Myricetin, a naturally occurring flavonol, shows multifarious pharmacological activities, e.g., antidiabetic, antioxidant, anti-inflammatory, antitumor, and liver protection effects. In order to obtain an understanding of the myricetin’s metabolism in vivo, a rapid and sensitive method by high-performance liquid chromatography coupled with electrospray-ionization mass spectrometry (HPLC-MSn) techniques was employed to investigate the biotransformation in rats after oral administration of myricetin. Recognition and structural exposition of the metabolites were operated by comparing the changes in molecular mass (ΔM) and MSn spectra with the parent drug. As a result, the parent compound and seven metabolites were found in rat plasma, urine, and feces. In addition, besides 3,5-dihydroxyphenylacetic acid (M1) and 3,4,5-trihydroxyphenylacetic acid (M2), five other compounds were first discovered in the metabolite research of myricetin. These results indicated that, besides ring-fission, there were methylate (M3, M4, M5) and glucuronide (M6, M7) biotransformations of myricetin occurring in vivo.
Chitosan (CS) is expected to be an ideal gene carrier for its high biosafety. In this work, CS with low molecular weight were prepared through the γ-ray radiation on the acetic acid solution of CS. The CS chains were scissioned under the γ-ray radiation, and the molecular weight (MW) of CS decreased with the absorbed dose. When the absorbed dose was above 30 kGy, the molecular weight of CS decreased about an order of magnitude. The γ-ray-radiation-scissioned CS can e ectively bind with plasmid (pEGFP) through complex coacervation method, forming pEGFP/ γ-ray-radiation-scissioned CS complex particles with a size of 200-300 nm. The complex particles have good stability and little cytotoxicity. The in uitro gene transfection efficiencies of the pEGFP/ γ-ray-radiation-scissioned CS complex particles were investigated by fluorescence microscope and flow cytometry. The results showed that the gene vectors using γ-ray-radiation-scissioned CS as the carrier will possess better gene transfection efficiency than those using natural high-MW CS as the carrier. The higher the absorbed dose, the smaller the MW of CS and the better transfection efficiency of the corresponding gene vector. This work provides a green and simple method on the preparation of CS-based gene vectors with high efficiency and biosafety. 相似文献
This Letter is to provide a new approach to study the phenomena of degeneracy of the number of the collinear central configurations under geometric equivalence. A direct and simple explicit parametric expression of the singular surface H3 is constructed in the mass space (m1,m2,m3)∈3(R+). The construction of H3 is from an inverse respective, that is, by specifying positions for the bodies and then determining the masses that are possible to yield a central configuration. It reveals the relationship between the phenomena of degeneracy and the inverse problem of central configurations. We prove that the number of central configurations is decreased to 3!/2−1=2, m1, m2, and m3 are mutually distinct if m∈H3. Moreover, we know not only the number of central configurations but also what the nonequivalent central configurations are. 相似文献
In this paper we describe a semi-empirical quantum method for predicting the wavelength of maximum fluorescence excitation
and emission for several known and new maleimide derivatives. All new maleimides, containing a N-Benzyl attachment, were successfully synthesised via a tandem Suzuki reaction with aryl boronic acids containing either an electron donating, electron withdrawing functional
groups. Absorption and emission spectra calculated using the semi-empirical AM1 method with excited state ZINDO calculations
proved more reliable than either Hartree-Fock Configuration interaction or time dependent density functional methods. Calculated
absorption and emission wavelengths were compared with 26 experimental spectra from known or newly synthesised maleimides
and found to have provide reasonable predictions, with an average deviation of less the 6% for absorption maxima and less
than 4% for emission peaks. The described method provides a strong benchmark for the accuracy that can be expected from theoretical
predictions of fluorescence spectra. 相似文献
A tripeptide (β-AspFF) gelator was designed and synthesised using solid-phase peptide synthesis. The as-prepared gelator formed a stable and clear multi-responsive gel in toluene solution. Encapsulating the quantum dots with β-AspFF effectively increased stability and antioxidisation ability which are beneficial for optical identification. 相似文献
The effect of variation of injection conditions and addition of nano-calcium carbonate (CaCO3), nano-silicon dioxide (SiO2) and full-vulcanized nano-powdered styrene butadiene rubber (PSBR) on the shrinkage of injection-molded polypropylene-ethylene copolymer (90/10, co-PP) were investigated. The results showed that the shrinkage was different for different locations along the flow path. The shrinkage in the length direction of the injection-molded sample varied with the adjustment of the processing parameters, while the shrinkage in the width and thickness direction was almost unchanged. The addition of nano-CaCO3 and PSBR decreased the shrinkage of co-PP, while the shrinkage of co-PP/ SiO2 composite was almost unchanged. 相似文献