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91.
CdTe quantum dots (QDs), capped with mercaptopropionic acid (MPA), were synthesized and the variation of their fluorescence properties (steady state and lifetime) with pH was assessed in solution and when immobilized in a sol-gel host. Three different sizes of CdTe QDs with excited state lifetimes ranging from 42 to 48 ns and with emission maximum at 540 nm (QD540), 580 nm (QD580) and 625 nm (QD625) were selected. The solution pH affects the maximum emission wavelength (shifts to higher wavelengths of 23, 24 and 27 nm for QD540, QD580 and QD625, respectively), the excited state lifetime and the fluorescence intensity in a reversible way. Linearization of the maximum emission wavelength variation with the pH allows the estimation of an apparent ionization constant (pKa) for each QD: 6.5 ± 0.1 (QD540), 6.1 ± 0.5 (QD580) and 5.4 ± 0.3 (QD625). The variation of the QDs fluorescence properties was further explored using confocal laser scanning microscopy allowing the implementation of a new calibration method for pH imaging in solution. QDs were successfully immobilized on the tip of an optical fiber by dip-coating using sol-gel procedure. The immobilized QDs showed a similar pH behaviour to the one observed in solution and an apparent lifetime of 80, 68 and 99 ns, respectively. The proposed QDs based methodology can be successfully used to monitor pH using wavelength encoded data in imaging and fiber optic sensing applications. 相似文献
92.
Plínio C. Sathler Charles S. Craik Toshihiko Takeuchi Russolina B. Zingali Helena C. Castro 《Applied biochemistry and biotechnology》2010,160(8):2355-2365
Ecotin is a bidentate, fold-specific inhibitor of mammalian serine-proteases produced by Escherichia coli. This molecule may be engineered to increase and/or change its affinity and specificity providing significant biotechnological
potential. Since ecotin binds tightly to serine proteases of the trypsin fold, it may help to identify the role of these enzymes
in different biological processes. In this work, we tested ecotin variants as an affinity purification reagent for identifying
enzymes in samples of tumor progression and mammary gland involution. Initially, we used a commercial source of urokinase-type
plasminogen activator (u-PA) that remained fully active after elution from an affinity column of the ecotin variant (M84R,
M85R). We then successfully identified u-PA from more complex mixtures including lysates from a prostate cancer cell line
and involuting mouse mammary glands. Interestingly, a membrane-type serine protease 1 was isolated from the Triton X-100-solubilized
PC-3 cell lysates, and surprisingly, haptoglobin, a serine-protease homolog protein, was also identified in mammary gland
lysates and in blood. Haptoglobin does not prevent ecotin inhibition of u-PA, but it may act as a carrier within blood when
ecotin is used in vivo. Finally, this affinity purification matrix was also able to identify a thrombin-like enzyme from snake venom using an ecotin
variant directed against thrombin. Overall, the ecotin variants acted as robust tools for the isolation and characterization
of proteins with a trypsin fold. Thus, they may assist in the understanding of the role of these serine proteases and homologous
proteins in different biological processes. 相似文献
93.
Bodzon-Kulakowska A Suder P Drabik A Kotlinska JH Silberring J 《Analytical and bioanalytical chemistry》2010,398(7-8):2939-2942
Glutamine synthetase is a key enzyme which has a regulatory role in the brain glutamate pool. According to previously published proteomic analysis, it was shown that the expression level of this enzyme is affected by morphine administration. In our study, we examined the activity of glutamine synthetase in various structures of rat brain (cortex, striatum, hippocampus and spinal cord) that are biochemically and functionally involved in drug addiction and antinociception caused by morphine. We were not able to observe any significant changes in the enzyme activity between morphine-treated and control samples despite previously reported changes in the expression levels of this enzyme. These findings stressed the fact that changes observed in the expression of particular proteins during proteomic studies may not be correlated with its activity. 相似文献
94.
Helena Řehulková Jana Chalupová Marek Šebela Pavel Řehulka 《Journal of mass spectrometry : JMS》2010,45(1):104-111
Peptide samples derived from enzymatic in‐gel digestion of proteins resolved by gel electrophoresis often contain high amount of salts originating from reaction and separation buffers. Different methods are used for desalting prior to matrix‐assisted laser desorption/ionization (MALDI) mass spectrometry (MS), e.g. reversed‐phase pipette tip purification, on‐target washing, adding co‐matrices, etc. As a suitable matrix for MALDI MS of peptides, α‐cyano‐4‐hydroxycinnamic acid (CHCA) is frequently used. Crystalline CHCA shows the ability to bind peptides on its surface and because it is almost insoluble in acidic water solutions, the on‐target washing of peptide samples can significantly improve MALDI MS signals. Although the common on‐target washing represents a simple, cheap and fast procedure, only a small portion of the available peptide solution is efficiently used for the subsequent MS analysis. The present approach is a combination of the on‐target washing principle carried out in a narrow‐end pipette tip (e.g. GELoader tip) and preconcentration of peptides from acidified solution by passing it through small CHCA crystals captured inside the tip on a glass microfiber frit. The results of MALDI MS analysis using CHCA‐tip peptide preconcentration are comparable with the use of homemade POROS R2 pipette tip microcolumns. Advantages and limitations of this approach are discussed. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
95.
Annelien Deneckere Walter Schudel Marina Van Bos Helena Wouters Anna Bergmans Peter Vandenabeele Luc Moens 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2010,75(2):511-519
X-ray fluorescence spectroscopy (XRF) and Raman spectroscopy have been used to examine 15th century mediaeval and 16th century renaissance vault paintings in the Our Lady's Cathedral (Antwerp, Belgium) in view of their restoration. The use of mobile instruments made it possible to work totally non-destructively. This complementary approach yields information on the elemental (XRF) and on the molecular composition (Raman) of the pigments. For the 15th century vault painting the pigments lead–tin yellow (Pb2SnO4), lead white (2PbCO3·Pb(OH)2), vermilion (HgS), massicot (PbO) and azurite (2CuCO3·Cu(OH)2) could be identified. The pigments used for the 16th century vault painting could be identified as red lead (Pb3O4), hematite (Fe2O3), lead white (2PbCO3·Pb(OH)2) and azurite (2CuCO3·Cu(OH)2). For both paintings the presence of the strong Raman scatterer calcite (CaCO3) resulted in a difficult identification of the pigments by Raman spectroscopy. The presence of gypsum (CaSO4·2H2O) on the mediaeval vault painting probably indicates that degradation took place. 相似文献
96.
A mixed‐polymeric electrokinetic chromatography system has been developed for the simultaneous determination of a contaminant like oversulfated condroitin sulfate (OSCS) and impurities expressed as dermatan (Der) in heparin (Hep) samples. The EKC system consisted of 0.5% w/v polymeric β‐CD, 0.4% w/v tetronic® 1107 and 400 mM tris‐phosphate buffer at pH 3.5. The optimized electrophoretic conditions included the use of an uncoated‐silica capillary of 50 cm of total length and 75 μm id, an applied voltage of ?7 kV, a temperature of 30°C and 200 nm UV‐detection. The highly sensitive method developed showed low values of LOD, 0.07% w/w (0.07 μg/mL) (OSCS) and 0.1% w/w (0.1 μg/mL) (Der), and values of LOQ 0.2% w/w (0.2 μg/mL) (OSCS) and 0.3% w/w (0.3 μg/mL) (Der) with a concentration level of Hep sample as low as 0.1 mg/mL. Additional parameters of validation such as specificity, linearity, accuracy, and robustness were evaluated according to international guidelines. Owing to its simplicity, high sensitivity, and reliability, the proposed method can be an advantageous alternative to the traditional methodologies for the analysis of Hep in raw material and specially in finished products because of the low amounts of Hep sample required. 相似文献
97.
Rosa Maria da Rocha Esperidiana A.B. Moura José Carlos Bressiani Ana Helena A. Bressiani 《Radiation Physics and Chemistry》2010,79(3):301-305
Methylsilicone resin as a polymer precursor for a SiOC ceramic material was cured and foamed by electron beam (EB) irradiation in air prior to the pyrolysis under an inert atmosphere. Methylsilicone foams were obtained without additional foaming agent when exposed to accelerated electrons with radiation doses up to 9 MGy and dose rate of 2.8 kGy/s. During irradiation the polymer was melted and simultaneously gaseous products were formed by the methyl group oxidation and by the poly-condensation crosslinking reactions. The formed gases could not escape from the molten polymer and began to aggregate into bubbles. The effect of the radiation dose on the polymer foam molecular structure, the gel fraction and the ceramic yield was analyzed. The results indicate that the maximum amount of crosslinking in methylsilicone, when EB radiation is used, occurred between 1.0 and 2.0 MGy radiation dose. Methylsilicone foams were pyrolysed in N2 atmosphere at temperatures of 1200 and 1500 °C, resulting in amorphous SiOC and partially crystalline ceramic foams, respectively. A porosity of ~84% was achieved in the pyrolyzed foams, with cell size ranging from 30 to 300 μm and density of about 0.31 g cm?3. 相似文献
98.
Mohammad Haji-Saeid Agnes Safrany Maria Helena de O. Sampa Natesan Ramamoorthy 《Radiation Physics and Chemistry》2010,79(3):255-260
Radiation processing offers a clean and additive-free method for preparation of value-added novel materials based on renewable, non-toxic, and biodegradable natural polymers. Crosslinked natural polymers can be used as hydrogel wound dressings, face cleaning cosmetic masks, adsorbents of toxins, and non-bedsore mats; while low molecular weight products show antibiotic, antioxidant, and plant-growth promoting properties. Recognizing the potential benefits that radiation technology can offer for processing of natural polymers into useful products, the IAEA implemented a coordinated research project (CRP) on “Development of Radiation-processed products of Natural Polymers for application in Agriculture, Healthcare, Industry and Environment”. This CRP was launched at the end of 2007 with participation of 16 MS to help connecting radiation technology and end-users to derive enhanced benefits from these new value-added products of radiation-processed natural materials. In this paper the results of activities in participating MS related to this work will be presented. 相似文献
99.
100.
Helena Gaspars-Wieloch 《Central European Journal of Operations Research》2014,22(4):779-794
The Hurwicz’s criterion is one of the classical decision rules applied in decision making under uncertainty as a tool enabling to find an optimal pure strategy both for interval and scenarios uncertainty. The interval uncertainty occurs when the decision maker knows the range of payoffs for each alternative and all values belonging to this interval are theoretically probable (the distribution of payoffs is continuous). The scenarios uncertainty takes place when the result of a decision depends on the state of nature that will finally occur and the number of possible states of nature is known and limited (the distribution of payoffs is discrete). In some specific cases the use of the Hurwicz’s criterion in the scenarios uncertainty may lead to quite illogical and unexpected results. Therefore, the author presents two new procedures combining the Hurwicz’s pessimism-optimism index with the Laplace’s approach and using an additional parameter allowing to set an appropriate width for the ranges of relatively good and bad payoffs related to a given decision. The author demonstrates both methods on the basis of an example concerning the choice of an investment project. The methods described may be used in each decision making process within which each alternative (decision, strategy) is characterized by only one criterion (or one synthetic measure). 相似文献