排序方式: 共有125条查询结果,搜索用时 31 毫秒
61.
E. Jane Maxwell Chitra Ratnayake Roxana Jayo Xuefei Zhong David D. Y. Chen 《Electrophoresis》2011,32(16):2161-2166
A method for adapting widely used CE conditions for the separation of fluorescently labeled carbohydrates to permit online ESI‐MS detection is presented. Reverse polarity separations were performed in bare fused‐silica capillaries with an acidic BGE. Under these conditions, negatively charged 8‐aminopyrene 1,3,6‐trisulfonate‐labeled carbohydrates migrate forward against the EOF, which is towards the capillary inlet. Therefore, the CE‐MS interface must simultaneously back‐fill the capillary, in order to maintain the CE circuit, and provide a stable forward flow at the sprayer tip to support the electrospray process. This was achieved using a junction‐at‐the‐tip interface, which provides a flow of solution to the junction formed by the capillary terminus and the inner wall of the emitter needle tip. Because the flow rate required for this arrangement is much less than in conventional sheath flow interfaces, dilution of the analytes is minimized. Optimized separation conditions permit baseline resolution of glucose oligomers containing up to 15 glucose units, while longer oligomers, up to 33 glucose units, were observed as resolved peaks in the negative ion mode mass spectrum. 相似文献
62.
Zoran Maria A. Savastru Roxana S. Savastru Dan M. Penache Maria-Cristina V. 《Journal of Radioanalytical and Nuclear Chemistry》2019,320(1):55-70
Journal of Radioanalytical and Nuclear Chemistry - The use of carbon monoxide (CO) and radon (222Rn) during 1 year continuous monitoring in Bucharest, Romania in relation with other air... 相似文献
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Roxana Magaly Flores-Ancona Fanny Yocelin García-Gómez Ana María Jiménez-Betanzos Mario Solis-Paredes Violeta Castro-Leyva Alfredo Cruz-Orea Francisco Arenas-Huertero Eva Ramón-Gallegos 《Photochemistry and photobiology》2009,85(5):1182-1188
The damage induced by end products of photodynamic therapy (PDT) in astrocytoma tumors leads to cytotoxicity and cell death. Chromatin modifiers such as sodium butyrate (NaB) induce several genes involved in apoptosis, among others. The PDT improvement was evaluated by the measurement of its effectiveness in the treatment of U373-MG and D54-MG astrocytoma cell lines exposed to NaB. Cells exposed to 80 μg mL−1 of δ-aminolevulinic acid (ALA) as precursor of endogenous photosensitizer (PS), protoporphyrin IX (PpIX), induced 16.67% and 28.9% of mortality in U373-MG and D54-MG, respectively. The mortality increased to 70.62% and 96.7%, respectively, when U373-MG and D54-MG cells were exposed for 24 h to 8 m m NaB prior to ALA-induction. In this condition, re-expression of some genes related to apoptosis in U373-MG, and differentiation in D54-MG were induced. PpIX accumulation was higher than ALA-induction and the acetylation of histone H4 induced by NaB was verified by immunocytochemistry in both cells. It can be concluded that modified chromatin and genes induced by NaB increment the cellular death induced by PDT in astrocytoma cells using PpIX as endogenous PS. 相似文献
65.
Ramona Wortmann Alexander Hoffmann Roxana Haase Ulrich Flörke Sonja Herres‐Pawlis Dr. 《无机化学与普通化学杂志》2009,635(1):64-69
Syntheses and Structures of Cobalt(II) and Copper(I) Complexes with Guanidine‐Pyridine Hybridligands The guanidine‐pyridine hybridligands N‐(1,3‐dimethylimidazolidin‐2‐ylidene)‐2‐(pyridine‐2‐yl)ethanamine (DMEGepy, L1 ) and 1,1,3,3‐tetramethyl‐2‐(2‐(pyridine‐2‐yl)ethyl)guanidine (TMGepy, L2 ) have been synthesized and characterized. The reaction of DMEGepy with CoCl2 and TMGepy with CuI lead to the mononuclear complexes {N‐(1,3‐dimethylimidazolidin‐2‐ylidene)‐2‐(pyridine‐2‐yl)ethanamine}cobalt(II) dichloride ( 1 ) and {1,1,3,3‐tetramethyl‐2‐(2‐(pyridine‐2‐yl)ethyl)guanidine}copper(I) iodide ( 2 ). By the characterization of these complexes we are able to compare the complexation chemistry of the hybridguanidine and bisguanidine ligands with regard to the various N donor functions systematically. 相似文献
66.
Hctor M. Alvarez Martín A. Hernndez Mariana P. Lanfranconi Roxana A. Silva María S. Villalba 《Molecules (Basel, Switzerland)》2021,26(16)
Bacteria belonging to the Rhodococcus genus are frequent components of microbial communities in diverse natural environments. Some rhodococcal species exhibit the outstanding ability to produce significant amounts of triacylglycerols (TAG) (>20% of cellular dry weight) in the presence of an excess of the carbon source and limitation of the nitrogen source. For this reason, they can be considered as oleaginous microorganisms. As occurs as well in eukaryotic single-cell oil (SCO) producers, these bacteria possess specific physiological properties and molecular mechanisms that differentiate them from other microorganisms unable to synthesize TAG. In this review, we summarized several of the well-characterized molecular mechanisms that enable oleaginous rhodococci to produce significant amounts of SCO. Furthermore, we highlighted the ability of these microorganisms to degrade a wide range of carbon sources coupled to lipogenesis. The qualitative and quantitative oil production by rhodococci from diverse industrial wastes has also been included. Finally, we summarized the genetic and metabolic approaches applied to oleaginous rhodococci to improve SCO production. This review provides a comprehensive and integrating vision on the potential of oleaginous rhodococci to be considered as microbial biofactories for microbial oil production. 相似文献
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Superior biolubricant from a species of red microalga 总被引:1,自引:0,他引:1
Arad SM Rapoport L Moshkovich A van Moppes D Karpasas M Golan R Golan Y 《Langmuir : the ACS journal of surfaces and colloids》2006,22(17):7313-7317
The rheological properties of the sulfated polysaccharide of the red microalga Porphyridium sp., a heteropolymer with a molecular weight of 3-5 x 10(6) Da, indicated that this material might be an excellent candidate for lubrication applications: the viscosity of the polysaccharide is stable over a range of temperatures, pH values, and salinities. In this study, various rheological and lubricant properties of the polysaccharide were evaluated in comparison with those of a widely used biolubricant, hyaluronic acid. The viscosity of the Porphyridium sp. polysaccharide remained essentially unchanged in a temperature range of 25-70 degrees C. In tribology tests on a ball-on-flat ceramic pair, the values for the friction coefficient and wear rate for the pair lubricated with polysaccharide were remarkably lower than those for hyaluronic acid, especially at high loads. In a test on a steel ring/ultrahigh-molecular-weight polyethylene (UHMWPE) block pair, the wear tracks on the surface of the UHMWPE were more pronounced for hyaluronic acid than for the polysaccharide. Atomic force microscopy showed that the polysaccharide was effectively adsorbed onto mica surfaces, forming ultrathin coating layers in the nanometer range. As is required for biolubricant applications, the polysaccharide was not degraded by hyaluronidase. The stability of the Porphyridium sp. polysaccharide to heat and to hyaluronidase combined with its ability to reduce friction and wear indicate its potential as an advantageous biolubricant. 相似文献
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Amination of the C‐isopropyldimethylsilyl P‐chlorophosphaalkene (iPrMe2Si)2C=PCl ( 1 ) leads to the P‐aminophosphaalkenes (iPrMe2Si)2C=PN(R)R′ (R, R′ = Me ( 2 ), R = H, R′ = nPr ( 3 ), R = H, R′ = iPr ( 4 ), R = H, R′ = tBu ( 5 ), R = H, R′ = 1‐Ada ( 6 ), R = H, R′ = CPh3 ( 7 ), R = H, R′ = Ph ( 8 ), R = H, RR′ = 2,6‐iPr2Ph (= DIP) ( 10 ), R = H, R′ = 2,4,6‐Me3Ph (= Mes) ( 11 ), R = H, R′ = 2,4,6‐tBu3Ph (= Mes*)] ( 12 ), R = H, R′ = SiMe3 ( 13 ), and R, R′ = SiMe2Ph (1 4 ). 31P‐NMR spectra confirm that phosphaalkenes 2 – 7 and 10 – 14 are monomeric in solution; the structures of 7 , 10 , and 12 were determined by X‐ray crystallography. Freshly prepared (iPrMe2Si)2C=PN(H)Ph ( 8 ) is a monomer that dimerizes with (N→C) proton migration within several hours to the stable diazadiphosphetidine [(iPrMe2Si)2CHPNPh]2 ( 9 ). NMR‐scale reactions of deprotonated 5 and 13 with tBuiPrPCl provide by P–P bond formation the P‐phosphanyl iminophosphoranes [(iPrMe2Si)2C=](RN=)PPtBu(iPr) [R = tBu ( 15 ), R = Me3Si ( 17 )]. Deprotonated 5 and Me3GeCl deliver by N–Ge bond formation the aminophosphaalkene (iPrMe2Si)2C=PN(tBu)GeMe3 ( 20 ), which with elemental selenium 5 undergoes (N→C) proton migration to form the alkyl(imino)(seleno)phosphorane [(iPrMe2Si)2CH](tBuN=)P=Se ( 21 ), which is a selenium‐bridged cyclic dimer in the solid state. 相似文献
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Pologea-Moraru R Kovacs E Iliescu KR Calota V Sajin G 《Bioelectrochemistry (Amsterdam, Netherlands)》2002,56(1-2):223-225
Due to the extensive use of electromagnetic fields in everyday life, more information is required for the detection of mechanisms of interaction and the possible side effects of electromagnetic radiation on the structure and function of the organism.In this paper, we study the effects of low-power microwaves (2.45 GHz) on the membrane fluidity of rod photoreceptor cells. The retina is expected to be very sensitive to microwave irradiation due to the polar character of the photoreceptor cells [Biochim. Biophys. Acta 1273 (1995) 217] as well as to its high water content [Stud. Biophys. 81 (1981) 39]. 相似文献
70.
Jordi Borrs Julie Foster Roxana Kashani Laura Melndez-Alafort Jane Sosabowski Joan Suades Ramon Barnadas-Rodríguez 《Molecules (Basel, Switzerland)》2021,26(8)
The zinc dithiocarbamates functionalized with folic acid 2Zn and 3Zn were synthesized with a simple straightforward method, using an appropriated folic acid derivative and a functionalized zinc dithiocarbamate (1Zn). Zinc complexes 2Zn and 3Zn show very low solubilities in water, making them useful for preparing Tc-99m radiopharmaceuticals with a potentially high molar activity. Thus, the transmetallation reaction in water medium between the zinc complexes 2Zn or 3Zn and the cation fac-[99mTc(H2O)3(CO)3]+, in the presence of the monodentate ligand TPPTS, leads to the formation of the 2 + 1 complexes fac-[99mTc(CO)3(SS)(P)] bioconjugated to folic acid (2Tc and 3Tc). In spite of the low solubility of 2Zn and 3Zn in water, the reaction yield is higher than 95%, and the excess zinc reagent is easily removed by centrifugation. The Tc-99m complexes were characterized by comparing their HPLC with those of the homologous rhenium complexes (2Re and 3Re) previously synthesized and characterized by standard methods. Preliminary in vivo studies with 2Tc and 3Tc indicate low specific binding to folate receptors. In summary, Tc-99m folates 2Tc and 3Tc were prepared in high yields, using a one-pot transmetallation reaction with low soluble zinc dithiocarbamates (>1 ppm), at moderate temperature, without needing a subsequent purification step. 相似文献