The thermal properties of buckwheat (Fagopyrum esculentum Moench) proteins with different lipid contents (2.5, 6.5 and 17.8%) were studied by differential scanning calorimetry (DSC)
under various medium conditions. From DSC curves, many DSC characteristics including denaturation temperature (Td), enthalpy change (ΔH) and the width at half peak height (ΔT1/2) of endothermic peaks were obtained and evaluated. The DSC curves of various buckwheat proteins (BWPs) in the 0.05 M phosphate
buffer (pH 7.0) showed a major endotherm at about 102°C and a minor endotherm at about 80°C, attributed to thermal transitions
of 13S and 8S globulins, respectively. Td and ΔH of the globulins of BWPs were independent of their lipid contents, while the presence of high lipid content (17.8%) to some
extent increased the ΔT1/2. The progressive increase in Td of 13S globulins with increase in NaCl concentration, suggests a more compact conformation with higher thermal stability.
The influence of chaotropic salts on the DSC characteristics of 13S globulins was also independent of their lipid contents.
Thermal analysis of the 13S globulins in the presence of protein perturbants (including urea, sodium dodecyl sulfate, ethylene
glycol, dithiothreitol and N-ethylmaleimide) indicated that hydrophobic and hydrogen bondings are the major interactions for
stabilizing protein conformation of buckwheat 13S globulins and the SS-SH interchange also attributes to the stabilization
of the protein conformation.
Uranium in aqueous solution can be extracted by sym-dibenzo-16-crown-5-oxy-acetic acid and its modified analogue 2-/sym-dibenzo-16-crown-5-oxy/-hexanoic acid into chloroform in the pH range 5.5–6.0. The extraction method combined with neutron activation analysis provides a sensitive method for the determination of uranium in natural waters.
Liquid crystalline polymer/polyamide 66 (LCP/PA66) and LCP/poly(butyl terephthalate) (LCP/PBT) blends were compounded using
a Brabender Plasticorder equipped with a mixing chamber. The LCP employed was a semi-flexible liquid crystalline copolyesteramide
based on 30 mol% of p-amino benzoic acid (ABA) and 70 mol% of poly(ethylene terephthalate) (PET). The Flory-Huggins interaction parameters (χ12)
of the LCP/ PA66 and LCP/PBT blends are estimated by melting point depression from DSC measurement. The results indicate that
c12 values all are negative for LCP/PA66 and LCP/PBT blends, and when the LCP content in these blends is more than 10 mass%,
the absolute value of χ12 decreases. Thereby, we can conclude that LCP/PA66 and LCP/PBT blends are fully miscible in the molten state, the molecular
interaction between the LCP and PA66 is stronger than that between LCP and PBT. As the LCP content in LCP/PA66 and LCP/PBT
blends is more than 10 mass%, the molecular interaction between LCP and matrix polymer decreases.
Authors:W.-C. Xie, X.-H. Gu, Z.-C. Tan, J. Tang, G.-Y. Wang, C.-R. Luo, and L.-X. Sun
To develop thermal stable flavor, two glycosidic bound flavor precursors, geranyl-tetraacetyl-β-D-glucopyranoside (GLY-A) and geranyl-β-D-glucopyranoside (GLY-B) were synthesized by the modified Koenigs–Knorr reaction. The thermal decomposition process and pyrolysis products of the two glycosides were extensively investigated by thermogravimetry (TG), differential scanning calorimeter (DSC) and on-line pyrolysis-gas chromatography mass spectroscopy (Py-GC-MS). TG showed the Tp of GLY-A and GLY-B were 254.6 and 275.7°C. The Tpeak of GLY-A and GLY-B measured by DSC were 254.8 and 262.1°C respectively.
Py-GC-MS was used for the simply qualitative analysis of the pyrolysis products at 300 and 400°C. The results indicated that: 1) A large amount of geraniol and few by-products were produced at 300°C, the by-products were significantly increased at 400°C; 2) The characteristic pyrolysis product was geraniol; 3) The primary decomposition reaction was the cleavage of O-glycosidic bound of the two glycosides flavor precursors. The study on the thermal behavior and pyrolysis products of the two glycosides showed that this kind of flavor precursors could be used for providing the foodstuff with specific flavor during heating process.
Authors:Z. Chen, S. Wang, J. Tang, X. Li, C. Liu, X. Xu, and G. Cao
To provide a convenient and facile method to evaluate the radiochemical purity (RCP) of 99mTc-TRODAT-1 in quality control of routine clinical application, a simplified method of single-strip thin layer chromatography
(TLC) was developed and validated by high performance liquid chromatography (HPLC). The RCP data of TLC correlated well with
Authors:Y. Zhang, W. Zheng, Q.C. Ying, L.-E. Shi, Z.-L. Zhang, M.-Z. Shi, and Z.-X. Tang
The sub-acute toxicity of E. faecalis HZNU P2 was investigated in rats fed with different doses for 14 days. To evaluate the acute oral toxicity of E. faecalis HZNU P2, rats were fed with E. faecalis HZNU P2 at a high dose of 2×1011 CFU kg−1 for 10 days. Results showed that there were no abnormal clinical signs in any of the groups during the experiment. There were no significant differences in live weight gain among rats fed with E. faecalis HZNU P2, compared to those in control group. Macroscopic or microscopic examinations of organs revealed no abnormalities, indicating that E. faecalis HZNU P2 did not adversely affect the health of rats. Results of this study demonstrated that digestion of E. faecalis HZNU P2 in rats did not show any obvious signs of toxicity.