Gene/Protein Disease Symptom Drug Enzyme Compound
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 172,036 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In order to measure the digestibility of feed with an indicator method two trials were realized on the dairy research farm "Karkendamm". The first trial was to test the suitability of TiO2 as an indicator to determine the digestibility in cows. The rate of recovery of the indicator was 98.8% (95.5%-101.9%). The concentration of TiO2 of the rectal samples in the morning (daily or every second day) corresponded very well with the values from total faeces collection. The samples taken in the evening showed lower concentrations. The estimation of digestibility of organic matter led to the same values with the total collection or the indicator method with morning samples. The digestibility derived from evening samples were 1.7-2.3%-units digestibility derived from evening samples were 1.7-2.3%-units lower in comparison to total collection. In the second trial the digestibility derived from the in vitro method "Hohenheimer-Futterwert-Test" and from a digestion trial with 30 cows using the indicator method were compared. The digestibility calculated from the date of the in vivo trial was 9.9%-units lower than the one from the "Hohenheimer-Futterwert-Test". The depression of digestibility was due to the variation in concentrate feeding between cows. If the cows got less than 8 kg concentrates the depression in digestibility was 1.9% when increasing the level of feeding one unit of maintenance requirement. If the cows got more than 8 kg concentrates the depression was 3.1%-units. It could be concluded that the "Hohenheimer-Futterwert-Test" underestimates the digestibility if the level of feeding is increased to a certain extent.
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PMID:[Estimate of digestibility in dairy cows using an indicator method in comparison to the Hohenheimer feed value test]. 322 55

This work is focused on improvement in photocatalytic activity of anatase-TiO2 (a-TiO2) photocatalyst under visible-light irradiation by adding nitrogen-doped TiO2 (N-TiO2) for depression of recombination rate between photoexcited electron and hole. The composites (a-TiO2/N-TiO2) were prepared by grinding in ethanol solvent at 200 rpm for 15 min with change in weight ratio of N-TiO2. In addition to the characterizations by X-ray diffraction and X-ray photoelectron spectroscopy, measurements of existing singlet oxygen by chemiluminescens method and photocatalytic activity by using NO(x) decomposition were conducted. The increases in singlet oxygen and photocatalytic activity have been observed and the phenomena are discussed based on the efficient prevention of recombination between photoexcited electron and hole within the prepared composite.
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PMID:Improvement in photocatalytic activity of TiO2 under visible irradiation through addition of N-TiO2. 1854 99

In this study, the binding and enzyme activity inhibitory effect of nano-TiO(2) on pepsin was explored compared with micro-TiO(2). Nano-TiO(2) was about 60 nm and micro-TiO(2) was about 200 nm, both round in shape. The activity of pepsin was depressed significantly by nano-TiO(2) comparing to micro-ones. The results of UV spectrometry, HPLC, SDS-PAGE and CD assay proved that micro-TiO(2) has only physical absorption effect on pepsin, but no impairment on primary sequences or secondary structure. However, nano-TiO(2) had coordination interaction with pepsin besides physical binding effect. The secondary structure of pepsin was unfolded with the treatment of nano-TiO(2) at pH 6.5 and pH 3.53, which might consequently affect the beta-hairpin loop that protects the active center of pepsin, and then reduce the enzyme activity. Furthermore, the thermodynamic mechanisms of interaction between nano-TiO(2) and pepsin were explored by fluorescence spectrum and ITC analysis. According to the results of thermodynamic analysis, the K value was 3.64x10(6), stoichiometry (N(pepsin:nano-TiO2)) was 3.04x10(3), the total DeltaH was -2277 cal/mol, DeltaS was 22.7 cal/(K mol), therefore the nano-TiO(2)-pepsin interaction is spontaneous. The depression of activity and the unfolding of secondary structure of pepsin were resulted from non-covalent reactions, including electrostatic force and hydrophobic binding. This work studied the different inhibitory effects and revealed mechanisms of the interaction between micro/nano-TiO(2) and pepsin, and provided a useful approach for evaluating the health risk of nano-materials on level of proteins.
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PMID:Enzyme activity inhibition and secondary structure disruption of nano-TiO2 on pepsin. 2054

In this work, silver-doped TiO2 (Ag/TiO2) nanoparticles were synthesized using a photodeposition technique. The prepared Ag/TiO2 nanoparticles were characterized using TEM, SEM, XRD, and EDX techniques. The characterization of Ag/TiO2 nanoparticles using SEM and EDX techniques revealed the dispersion of Ag metal on the surface of TiO2. The photocatalytic activity of Ag/TiO2 and bare TiO2 in the presence of ultraviolet irradiation was investigated in the removal of chloramphenicol (CAP) as an antibiotic. CAP is a broad-spectrum antibiotic exhibiting activity against both Gram-positive and Gram-negative bacteria, as well as other groups of microorganisms. However, it is, in certain susceptible individuals, associated with serious toxic effects in humans including bone marrow depression, particularly severe in the form of fatal aplastic anaemia. The effects of the operational factors, such as doping content of Ag, photocatalyst dosage and calcination temperature were evaluated in the catalytic activity of Ag/TiO2. The results showed that the photocatalytic efficiency of TiO2 nanoparticles for the degradation of CAP, can be significantly improved by deposition an optimum amount of Ag nanoparticles (0.96 wt%) in the calcination temperature 300 degrees C. It was found that 900 mg/L of Ag/TiO2 is the optimum dosage in the removal of CAP with 20 mg/L initial concentration. The highest removal efficiency of CAP (-100%) at the optimum conditions was observed in 20 min. A mineralization study under optimum conditions showed about 88% reduction in total organic carbon after 120 min of irradiation time.
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PMID:Photocatalytic degradation of chloramphenicol in an aqueous suspension of silver-doped TiO2 nanoparticles. 2419 48

A total of 163 soil samples (0-20 cm layer) were collected from the grid sampling plots (80 m x 80 m) in Huanjiang Observation and Research Station of Karst Ecosystem in a small catchment in Karst cluster-peak depression area, South China. By using classical statistics and geostatistics, the spatial heterogeneity of mineral components (SiO2, Fe2O3, CaO, MgO, Al2O3, MnO, and TiO2) in the soils were studied. The contents of the seven soil mineral components in the study area differed greatly, being in the order of SiO2 > Al2O3 > CaO > MgO > Fe2O3 > TiO2 > MnO, and the variance coefficients also varied obviously, in the order of CaO > MgO > Fe2O3 > TiO2 > SiO2 > Al2O3 > MnO. The seven mineral components accounted for 69.4% of the total soil mass. The spatial patterns and the fittest models of the seven soil mineral components differed from each other. All the seven soil mineral components had a strong spatial autocorrelation, with shorter variation ranges and stronger spatial dependence. The Kriging contour maps indicated that the distribution patterns of soil SiO2, Fe2O3, Al2O3, MnO, and TiO2 were similar, being higher in south and east, lower in north and west, higher in depression, and lower in slope, while the distribution patterns of soil CaO and MgO were in adverse. Natural conditions (vegetation, bare rock rate, slope degree, and slope aspect, etc. ) and human disturbance were the most important factors affecting the spatial patterns of the soil mineral components.
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PMID:[Spatial heterogeneity of surface soil mineral components in a small catchment in Karst peak-cluster depression area, South China]. 2456 47

Nanosized TiO2 (n-TiO2), CeO2 (n-CeO2), and ZnO (n-ZnO) and bulk ZnO were chosen for a 4-h exposure study on a model ammonia oxidizing bacterium, Nitrosomonas europaea. n-ZnO displayed the most serious cytotoxicity while n-TiO2 was the least toxic one. The change of cell morphologies, the retardance of specific oxygen uptake rates and ammonia oxidation rates, and the depression of amoA gene expressions under NP stresses were generally observed when the cell densities and membrane integrities were not significantly impaired yet. The TEM imaging and the synchrotron X-ray fluorescence microscopy of the NPs impacted cells revealed the increase of the corresponding intracellular Ti, Ce or Zn contents and suggested the intracellular NP accumulation. The elevation of intracellular S contents accompanied with higher K contents implied the possible activation of thiol-containing glutathione and thioredoxin production for NP stress alleviation. The NP cytotoxicity was not always a function of NP concentration. The 200 mg L(-1) n-TiO2 or n-CeO2 impacted cells displayed the similar ammonia oxidation activities but higher amoA gene expression levels than the 20 mg L(-1) NPs impacted ones. Such phenomenon further indicated the possible establishment of an anti-toxicity mechanism in N. europaea at the genetic level to redeem the weakened AMO activities along with the NP aggregation effects.
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PMID:Short-term effects of TiO2, CeO2, and ZnO nanoparticles on metabolic activities and gene expression of Nitrosomonas europaea. 2571 Mar 20

The photocatalytic activity and photostability of CdS quantum dot (QD) can be remarkably enhanced by hybridization with Rh-substituted layered titanate nanosheet even at very low Rh substitution rate (<1%). Mesoporous CdS-Ti(5.2-x)/6 Rhx/2O2 nanohybrids are synthesized by a self-assembly of exfoliated Ti(5.2-x)/6 Rhx/2O2 nanosheets with CdS QDs. The partial substitution of Rh(3+)/Rh(4+) ions for Ti(4+) ions in layered titanate is quite effective in enhancing an electronic coupling between hybridized CdS and titanate components via the formation of interband Rh 4d states. A crucial role of Rh substituent ion in the internal electron transfer is obviously evidenced from in situ X-ray absorption spectroscopy showing the elongation of (RhO) bond under visible light irradiation. This is the first spectroscopic evidence for the important role of substituent ion in the photoinduced electron transfer of hybrid-type photocatalyst. The CdS-Ti(5.2-x)/6 Rhx/2O2 nanohybrids show much higher photocatalytic activity for H2 production and better photostability than do CdS and unsubstituted CdS-TiO2 nanohybrid. This result is ascribable to the enhancement of visible light absorptivity, the depression of electron-hole recombination, and the enhanced hole curing of CdS upon Rh substitution. The present study underscores that the hybridization with composition-controlled inorganic nanosheet provides a novel efficient methodology to optimize the photo-related functionalities of semiconductor nanocrystal.
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PMID:A Crucial Role of Rh Substituent Ion in Photoinduced Internal Electron Transfer and Enhanced Photocatalytic Activity of CdS-Ti(5.2-x)/6 Rhx /2 O2 Nanohybrids. 2645 93

Synaptic plasticity plays a crucial role in allowing neural networks to learn and adapt to various input environments. Neuromorphic systems need to implement plastic synapses to obtain basic "cognitive" capabilities such as learning. One promising and scalable approach for implementing neuromorphic synapses is to use nano-scale memristors as synaptic elements. In this paper we propose a hybrid CMOS-memristor system comprising CMOS neurons interconnected through TiO2-x memristors, and spike-based learning circuits that modulate the conductance of the memristive synapse elements according to a spike-based Perceptron plasticity rule. We highlight a number of advantages for using this spike-based plasticity rule as compared to other forms of spike timing dependent plasticity (STDP) rules. We provide experimental proof-of-concept results with two silicon neurons connected through a memristive synapse that show how the CMOS plasticity circuits can induce stable changes in memristor conductances, giving rise to increased synaptic strength after a potentiation episode and to decreased strength after a depression episode.
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PMID:Implementation of a spike-based perceptron learning rule using TiO2-x memristors. 2648 29

Neuromorphic computational systems that emulate biological synapses in the human brain are fundamental in the development of artificial intelligence protocols beyond the standard von Neumann architecture. Such systems require new types of building blocks, such as memristors that access a quasi-continuous and wide range of conductive states, which is still an obstacle for the realization of high-efficiency and large-capacity learning in neuromorphoric simulation. Here, we introduce hydrogen and sodium titanate nanobelts, the intermediate products of hydrothermal synthesis of TiO2 nanobelts, to emulate the synaptic behavior. Devices incorporating a single titanate nanobelt demonstrate robust and reliable synaptic functions, including excitatory postsynaptic current, paired pulse facilitation, short term plasticity, potentiation and depression, as well as learning-forgetting behavior. In particular, the gradual modulation of conductive states in the single nanobelt device can be achieved by a large number of identical pulses. The mechanism for synaptic functionality of the titanate nanobelt device is attributed to the competition between an electric field driven migration of oxygen vacancies and a thermally induced spontaneous diffusion. These results provide insight into the potential use of titanate nanobelts in synaptic applications requiring continuously addressable states coupled with high processing efficiency.
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PMID:Oxygen vacancy migration/diffusion induced synaptic plasticity in a single titanate nanobelt. 2954 96