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ABSTRACT: The single-scattering properties of concave fractal polyhedra are investigated, with particle size parameters ranging from the Rayleigh to geometric-optics regimes. Two fractal shape parameters, irregularity and aspect ratio, are used to iteratively construct "generations" of irregular fractal particles. The pseudospectral time-domain (PSTD) method and the improved geometric-optics method (IGOM) are combined to compute the single-scattering properties of fractal particles over the range of size parameters. The effects of fractal generation, irregularity, and aspect ratio on the single-scattering properties of fractals are investigated. The extinction efficiency, absorption efficiency, and asymmetry factor, calculated by the PSTD method for fractal particles, with small-to-moderate size parameters, smoothly bridges the gap between those size parameters and size parameters for which solutions given by the IGOM may be used. Somewhat surprisingly, excellent agreement between values of the phase function of randomly oriented fractal particles calculated by the two numerical methods is found, not only for large particles, but in fact extends as far down in equivalent-projected-area size parameters as 25. The agreement in the case of other nonzero phase matrix elements is not as good at so small a size. Furthermore, the numerical results of ensemble-averaged phase matrix elements of a single fractal realization are compared with dust particle measurements, and good agreement is found by using the fractal particle model to represent data from a study of feldspar aerosols.
Applied Optics 02/2013; 52(4):640-52. · 1.41 Impact Factor
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ABSTRACT: The pseudo-spectral time domain (PSTD) and the discrete dipole approximation (DDA) are two popular and robust methods for the numerical simulation of dielectric particle light scattering. The present study compares the numerical performances of the two methods in the computation of the single-scattering properties of homogeneous dielectric spheres and spheroids for which the exact solutions can be obtained from the Lorenz-Mie theory and the T-matrix theory. The accuracy criteria for the extinction efficiency and the phase function are prescribed to be the same for the PSTD and DDA in order that the computational time can be compared in a fair manner. The computational efficiency and applicability of the two methods are each shown to depend on both the size parameter and the refractive index of the scattering particle. For a small refractive index, a critical size parameter, which decreases from 80 to 30 as the refractive index increases from 1.2 to 1.4, exists below which the DDA outperforms the PSTD. For large refractive indices (>1.4), the PSTD is more efficient than the DDA for a wide size parameter range and has a larger region of applicability. Furthermore, the accuracy shown by the two methods in the computation of backscatter, linear polarization, and asymmetry factor is comparable. The comparison was extended to include spheroids with typical refractive indices of ice and dust and similar conclusions were drawn., "Systematic comparison of the discrete dipole approximation and the finite difference time domain method for large dielectric scatterers,, "The discrete dipole approximation for simulation of light scattering by particles much larger than the wavelength of the discrete dipole approximation and the discrete source method for simulation of light scattering by red blood cells,
Optics Express 07/2012; 20(15):16763-16776. · 3.59 Impact Factor
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ABSTRACT: Previous research showed that nano-TiO2 could significantly promote photosynthesis and greatly improve growth of spinach, but, we also speculated that an increase
of spinach growth by nano-TiO2 treatment might be closely related to the change of nitrogen metabolism. The effects of nano-anatase TiO2 on the nitrogen metabolism of growing spinach were studied by treating them with nano-anatase TiO2. The results showed that, nano-anatase TiO2 treatment could obviously increase the activities of nitrate reductase, glutamate dehydrogenase, glutamine synthase, and
glutamic-pyruvic transaminase during the growing stage. Nano-anatase TiO2 treatment could also promote spinach to absorb nitrate, accelerate, inorganic nitrogen (such as NO
3
t-
−N and NH
4
+
−N) to be translated into organic nitrogen (such as protein and chlorophyll), and enhance the fresh weight and dry weights.
Biological Trace Element Research 04/2012; 110(2):179-190. · 1.92 Impact Factor
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Yanmei Duan,
Huiting Liu,
Jinfang Zhao, Chao Liu,
Zhongrui Li,
Jinying Yan,
Linglan Ma,
Jie Liu,
Yaning Xie,
Jie Ruan,
Fashui Hong
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ABSTRACT: 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 (5nm) 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 2.41Å. 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.
Biological Trace Element Research 04/2012; 130(2):162-171. · 1.92 Impact Factor
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ABSTRACT: Having a photocatalyzed characteristic, our previous research had proved that nano-anatase TiO2 is closely related to the photosynthesis of spinach. It could not only improve the light absorbance and the transformation
from light energy to electron energy and to active chemical energy but also promote carbon dioxide (CO2) assimilation of spinach. However, the mechanism of carbon reaction promoted by nano-anatase TiO2 remains largely unclear. By electrophoresis and Western blot methods, the results of the experiments proved that Rubisco
from the nano-anatase TiO2-treated spinach during the extraction procedure of Rubisco was found to consist of Rubisco and a heavier molecular-mass protein
(about 1200 kDa) comprising both Rubisco and Rubisco activase. The Rubisco carboxylase activity was 2.67 times that of Rubisco
from the control and it could hydrolyze ATP in the same manner as Rubisco activase. The total sulfhydryl groups and available
sulfhydryl groups of the Rubisco were 32-SH and 21-SH per mole of enzyme more than those of the Rubisco purified from the
control, respectively. The circular dichroism spectra showed that the secondary structure of Rubisco from the nano-anatase
TiO2-treated spinach was very different from Rubisco of the control. It suggested that the mechanism of nano-anatase TiO2 activating Rubisco of spinach was that the complex of Rubsico and Rubisco activase was induced in spinach, which promoted
Rubsico carboxylation and increased the rate of photosynthetic carbon reaction.
Biological Trace Element Research 04/2012; 111(1):239-253. · 1.92 Impact Factor
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ABSTRACT: The complex of Rubisco and Rubisco activase from LaCl3
™, CeCl3
™ treated spinachin vivo is induced. SDS-PAGE result shows that the purified proteins from LaCl3
™, CeCl3
™ treated spinach have not only large and small subunits (55 kD, 14.4 kD) of Rubisco, but also two large subunits of 45 kD
and 41 kD near the large subunits of Rubisco. Native-PAGE shows that the purified proteins from LaCl3
™, CeCl3
™ treated spinach have not only a band of Rubisco (560 kD), but also a band of about 1100 kD, about twice distant from Rubisco,
which might be a complex of Rubisco and Rubisco activase. The purified enzyme activities from LaCl3
™, CeCl3
™ treated spinach are 1.8 and 2.8 times that of the control, the intensities of absorption and fluorescence are significantly
higher than that of the purified Rubisco from the control, and the total sulfhydryl groups and available sulfhydryl groups
are 36–39 ™SH per mol enzyme, 14–25 ™SH per mol enzyme more than those of the purified Rubisco from the control, respectively.
The CD spectra show that the secondary structure of the purified enzyme from LaCl3
™, CeCl3
™ treated spinach is very different from the control. The enzyme activities from LaCl3
™, CeCl3
™ treated spinachin vivo are 1.5 and 1.9 times those of the control.
Science in China Series B Chemistry 04/2012; 48(1):67-74. · 1.20 Impact Factor
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ABSTRACT: It was studied by spectroscopy that PSII reaction center complex consisting of three polypeptides, D1, D2 and Cytb559, were purified from PSII particle of CeCl3 treated spinach. The results of the experiment show that Ce3+ could improve the growth of spinach, and accelerate electron transport of PSII particles. Of chl-a of UV-Vis spectrum of
D1/D2/Cytb559 complex, Soret band was blue-shifted by 3 nm and Q band by 2 nm, respectively, and the fluorescence emission
peak was blue-shifted by 5 nm in CeCl3-treated spinach compared with the one in control. By the extended X-ray absorption fine structure (EXAFS) spectroscopy methods,
it has been found that Ce3+ is coordinated with 8 nitrogen atoms in the first coordination shell with Ce-N bond length of 0.253 nm, and Ce3+ with 6 oxygen atoms in the second coordination shell with Ce-O bond length of 0.32 nm. However, the secondary structure of
D1/D2/Cytb559 complex by circular dichroism (CD) spectroscopy has no significant change after CeCl3 treated. It might be that Ce3+ binds to porphyrin rings of chlorophyll and oxygen of amino acid residue of polypeptide in D1/D2/Cytb559 complex, and then
accelerates the primary reaction of PSII, intensifies function of P680+ primary electron donor of D1/D2/Cytb559, but there is little change in conformation of PSII reaction center complex.
Science in China Series B Chemistry 04/2012; 46(1):42-50. · 1.20 Impact Factor
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ABSTRACT: Magnesium (Mg) deficiency has been reported to affect plant photosynthesis and growth, and cerium (Ce) was considered to be able to improve plant growth. However, the mechanisms of Mg deficiency and Ce on plant growth remain poorly understood. The main aim of this work is to identify whether or not Mg deprivation affects the interdependent nitrogen and carbon assimilations in the maize leaves and whether or not Ce modulates the assimilations in the maize leaves under Mg deficiency. Maize plants were cultivated in Hoagland’s solution. They were subjected to Mg deficiency and to cerium chloride administration in the Mg-present Hoagland’s media and Mg-deficient Hoagland’s media.After 2 weeks,we measured chlorophyll (Chl) a fluorescence and the activities of nitrate reductase (NR), sucrose-phosphate synthase(SPS), and phosphoenolpyruvate carboxylase (PEPCase)in metabolic checkpoints coordinating primary nitrogen and carbon assimilations in the maize leaves. The results showed that Mg deficiency significantly inhibited plant growth and decreased the activities of NR, SPS, and PEPCase and the synthesis of Chl and protein. Mg deprivation in maize also significantly decreased the oxygen evolution, electron transport,and efficiency of photochemical energy conversion by photosystem II (PSII). However, Ce addition may promote nitrogen and carbon assimilations, increase PSII activities,and improve maize growth under Mg deficiency. Moreover,our findings would help promote usage of Mg or Ce fertilizers in maize production.
Biological trace element research 02/2012; 148(1):102-9. · 1.92 Impact Factor
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ABSTRACT: The mechanism of the fact that manganese deprivation and cerium addition affect the photochemical efficiency of plants is unclear. In this study, we investigated the improvement by cerium of the damage of the photochemical function of maize chloroplasts under manganese-deprived stress. Chlorophyll fluorescence induction measurements showed that the ratio of variable to maximum fluorescence (Fv/Fm) underwent great decreases under manganese deficiency, which was attributed to the reduction of intrinsic quantum efficiency of the photosystem II units. The electron flow between the two photosystems, activities of Mg(2+)-ATPase and Ca(2+)-ATPase, and rate of photophosphorylation on the thylakoid membrane of maize chloroplasts were reduced significantly by exposure to manganese deprivation. Furthermore, the inhibition of cyclic photophosphorylation was more severe than non-cyclic photophosphorylation under manganese deficiency. However, added cerium could relieve the inhibition of the photochemical reaction caused by manganese deprivation in maize chloroplasts. It implied that manganese deprivation could disturb photochemical reaction of chloroplasts strongly, which could be improved by cerium addition.
Biological trace element research 10/2011; 146(1):94-100. · 1.92 Impact Factor
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ABSTRACT: Rare earth elements can promote photosynthesis, but their mechanisms are still poorly understood under magnesium deficiency. The present study was designed to determine the role of cerium in magnesium-deficient maize plants. Maize was cultivated in Hoagland's solution added with cerium with and without adequate quantities of magnesium. Under magnesium-deficient conditions, cerium can prevents inhibition of synthesis of photosynthetic pigment, improves light energy absorption and conversion, oxygen evolution, and the activity of photo-phosphorelation and its coupling factor Ca(2+)-ATPase. These results suggest that cerium could partly substitute magnesium, improving photosynthesis and plant growth.
Biological trace element research 09/2011; 142(3):760-72. · 1.92 Impact Factor
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ABSTRACT: The influence of LaCl(3), CeCl(3), and NdCl(3) on the antioxidative defense system in maize seedlings under cold stress was investigated. It was found that maize seedlings cultivated in cold stress developed distinct cold symptoms, and the plant growth was significantly inhibited as expected, while Ln-treated seedling growth was improved. Cold stress in maize seedlings also increased the permeability of plasma membrane, malondialdehyde as a degradation product of lipid peroxidation, and reactive oxygen species such as superoxide radicals and hydrogen peroxide, and decreased activities of the antioxidant enzymes such as superoxide dismutase, catalase, ascorbate peroxidase, and glutathione content; however, Ln treatments cultivated in cold stress decreased the permeability of plasma membrane, malondialdehyde, and reactive oxygen species, and increased activities of the antioxidative defense system. It implied that Ln could increase oxidative-stress resistance under cold stress. On the other hand, the assay of physiological and biochemical parameters demonstrated that Ce relieving chilling injury of maize seedlings caused by cold stress was most significant, medium in the Nd treatment, and last in the La treatment. These results suggested that the increase of cold resistance of maize seedlings caused by Ln might be closely related to its properties of 4f electron shell and variable valence.
Biological trace element research 09/2011; 142(3):819-30. · 1.92 Impact Factor
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ABSTRACT: Manganese is one of the essential microelements for plant growth, and cerium is a beneficial element for plant growth. However, whether manganese deficiency affects nitrogen metabolism of plants and cerium improves the nitrogen metabolism of plants by exposure to manganese-deficient media are still unclear. The main aim of the study was to determine the effects of manganese deficiency in nitrogen metabolism and the roles of cerium in the improvement of manganese-deficient effects in maize seedlings. Maize seedlings were cultivated in manganese present Meider's nutrient solution. They were subjected to manganese deficiency and to cerium chloride administered in the manganese-present and manganese-deficient media. Maize seedlings grown in the various media were measured for key enzyme activities involved in nitrogen metabolism, such as nitrate reductase, glutamate dehydrogenase, glutamine synthetase, and glutamic-oxaloace transaminase. We found that manganese deficiency restricted uptake and transport of NO(3)(-), inhibited activities of nitrogen-metabolism-related enzymes, such as nitrate reductase, glutamine synthetase, and glutamic-oxaloace transaminase, thus decreasing the synthesis of chlorophyll and soluble protein, and inhibited the growth of maize seedlings. Manganese deficiency promoted the activity of glutamate dehydrogenase and reduced the toxicity of excess ammonia to the plant, while added cerium relieved the damage to nitrogen metabolism caused by manganese deficiency in maize seedlings. However, cerium addition exerted positively to relieve the damage of nitrogen metabolism process in maize seedlings caused by exposure to manganese-deficient media.
Biological trace element research 06/2011; 144(1-3):1240-50. · 1.92 Impact Factor
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ABSTRACT: It had been proved that manganese (Mn) deficiency could damage the photosynthesis of plants, and lanthanides could improve photosynthesis and greatly promote plant growth. However, the mechanisms on how Mn deficiency and cerium (Ce) addition affects the photosynthetic carbon reaction of plants under manganese deficiency are still poorly understood. In this study, the main aim was to determine Mn deficiency and cerium addition effects in key enzymes of CO(2) assimilation of maize. Maize plants were cultivated in Hoagland's solution. They were subjected to Mn deficiency and to Ce administered in the Mn-present Hoagland's media and Mn-deficient Hoagland's media. The growth condition, chlorophyll synthesis, and oxygen evolution were significantly destroyed by manganese deficiency, the activities of ribulose-1, 5-bisphosphate caroxylase/oxygenase (Rubisco), and Rubisco activase, and their genes expressions were inhibited by Mn deficiency. However, Ce treatment promoted the chlorophyll synthesis, oxygen evolution, and the activities of two key enzymes in CO(2) assimilation. Reverse transcription polymerase chain reaction was carried out, and the results showed that the mRNA expressions of Rubisco small subunit (rbcS), Rubisco large subunit (rbcL), and Rubisco activase subunit (rca) in the cerium-treated maize were obviously increased. One of the possible mechanisms of carbon reaction promoted by Ce is that the Ce treatment resulted in the enhancements of Rubisco and Rubisco activase mRNA amounts, the protein levels, and activities of Rubisco and Rubisco activase, thereby leading to the high rate of photosynthetic carbon reaction and enhancement of maize growth under Mn-deficient conditions. Together, the experimental study implied that Ce could partly substitute for magnesium and increase the oxidative stress-resistance of spinach chloroplast grown in Mn-deficiency conditions, but the mechanisms need further study.
Biological trace element research 06/2011; 141(1-3):305-16. · 1.92 Impact Factor
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ABSTRACT: The main aim of this work is to identify how the combined stresses affect the interdependent nitrogen and photosynthetic carbon assimilations in maize. Maize plants were cultivated in Meider's solution. They were subjected to salt stress and potassium deficiency in the K-present Meider's media and K-deficient Meider's media. After 5 weeks, we measured chlorophyll a fluorescence and the activities of several enzymes in metabolic checkpoints coordinating primary nitrogen and carbon assimilation in the leaves of maize. The study showed that the combination of salt stress and potassium-deficient stress more significantly decreased nitrate uptake, plant growth, the activities of nitrate reductase, glutamate dehydrogenase, glutamate synthase, urease, glutamic-pyruvic transaminase, glutamic-oxaloace transaminase, sucrose-phosphate synthase, phosphoenolpyruvate carboxylase, and the synthesis of free amino acids, chlorophyll, and protein than those of each individual stress, respectively. However, the combined stresses significantly increased the accumulation of ammonium and carbohydrate products. The combined stresses also significantly decreased the oxygen evolution, the electron transport, and the efficiency of photochemical energy conversion by photosystem II in maize seedlings. Taken together, a combination of salt stress and potassium-deficient stress impaired the assimilations of both nitrogen and carbon and decreased the photosystem II activity in maize.
Biological trace element research 04/2011; 144(1-3):1159-74. · 1.92 Impact Factor
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ABSTRACT: Recent studies demonstrated that titanium dioxide nanoparticles (TiO2 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 TiO2 NPs treated. The results showed that TiO2 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 TiO2 (bulk-TiO2) treatment. Meanwhile, spectroscopy assays indicated that TiO2 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. TiO2 NPs treatment could reduce F480/F440 ratio and increase F650/F680 ratio and accelerate the rate of whole chain electron transport and oxygen evolution of the chloroplast. However, the photosynthesis improvement of the non-nanoTiO2 treatment was far less effective than TiO2 NPs treatment. Taken together, TiO2 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.
Biological trace element research 11/2010; 143(2):1131-41. · 1.92 Impact Factor
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ABSTRACT: Titanium dioxide nanoparticles (TiO(2) NPs) are now in daily use including popular sunscreens, toothpastes, and cosmetics. However, the effects of TiO(2) NPs on human body, especially on the central nervous system, are still unclear. The aim of this study was to determine whether TiO(2) NPs exposure results in persistent alternations in nervous system function. ICR mice were exposed to TiO(2) NPs through intragastric administration at 0, 5, 10 and 50 mg/kg body weight every day for 60 days. The Y-maze test showed that TiO(2) NPs exposure could significantly impair the behaviors of spatial recognition memory. To fully investigate the neurotoxicological consequence of TiO(2) NPs exposure, brain elements and neurochemicals were also investigated. The contents of Ca, Mg, Na, K, Fe and Zn in brain were significantly altered after TiO(2) NPs exposure. Moreover, TiO(2) NPs significantly inhibited the activities of Na(+)/K(+)-ATPase, Ca(2+)-ATPase, Ca(2+)/Mg(2+)-ATPase, acetylcholine esterase, and nitric oxide synthase; the function of the central cholinergic system was also noticeably disturbed and the contents of some monoamines neurotransmitters such as norepinephrine, dopamine and its metabolite 3, 4-dihydroxyphenylacetic acid, 5-hydroxytryptamine and its metabolite 5-hydroxyindoleacetic acid were significantly decreased, while the contents of acetylcholine, glutamate, and nitric oxide were significantly increased. These first findings indicated that exposure to TiO(2) NPs could possibly impair the spatial recognition memory ability, and this deficit may be possibly attributed to the disturbance of the homeostasis of trace elements, enzymes and neurotransmitter systems in the mouse brain. Therefore, the application of TiO(2) NPs and exposure effects especially on human brain for long-term and low-dose treatment should be cautious.
Biomaterials 11/2010; 31(31):8043-50. · 7.40 Impact Factor
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ABSTRACT: The mechanism of the molecular interaction between Ce3+, a member of rare earth elements, and Rubisco in vitro is investigated. The carboxylase activity of Rubisco greatly increased under low concentrations of Ce3+ and decreased under high concentrations of Ce3+. The ultraviolet absorption spectra show that the various concentrations of Ce3+ treatment do not shift the characteristic peaks of Rubisco while the characteristic peak intensity of Rubisco increases with increasing Ce3+ concentration. The Rubisco-Ce3+ interactions also do not cause any noticeable change in the λmax of Rubisco fluorescence spectra. However, the fluorescence intensity of Rubisco is found quenched by the addition of Ce3+, which strongly suggests that Ce3+ could directly bind to the Rubisco protein. and the binding sites is estimated to 1.52 per protein. The binding between Ce3+ and Rubisco is also proved by extended X-ray absorption fine-structure essay; Ce3+ coordinated with eight oxygen atoms of Rubisco in first shells and six oxygen atoms in second shells. The results implied that Ce3+ might improve the microenvironment of Rubisco and, in turn, affected the carboxylase capacity of Rubisco greatly.
Biological trace element research 10/2010; 143(2):1110-20. · 1.92 Impact Factor
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ABSTRACT: In order to study the mechanisms underlying the effects of TiO(2) nanoparticles on lactate dehydrogenase (LDH, EC1.1.1.27), Institute of Cancer Research region mice were injected with nanoparticulate anatase TiO(2) (5 nm) of various doses into the abdominal cavity daily for 14 days. We then examined LDH activity in vivo and in vitro and direct evident for interaction between nanoparticulate anatase TiO(2) and LDH using spectral methods. The results showed that nanoparticulate anatase TiO(2) could significantly activate LDH in vivo and in vitro; the kinetics constant (Km) and Vmax were 0.006 microM and 1,149 unit mg(-1) protein min(-1), respectively, at a low concentration of nanoparticulate anatase TiO(2), and 3.45 and 0.031 microM and 221 unit mg(-1) protein min(-1), respectively, at a high concentration of nanoparticulate anatase TiO(2). By fluorescence spectral assays, the nanoparticulate anatase TiO(2) was determined to be directly bound to LDH, and the binding constants of the binding site were 1.77 x 10(8) L mol(-1) and 2.15 x 10(7) L mol(-1), respectively, and the binding distance between nanoparticulate anatase TiO(2) and the Trp residue of LDH was 4.18 nm, and nanoparticulate anatase TiO(2) induced the protein unfolding. It was concluded that the binding of nanoparticulate anatase TiO(2) altered LDH structure and function.
Biological trace element research 10/2009; 136(3):302-13. · 1.92 Impact Factor
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ABSTRACT: The effects of Mn(2+) deficiency on light absorption, transmission, and oxygen evolution of maize chloroplasts were investigated by spectral methods. Several effects of Mn(2+) deficiency were observed: (1) the skeleton of pigment protein complexes and oxygen-evolving center and the combination between pigment and protein were damaged; (2) the light absorption of chloroplasts was obviously decreased; (3) the energy transfer among amino acids within PS II protein-pigment complex and decreased energy transport from tyrosine residue to chlorophyll a and from chlorophyll b and carotenoid to chlorophyll a were inhibited; (4) the oxygen-evolving of chloroplast was significantly inhibited. However, Mn(2+) addition decreased the damage of light absorption, transmission, and oxygen evolution of maize chloroplasts caused by Mn(2+) deficiency.
Biological trace element research 10/2009; 136(3):372-82. · 1.92 Impact Factor
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ABSTRACT: The activity of alanine aminotransferase (ALT; E.C. 2.6.1.2) is often changed upon inflammatory responses in animals. Rare earths was shown to provoke various inflammatory responses both in rats and mice; however, the molecular mechanism by which rare earths exert its toxicity has not been completely understood, especially, we know little about the mechanism of the interaction between CeCl(3) and ALT. In this report, we investigated the mechanisms of CeCl(3) on ALT activity in vivo and in vitro. Our results showed that Ce(3+) could significantly activate ALT in vivo and in vitro; the kinetics constant (Km) and Vmax were 0.018 microM and 1,380 unit mg(-1) protein min(-1), respectively, at a low concentration of Ce(3+), and 0.027 microM and 624 unit mg(-1) protein min(-1), respectively, at a high concentration of Ce(3+). By UV absorption and fluorescence spectroscopy assays, the Ce(3+) was determined to be directly bound to ALT; the binding site of Ce(3+) to ALT was 1.72, and the binding constants of the binding site were 4.82 x 10(8) and 9.05 x 10(7) L mol(-1). Based on the analysis of the circular dichroism spectra, it was concluded that the binding of Ce(3+) altered the secondary structure of ALT, suggesting that the observed enhancement of ALT activity was caused by a subtle structural change in the active site through the formation of the complex with Ce(3+).
Biological trace element research 10/2009; 136(2):187-96. · 1.92 Impact Factor
