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441.
Film thickness dependence of protein adsorption from blood serum and plasma onto poly(sulfobetaine)-grafted surfaces 总被引:1,自引:0,他引:1
Yang W Chen S Cheng G Vaisocherová H Xue H Li W Zhang J Jiang S 《Langmuir : the ACS journal of surfaces and colloids》2008,24(17):9211-9214
In this work, we investigate protein adsorption from single protein solutions and complex media such as 100% blood serum and plasma onto poly(sulfobetaine methacrylate) (polySBMA)-grafted surfaces via atom transfer radical polymerization (ATRP) at varying film thicknesses. It is interesting to observe that protein adsorption exhibits a minimum at a medium film thickness. Results show that the surface with 62 nm polySBMA brushes presents the best nonfouling character in 100% blood serum and plasma although all of these surfaces are highly resistant to nonspecific protein adsorption from single fibrinogen and lysozyme solutions. Surface resistance to 100% blood serum or plasma is necessary for many applications from blood-contacting devices to drug delivery. This work provides a new in vitro evaluation standard for the application of biomaterials in vivo. 相似文献
442.
Cahová H Pohl R Bednárová L Nováková K Cvacka J Hocek M 《Organic & biomolecular chemistry》2008,6(20):3657-3660
dATP derivatives bearing Br, Me or Ph groups in position 8 were prepared and tested as substrates for DNA polymerases to show that 8-Br-dATP and 8-Me-dATP were efficiently incorporated, while 8-Ph-dATP was a poor substrate due to its bulky Ph group. 相似文献
443.
Diffusion of biological molecules on 2D biological membranes can play an important role in the behavior of stochastic biochemical reaction systems. Yet, we still lack a fundamental understanding of circumstances where explicit accounting of the diffusion and spatial coordinates of molecules is necessary. In this work, we illustrate how time-dependent, non-exponential reaction probabilities naturally arise when explicitly accounting for the diffusion of molecules. We use the analytical expression of these probabilities to derive a novel algorithm which, while ignoring the exact position of the molecules, can still accurately capture diffusion effects. We investigate the regions of validity of the algorithm and show that for most parameter regimes, it constitutes an accurate framework for studying these systems. We also document scenarios where large spatial fluctuation effects mandate explicit consideration of all the molecules and their positions. Taken together, our results derive a fundamental understanding of the role of diffusion and spatial fluctuations in these systems. Simultaneously, they provide a general computational methodology for analyzing a broad class of biological networks whose behavior is influenced by diffusion on membranes. 相似文献
444.
A selective reduction of a broad variety of ketones is described. The method is based on the combination of a Ni-Al alloy and high hydrostatic pressure (HHP, 2.8 kbar) in an aqueous medium. The reaction of the Ni-Al alloy with water provides in situ hydrogen generation and the high pressure ensures that the H(2) formed remains in the solution, thus the C[double bond, length as m-dash]O reduction readily occurs. The application of the HHP resulted in selective formation of the desired products and the common problem of non-selective overhydrogenation could be avoided. In most cases the reductions resulted in high yields and excellent selectivities without the use of any base. 相似文献
445.
Kyung-Ran Kim Hyeon-Ju Jeong Yoonsub Kim Seung Yeon Lee Yujin Kim Hyun-Ji Kim Suk-Ho Lee Hana Cho Jong-Sun Kang Won-Kyung Ho 《Experimental & molecular medicine》2021,53(7):1134
Calbindin, a major Ca2+ buffer in dentate granule cells (GCs), plays a critical role in shaping Ca2+ signals, yet how it regulates neuronal function remains largely unknown. Here, we found that calbindin knockout (CBKO) mice exhibited dentate GC hyperexcitability and impaired pattern separation, which co-occurred with reduced K+ current due to downregulated surface expression of Kv4.1. Relatedly, manipulation of calbindin expression in HT22 cells led to changes in CaMKII activation and the level of surface localization of Kv4.1 through phosphorylation at serine 555, confirming the mechanism underlying neuronal hyperexcitability in CBKO mice. We also discovered that Ca2+ buffering capacity was significantly reduced in the GCs of Tg2576 mice to the level of CBKO GCs, and this reduction was restored to normal levels by antioxidants, suggesting that calbindin is a target of oxidative stress. Our data suggest that the regulation of CaMKII signaling by Ca2+ buffering is crucial for neuronal excitability regulation.Subject terms: Cellular neuroscience, Intrinsic excitability 相似文献
446.
Vasil Andruch Carolina Cecilia Acebal Jana Škrlíková Hana Sklenářová Petr Solich Ioseph S. Balogh Ferenc Billes Lívia Kocúrová 《Microchemical Journal》2012
A novel approach for sequential injection-dispersive liquid–liquid microextraction (SI-DLLME) has been suggested. The method is based on the aspiration and mixing of a sample and all required aqueous reagents in the holding coil of an SIA system, delivering it into a conical tube and adding in a mixture of extraction solvent, auxiliary solvent and disperser solvent at high flow rate, resulting in the formation of a cloudy state and the extraction of an analyte. The mixture of extraction and auxiliary solvent is immiscible with water and has a density significantly higher than that of water; consequently, the resulting fine droplets in the mixture, which contain the extracted analyte, are self-sedimented in a short time at the bottom of conical tube. Thus, no centrifugation and no use of a microcolumn are required for separation of the extraction phase. Afterwards, the extracted analyte is aspirated and transferred to a micro-volume Z-flow cell, and the absorbance is measured.The performance of the suggested approach is demonstrated by the SI-DLLME of thiocyanate ions in the form of ion associate with dimethylindocarbocyanine reagent, followed by spectrophotometric detection. A mixture of amyl acetate (as extraction solvent), tetrachloromethane (as auxiliary solvent) and acetonitrile (as disperser solvent) was selected for the DLLME procedure. The appropriate experimental conditions for conventional DLLME and automated SI-DLLME were investigated. The analytical performance of both these procedures was compared. The absorbance of the colored extracts at wavelength 555 nm obeys Beer's law in the range of 3.13–28.2 for conventional DLLME and 0.29–5.81 mg L? 1 of SCN for SI-DLLME, and the limit of detection, calculated from a blank test based on 3 s, is 0.110 for conventional DLLME and 0.017 mg L? 1 for SI-DLLME. 相似文献
447.
Simona Zlá Bed?ich Smetana Monika ?aludová Jana Dobrovská Vlastimil Vodárek Kate?ina Kone?ná Vlastimil Matějka Hana Francová 《Journal of Thermal Analysis and Calorimetry》2012,110(1):211-219
The presented paper deals with the study of thermophysical properties of cast and complex alloyed nickel based on superalloy Inconel 713LC (IN713LC). In this work, the technique of Differential Thermal Analysis was selected for determination of the phase transformation temperatures and for the study of the effect of varying heating/cooling rate at these temperatures. The samples taken from as-received state of superalloy were analysed at heating and cooling rates of 1, 5, 10, 20 and 50?°C?min?1 with the help of the experimental system Setaram SETSYS 18TM. Moreover, the transformation temperatures at zero heating/cooling rate were calculated. The recommended values for IN713LC after correcting to a zero heating rate, are 1,205?°C (T ?á?,solvus), 1,250?°C (solidus) and 1,349?°C (liquidus). Influence of heating/cooling rate on shift of almost all temperatures of phase transformations was established from the DTA curves. Undercooling was observed at the cooling process. The samples before and after DTA analysis were also subjected to the phase analysis by scanning electron microscopy using the microscope JEOL JSM-6490LV equipped with an energy dispersive analyser EDAX (EDS INCA x-act). Documentation of the microstructure was made in the mode of secondary (SEI) and backscattered (BEI) electron imaging. On the basis of DTA analysis and phase analysis it may be stated that development of phase transformations of the alloy IN713LC will probably correspond to the following scheme: melting?????? phase; melting???????+?MC; melting????eutectics ??/?á?; melting???????+?minority phases (e.g. borides); and matrix ???????á?. 相似文献
448.
Ahmed?Khalaf?MheemeedEmail author Hana?Ihsan?Hasan Firas?Mohammed?Al-Jomaily 《Journal of Radioanalytical and Nuclear Chemistry》2012,291(3):653-659
In the present study five samples of special rubber–lead were fabricated each of them consists of lead and rubber with different
weight ratios. The fabrication was carried out through the process of mixing under compression pressure. Gamma-ray transmission
method was employed to determine the linear attenuation coefficient for narrow collimated mono-energetic beams of gamma-rays
emitted from 241Am 0.059, 152Eu 0.13 and 137Cs 0.662 MeV. The linear attenuation coefficient of standard rubber–lead shield was also experimentally determined. The percentage
of lead in standard rubber–lead shield was determined through the calibration curve or by a simple computer program written
in MATLAB. All prepared samples are characterized as flexible and gives a good homogeneity. samples no. 4 & 5 offers the best
performance as a radiation protection shields. The results showed an inverse proportionality between the linear attenuation
coefficient μl and E, and μl has a direct proportionality with mixing ratios (sample density). The results showed an inverse proportional between the
half value layers and the average linear attenuation coefficients of the various samples. 相似文献
449.
A permanental vector is a generalization of a vector with components that are squares of the components of a Gaussian vector, in the sense that the matrix that appears in the Laplace transform of the vector of Gaussian squares is not required to be either symmetric or positive definite. In addition, the power of the determinant in the Laplace transform of the vector of Gaussian squares, which is −1/2, is allowed to be any number less than zero. 相似文献
450.
A new rearrangement of fused tetracyclic heterocycles in an acidic medium in the presence of NaBH3CN
In an acidic medium the criss-cross cycloadduct 2 with four fused five-membered rings rearranges to a heterocyclic compound 3 with a completely different structure consisting of two six-membered and two five-membered rings. This newly discovered rearrangement was observed in the presence of a reducing agent (NaBH3CN). The rearrangement proceeds easily and with an extremely high yield. 相似文献