[Study of Reaction Dynamics between Bovine Serum Albumin and Folic Acid by Stopped-Flow/Fluorescence].

As a kind of coenzyme of one-carbon enzymes in vivo, folic acid belongs to B vitamins, which can interact with other vitamins and has great significance for converting among amino acids, dividing growth of cells and protein synthesis reactions. Half-life, concentration and reaction rate constant of drugs are important parameters in pharmacokinetic study. In this paper, by utilizing fluorescence spectrophotometer and stopped-flow spectrum analyzer, reaction kinetic parameters between bovine serum albumin(BSA) and folic acid in a bionic system have been investigated, which provide references for parameters of drug metabolism related to folic acid. By using Stern-Volmer equation dealing with fluorescence quenching experiments data, we concluded that under 25, 30, and 37 degrees C, the static quenching constants of folic acid to intrinsic fluorescence from bovine serum albumin were 2.455 x 10(10), 4.900 x 10(10) and 6.427 x 10(10) L x mol(-1) x s(-1) respectively; The results of kinetic reaction rate have shown that the reaction rate of BSA and folic acid are greater than 100 mol x L(-1) x s(-1) at different temperatures, pH and buffering media, illustrating that the quenching mechanism between BSA and folic acid is to form composite static quenching process. Reaction concentration of bovine serum albumin and its initial concentration were equal to the secondary reaction formula, and the correlation coefficient was 0.998 7, while the half-life (t1/2) was 0.059 s at physiological temperature. With the increase of folic acid concentration, the apparent rate constant of this reaction had a linear increasing trend, the BSA fluorescence quenching rate constant catalyzed by folic acid was 3.174 x 10(5) mol x L(-1) x s(-1). Furthermore, with different buffer, the apparent rate constant and reaction rate constant of BSA interacting with folic acid were detected to explore the influence on the reaction under physiological medium, which is of great significance to determine the clinical regimen, forecast the efficacy and toxicity of drugs and rational drug.

[The Synthesis, Luminescence and Energy Transmission of NaLa(MoO4) 2 : Eu3+/Tb3+/Tm3+ Materials].

A series of Eu3+ /Tb3+ /Tm3+ single/co-doped NaLa(MoO4)2 (NLM) phosphors have been synthesized by microemulsion-hydrothermal method. Phosphor crystal structure, morphology and luminescent properties were tested and studied by X-ray diffraction (XRD), scanning electron microscopy (SEM) and fluorescence spectroscopy. The results show that the prepared samples are all tetragonal single crystals. By way of substitution, the sites of La3+ are replaced by Eu3+, Tb3+ and Tm3+. Morphology of the samples are tetragonal sheet structure and the size of particles is 1 - 1.5 µm. When the doping concentration of Eu3+ is 9%, NLM : 9%Eu3+ phosphor emission peak is the strongest at 616 nm, the critical transfer distance (R(c)) between Eu3+ in the NLM matrix is about 15.20 Å at this time. At the emission spectrum of NLM : 9%Eu3+, the peak at 591 nm is the magnetic dipole transition of 5D0 to 7F1 of Eu3+. The peak at 616 nm is the electric dipole transition of 5D0 to 7 F2 of Eu3+. Electric dipole transition emission intensity is about 10 times of the strength of the magnetic dipole transition. This indicates that Eu3+ is located at noninversion symmetry site. By Fixing Eu3+ (Tb3+) concentration and varying the concentration of Tb3+ (Eu3+), the energy transfer mechanism between Eu3+ and Tb3+ was studied. By adjusting the Eu3+, Tb3+ and Tm3+ doping concentrations, tunable luminescence of visible light region is implemented under the single matrix. The luminescence of NLM x%Eu3+, y%Tb3+, z%Tm3+ phosphors are translated from blue (0.205, 0.135) to pseudo-white (0.305, 0.266) under 360 nm irradiation.

[The Different Phase, Morphology Controllable Synthesis and Luminescent Properties Investigation of NaYF4: Yb, Er].

Using sodium fluoride and rare earth nitrate as raw materials and sodium citrate as surfactant, micron grade NaYF4 upconversion luminescent materials were prepared by hydrothermal method. By X-ray diffraction(XRD), scanning electron microscope(SEM) and fluorescence spectrometer, the crystal phase, morphology and luminescent characteristics of the prepared samples were investigated. The results showed that the phase of the samples could generate a transition from cubic phase to hexagonal phase by adjusting the proportion (5, 6, 7, 8, 9, 11) of NaF/RE , and the X ray diffraction peaks for the cubic and hexagonal phase of samples exactly matched with those of the standard card of PDF# 77-2042 and PDF# 16-0334, respectively. The SEM photographs showed that the crystallinity of samples was high and the dispersibility was favourable, the morphology were translated from microrods to hexagonal microplates. The samples upconversion luminescent spectra showed the intensity enhancement of red and green light emission peaks with increasement of the ratio of NaF/RE3+. The green emission peaks of samples at 520 and 539 nm corresponded to the ²H¹¹/²-4-->I15/2 and 4S3/2-->4I15/2 level transition of Er³âº ion, and the red light emission peaks of samples at 653 nm corresponded to the 4F9/2-->4I15/2 levelt ransition of Er+ ion. The chromaticity coordinate diagram exhibited that the change of the luminescent color of samples could be achieved by adjusting the ratio of NaF/RE³âº. With the increasing of NaF/RE³âº ratio, for the whole light-emitting colors of samples, the shift from yellow region to near red region could be realized. It can be concluded that through the relatively simple experimental procedure and lower cost materials, the change of phase and morphology, the moving of light-emitting color for sample NaYF4:Yb³âº, Er³âº could be well controlled only by changing the single component (NaF) molar ratio in the raw materials. The effect of phase and morphology of fluorescent materials on their upconversion luminescence has great potential applications in photonic devices and bioanalysis research.

[Soil denitrification rates in different type riparian zones in maoershan mountainous region of China].

Soil samples were collected from forested, clear-cut, and grassy riparian zones under forest background and from forested and barren riparian zones under cropland background in the Maoershan mountainous region of China. The samples were incubated in laboratory, and their denitrification potentials were determined by nitrate-deduction method. The results showed that under crop-land background, soil denitrification rate was the highest in forested riparian zone and the lowest in barren riparian zone, with the deduction rate of nitrate varied from 46.79%-91.13% and 15.64% -81.84%, respectively. Under forest background, soil denitrification rate decreased in the order of clearcut > forested > grassy riparian zone, with the deduction rate of nitrate being 42.06%-90.39%, 28.24%-85.73% and 21.44%-83.11%, respectively. The denitrification rate was higher in subsurface layer than in deeper layer, and the denitrification potential was limited by the available carbon and nitrate, being the greatest in the forested riparian zone under cropland background.

[Retaining and transformation of incoming soil N from highland to adjacent terrestrial water body in riparian buffer zone].

Highland soil nitrogen can enter adjacent water body via erosion and leaching, being one of the important pollutants in terrestrial water bodies. Riparian buffer zone is a transitional zone between highland and its adjacent water body, and a healthy riparian buffer zone can retain and transform the incoming soil N through physical, biological, and biochemical processes. In this paper, the major pathways through which soil nitrogen enters terrestrial water body and the mechanisms the nitrogen was retained and transformed in riparian buffer zone were introduced systematically, and the factors governing the nitrogen retaining and transformation were analyzed from the aspects of hydrological processes, soil characters, vegetation features, and human activities. The problems existing in riparian buffer zone study were discussed, and some suggestions for the further study in China were presented.