Authors:S.F. Wu, W. Qi, Y.F. Wang, R.X. Su, and Z.M. He
Casein peptides with calcium-chelating capacity were rapidly enriched by using a novel ceramic matrix (CM)-based Ti4+-IMAC adsorbent. The ability of calcium-chelating peptides (CCPs) to bind calcium and the physical properties of complexes formed between CCPs and calcium were investigated. Results demonstrated that the amount of calcium bound depended on the degree of hydrolysis (DH) of casein hydrolysates. The highest calcium binding capacity (683 mg g−1) occurred when bovine casein was hydrolysed by pancreatin at a DH of 0.14%, meanwhile, the calcium content of CCPs-Ca complex exhibited the maximum level (134.96 mg g−1). In addition, CCPs showed a higher radical scavenging capacity (50 µg ml−1; 99% inhibition, or an equivalent activity of 9.91×10−3 M Trolox) compared to casein digest. Moreover, Fourier-transform infrared spectroscopy and fluorescence spectroscopy were used to explore the interaction between CPPs and calcium, and the results demonstrated that phosphoserine residues as well as COO- groups of CCPs were involved in the formation of CCPs-Ca complex.
Authors:Z. Wu, F. Li, L. Huang, Y. Shi, X. Jin, S. Fang, K. Chuang, R. Lyon, F. Harris, and S. Cheng
The thermal mechanical properties and degradation behaviors were studied on fibers prepared from two high-performance, heterocyclic polymers, poly(p-phenylenebenzobisthiazole) (PBZT) and poly(p-phenylenebenzobisoxazole) (PBZO). Our research demonstrated that these two fibers exhibited excellent mechanical properties and outstanding thermal and thermo-oxidative stability. Their long-term mechanical tensile performance at high temperatures was found to be critically associated with the stability of the C—O or C—S linkage at the heterocyclic rings on these polymers' backbones. PBZO fibers with the C—O linkages displayed substantially higher thermal stability compared to PBZT containing C—S linkages. High resolution pyrolysis-gas chromatography/mass spectrometry provided the information of the pyrolyzates' compositions and distributions as well as their relationships with the structures of PBZT and PBZO. Based on the analysis of the compositions and distributions of all pyrolyzates at different temperatures, it was found that the thermal degradation mechanisms for both of these heterocyclic polymers were identical. Kevlar®-49 fibers were also studied under the same experimental conditions in order to make a comparison of thermo-oxidative stability and long-term mechanical performance at high temperatures with PBZO and PBZT fibers. The data of two high-performance aromatic polyimide fibers were also included as references.
Authors:Y. Li, F.Q. Lu, Y. Feng, Z.D. He, and X.L. Wu
Analysis of the binding interaction of (−)-epigallocatechin-3-gallate (EGCG) and pepsin is important for understanding the inhibition of digestive enzymes by tea polyphenols. We studied the binding of EGCG to pepsin using fluorescence spectroscopy, Fourier transform infrared spectroscopy, isothermal titration calorimetry, and protein-ligand docking. We found that EGCG could inhibit pepsin activity. According to thermodynamic parameters, a negative ΔG indicated that the interaction between EGCG and pepsin was spontaneous, and the electrostatic force accompanied by hydrophobic binding forces may play major role in the binding. Data from multi-spectroscopy and docking studies suggest that EGCG could bind pepsin with a change in the native conformation of pepsin. Our results provide further understanding of the nature of the binding interactions between catechins and digestive enzymes.
Authors:R. Wang, A. Chau, F. Liu, H. Cheng, P. Nar, X. Chen, and Q. Wu
The aim of this paper is to consider using effective natural minerals in studying the retardation and migration of radium under the influence of groundwater in the far-field of a radioactive waste repository. The properties of adsorbing radium by minerals are studied by adopting the static and dynamic adsorption method. Preliminary experimental results give confidence in the validity of using Maifanshih and barite to adsorb radium in water and to serve as effective retarding materials in radioactive waste repositories, their Kd values being 3815 and 2955, respectively. The study on a certain number of conditions of adsorbing radium by the promissing material Maifanshih is reported for the first time. The mechanism of radium adsorption has been discussed and modeling of migration of radium in the minerals has been presented to establish a rational basis for the longterm prediction required for safety assessment of underground disposal of radioactive waste.
Authors:Z. Wu, A. Zhang, D. Shen, M. Leland, F. W. Harris, and S. Z. D. Cheng
Three aromatic polyimides based on 3,3′,4,4′-biphenyl-tetracarboxylic dianhydride (BPDA) and three different diamines 2,2′-bis(trifluoromethyl)-4,4′-diaminobiphenyl (PFMB), 2,2′-dimethyl-4, 4′-diaminophenyl (DMB) or 3,3′-dimethylbenzidine (OTOL) have been synthesized. These polyimides are soluble in hotp-chlorophenol,m-cresol or other phenolic solvents. Fibers have been spun from isotropic solutions using a dry-jet wet spinning method. The as-spun fibers generally exhibit low tensile properties, and can be drawn at elevated temperatures (>380° C) up to a draw ratio of 10 times. Remarkable increases in tensile strength and modulus are achieved after drawing and annealing. The crystal structures of highly drawn fibers were determinedvia wide angle X-ray diffraction (WAXD). The crystal unit cell lattices have been determined to be monoclinic for BPDA-PFMB and triclinic for both BPDA-DMB and BPDA-OTOL. Thermomechanical analysis (TMA) was used to measure thermal shrinkage stress and strain. A selfelongation has been found in the temperature region around 450°C. This phenomenon can be explained as resulting from the structural development in the fibers as evidencedvia WAXD observations.
Authors:W.-Y. Liu, Sh.-L. Xie, X.-Zh. Xu, Ch.-Y. Wu, and F. Feng
Oroxylin A (5,7-dihydroxy-6-methoxyflavone), which has showed multiple pharmacological effects, was semi-synthesized chemically as a pharmaceutical agent. Its impurities, degradation products and their formation pathways remain unknown. In the present study, two impurities (5,6,7-trihydroxyflavone, 5-hydroxy-6,7-dimethoxytlavone) and a degradation product (5,7-dihydroxy-8-methoxyflavone) in Oroxylin A bulk drug substance were identified, and their formation pathways were proposed. A reversed phase liquid chromatographic method for the simultaneous determination of Oroxylin A and the three compounds was developed on a C18 column using methanol-acetonitrile-0.1% acetic acid (54:23:23, v/v/v) as the mobile phase. The detection was performed at 271 nm. The method was validated to be robust, precise, specific and linear between 4 and 40 μg mL−1; the limits of detection and quantification of Oroxylin A were 0.01 and 0.04 μg mL−1, respectively. The developed method was found to be suitable to check the quality of bulk samples of Oroxylin A at the time of batch release and also during its stability studies (long term and accelerated stability).
Authors:H. Yang, N. Tan, F. WU, H. Liu, M. Sun, Z. She, and Y. Lin
The uranium(VI) accumulation was studied in detail by using the biomass of mangrove endophytic fungus Fusarium sp.#ZZF51 from the South China Sea. The uranium(VI) biosorption process onto the tested fungus powders was optimized at pH 4.0,
adsorption time 60 min, and uranium(VI) initial concentration 50 mg L−1 with 61.89% of removal efficiency. According to Fourier transform infrared spectra for the tested fungus before and after
loaded with uranium(VI), the results showed that both of hydroxyl and carboxyl groups acted as the important roles in the
adsorption process. In addition, the experimental data were analyzed by using parameter and kinetic models, and it was obtained
that the Langmuir isotherm model and the pseudo-second-order kinetic model provided better correlation with the experimental
data for adsorption of uranium(VI).
Authors:W.-Y. Liu, M.-L. Wei, C.-Y. Wu, H.-Y. Zhu, F. Feng, and N. Xie
Patrinia scabra Bunge has long been used in clinic as a traditional Chinese medicine for treating leukemia and cancer and regulating host immune response. Despite their wide use in China, no report on system analysis on their chemical constituents is available so far. The current study was designed to profile the fingerprint of ethyl acetate extract of it, and in addition, to characterize the major fingerprint peaks and determine their quantity. Therefore, a detailed gradient high-performance liquid chromatography was described to separate more than 30 compounds with satisfactory resolution in P. scabra Bunge. Based on the chromatograms of 10 batches samples, a typical high-performance liquid chromatographic (HPLC) fingerprint was established with 23 chromatographic peaks being assigned as common fingerprint peaks. Furthermore, a quadrupole time of flight mass spectrometry (Q-TOF/MS) was coupled for the characterization of major compound. As (+)-nortrachelogenin was the most predominant compound in P. scabra Bunge, the quantification on it was also carried out with the method being validated. As a result, (+)-nortrachelogenin was found to be from 1.33 to 2.21 mg g−1 in this plant material. This rapid and effective analytical method could be employed for quality assessment of P. scabra Bunge, as well as pharmaceutical products containing this herbal material.
Authors:F. Gao, J. Bao, J. Xue, J. Huang, W. Huang, S. Wu, and Li-Fan Zhang
This study was designed to test the hypothesis that a medium-term simulated microgravity by tail-suspension (SUS) induces hypertrophic and atrophic changes in the common carotid artery and abdominal aorta with their innermost smooth muscle (SM) layers being most profoundly affected. The second purpose was to elucidate whether vascular local renin-angiotensin system (L-RAS) plays an important role in the differential remodeling of the two kinds of large arteries by examining the gene and protein expression of angiotensinogen (A
) and angiotensin II receptor type 1 (AT1R) and their localization in the vessel wall. The results showed that SUS induced an increase in the media thickness of the common carotid artery due to hypertrophy of the four SM layers and a decrease in the total cross-sectional area of the nine SM layers of the abdominal aorta without significant change in its media thickness. Irrespective of the nature of remodeling, the most prominent changes were in the innermost layers. Immunohistochemistry,
hybridization, Western blot, and real time quantitative PCR analysis revealed that SUS induced an up- and down-regulation in A
and AT1R expression in the common carotid artery and abdominal aorta, respectively. In conclusion, our findings have demonstrated some special features in the structural adaptation of large elastic arteries due to a medium-term simulated microgravity.
Authors:T. Wu, W. Dai, G. Xiao, F. Shu, J. Yao, and J. Li
With the low permeability and high swelling property, Gaomiaozi (GMZ) bentonite is regarded as the favorable candidate backfilling
material for a potential repository. The diffusion behaviors of HTO in GMZ bentonite were studied to obtain effective diffusion
coefficient (De) and accessible porosity (ε) by through- and out-diffusion experiments. A computer code named Fitting for diffusion coefficient
(FDP) was used for the experimental data processing and theoretical modeling. The De and ε values were (5.2–11.2) × 10−11 m2/s and 0.35–0.50 at dry density from 1,800 to 2,000 kg/m3, respectively. The De values at 1,800 kg/m3 was a little higher than that of at 2,000 kg/m3, whereas the De value at 1,600 kg/m3 was significantly higher (approximately twice) than that of at 1,800 and 2,000 kg/m3. It may be explained that the diffusion of HTO mainly occurred in the interlayer space for the highly compacted clay (dry
density exceeding 1,300 kg/m3). 1,800 and 2,000 kg/m3 probably had similar interlayer space, whereas 1,600 kg/m3 had more. Both De and ε values decreased with increasing dry density. For compacted bentonite, the relationship of De and ε could be described by Archie’s law with exponent n = 4.5 ± 1.0.