To reveal the denaturation mechanism of lysozyme by dimethyl sulfoxide (DMSO), thermal stability of lysozyme and its preferential
solvation by DMSO in binary solutions of water and DMSO was studied by differential scanning calorimetry (DSC) and using densities
of ternary solutions of water (1), DMSO (2) and lysozyme (3) at 298.15 K. A significant endothermic peak was observed in binary
solutions of water and DMSO except for a solution with a mole fraction of DMSO (x2) of 0.4. As x2 was increased, the thermal denaturation temperature Tm decreased, but significant increases in changes in enthalpy and heat capacity for denaturation, ΔHcal and ΔCp, were observed at low x2 before decreasing. The obtained amount of preferential solvation of lysozyme by DMSO (∂g2/∂g3) was about 0.09 g g−1 at low x2, indicating that DMSO molecules preferentially solvate lysozyme at low x2. In solutions with high x2, the amount of preferential solvation (∂g2/∂g3) decreased to negative values when lysozyme was denatured. These results indicated that DMSO molecules do not interact directly
with lysozyme as denaturants such as guanidine hydrochloride and urea do. The DMSO molecules interact indirectly with lysozyme
leading to denaturation, probably due to a strong interaction between water and DMSO molecules.
In order to identify the kinetic process of self-heating in DSC experiment for Ti+3Al→TiAl3 reaction, two approaches, linear-fitting approach developed from Semenov"s theory of spontaneous ignition and variation of
Friedman method, were carried out with cylindrical Ti-75 at% Al samples. Following these approaches, two identical activation
energies are obtained as 16915 kJ mol-1 and 1705 kJ mol-1, respectively. Compared with the activation energies of reactions and interdiffusions between Ti and Al, the possible rate-controlling
process of self-heating in DSC experiment for Ti+3Al→TiAl3 reaction is the interdiffusion between Ti and Al through TiAl3-layer.
Three yeasts from the genus Williopsis (W. saturnus var. mrakii NCYC500, W. saturnus var. saturnus CBS254 and W. californica NCYC2590) were examined for their ability to ferment longan juice and to enhance formation of longan wine aroma compounds. The three yeasts showed similar growth kinetics and pH changes during fermentation. W. californica was the least sugar consumer. Many of the naturally occurring volatiles (ethyl esters, fatty acids, aldehydes, and terpenes) in the juice were partially or completely degraded. The three yeasts varied with their ability to produce and utilise volatiles. Esters were the major volatiles produced with some esters being catabolised while other esters remained stable. The amount of most alcohols increased while of aldehydes decreased. W. saturnus CBS254 was the best producer of ethyl acetate, isobutyl acetate, isoamyl acetate and 2-phenethyl acetate, whereas W. californica NCYC2590 was the highest producer of butyl acetate. Ethanol was produced in similar amounts by W. mrakii and W. saturnus but at a minimal level by W. californica. W. mrakii formed the highest amount of isobutyl alcohol, isoamyl alcohol and 2-phenylethyl alcohol. Although the amounts of most of the major volatiles at the end of fermentation (day 14) differed statistically among the yeasts, it remained to be seen whether the quantitative differences can be detected organoleptically. These fi ndings suggest that yeasts from the genus Williopsis could be exploited for longan wine aroma enhancement either singly or in co-inoculation with Saccharomyces.
Authors:Z. Zeng, T. Zhang, G. Li, C. Liu, and Z. Yang
A synthetic autopolyploid was developed from diploid Aegilops tauschii, D genome progenitor of common wheat (Triticum aestivum). The tetraploid Ae. tauschii displayed a markedly larger organ size than the diploid donor. Fluorescence in situ hybridization (FISH) and DNA marker analysis revealed that there is no clear variation at either the chromosomal or DNA level between the diploid and tetraploid plants. We analyzed the variation in cytosine methylation patterns between the diploid and tetraploid plants by methylation-sensitive amplified polymorphism (MSAP) and detected 228 and 232 methylated sites in diploid and tetraploid plants, respectively. Statistical comparison indicated that the tetraploid Ae. tauschii genotype displayed no significant difference in polymorphic methylation level compared to the diploid ones. Twenty-two different genomic fragments displaying different methylation behavior during the ploidy conversions were isolated and sequenced. It demonstrated that alterations in the level of methylation have the most profound effects on coding genes. We demonstrated that there are some genes expressions modified by DNA methylation may be correlated with phenotypic alteration after autotetraploidization.
Authors:X. X. Liu, L. Wang, J. Yang, T. T. Zhang, X. D. Deng, and Q. Wang
Rapid high-performance liquid chromatographic methods with evaporative light scattering detection (HPLC-ELSD) and electrospray ionization multistage mass spectrometry (HPLC-ESI-MSn) have been established and validated for simultaneous qualitative and quantitative analysis of eight steroidal saponins in ten batches of Gongxuening capsule (GXN), a widely commercially available traditional Chinese preparation. The optimum chromatographic conditions entailed use of a Kromasil C18 column with acetonitrile-water (30:70 to 62:38, υ/υ) as mobile phase at a flow rate of 1.0 mL min−1. The drift tube temperature of the ELSD was 102°C and the nebulizing gas flow rate was 2.8 L min−1. Separation was successfully achieved within 25 min. LC-ESI-MSn was used for unequivocal identification of the constituents of the samples by comparison with reference compounds. The assay was fully validated for precision, repeatability, accuracy, and stability, then successfully applied to quantification of the eight compounds in samples. The method could be effective for evaluation of the clinical safety and efficacy of GXN.
Authors:L. Liu, T. Zhao, X. M. Cheng, C. H. Wang, and Z. T. Wang
Harmaline and harmine accounted for more than 70% in composition in extracts of P. harmala. More attention, however, should be paid to the other alkaloids which would be favorable or unfavorable to the efficacy and safety of the products. It was necessary to determine these trace alkaloids in the extracts; thereafter, most of them have been characterized. Diglycoside vasicine, vasicine, vasicinone, harmalol, harmol, tetrahydroharmine, 8-hydroxy-harmine, ruine, harmaline, and harmine were separated and identified with reference substances and characteristic MS spectra in extracts by liquid chromatography-electrospray ionization-mass spectrometry (LC-ESI-MS) and high-performance liquid chromatography (HPLC). Three trace alkaloids, vasicine, harmalol, and harmol were determined using the developed chromatographic separation method subsequently. The average contents of vasicine, harmalol, and harmol in extracts of ten batches were 2.53 ± 0.73, 0.54 ± 0.19, and 0.077 ± 0.03%, respectively. The total content of the three alkaloids was 3.23 ± 0.90% (from 1.81 to 4.48%). For rough estimation of all the relative alkaloids except of harmaline and harmine, the average total areas of all peaks in extracts varied from 4.35 to 26.64% detected at 220, 254, 265, 280, and 380 nm, respectively. The results indicated that area normalization method was powerless for the quality evaluation for traditional herb medicine consisting of numerous compounds with highly differential features. It might be concluded that LC-MS or HPLC could be utilized as a qualitative and quantitative analytical method for quality control of the extracts from seeds of P. harmala L.
Authors:C. Li, C. Wang, X. Liu, Z. Zheng, L. Wang, Q. Zhu, M. Kang, T. Chen, and C. Liu
In terms of pre-safety assessment of a potential site for high-level radioactive wastes disposal in China, the geochemical
behavior of key radionuclides which tend to be released from the repository must be thoroughly investigated. 99Tc is a long-lived fission product with appreciable productivity in nuclear fuel, and Tc (+7) has unlimited solubility in
near-field geochemical environments. In this study, the effects of ionic strength and humic acid on 99TcO4− sorption and diffusion in Beishan granite were investigated with through-diffusion and batch sorption experiments. Results
indicated that the effective diffusion coefficients (De) of 99TcO4− in Beishan granite varied from 1.07 × 10−12 to 1.28 × 10−12 m2/s without change with ionic strength, while the distribution coefficients (Kd) negatively correlated with ionic strength of the rock/water system. This study also indicates that there is no evident influence
of humic acid concentration on the diffusion behavior of 99TcO4− in Beishan granite, due to the limited interaction between humic acid and 99TcO4−.
Authors:L.J. Wu, Y. Shang, T. Liu, W.J. Chen, B.L. Liu, L.Q. Zhang, D.C. Liu, B. Zhang, and H.G. Zhang
In this study, the cDNA of homocysteine S-methyltransferase was isolated from Aegilops tauschii Coss., with the gene accordingly designated as AetHMT1. Similar to other methyltransferases, AetHMT1 contains a GGCCR consensus sequence for a possible zinc-binding motif near the C-terminal and a conserved cysteine residue upstream of the zinc-binding motif. Analysis of AetHMT1 uncovered no obvious chloroplast or mitochondrial targeting sequences. We functionally expressed AetHMT1 in Escherichia coli and confirmed its biological activity, as evidenced by a positive HMT enzyme activity of 164.516 ± 17.378 nmol min−1 mg−1 protein when catalyzing the transformation of L-homocysteine. Compared with the bacterium containing the empty vector, E. coli harboring the recombinant AetHMT1 plasmid showed much higher tolerance to selenate and selenite. AetHMT1 transcript amounts in different organs were increased by Na2SeO4 treatment, with roots accumulating higher amounts than stems, old leaves and new leaves. We have therefore successfully isolated HMT1 from Ae. tauschii and characterized the biochemical and physiological functions of the corresponding protein.
Authors:J.Q. Xu, L. Wang, B.L. Liu, T.F. Xia, D.C. Liu, X. Chang, T.W. Zhang, H.G. Zhang, and Y.H. Shen
As one of the world’s earliest domesticated crops, barley is a model species for the study of evolution and domestication. Domestication is an evolutionary process whereby a population adapts, through selection; to new environments created by human cultivation. We describe the genome-scanning of molecular diversity to assess the evolution of barley in the Tibetan Plateau. We used 667 Diversity Arrays Technology (DArT) markers to genotype 185 barley landraces and wild barley accessions from the Tibetan Plateau. Genetic diversity in wild barley was greater than in landraces at both genome and chromosome levels, except for chromosome 3H. Landraces and wild barley accessions were clearly differentiated genetically, but a limited degree of introgression was still evident. Significant differences in diversity between barley subspecies at the chromosome level were observed for genes known to be related to physiological and phenotypical traits, disease resistance, abiotic stress tolerance, malting quality and agronomic traits. Selection on the genome of six-rowed naked barley has shown clear multiple targets related to both its specific end-use and the extreme environment in Tibet. Our data provide a platform to identify the genes and genetic mechanisms that underlie phenotypic changes, and provide lists of candidate domestication genes for modified breeding strategies.
Authors:T. Tanaka, M. Mukai, T. Maeda, J. Matsumoto, H. Ogawa, Zhentang Li, Xudong Wang, Zhiwen Fan, Liangtian Guo, and Cunli Liu
Migration experiments with 237Np(V) and 241Am(III) have been performed using a column system, packed with loess, taken from Shanxi, China. The adsorption mechanism of 237Np and 241Am on the loess was examined by a chemical extraction method. Most of 237Np was adsorbed on the influent edge of the column, and the adsorbtion was mainly controlled by surface complexation. However, the migration of 237Np in loess media could be roughly evaluated by the distribution coefficient. In the case of 241Am, particulate, the 241Am species was formed in the influent solution and moved in the column. The 241Am adsorbed on loess was controlled by irreversible reactions. The migration behavior of particulate 241Am in loess media could be expressed by the filtration theory.