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991.
反相高效液相色谱柱前衍生荧光法测定肠粘膜中的谷氨酰胺 总被引:1,自引:0,他引:1
以邻苯二甲醛及3-巯基丙酸为衍生试剂,50mmol/L磷酸缓冲液(pH7.0)-乙腈(94∶6,V/V)为流动相,在LichrosorbRP18(150mm×4.6mmi.d.,5μm)柱上,研究并建立了测定动物肠粘膜中谷氨酰胺(Gln)的柱前衍生荧光RP-HPLC法。样品与衍生剂按4∶1进行衍生反应,Ex=230nm,Em=389nm;流速为2.0mL/min。Gln的保留时间为3.158min,检测限为25μmol/L(S/N=3.5),线性范围为50~3200μmol/L,r=0.9996。 相似文献
992.
993.
铅与meso—四(4—溴苯基)卟啉显色体系的研究及食品中铅的测定 总被引:3,自引:0,他引:3
研究了在pH9.2,βCD存在时,非水溶性试剂meso四(4溴苯基)卟啉与铅的显色反应,络合物的最大吸收波长为468nm,组成摩尔比为1∶1,铅含量在0~0.48mg/L范围内有较好的线性,表观摩尔吸光系数为5.4×105L·mol1·cm1。在混合掩蔽剂存在时,此法用于大米、面粉和皮蛋等食品中痕量铅的测定,结果与AAS比较令人满意。 相似文献
994.
Cun Feng Fan Tahir agin Wen Shi Kennith A. Smith 《Macromolecular theory and simulations》1997,6(1):83-102
Constant pressure constant temperature molecular dynamics method is employed to investigate the atomistic scale dynamics of a model Bisphenol A polycarbonate in the vicinity of its glass transition temperature. First, the glass transition temperature and the thermal expansion coefficients of the polymer are predicted by performing simulations at different temperatures. To explore the significance of different modes of motion, various types of time correlation functions are utilized in analyzing the trajectories. In these nanosecond scale simulations, the motion of the chain segments is found to be highly localized with little reorientation of the vectors representing these segments. Detailed analysis of trajectories and the correlation functions of the backbone dihedrals and side methyl groups indicates that they exhibit numerous conformational transitions. The activation energies of the conformational transitions obtained from the simulation are generally larger than the potential barriers for the rotations of these dihedrals, however, both show the same trend. We also have estimated the phenylene ring flip activation energy as 12.6 kcal/mol and the flip frequency as 0.77 MHz at 300 K. These values fall either fall within the range determined by various NMR spectroscopy experiments or slightly out of the range. The study shows that the conformational transitions between the adjacent dihedrals are strongly correlated. Three basic cooperative modes are identified from the simulation. They are: a positive synchronous rotation of two phenylene rings, a negative synchronous rotation of two phenylene rings, and a carbonate group rotation. Above the glass transition temperature, the large scale cooperative motions become much more significant. 相似文献
995.
Pu Zhang Amit Fischer Yu Ouyang Jianbang Wang Yang Sung Sohn Rachel Nechushtai Eli Pikarsky Chunhai Fan Itamar Willner 《Chemical science》2021,12(43):14473
UiO-66 metal–organic framework nanoparticles (NMOFs) gated by aptamer-functionalized DNA tetrahedra provide superior biomarker-responsive hybrid nano-carriers for biomedical applications. Hybrid nano-carriers consisting of ATP-aptamer or VEGF-aptamer functionalized tetrahedra-gated NMOFs are loaded with the chemotherapeutic drug, doxorubicin (DOX). In the presence of ATP or VEGF, both abundant in cancer cells, the tetrahedra-gated NMOFs are unlocked to release the drug. Enhanced and selective permeation of the DOX-loaded ATP/VEGF-responsive tetrahedra-gated NMOFs into MDA-MB-231 breast cancer cells as compared to the reference ATP/VEGF-responsive duplex-gated NMOFs or non-malignant MCF-10A epithelial breast cells is observed. This results in enhanced and selective cytotoxicity of the tetrahedra-gated DOX-loaded NMOFs toward the malignant cells. Additional nano-carriers, consisting of photosensitizer Zn(ii) protoporphyrin IX (Zn(ii)-PPIX)-loaded VEGF-responsive tetrahedra-gated NMOFs, are introduced. The VEGF-triggered unlocking of the NMOFs yields separated G-quadruplex-VEGF aptamer complexes conjugated to the tetrahedra, resulting in the release of loaded Zn(ii)-PPIX. Association of the released Zn(ii)-PPIX to the G-quadruplex structures generates highly fluorescent supramolecular Zn(ii)-PPIX/G-quadruplex VEGF aptamer-tetrahedra structures. The efficient and selective generation of the highly fluorescent Zn(ii)-PPIX/G-quadruplex VEGF aptamer-tetrahedra nanostructures in malignant cells allows the light-induced photosensitized generation of reactive oxygen species (ROS), leading to high-efficacy PDT treatment of the malignant cells.UiO-66 metal–organic framework nanoparticles (NMOFs) gated by aptamer-functionalized DNA tetrahedra provide superior biomarker-responsive hybrid nano-carriers for biomedical applications. 相似文献
996.
Yan Fan Tao Wang Yinwei Qiu Yinli Yang Qiubo Pan Jun Zheng Songwei Zeng Wei Liu Gang Lou Liang Chen 《Molecules (Basel, Switzerland)》2021,26(22)
Graphene p-n junctions have important applications in the fields of optical interconnection and low–power integrated circuits. Most current research is based on the lateral p-n junction prepared by chemical doping and other methods. Here, we report a new type of pure graphene oxide (pGO) vertical p-n junctions which do not dope any other elements but only controls the oxygen content of GO. The I–V curve of the pGO vertical p–n junction demonstrates a remarkable rectification effect. In addition, the pGO vertical p–n junction shows stability of its rectification characteristic over long-term storage for six months when sealed and stored in a PE bag. Moreover, the pGO vertical p–n junctions have obvious photoelectric response and various rectification effects with different thicknesses and an oxygen content of GO, humidity, and temperature. Hall effect test results show that rGO is an n–type semiconductor; theoretical calculations and research show that GO is generally a p–type semiconductor with a bandgap, thereby forming a p–n junction. Our work provides a method for preparing undoped GO vertical p–n junctions with advantages such as simplicity, convenience, and large–scale industrial preparation. Our work demonstrates great potential for application in electronics and highly sensitive sensors. 相似文献
997.
Yueyue Fan Wenyan Hao Yuexin Cui Mengyu Chen Xiaoyang Chu Yang Yang Yuli Wang Chunsheng Gao 《Molecules (Basel, Switzerland)》2021,26(16)
Effective intracerebral delivery is key for glioma treatment. However, the drug delivery system within the brain is largely limited by its own adverse physical and chemical properties, low targeting efficiency, the blood–brain barrier and the blood–brain tumor barrier. Herein, we developed a simple, safe and efficient biomimetic nanosuspension. The C6 cell membrane (CCM) was utilized to camouflaged the 10-hydroxycamptothecin nanosuspension (HCPT-NS) in order to obtain HCPT-NS/CCM. Through the use of immune escape and homotypic binding of the cancer cell membrane, HCPT-NS/CCM was able to penetrate the blood–brain barrier and target tumors. The HCPT-NS is only comprised of drugs, as well as a small amount of stabilizers that are characterized by a simple preparation method and high drug loading. Similarly, the HCPT-NS/CCM is able to achieve targeted treatment of glioma without any ligand modification, which leads it to be stable and efficient. Cellular uptake and in vivo imaging experiments demonstrated that HCPT-NS/CCM is able to effectively cross the blood–brain barrier and was concentrated at the glioma site due to the natural homing pathway. Our results reveal that the glioma cancer cell membrane is able to promote drug transport into the brain and enter the tumor via a homologous targeting mechanism. 相似文献
998.
Baicalin which has multiple biological activities is the main active component of the root of Scutellaria baicalensis Georgi (SBG). Although its isolation and purification by adsorption methods have aroused much interest of the scientific community, it suffered from the poor selectivity of the adsorbents. In this work, an environmentally benign method was developed to prepare ionic liquids (ILs) grafted silica by using IL 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([C4mim]NTf2) and ethanol as reaction media. The IL 1-propyl-3-methylimidazolium chloride ([C3mim]Cl) grafted silica ([C3mim]+Cl−@SiO2) was used to adsorb and purify baicalin from the root extract of Scutellaria baicalensis Georgi (SBG). Experimental results indicated that the adsorption equilibrium can be quickly achieved (within 10 min). The adsorption behavior of [C3mim]+Cl−@SiO2 for baicalin was in good agreement with Langmuir and Freundlich models and the adsorption was a physisorption process as suggested by Dubinin–Radushkevich model. Compared with commercial resins, [C3mim]+Cl−@SiO2 showed the strongest adsorption ability and highest selectivity. After desorption and crystallization, a purity of baicalin as high as 96.5% could be obtained. These results indicated that the ILs grafted silica materials were promising adsorbents for the adsorption and purification of baicalin and showed huge potential in the purification of other bioactive compounds from natural sources. 相似文献
999.
Wei-Qun Yang Wei Tang Xiao-Jun Huang Jian-Guo Song Yue-Yue Li Yu Xiong Chun-Lin Fan Zhen-Long Wu Ying Wang Wen-Cai Ye 《Molecules (Basel, Switzerland)》2021,26(19)
A phytochemical investigation on the roots of medicinal plant Eurycoma longifolia resulted in the isolation of 10 new highly oxygenated C20 quassinoids longifolactones G‒P (1–10), along with four known ones (11–14). Their chemical structures and absolute configurations were unambiguously elucidated on the basis of comprehensive spectroscopic analysis and X-ray crystallographic data. Notably, compound 1 is a rare pentacyclic C20 quassinoid featuring a densely functionalized 2,5-dioxatricyclo[5.2.2.04,8]undecane core. Compound 4 represents the first example of quassinoids containing a 14,15-epoxy functionality, and 7 features an unusual α-oriented hydroxyl group at C-14. All isolated compounds were evaluated for their anti-proliferation activities on human leukemia cells. Among the isolates, compounds 5, 12, 13, and 14 potently inhibited the in vitro proliferation of K562 and HL-60 cells with IC50 values ranging from 2.90 to 8.20 μM. 相似文献
1000.
Liping Zhang Yun Geng Lijuan Li Xiaofan Tong Shi Liu Xingman Liu Zhongmin Su Zhigang Xie Dongxia Zhu Martin R. Bryce 《Chemical science》2021,12(16):5918
Near-infrared (NIR) emitters are important probes for biomedical applications. Nanoparticles (NPs) incorporating mono- and tetranuclear iridium(iii) complexes attached to a porphyrin core have been synthesized. They possess deep-red absorbance, long-wavelength excitation (635 nm) and NIR emission (720 nm). TD-DFT calculations demonstrate that the iridium–porphyrin conjugates herein combine the respective advantages of small organic molecules and transition metal complexes as photosensitizers (PSs): (i) the conjugates retain the long-wavelength excitation and NIR emission of porphyrin itself; (ii) the conjugates possess highly effective intersystem crossing (ISC) to obtain a considerably more long-lived triplet photoexcited state. These photoexcited states do not have the usual radiative behavior of phosphorescent Ir(iii) complexes, and they play a very important role in promoting the singlet oxygen (1O2) and heat generation required for photodynamic therapy (PDT) and photothermal therapy (PTT). The tetranuclear 4-Ir NPs exhibit high 1O2 generation ability, outstanding photothermal conversion efficiency (49.5%), good biocompatibility, low half-maximal inhibitory concentration (IC50) (0.057 μM), excellent photothermal imaging and synergistic PDT and PTT under 635 nm laser irradiation. To our knowledge this is the first example of iridium–porphyrin conjugates as PSs for photothermal imaging-guided synergistic PDT and PTT treatment in vivo.Iridium–porphyrin conjugates assembled in nanoparticles are photosensitizers that exhibit excellent photothermal imaging and synergistic PDT and PTT in vivo. 相似文献