– transport systems for fixation. However, leakage of CO₂ from air-grown cells was only observed when the active CO₂ transport system was inhibited by darkness or the CO₂ analogue carbon oxysulfide.Abbreviations BTP bistrispropane - C_i inorganic carbon (=CO₂+HCO₃^-+CO₃^2-) - CA carbonic anhydrase - Chl chlorophyll - COS carbon oxysulfide - MSX methionine sulfoximine - PAR photosynthetically active radiation - Rubisco ribulose bisphosphate carboxylase/oxygenase     

The effect of pH on the reduction kinetics of P-680 in tris-treated chloroplasts

The primary donor of Photosystem II (PS II), P-680, was photo-oxidized by a short flash and its rate of reduction was measured at different pH values by following the recovery of the absorption change at 820 nm in chloroplasts pretreated with a high concentration of Tris. The re-reduction is biphasic with a fast phase (dominant after the first flash) attributed to the donation by a donor, D₁, and a slow phase (usually dominant after the second flash) attributed to a back-reaction with the primary acceptor.

It is found that pH has a strong influence on the donation from D₁ (τ = 2 μs at pH 9, 44 μs at pH 4), but no influence on the back reaction (τ ≈ 200 μs). pH also influences the stability of the charge separation since the contribution of donation from D₁ at the second flash increases at lower pH, getting close to 100% at pH 4.     

Antibacterial performance of nanoscaled visible-light responsive platinum-containing titania photocatalyst in vitro and in vivo

Background

Traditional antibacterial photocatalysts are primarily induced by ultraviolet light to elicit antibacterial reactive oxygen species. New generation visible-light responsive photocatalysts were discovered, offering greater opportunity to use photocatalysts as disinfectants in our living environment. Recently, we found that visible-light responsive platinum-containing titania (TiO₂–Pt) exerted high performance antibacterial property against soil-borne pathogens even in soil highly contaminated water. However, its physical and photocatalytic properties, and the application in vivo have not been well-characterized.

Methods

Transmission electron microscopy, energy dispersive spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction, ultraviolet–visible absorption spectrum and the removal rate of nitrogen oxides were therefore analyzed. The antibacterial performance under in vitro and in vivo conditions was evaluated.

Results

The apparent quantum efficiency for visible light illuminated TiO₂–Pt is relatively higher than several other titania photocatalysts. The killing effect achieved approximately 2 log reductions of pathogenic bacteria in vitro. Illumination of injected TiO₂–Pt successfully ameliorated the subcutaneous infection in mice.

Conclusions

This is the first demonstration of in vivo antibacterial use of TiO₂–Pt nanoparticles. When compared to nanoparticles of some other visible-light responsive photocatalysts, TiO₂–Pt nanoparticles induced less adverse effects such as exacerbated platelet clearance and hepatic cytotoxicity in vivo.

General significance

These findings suggest that the TiO₂–Pt may have potential application on the development of an antibacterial material in both in vitro and in vivo settings.     

Chloroplast development and the synthesis of chlorophyll and protochlorophyllide in Zostera transferred to darkness

Intact plants and isolated leaves of Zostera capricornii Martens ex Aschers were transferred from daylight to darkness. Substantial amounts of chloropyll a and b continued to accumulate in immature and mature tissue in the same ratio as in the light and were incorporated into chlorophyll-protein complexes in the thylakoids. A small amount of protochlorophyllide also accumulated in immature tissue in the dark. Proplastids and immature chloroplasts continued to develop into mature chloroplasts in the dark in the normal manner but prolamellar bodies, which are a conspicuous feature of immature chloroplasts, took longer to disperse than in the light. Protochlorophyllide accumulation and prolamellar-body formation were not correlated. The results indicate that Zostera has a genetic capacity for dark chlorophyll synthesis which is expressed in immature and mature leaf tissue and enables this plant to continue synthesising chlorophyll and assembling chloroplasts at night.Abbreviations Chl chlorophyll - T_o time of transfer to darkness     

The Effects of Nano-anatase TiO2 on the Activation of Lactate Dehydrogenase from Rat Heart

Lactate dehydrogenase (LDH, EC1.1.1.27), widely expressed in the heart, liver, and other tissues, plays an important role in glycolysis and glyconeogenesis. The activity of LDH is often altered upon inflammatory responses in animals. Nano-TiO₂ was shown to provoke various inflammatory responses both in rats and mice; however, the molecular mechanism by which TiO₂ exerts its toxicity has not been completely understood. In this report, we investigated the mechanisms of nano-anatase TiO₂ (5 nm) on LDH activity in vitro. Our results showed that LDH activity was greatly increased by low concentration of nano-anatase TiO₂, while it was decreased by high concentration of nano-anatase TiO₂. The spectroscopic assays revealed that the nano-anatase TiO₂ particles were directly bound to LDH with mole ratio of [nano-anatase TiO₂] to [LDH] was 0.12, indicating that each Ti atom was coordinated with five oxygen/nitrogen atoms and a sulfur atoms of amino acid residues with the Ti–O(N) and Ti–S bond lengths of 1.79 and 2.41 Å. We postulated that the bound nano-anatase TiO₂ altered the secondary structure of LDH, created a new metal ion-active site for LDH, and thereby enhanced LDH activity.     

Effects of Nano-anatase on Spectral Characteristics and Distribution of LHCII on the Thylakoid Membranes of Spinach

In the article, we report that effects of nano-anatase on the spectral characteristics and content of light-harvesting complex II (LHCII) on the thylakoid membranes of spinach were investigated. The results showed that nano-anatase treatment could increase LHCII content on the thylakoid membranes of spinach and the trimer of LHCII; nano-anatase could enter the spinach chloroplasts and bind to PSII. Meanwhile, spectroscopy assays indicated that the absorption intensity of LHCII from nano-anatase-treated spinach was obviously increased in the red and the blue region, fluorescence quantum yield near 685 nm of LHCII was enhanced, the fluorescence excitation intensity near 440 and 480 nm of LHCII significantly rose and F ₄₈₀/F ₄₄₀ ratio was reduced. Oxygen evolution rate of PSII was greatly improved. Together, nano-anatase promoted energy transferring from chlorophyll (chl) b and carotenoid to chl a, and nano-anatase TiO₂ was photosensitized by chl of LHCII, which led to enhance the efficiency of absorbing, transferring, and converting light energy.     

Error caused by carbon dioxide in determination of ammonium by direct steam distillation of tropical wetland rice soils

Summary A study was made with eight Philippine wetland rice soils to quantify the possible error caused by the CO₂ evolved during direct distillation of soil suspensions in aerobic and anaerobic conditions with MgO. The error caused by CO₂ was eliminated by absorbing the ammonia distilled in H₂SO₄, which was gently boiled to derive off the CO₂ absorbed. The possible error caused by CO₂ was not eliminated when boric acid was used for absorbing ammonia. The difference in NH₄ ⁺ values determined by using sulfuric acid and boric acid methods gave an estimate of the error caused by CO₂. It was found that CO₂ evolved caused negative error in the NH₄ ⁺ values obtained using the direct distillation of soil suspensions with MgO in presence of KCl. The magnitude of error was higher and significant with anaerobic soil samples but this error was negligible with aerobic soils.     

Glucose biosensor based on the room-temperature phosphorescence of TiO2/SiO2 nanocomposite

The direct immobilization of glucose oxidase (GOD) on TiO₂/SiO₂ nanocomposite and its application as glucose biosensor were investigated. The room-temperature phosphorescence of TiO₂/SiO₂ nanocomposite can be quenched by hydrogen peroxide (H₂O₂). The detection of glucose may be accomplished by monitoring the formation of hydrogen peroxide which generated in the oxidation process of glucose with the catalysis of GOD. To our surprise, by using a 96-hole polyporous plate accessory of fluorescence spectrophotometer, the biosensor exhibits excellent linear response to glucose concentrations ranging from 1.0 × 10⁻⁹ to 1.0 × 10⁻² M with a detection limit of 1.2 × 10⁻¹⁰ M. The TiO₂/SiO₂ nanocomposite can be used as both supporting material and signal transducer. The phosphorescence intensity and color of the biosensor change obviously and even could be observed with naked eyes by continuous addition of glucose. Based on the room-temperature phosphorescence of TiO₂/SiO₂ nanocomposite, a new method of solid substrate-room-temperature phosphorimetry (SS-RTP) for glucose determination is proposed. A glucose biosensor was fabricated with wide determination concentration range, low detection limit, high sensitivity, and fast response time. And the biosensor has been successfully applied to the determination of glucose in human blood serum. The coacervation of GOD enzyme and its interaction with TiO₂/SiO₂ nanocomposite enlarge the surface area and enhance the chemical stability of GOD. The nice biocompatibility, large surface area, good chemical stability and nontoxicity of the TiO₂/SiO₂ nanocomposite have made this material suitable for functioning as biosensor.     

Modulation of the Photosynthetic Source:Sink Relationship in Cultures of the Cyanobacterium Nostoc Rivulare

Nostoc rivulare was grown in batch cultures under controlled CO₂ and NO₃ ^– concentrations to modulate the photosynthetic source:sink relationship. Increasing CO₂ supply accelerated the accumulation of chlorophyll (Chl) a, i.e., supplemental CO₂ combined with double concentrations of NO₃ ^– more than doubled the amounts of Chl a relative to those of the original medium. Photosynthetic oxygen evolution and respiratory oxygen uptake were both enhanced by elevated CO₂ and NO₃ ^–. Contents of soluble sugars and starch (total non-structural saccharides) as well as insoluble saccharides (structural fraction) were affected by altering CO₂-NO₃ ^– combinations. Uptake as well as reduction of either NO₃ ^– or NO₂ ^– was inhibited by CO₂ deprivation. Expanding the sink size via increasing NO₃ ^– supply enhanced photosynthesis and thus the sink (NO₃ ^–) acted as a feed forward stimulator of the source (photosynthesis). The regulatory role of nitrate on photosynthesis was most influential in CO₂-deprived cultures since it could enhance photosynthesis to higher levels than CO₂-supplemented, nitrate-free cultures.     

Dietary Effects of Eicosapentaenoic and Docosahexaenoic Acid Esters on Lipid Metabolism and Immune Parameters in Sprague-Dawley Rats

Sprague-Dawley rats were fed eicosapentaenoic (EPA) and docosahexaenoic acid (DHA) ethyl esters at the 2% level for 3 weeks to clarify their effects on immune functions. In the rats fed EPA or DHA, serum cholesterol, triglyceride, and phospholipid (PL) levels were significantly lower than those in the rats fed safflower oil. In PL fractions of serum, liver, lung, splenocytes, and peritoneal exudate cells (PEC), increases in linoleic and dihomo-γ-linolenic acid contents and a decrease in arachidonic acid (AA) content were observed in the rats fed EPA or DHA. In addition, the EPA content increased in the rats fed EPA and DHA. In the rats fed EPA or DHA, a decrease of LTB₄ productivity and an increase of LTB₅ productivity were observed in the PEC, in response to the treatment with 5 μM calcium ionophore A23187 for 20 min. The changes in leukotriene production were more marked in EPA-fed rats than in DHA-fed rats. These results suggest that dietary EPA affects lipid metabolism and leukotriene synthesis more strongly than DHA.