The interactions of lanthanide ions (Ln3+) with bovine serum albumin (BSA) under mimetic physiological conditions (310.15 K, pH 6.7, 0.1MNaCl) were studied by microcalorimetry.
For the first time, based on Two Sets of Independent Sites Model, molar enthalpies (ΔrHm1, ΔrHm2) and coordination number (n1, n2) of the two sets of binding sites with different affinity were obtained directly from the microcalorimetric results. It was
shown that the interactions are endothermic and entropy-driving processes. By combining with fluorescence spectroscopy, other
thermodynamic parameters (ΔrGm1, ΔrSm1) were determined for high-affinity specific sites.
In order to enrich the thermokinetic research methods and enlarge the applicable range of the thermokinetic time-parameter
method, the integral and differential thermokinetic equations of consecutive first-order reaction have been deduced, and the
mathematical models of the time-parameter method for consecutive first-order reactions have been proposed in this paper. The
rate constants of two steps can be calculated from the same thermoanalytical curve measured in a batch conduction calorimeter
simultaneously with this method. The thermokinetics of saponifications of diester in aqueoushanol solvent has been studied.
The experimental results indicate that the time-parameter method for the consecutive first-order reaction is correct.
Small-scale vegetation patterns are frequently the results of plant-plant interactions such as facilitation and competition. Facilitation should be particularly pronounced when both abiotic and biotic stresses are high, but few studies were conducted in such habitats. In heavily-grazed pastures on the eastern Tibetan Plateau, an area with both high abiotic stress and strong biotic disturbance, we made relevés of herb species both beneath and outside canopies of three shrub species (Spiraea alpina, Sibiraea angustata and Potentilla fruticosa) differing in palatability and canopy structure. Herb species richness (S), pooled cover (PC) of all species, number of flowering species (FS) and number of inflorescences of all species (IN) were greater outside than beneath the shrub canopies. Evenness (J), in contrast, was smaller outside, while Shannon’s diversity index (H) was the same. Differences in S and J between plots beneath and outside the shrub canopies were greater in the case of P. fruticosa than in the cases of S. angustata and S. alpina, but differences in PC, FS or IN did not depend on the shrub species. Among the common species (frequency ≥6), 47–85% were equally frequent beneath and outside the shrubs, 13–39% were more frequent outside and 3–13% were more frequent beneath the shrubs. For the rarest species (frequency < 6), however, more species occurred beneath than outside the shrubs. The ordination diagram showed a clear separation between the relevés outside and beneath the shrubs and a gradient from P. fruticosa via S. alpina to S. angustata, accompanied by a distinct decrease in the extent of the difference between the vegetation beneath and outside the shrub canopies. In conclusion, the three shrub species facilitated some species in the herb layer and each shrub species had a specific impact, related to its canopy structure and palatability but also to the grazing pressure, which was greater around the P. fruticosa shrubs than around S. alpina and S. angustata.
Authors:G. Zhang, X. Li, S. Tian, J. Li, J. Wang, X. Lou, and Q. Cheng
The stability of β-cyclodextrinethyl benzoate6H2O(β-CDC6H5COOC2H56H2O) was investigated by TG and DSC. The mass loss takes place in three stages: the dehydration occurs at 50-120C; the dissociation
of β-CDC6H5COOC2H5occurs at 200-260C; the decomposition of β-CD begins at 280C. The kinetics of the dissociation of β-CDC6H5COOC2H5in a dry nitrogen flow was studied by means of thermogravimetry both at constant temperature and linearly increasing temperature.
The results show that the dissociation of β-CDC6H5COOC2H5is dominated by a three-dimensional diffusion process (D3). The activation energy E is 116.19 kJ mol-1and the pre-exponential factor A 6.5358109min-1.
Cyclodextrin is able to form inclusion complexes with a great variety of guest molecules, and the studies focus on the energy
of binding between cyclodextrin and the guest molecule. In this paper, the β-cyclodextrinethyl benzoate inclusion complex
was studied by fluorescence spectrophotometry and infrared absorption spectroscopy, and the results show that the stable energy
of inclusion complexes of β-CD with weakly polar guest molecules consists mainly of van der Waals interaction.
Authors:X. Qiu, L. Lv, G. Li, W. Han, X. Wang, and L. Li
Vibration spectral properties and dehydration behaviors of goethite nanorods with diameters ranging from 13 to 32 nm were
investigated using infrared spectroscopy, thermogravimetric analysis, and X-ray diffraction. All goethite nanorods were highly
hydrated with physisorbed and chemisorbed water. As the diameters of goethite nanorods increased, the hydroxyl deformation
vibration in the a-b plane showed a significant blue shift, while the Fe-O vibration in the a-b plane shifted to lower frequencies, indicating an enhancement of O-H bond and the ionicity of Fe-O in a-b plane. The hydrated goethite nanorods are also proved to be useful in environmental remedy because of their excellent removal
ability of heavy metal ions.
A two-year field experiment with a split-split plot design was conducted to investigate the effects of soil N(0, 120 and 240 kg N·ha−1) and foliar Zn applications at different growth stages (jointing, flowering, early grain filling, and late grain filling) on Zn translocation and utilization efficiency in winter wheat grown on potentially Zn-deficient soil. Our results showed that foliar Zn application at the early grain filling stage significantly increased the Zn concentration in the grain (by 82.9% compared to control) and the Zn utilization efficiency (by 49% compared to jointing). The Zn concentration in the straw consistently increased with the timing of the foliar Zn application and was highest at late grain filling. However, the timing of the Zn application had little effect on Zn uptake in the grain and straw. A high N supply significantly increased the Zn concentration in and uptake by grain and straw, but it had little effect on the efficiency of Zn utilization. Consequently, a foliar Zn application at early grain filling causes Zn to re-translocate into grain from vegetative tissues, resulting in highly nutritional wheat grain. Finally, these practices improved the efficiency of Zn utilization in winter wheat and led to Zn-enriched straw, which may contribute to Zn recycling if it is returned to the field. The results also indicated that N nutrition is a critical factor in both the concentration and translocation of Zn in wheat.
Authors:X. Yin, X. Wang, X. Zhang, W. Li, Z. Tao, and J. Du
A radioactive multitracer solution was prepared from the reaction of selenium with 25 MeV/nucleon40Ar ions. Using off-line -ray spectrometry, the solution containing 47 radioactive isotopes of 24 elements was obtained. The nucleide with the longest half-life was22Na, and the shortest-lived one was81Rb8.
Authors:X. Wang, X. Li, H. Yan, Y. Qu, G. Sun, X. Xie, and Y. Zhang
The kinetic characteristic of thermal decomposition of the Emulsion Explosive Base Containing Fe and Mn elements (EEBCFM)
which was used to prepare nano-MnFe2O4 particles via detonation method was investigated by means of non-isothermal DSC and TG methods at various heating rates of
2.5, 5 and 7.5°C min−1respectively under the atmosphere of dynamic air from room temperature to 400°C.
The results indicated that the EEBCFM was sensitive to temperature, especially to heating rate and could decompose at the
temperature up to 60°C. The maximum speed of decomposition (dα/dT)m at the heating rate of 5 and 7.5°C min−1 was more than 10 times of that at 2.5°C min−1 and nearly 10 times of that of the second-category coal mine permitted commercial emulsion explosive (SCPCEE). The plenty
of metal ions could seriously reduce the thermal stability of emulsion explosive, and the decomposition reaction in the conversion
degree range of 0.0∼0.6 was most probably controlled by nucleation and growth mechanism and the mechanism function could be
described with Avrami-Erofeev equation with n=2. When the fractional extent of reaction α>0.6, the combustion of oil phase primarily controlled the decomposition reaction.
Authors:J.R. Li, D.X. Li, L. Li, W.L. Deng, L.S. Ding, H.X. Xu, and Y. Zhou
A rapid and sensitive ultraperformance liquid chromatography-multiple reaction monitoring-multi-stage/mass spectrometry (UPLC-MRM-MS/MS) method has been developed for simultaneous quantification of salvianolic acid B and tanshinone IIA of salvia tropolone tablets in dog plasma. This was achieved by performing quantification using the MRM acquisition with two channels of MRM-MS/MS and MS full scan for more accuracy qualitative results, and the fragmentation transitions of m/z 295→249, 191 for tanshinone IIA and m/z 297→279, 251 for IS in positive mode, m/z 717→519, 321 for salvianolic acid B and m/z 295→267, 239 for IS in negative mode were selected. The UPLC separation was achieved within 3 min in a single UPLC run. Linear calibration curves were obtained over the concentration range of 10 pg/mL−1 ng/mL for tanshinone IIA and 100 pg/mL−1 for salvianolic acid B. Lower limit of quantitation (LLOQ) was 10 pg/mL and 100 pg/mL for tanshinone IIA and salvianolic acid B, respectively. The inter-day and intra-day precision (relative standard deviation, RSD) in all samples were less than 8.21%, and the recoveries were over 85.9% for both tanshinone IIA and salvianolic acid B. The two channels of MRM with MS full scan approach could provide both qualitative and quantitative results without the need for repetitive analyses and resulted in the reduction of further confirmation experiments and analytical time. The pharmacokinetic study of the two active components of salvia tropolone tablets following oral gavage administration of dogs was thus explored with this method.
Authors:Q. Chen, P. Li, B. Li, F. Yuan, X. Li, and J. Zhu
A rapid and sensitive method for the identification and quantification of yohimbine in Pausinystalia yohimbe is described. The method used is liquid chromatography-quadrupole ion trap mass spectrometry (LC-QIT/MS). The yohimbine standard solution was directly infused into the ion trap mass spectrometers (IT/MS) for collecting the MSn spectra. The major fragment ions of yohimbine were confirmed by MSn at m/z 355, 224, 212, and 144, in the positive-ion mode. The possible main fragment ion cleavage pathway was studied. Yohimbine provided good signals corresponding to the protonated molecular ion [M + H]+. The method is reliable and reproducible, and the detection limit is 0.1 ng mL-1. The method was validated in the concentration range 0.1–50 μg mL−1; the intra- and interday precision ranged from 1.36% to 2.73% and the accuracy was 96.5–108.2%. The mean recovery of yohimbine was 97.1–101% with a relative standard deviation (RSD) <1.93%. The LC-IT/MS method was successfully applied to determine the yohimbine in P. yohimbe.