Mn(II)-monosubstituted polyoxometalates as candidates for contrast agents in magnetic resonance imaging

Two mono-substituted manganese polyoxometalates, K6MnSiW11O39 (MnSiW11) and K8MnP2W17O61 (MnP2W17), have been evaluated by in vivo and in vitro experiments as the candidates of potential tissue-specific contrast agents for magnetic resonance imaging (MRI). T-1-relaxivities of 12.1 mM(-1) s(-1) for MnSiW11 and 4.7 mM(-1) s(-1) for MnP2W17 (400 MHz, 25 degrees C) were higher than or similar to that of the commercial MRI contrast agent (GdDTPA). Their relaxivities in BSA and hTf solutions were also reported. After administration of MnSiW11 and MnP2W17 to Wistar rats, MR imaging showed longer and remarkable enhancement in rat liver and favorable renal excretion capability. The signal intensity increased by 74.0 +/- 4.9% for the liver during the whole imaging period (90 min) and by 67.2 +/- 5.3% for kidney within 20-70 min after injection at 40 +/- 3 mu mol kg(-1) dose for MnSiW11. MnP2W17 induced 71.5 +/- 15.1%. enhancement for the liver in 10-45 min range and 73.1 +/- 3.2% enhancement for kidney within 5-40 min after injection at 39 +/- 3 mu mol kg(-1) dose. In vitro and in vivo study showed MnSiW11 and MnP2W17 being favorable candidates as the tissue-specific contrast agents for MRI.

The gadolinium complexes with polyoxometalates as potential MRI contrast agents

The two gadolinium (Gd) polyoxometalates, K-15[Gd(BW11O39)(2)] [Gd(BW11)(2)] and K-17[Gd(CuW11O39)(2)] [Gd(CuW11)(2)] have been evaluated by in vivo and in vitro experiments as the candidates of potential tissue-specific magnetic resonance imaging (MRI) contrast agents. T-1 relaxivities of 17.12 mM(-1) . s(-1) for Gd(BW11)(2) and 19.95 mM(-1) . s(-1) for Gd(CuW11)(2) (400MHz, 25 degrees C) were much higher than that of the commercial MRI contrast agent (GdDTPA). Their relaxivities in bovine serum albumin and human serum transferrin solutions were also reported. After administration of Gd(BW11)(2) and Gd(CuW11)(2) to Wistar rats, MRI showed longer and remarkable enhancement in rat liver and favorable renal excretion capability. The signal intensity increased by 37.63 +/- 3.45% for the liver during the whole imaging period (100 min) and by 61.47 +/- 10.03% for kidney within 5-40 min after injection at 40 +/- 1-mu mol . kg(-1) dose for Gd(CuW11)(2), and Gd(BW11)(2) induced 50.44 +/- 3.51% enhancement in the liver in 5-50-min range and 61.47 +/- 10.03% enhancement for kidney within 5-40 min after injection at 39 +/- 4 mu mol . kg(-1) dose. In vitro and in vivo study showed that Gd(BW11)(2) and Gd(CuW11)(2) are favorable candidates as tissue-specific contrast agents for MRI.

Investigation of sandwiched gadolinium(III) complexes with tungstosilicates as potential MRI contrast agents

Two gadolinium-sandwiched complexes with tungstosilicates, K-13[Gd(SiW11O39)(2)] (Gd(SiW11)(2)) and K11H6[Gd2O3(SiW9O34)(2)] (Gd-3(SiW9)(2)), have been investigated by in vitro and in vivo experiments as potential contrast agents for magnetic resonance imaging (MRI). T-1-relaxivity of Gd(SiW11)(2)was 6.59 mM(-1) . s(-1) in aqueous solution and 6.85 mM(-1) . s(-1) in 0.725 mmol . L-1 bovine serum albumin solution at 25degreesC and 9.39 T, respectively. The corresponding T-1-relaxivity of Gd-3(SiW9)(2) was 12.6 and 19.3 mM(-1) . s(-1) per Gd, respectively. MRI for Sprague-Dawley rats showed longer and more remarkable enhancement in rat liver after i.v. injection of these two complexes: 39.4 +/- 3.9% and 57.4 +/- 11.6% within the first 30 min after injection, 31.2 +/- 2.6% and 39.9 +/- 7.6% in the next 60 min for Gd(SiW11)(2) and Gd-3(SiW9)(2) at doses of 0.081 and 0.084 mmol Gd/kg, respectively. Our preliminary in vitro and in vivo study indicates that Gd(SiW11)(2) and Gd-3(SiW9)(2) are favorable candidates for hepatic contrast agents for MRI. However, the two complexes exhibit higher acute toxicity and need to be modified and studied further before clinical use.

Comparison between Gd-DTPA and several bisamide derivatives as potential MRI contrast agents

Four neutral gadolinium complexes of diethylenetriaminepentaacetic acid (DTPA)-bisamide derivatives have been synthesized and characterized. Their potential application as tissue-specific and low-osmolarity MRI contrast agents has been evaluated by in vitro and in vivo experiments. Their measured relaxivities in D2O, bovine serum albumin and human serum transferrin solutions showed favorable relaxation ability. In vivo studies have proven that Gd(DTPA-BDMA), Gd(DTPA-BIN), and Gd(cyclic-DTPA-1,2-pn) could be promising liver-specific MRI contrast agents and Gd(DTPA-BDMA), and Gd(cyclic-DTPA-1,2-pn) have favorable renal excretion capability. Among them, Gd(cyclic-DTPA-1,2-pn) is a more powerful hepatic contrast agent and Gd(DTPA-BIN) provides the stable imaging contrast for several hours. They also show a lower toxicity.

Comparison between GdDTPA and two gadolinium polyoxometalates as potential MRI contrast agents

Two gadolinium polyoxometalates, Gd2P2W18O62 and K-15[(GdO)(3)(PW9O34)(2)], have been evaluated by in vivo as well as in vitro experiments as the candidates of tissue-specific magnetic resonance imaging (MRI) contrast agents. T-1-relaxivities of 28.4 mM(-1)-s(-1) for Gd2P2W18O62 and 11.2 mM(-1)-s(-1) for K-15[(GdO)(3)(PW9O34)(2)] (400 MHz, 25 degreesC) were higher than that of the commercial MRI contrast agent (GdDTPA). Their relaxivities in bovine serum albumin and human serum transferrin were also reported. The favorable liver-specific contrast enhancement and renal excretion capability in in vivo MRI with Sprague-Dawley rats after i.v. administration of K-15[(GdO)(3)(PW9O34)(2)] was demonstrated. In vivo and in vitro assay showed that K-15[(GdO)(3)(PW9O34)(2)] is a promising liver-specific MRI contrast agent. However, Gd2P2W18O62 did not show the favorable quality in vivo as expected from its high relaxivity in vitro, which was attributed to low bioavailability, indicating that it is of limited value as tissue-specific MRI contrast agent.

Effect of nucleating agents on the crystallization of poly(3-hydroxybutyrate-co-3-hydroxyvalerate)

The effect of nucleating agents on the crystallization behavior of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) was studied. A differential scanning calorimeter was used to monitor the energy of the crystallization process from the melt and melting behavior. During the crystallization process from the melt, nucleating agent led to an increase in crystallization temperature (T-c) of PHBV compared with that for plain PHBV (without nucleating agent). The melting temperature of PHBV changed little with addition of nucleating agent. However, the areas of two melting peaks changed considerably with added nucleating agent. During isothermal crystallization, dependence of the relative degree of crystallization on time was described by the Avrami equation. The addition of nucleating agent caused an increase in the overall crystallization rate of PHBV, but did not influence the mechanism of nucleation and growth of the PHB crystals. The equilibrium melting temperature of PHBV was determined as 187degreesC. Analysis of kinetic data according to nucleation theories showed that the increase in crystallization rate of PHBV in the composite is due to the decrease in surface energy of the extremity surface.

High-throughput synergy screening identifies microbial metabolites as combination agents for the treatment of fungal infections

The high mortality rate of immunocompromised patients with fungal infections and the limited availability of highly efficacious and safe agents demand the development of new antifungal therapeutics. To rapidly discover such agents, we developed a high-throughput synergy screening (HTSS) strategy for novel microbial natural products. Specifically, a microbial natural product library was screened for hits that synergize the effect of a low dosage of ketoconazole (KTC) that alone shows little detectable fungicidal activity. Through screening of approximate to 20,000 microbial extracts, 12 hits were identified with broadspectrum antifungal activity. Seven of them showed little cytotoxicity against human hepatoma cells. Fractionation of the active extracts revealed beauvericin (BEA) as the most potent component, because it dramatically synergized KTC activity against diverse fungal pathogens by a checkerboard assay. Significantly, in our immunocompromised mouse model, combinations of BEA (0.5 mg/kg) and KTC (0.5 mg/kg) prolonged survival of the host infected with Candida parapsilosis and reduced fungal colony counts in animal organs including kidneys, lungs, and brains. Such an effect was not achieved even with the high dose of 50 mg/kg KTC. These data support synergism between BEA and KTC and thereby a prospective strategy for antifungal therapy.

Synthesis and QSAR studies of novel triazole compounds containing thioamide as potential antifungal agents

Eighteen novel triazole compounds containing thioamide were designed and synthesized. Their structures were confirmed by elemental analysis, H-1 NMR, IR, and MS. The title compounds exhibited certain antifungal activity. And the geometry structures of the title compounds were optimized by means of the density functional theory (DFT) method at B3LYP/6-31G* level. The quantitative structure-activity relationship (QSAR) of the title compounds was systematically investigated. A correlative equation between FA and DELH, V was well established by using the multiple linear regression (MLR). (c) 2006 Elsevier Ltd. All rights reserved.

长白山火山成因—物理机制和化学演化

This thesis is one of the contributions to NSFC project, “The Changbaishan Volcanism and its Links to the Northeast Asia Tectonic System”. The thesis presents our most recent works on Changbaishan Volcanism, on two aspects as (1) the chemical evolution of the Cenozoic volcanism and the physical links of magma genesis, (2) the Holocene activity of the Tianchi Volcano and risks of potential eruption. 1. Chemical evolution and physical links to the Changbaishan Volcanism Physical links to the Chanbaishan Volcanism, just like origins of most of the volcanisms in eastern China, has long been an enigma. A large scale of volcanic activity has dominated many places of eastern China in Meso-Cenozoic. Activity of these volcanisms in eastern China covers several quite different blocks, covers variety of tectonics, and covers a period of time over 200 million years. Such a large-scale and long-lived volcanism in a continental area challenges our knowledge on dynamics of the Earth’s interior. Some works on “Diwa” hypothesis and “lithospheric thinning” hypothesis present possible links between volcanisms and dynamic evolutions of the earth’s interior, but still cannot interpret where are the sources of the heat and fluid, which are essential to the volcanisms. Based on the study of this thesis, we suggest that dynamics of the deep subduction of western Pacific Plate is the critical factor to the Changbaishan Volcanism and volcanisms in NE China, and maybe even essential to most of the Meso-Cenozoic volcanisms in eastern China. In NE China, stagnant slabs flatted in the mantle transition zone (MTZ, ca. 660 km deep) transport and release significant hydrous fluid to the upper mantle. Metamorphism of the deep-subducted slabs and hence a series of mineral phases play an important role in the water transport, exchange, restore, and release. Dehydrated fluid of the wet slab ascending from the MTZ fertile the upper mantle, and also provide upward heat flow which is essential to the magma genesis. Then magma and volcanism occur with the deep subduction from Mesozoic to mordern time in eastern China. To discribe the exact chemical characteristics of the deep subduction releated volcanics is very difficult, because few researches has contributed to the chemical behaviors of fluid and trace elments in the very deep interior of the Earth, such 660 km deep, 410km or 350km where the fluid may ascend and react. However we can still find some chemical characteristics of oceanic subduction. Basalts of the Changbaishan Volcanism have siginficant characteristics of potassium rich, and even can be called a potassic igneous province. If there are only two possible ways, recycled continentical crust or oceanic crust, to fertile the mantle potossium element as we know now, it’s easy to attribute this to the deep-subducted of the west Pacific Plate. To the eastern China, fluid inclusions in mantle xenoliths from the Cenozic basalts also reveal potassium-rich characteristics. This reveals that the same potassium feritle agents may occur in the mantle sources of eastern China. 2. Holocene activiy of the Tianchi Volcano As one of the large volcanic center and complex volcanic cone, the Tianchi Volcano is a dangerous active volcano, with several Holocene eruptions. Among these eruptions, the Millennium Eruption is regardede as one of the biggist eruptions in the world in the last 2000 years. To estimate the potential danger of volcanic eruption, we discuss two essential factors, as (i) volcanic history of Holocene eruptions, including volcanic geolgy, chronnology and chemistry, (ii) state, evolution and relationship of the magma chambers in mantle and crust beneath the Tianchi Volcano.

A novel method to synthesize amorphous silica-alumina materials with mesoporous distribution without using templates and pore-regulating agents

In this study, a novel sol-gel method is used to synthesize amorphous silica-alumina materials with a narrow mesoporous distribution and various Si/Al molar ratios without using any templates and pore-regulating agents. During the preparation procedure, only inexpensive inorganic salts were used as raw materials, instead of expensive and harmful alkoxides. The precursor sol was dried at room temperature in a vacuum box kept at 60 mmHg until it began to form the gel. The results of a nitrogen sorption experiment indicate that the synthesized materials with different Si/Al molar ratios have similar mesoporous distributions (within 2-12 nm). Moreover, it was found that the material's pore size distribution remains at a similar value during the heat treatment from room temperature to 550 degreesC. On the basis of the nitrogen sorption, TEM, and AFM characterization results, a formation mechanism of mesopores which accounts for the experimental data is also suggested. This suggested mechanism involves rearrangement of the primary particles during the drying process to form the precursors of the similarly sized mesopores. The synthesized materials were characterized by XRD, thermal analysis (TG/DTA), Al-27 and Si-29 MAS NMR spectroscopy, SEM, TEM, and AFM. The results of Al-27 and 29Si MAS NMR indicate that the distribution of silicon and aluminum in the synthesized materials is more uniform and homogeneous than that in the mixed oxides prepared via the traditional sol-gel method even at high alumina contents. The type and density of the acid sites were studied using pyridine adsorption-desorption FTIR spectroscopy. It was shown that the acidity of the synthesized materials is higher than that of the silica-alumina materials prepared by conventional methods.