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1.
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 TiO 2 and studied the effect of nano-anatase TiO 2 on energy transfer in PSII by spectroscopy and on oxygen evolution. The results showed that nano-anatase TiO 2 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
TiO 2. This is viewed as evidence that nano-anatase TiO 2 can promote energy transfer and oxygen evolution in PSII of spinach. 相似文献
2.
The improvement of spinach growth is proved to relate to N 2 fixation by nano-anatase TiO 2 in this study. The results show that all spinach leaves kept green by nano-anatase TiO 2 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 TiO 2 treatment presented obvious enhancement compared with control. Whereas the improvements of yield of spinach were not as good
as nano-anatase TiO 2 treatment under N-deficient condition, confirming that nano-anatase TiO 2 on exposure to sunlight could chemisorb N 2 directly or reduce N 2 to NH 3 in the spinach leaves, transforming into organic nitrogen and improving the growth of spinach. Bulk TiO 2 effect, however, was not as significant as nano-anatase TiO 2. A possible metabolism of the function of nano-anatase TiO 2 reducing N 2 to NH 3 was discussed. 相似文献
3.
A decrease in CFU of gram-positive and gram-negative bacteria on the surface of UV illuminated TiO 2 films (wavelength of 380 nm) is shown. A 29, 45, and 47% decrease in bacterial viability of Staphylococcus aureus, Staphylococcus epidermidis, and Escherichia coli, respectively, was seen after 12-min exposition. It was first discovered that the reuse of TiO 2 films to test a bacterial suspension for viability removes UV-induced bactericidal activity. However, annealing of TiO 2 at a temperature above 400°C restores the photoinduced bactericidal activity to its initial state. 相似文献
4.
Colloidal silver has been known to have unique antimicrobial activity that may be useful in the construction of antibacterial materials (self-cleaning materials) to aid in the fight against bacteria-related infections. In this study, silver-coated TiO 2 (Ag/TiO 2) particles prepared through the photo-reduction of Ag + were investigated as an antibacterial agent against Escherichia coli and Staphylococcus aureus. The deposition of Ag onto the surface was confirmed with SEM and EDS analysis of the post-reaction particles. It was also determined that the initial concentration of Ag + in solution played a significant role in the effective size of the post-irradiation particles. The antibacterial effectiveness of the Ag/TiO 2 was evaluated through the determination of the minimum inhibitory concentration (MIC) of AgTiO 2 for each species of bacteria. The MIC values for the Ag/TiO 2, on both E. coli and S. aureus, were much lower than the MIC values for Ag metal, and quite comparable to the MIC values for AgNO 3. A disc diffusion/antibiotic sensitivity test was also performed using the Ag/TiO 2 particles and the results compared with the results obtained for Ag metal, AgNO 3 and common antibacterial agents; tetracycline, chloramphenicol, erythromycin, and neomycin. The zone of inhibition diameters for the Ag/TiO 2 particles were found to be comparable with those of the other antimicrobial agents. 相似文献
5.
We have investigated the possibility that photoexcited titanium dioxide (TiO 2) could inhibit the growth of malignant cells. We studied the anti-glioma effects of nano-TiO 2 excited with ultraviolet A (UVA) irradiation both in vitro and in vivo. Transmission electron microscopy demonstrated that
glioma cells take up TiO 2 by phagocytosis, and vital staining revealed that TiO 2 alone has no effect on glioma cell proliferation. However, if TiO 2 was combined with UVA irradiation the proliferation rate was decreased significantly compared to controls ( P < 0.05). RT–PCR suggested that TiO 2 induction of glioma cell apoptosis is associated with changes in the expression of genes encoding Bcl-2 family members. We
then investigated the in vivo antitumor effects of combined TiO 2 plus UVA treatment of established glioma tumors. TiO 2 plus UVA led to pronounced areas of necrosis, elevated indices of apoptosis, delayed tumor growth, and increased survival
compared with the TiO 2-alone control group ( P < 0.001). Log-rank survival analysis showed that median survival duration was prolonged ( P < 0.001). These findings suggest that nano-TiO 2 based photodynamic therapy has potential in the treatment of glioma. 相似文献
6.
Cu (II) and Ag(I) together with TiO 2 powder were deposited on conducting support substrates to enhance the photocatalytic ability. The catalytic efficiency was
tested by monitoring the photocatalytic degradation and detriment of methylene blue (MB) and bovine serum albumin (BSA). The
conformational change of BSA induced by catalysts was also observed by circular dichroism spectroscopy.The antibacterial activities
were studied by Escherichia coli. Both MB and BSA could be degraded more efficiently than pure TiO 2. After treatment with catalyst, the morphology of cells became twisted and rougher. Regular wrinkles were damaged and groove-like
rift appeared on the surface. The fluorescence polarization has shown a significant decrease in membrane fluidity and the
increase of permeability of cell membrane. Changes of the spectral profile of E. coli were observed, which suggested the damages of surface groups on the cell membrane. 相似文献
7.
The effects of nano-anatase TiO 2 on light absorption, distribution, and conversion, and photoreduction activities of spinach chloroplast were studied by spectroscopy.
Several effects of nano-anatase TiO 2 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 TiO 2 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. 相似文献
8.
Recent studies demonstrated that titanium dioxide nanoparticles (TiO 2 NPs) could significantly promote photosynthesis and plant growth, but its mechanism is still unclear. In this article, we
studied the mechanism of light absorption and transfer of chloroplasts of Arabidopsis thaliana caused by TiO 2 NPs treated. The results showed that TiO 2 NPs could induce significant increases of light-harvesting complex II (LHCII) b gene expression and LHCII II content on the
thylakoid membrane in A. thaliana, and the increases in LHCII were higher than the non-nano TiO 2 (bulk-TiO 2) treatment. Meanwhile, spectroscopy assays indicated that TiO 2 NPs obviously increased the absorption peak intensity of the chloroplast in red and blue region, the fluorescence quantum
yield near 680 nm, the excitation peak intensity near 440 and 480 nm and/or near 650 and 680 nm of the chloroplast. TiO 2 NPs treatment could reduce F
480/ F
440 ratio and increase F
650/ F
680 ratio and accelerate the rate of whole chain electron transport and oxygen evolution of the chloroplast. However, the photosynthesis
improvement of the non-nanoTiO 2 treatment was far less effective than TiO 2 NPs treatment. Taken together, TiO 2 NPs could promote the light absorption of chloroplast, regulate the distribution of light energy from PS I to PS II by increasing
LHCII and accelerate the transformation from light energy to electronic energy, water photolysis, and oxygen evolution. 相似文献
9.
The pollution of raw surface and underground water with pharmaceutical compounds has an impact on increasing the resistance of pathogenic microorganisms. Environmental challenges include investigating a novel and cost-effective therapeutic approach for the bactericidal treatment of water supplies. Ethyl acetate extracts from three marine algae (Caulerpa racemosa, Codium fragile, and Cystoseira myrica) obtained from the Red Sea (Hurghada, Egypt) were used for the green synthesis of TiO2 nanoparticles (TiO2-NPs). A highly crystalline nanoparticle structure with a stable tetragonal anatase structure was obtained; the mean concentrations were 2.43 to 6.09?×?108 NPs/mL and the average particle size was 125–131 nm. In ultrapure water, the TiO2-NPs were confirmed to be a stable solution following zeta potential analysis. UV light (λ?=?350 nm) for 2 h was used to activate the TiO2-NPs before the antibacterial activity tests. The application of UV-activated TiO2-NPs for 4 h treatments demonstrated promising bactericidal activity, with a 73.08% reduction in Salmonella typhi and a 91.51% reduction in Enterobacter ludwigii. Antibiofilm activities against the reference strains Salmonella typhi NCTC 12023/ATTC and Morganella morganii ATCC25829 and the bacterial isolates Klebsiella pneumoniae, Enterobacter ludwigii, and Enterococcus faecium were tested. The TiO2-NPs were nontoxic against the human normal cell line RPE1. Regarding the treatment of total and fecal coliform, in addition to fecal streptococci, in raw surface and underground water, the UV-activated TiO2-NPs prepared from the ethyl acetate extracts of Caulerpa racemosa showed high applicability. The present study offered insights into the nature and development of nontoxic and green TiO2-NP formulations for use as modern antibacterial alternatives against coliforms in aquatic systems. 相似文献
10.
Streptococcus mutans is one of the more significant pathogens involved in the development of dental caries in humans. The purpose of this research
was to design a TiO 2-coated dental instrument and to determine the bactericidal effects of the instrument on S. mutants. TiO 2 photocatalytic films were prepared by the low-pressure metal-organic chemical vapor deposition (LPMOCVD) method using titanium
tetraisopropoxide (TTIP) as precursor. The photocatalytic reaction was carried out on a TiO 2-coated pyrex petri dish with an ultraviolet (UV) light emitting diode (LED) illuminator or a fluorescent lamp light source.
Our data indicates that the relative survival ratio of S. mutans when plated onto TiO 2 photocatalytic films and under exposure to UV-A light for 15 min was 0.01%. In addition, a fluorescent lamp light source
also had bactericidal effects on the S. mutans plated TiO 2 photocatalytic films. These results indicate that TiO 2-coated dental materials or devices may be useful in dental treatments for the prevention of carious or enamel demineralization. 相似文献
11.
As has been previously shown, Saccharomyces cerevisiae grown in 2% or 0.025% glucose uses this carbohydrate by the fermentative or oxidative pathways, respectively. Depending on the glucose concentration in the medium, the effect of the addition of H 2O 2 on the level of ATP and on glyceraldehyde-3-phosphate dehydrogenase (GAPDH) activity differed. In the presence of 2% glucose, ATP and GAPDH decreased sharply during the first few minutes of treatment, whereas in the presence of 0.025% glucose, GAPDH activity decreased similarly, but the ATP level remained practically unchanged. The addition of 3 mM glutathione to the culture media prevented the depletion of ATP levels and GAPDH activity in the presence of H 2O 2. Catalase and superoxide dismutase activities did not vary significantly when yeast cells were grown either in 2% or in 0.025% glucose. 相似文献
12.
SiO 2-ionized loess was prepared from the reaction of loess and sodium hydroxide at 1,400°C for 2 h. The antibacterial activity
of SiO 2-ionized loess against Staphylococcus aureus, Bacillus subtilis, Escherichia coli, Pseudomonas aerusinosa, and Propionobacterium acnes causing acne was examined by comparing the results against those of untreated loess, and treatment efficacy was examined
for treating acne using soap containing SiO 2-ionized loess. The minimum inhibitory concentration value of SiO 2-ionized loess against S. aureus, P. aerusinosa, B. subtilis, E. coli, and P. acne was 10.0, 10.0, 2.5, 5.0, and 2.5 mg/mL, respectively. However, medium containing untreated loess had no antimicrobial activity.
A treatment efficacy test revealed that acne symptoms decreased as the duration of using soap containing SiO 2-ionized loess increased. 相似文献
13.
In the present article we report on the biological characterization and amino acid sequence of a new basic Phospholipases A 2 (PLA 2) isolated from the Crotalus durissus collilineatus venom (Cdcolli F6), which showed the presence of 122 amino acid residues with a pI value of 8.3, molecular mass of 14 kDa and revealed an amino acid sequence identity of 80 with crotalic PLA 2s such as Mojave B, Cdt F15, and CROATOX. This homology, however, dropped to 50 if compared to other sources of PLA 2s such as from the Bothrops snake venom. Also, this PLA 2 induced myonecrosis, although this effect was lower than that of BthTx-I or whole crotoxin and it was able to induce a strong blockage effect on the chick biventer neuromuscular preparation, independently of the presence of the acid subunid (crotapotin). The neurotoxic effect was strongly reduced by pre-incubation with heparin or with anhydrous acetic acid and q-BPB showed a similar reduction. The q-BPB did not reduce significantly the myotoxic activity induced by the PLA 2, but the anhydrous acetic acid treatment and the pre-incu-bation of PLA 2 with heparin reduced significantly its effects. This protein showed a strong antimicrobial activity against Xanthomonas axonopodis passiflorae (Gram-negative), which was drastically reduced by incubation of this PLA 2 with q-BPB, but this effect was marginally reduced after treatment with anhydrous acetic acid. Our findings here allow to speculate that basic amino acid residues on the C-terminal and molecular regions near catalytic site regions such as Calcium binding loop or b-wing region may be involved in the binding of this PLA 2 to the molecular receptor to induce the neurotoxic effect. The bactericidal effect, however, was completely dependent on the enzymatic activity of this protein. 相似文献
14.
The enzymatic extracts from seven species of microalgae ( Pediastrum duplex, Dactylococcopsis fascicularis, Halochlorococcum porphyrae, Oltmannsiellopsis unicellularis, Achnanthes
longipes, Navicula sp. and Amphora coffeaeformis) collected from three habitats (freshwater, tidal pool, and coastal benthic) at Jeju Island in Korea were investigated for
their antioxidant activity. Of the extracts tested, the AMG 300 L (an exo 1, 4-α- d-glucosidase) extract of P. duplex, the Viscozyme extract of Navicula sp., and the Celluclast extract of A. longipes provided the most potential as antioxidants. Meanwhile, the Termamyl extract of P. duplex in an H 2O 2 scavenging assay exhibited an approximate 60% scavenging effect. In this study, we report that the DNA damage inhibitory
effects of P. duplex (Termamyl extract) and D. fascicularis (Kojizyme extract) were nearly 80% and 69% respectively at a concentration of 100 μg/ml. Thus, it is suggested that the microalgae
tested in this study yield promising DNA damage inhibitory properties on mouse lymphoma L 5178 cells that are treated with
H 2O 2. Therefore, microalgae such as P. duplex may be an excellent source of naturally occurring antioxidant compounds with potent DNA damage inhibition potential. 相似文献
15.
This study examined the effects of season-long exposure of Chinese pine ( Pinus tabulaeformis) to elevated carbon dioxide (CO 2) and/or ozone (O 3) on indole-3-acetic acid (IAA) content, activities of IAA oxidase (IAAO) and peroxidase (POD) in needles. Trees grown in
open-top chambers (OTC) were exposed to control (ambient O 3, 55 nmol mol −1 + ambient CO 2, 350 μmol mol −1, CK), elevated CO 2 (ambient O 3 + high CO 2, 700 μmol mol −1, EC) and elevated O 3 (high O 3, 80 ± 8 nmol mol −1 + ambient CO 2, EO) OTCs from 1 June to 30 September. Plants grown in elevated CO 2 OTC had a growth increase of axial shoot and needle length, compared to control, by 20% and 10% respectively, while the growth
in elevated O 3 OTC was 43% and 7% less respectively, than control. An increase in IAA content and POD activity and decrease in IAAO activity
were observed in trees exposed to elevated CO 2 concentration compared with control. Elevated O 3 decreased IAA content and had no significant effect on IAAO activity, but significantly increased POD activity. When trees
pre-exposed to elevated CO 2 were transferred to elevated O 3 (EC–EO) or trees pre-exposed to elevated O 3 were transferred to elevated CO 2 (EO–EC), IAA content was lower while IAAO activity was higher than that transferred to CK (EC–CK or EO–CK), the change in
IAA content was also related to IAAO activity. The results indicated that IAAO and POD activities in Chinese pine needles
may be affected by the changes in the atmospheric environment, resulting in the change of IAA metabolism which in turn may
cause changes in Chinese pine’s growth.
An erratum to this article can be found at 相似文献
16.
The present work is emphasised with the herbicidal tolerance of Azolla pinnata R.Br. and its modulation with TiO 2 nano-particle. Both carbohydrate and nitrogen metabolism were effected with 2,4-D as herbicide and in few cases TiO 2-NP had recovered few detrimental effects. From the nutrient status in Azolla it recorded the recovery of nitrogen as well as potassium by TiO 2-NP but not in case of phosphorus. However, a conversion of nitrate to ammonium was more induced by TiO 2-NP under herbicidal toxicity. Similar results were obtained for inter-conversion of amino acid–nitrate pool, but no changes with glutamine synthase activity with TiO 2-NP. Initially, the effects of 2,4-D was monitored with changes of chlorophyll content but had not been recovered with nanoparticle. Photosynthetic reserves expressed as both total and reducing sugar were insensitive to TiO 2-NP interference but activity of soluble and wall bound invertase was in reverse trend as compared to control. The 2,4-D mediated changes of redox and its oxidative stress was ameliorated in plants with over expressed ADH activity. As a whole the Azolla bio system with TiO 2 supplementation may be useful in sustenance against 2,4-D toxicity through recovery of nitrogen metabolism. Thus, Azolla-TiO 2-NP bio system would be realised to monitor the herbicidal toxicity in soil and its possible bioremediation. 相似文献
17.
The clinical significance of exogenous hCG treatment is to stimulate steroidogenesis and spermatogenesis in the testis. However,
the pathogenesis of detrimental effects on the testis arising out of chronic hCG treatment is yet to be clearly ascertained.
In the present study we have shown that hCG treatment (100 IU/day) to rats for 30 days raises testicular oxidative stress
leading to germ cell apoptosis and impairment of spermatogenesis. The treatment raises testicular H 2O 2 levels along with increase in lipid peroxidation and concomitant decrease in the enzymatic antioxidant activities like superoxide
dismutase, catalase and glutathione-s-transferase. The rise in the number of apoptotic germ cells was associated with up regulation
of Fas protein expression and caspase-3 activity in the testis. However, serum testosterone which was elevated by 15 days
of hCG treatment declined to pretreatment levels by 30 days. No significant alteration in serum gonadotropins was observed.
The above findings indicate that the pathogenesis of deleterious effects following chronic hCG treatment is due to increase
in testicular oxidative stress with high H 2O 2 availability leading to apoptosis among germ cells. 相似文献
18.
The increasing CO 2 concentration in Earths atmosphere is expected to cause a greater decline in the nutritional quality of C 3 than C 4 plants. As a compensatory response, herbivorous insects may increase their feeding disproportionately on C 3 plants. These hypotheses were tested by growing the grasses Lolium multiflorum C 3) and Bouteloua curtipendula C 4) at ambient (370 ppm) and elevated (740 ppm) CO 2 levels in open top chambers in the field, and comparing the growth and digestive efficiencies of the generalist grasshopper Melanoplus sanguinipes on each of the four plant × CO 2 treatment combinations. As expected, the nutritional quality of the C 3 grass declined to a greater extent than did that of the C 4 grass at elevated CO 2; protein levels declined in the C 3 grass, while levels of carbohydrates (sugar, fructan and starch) increased. However, M. sanguinipes did not significantly increase its consumption rate to compensate for the lower nutritional quality of the C 3 grass grown under elevated CO 2. Instead, these grasshoppers appear to use post-ingestive mechanisms to maintain their growth rates on the C 3 grass under elevated CO 2. Consumption rates of the C 3 and C 4 grasses were also similar, demonstrating a lack of compensatory feeding on the C 4 grass. We also examined the relative efficiencies of nutrient utilization from a C 3 and C 4 grass by M. sanguinipes to test the basis for the C 4 plant avoidance hypothesis. Contrary to this hypothesis, neither protein nor sugar was digested with a lower efficiency from the C 4 grass than from the C 3 grass. A novel finding of this study is that fructan, a potentially large carbohydrate source in C 3 grasses, is utilized by grasshoppers. Based on the higher nutrient levels in the C 3 grass and the better growth performance of M. sanguinipes on this grass at both CO 2 levels, we conclude that C 3 grasses are likely to remain better host plants than C 4 grasses in future CO 2 conditions. 相似文献
19.
TiO 2-coated surfaces are increasingly studied for their ability to inactivate microorganisms. The activity of glass coated with
thin films of TiO 2, CuO and hybrid CuO/TiO 2 prepared by atmospheric Chemical Vapour Deposition (Ap-CVD) and TiO 2 prepared by a sol–gel process was investigated using the inactivation of bacteriophage T4 as a model for inactivation of
viruses. The chemical oxidising activity was also determined by measuring stearic acid oxidation. The results showed that
the rate of inactivation of bacteriophage T4 increased with increasing chemical oxidising activity with the maximum rate obtained
on highly active sol–gel preparations. However, these were delicate and easily damaged unlike the Ap-CVD coatings. Inactivation
rates were highest on CuO and CuO/TiO 2 which had the lowest chemical oxidising activities. The inactivation of T4 was higher than that of Escherichia coli on low activity surfaces. The combination of photocatalysis and toxicity of copper acted synergistically to inactivate bacteriophage
T4 and retained some self-cleaning activity. The presence of phosphate ions slowed inactivation but NaCl had no effect. The
results show that TiO 2/CuO coated surfaces are highly antiviral and may have applications in the food and healthcare industries. 相似文献
20.
Effects of exogenous H 2O 2 application on vinblastine (VBL) and its precursors, vindoline (VIN), catharanthine (CAT) and α-3′,4′-anhydrovinblastine
(AVBL), were measured in Catharanthus roseus seedlings in order to explore possible correlation of VBL formation with oxidative stress. VBL accumulation has previously
been shown to be regulated by an in vitro H 2O 2-dependent peroxidase (POD)-like synthase. Experimental exposure of plants to different concentrations of H 2O 2 showed that endogenous H 2O 2 and alkaloid concentrations in leaves were positively elevated. The time-course variations of alkaloid concentrations and
redox state, reflected by the concentrations of H 2O 2, ascorbic acid (AA), oxidative product of glutathione (GSSG) and POD activity, were significantly altered due to H 2O 2 application. The further correlation analysis between alkaloids and redox status indicated that VBL production was tightly
correlated with redox status. These results provide a new link between VBL metabolisms and redox state in C. roseus. 相似文献
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