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121.
siRNA. A guide for RNA silencing 总被引:19,自引:0,他引:19
RNAi is routinely used to eliminate gene activity for experimental purposes. However, the precise molecular mechanism of RNAi is unknown. Recent papers partially illuminate this mechanism in human cells, advancing the potential application of RNAi toward the treatment of human disease. 相似文献
122.
Beurer E Venkataraman NV Sommer M Spencer ND 《Langmuir : the ACS journal of surfaces and colloids》2012,28(6):3159-3166
An orthogonal, charge-density-versus-net-charge, surface-chemical gradient, composed of ternary mixed self-assembled monolayers, has been prepared from three hydrophilic components: positively chargeable amine-terminated, negatively chargeable carboxylic-acid-terminated, and hydroxyl-terminated alkanethiols, with the latter bearing a slight negative charge in electrolytes. The chemical composition and its distribution have been monitored by X-ray photoelectron spectroscopy. The adsorption behavior of negatively charged SiO(2) nanoparticles and positively charged amine-modified SiO(2) nanoparticles has been studied. Additionally, negatively charged proteins (bovine serum albumin and fibrinogen) and positively charged proteins (lysozyme) were adsorbed on the gradients. Negatively charged nanoparticles and proteins adsorb mainly in the positively charged region and vice versa, illustrating that the adsorption behavior is mainly influenced by electrostatic interactions, and showing the potential of the gradient for sorting applications. Despite literature reports to the contrary, no area was found that was completely resistant to protein adsorption. 相似文献
123.
Saptarshi Chattopadhyay Sheryl H. Ehrman Jayesh Bellare Chandra Venkataraman 《Journal of nanoparticle research》2012,14(4):779
Small liposome suspensions (hydrodynamic diameter, 80–130 nm) were nebulised, and the resulting changes in morphology and
bilayer integrity were found to be related to surface properties controlled by bilayer composition. Four separate liposome
compositions (or liposome types) were investigated using three different phospholipids with unique properties. Morphological
changes were studied using light scattering and imaging of liposomes before and after nebulisation, and structural integrity
was investigated on the basis of the retention of an encapsulated dye (probe molecule). Nebulisation generated droplets contained
liposomes. The liposome particles generated on droplet evaporation had a hollow structure as evidenced by electron imaging,
indicating that the lipid bilayer does not collapse on evaporation. The particles of all compositions had mobility diameters
between 50 and 90 nm, 1.4–1.6 times smaller than their diameters (hydrodynamic) measured before nebulisation, implying considerable
volume shrinkage. Liposomes that had polymer-conjugated lipids covering their external surface underwent aggregation during
nebulisation, evidenced by increased diameter after nebulisation. Incorporation of charged lipids reduced nebulisation-induced
aggregation, but induced greater membrane rupture during aerosol generation, causing leakage of encapsulated probe molecules.
Incorporation of both cholesterol and charged lipids prevented aggregation, but also preserved bilayer integrity, evidenced
by the maximum retention of encapsulated dye observed in these conditions (>85%). The findings suggest that liposome bilayer
composition can be manipulated to improve the efficiency of liposome aerosol delivery. 相似文献
124.
Ramaswamy Murugavel Mayank Pratap Singh M. Nethaji 《Journal of chemical crystallography》2012,42(1):12-17
Abstract
Condensation reaction involving substituted aminobenzoic acids (2-aminobenzoic acid and 4-aminobenzoic acid) and acetylacetone results in the formation of ketoimines [CH3C(= O)CH2C(CH3)(= NAr)] (Ar = C6H4COOH-4; 1 and C6H4COOH-2 2). Compounds 1 and 2 have been characterized by spectroscopic techniques and by single crystal X-ray diffraction studies. The absorption, emission and life-time measurement studies have also been performed for the new compounds. While compound 1 forms a linear chain type of aggregation though intermolecular hydrogen bonding, compound 2 forms a discrete dimer in the solid state. 相似文献125.
The ethyl acetate extracts of the bark and leaves of Ficus coronata were separated by column chromatography and the resulting fractions tested for their bioactivity toward methicillin-resistant-Staphylococcus aureus (MRSA) and M. luteus. The bioactive column chromatography fractions were further separated by preparative thin layer chromatography (TLC) and the resulting bands investigated by high-performance liquid chromatography-electrospray ionization-ion trap mass spectrometry (HPLC-ESI-MS(n) ) and ESI-MS(n) . The resulting retention times, molecular masses, their fragmentation patterns, and the chemnet database (www.chemnetbase.com) were then used in the dereplication process by structural elucidation of some of the compounds when compared with known structures of natural origin. Some molecular masses and the corresponding fragmentations were found that did not correlate with any known compounds thus revealing potentially novel natural products that could be investigated on a larger scale and could ultimately find application as new drugs against MRSA and other multidrug-resistant microorganisms. Structures are also proposed for known compounds that have not been previously reported for F. coronata. 相似文献
126.
A novel family of metal oxides with a chemical formula of Sr(2)Ce(1-x)Pr(x)O(4) (x = 0, 0.2, 0.5, 0.8, and 1) was developed as mixed oxide ion and electronic conductors for solid oxide fuel cells (SOFCs). All of the investigated samples were synthesized by the ceramic method at 1000 °C in air and characterized by powder X-ray diffraction (PXRD), selected area electron diffraction (SAED), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), and electrochemical impedance spectroscopy (EIS). Ex-situ PXRD reveals that the Sr(2)PbO(4)-type Sr(2)CeO(4) decomposes readily into a mixture of perovskite-type SrCeO(3) and rock-salt-type SrO at 1400 °C in air. Surprisingly, the decomposed products are converted back to the original Sr(2)PbO(4)-type Sr(2)CeO(4) phase at 800 °C in air, as confirmed by in-situ PXRD. Thermal decomposition is highly suppressed in Sr(2)Ce(1-x)Pr(x)O(4) compounds for Pr > 0, suggesting that Pr improves the thermal stability of the compounds. Rietveld analysis of PXRD and SAED supported that both Pr and Ce ions are located on the 2a site in Pbam (space group no. 55). The electrical transport mechanism could be correlated to the reduction of Pr and/or Ce ions and subsequent loss of oxide ions at elevated temperatures, as shown by TGA and in-situ PXRD. Conductivity increases with Pr content in Sr(2)Ce(1-x)Pr(x)O(4). The highest total conductivity of 1.24 × 10(-1) S cm(-1) was observed for Sr(2)Ce(0.2)Pr(0.8)O(4) at 663 °C in air. 相似文献
127.
Solving Large Airline Crew Scheduling Problems: Random Pairing Generation and Strong Branching 总被引:1,自引:0,他引:1
Diego Klabjan Ellis L. Johnson George L. Nemhauser Eric Gelman Srini Ramaswamy 《Computational Optimization and Applications》2001,20(1):73-91
The airline crew scheduling problem is the problem of assigning crew itineraries to flights. We develop a new approach for solving the problem that is based on enumerating hundreds of millions random pairings. The linear programming relaxation is solved first and then millions of columns with best reduced cost are selected for the integer program. The number of columns is further reduced by a linear programming based heuristic. Finally an integer solution is obtained with a commercial integer programming solver. The branching rule of the solver is enhanced with a combination of strong branching and a specialized branching rule. The algorithm produces solutions that are significantly better than ones found by current practice. 相似文献
128.
Venkataraman Thangadurai Robert A. Huggins Werner Weppner 《Journal of Solid State Electrochemistry》2001,5(7-8):531-537
The praseodymium oxide system contains a series of related phases with very narrow compositional width and unique extended
defect structures, rather than the more common isolated point defects. The electrical conductivity of three of these phases
has been measured by the use of AC complex impedance and DC methods in the temperature range 75–400 °C. The beta phase, Pr6O11, exhibits a total conductivity of 6.77×10–2 S/cm at 400 °C, with an activation energy of 0.52 eV/atom. The conductivity of the epsilon phase, Pr5O9, is slightly lower, with an activation energy of 0.51 eV/atom. The iota phase, Pr7O12, has a very low conductivity. The activation energies for electrical transport in the beta and epsilon phases are in the
general range found in a number of mixed conductors based upon LSGM oxides.
Electronic Publication 相似文献
129.
Jingyi Zhang Anuradha Krishnan Hao Wu Venkat Venkataraman 《Molecules (Basel, Switzerland)》2021,26(1)
S100B is a calcium-binding protein that governs calcium-mediated responses in a variety of cells—especially neuronal and glial cells. It is also extensively investigated as a potential biomarker for several disease conditions, especially neurodegenerative ones. In order to establish S100B as a viable pharmaceutical target, it is critical to understand its mechanistic role in signaling pathways and its interacting partners. In this report, we provide evidence to support a calcium-regulated interaction between S100B and the neuronal calcium sensor protein, neurocalcin delta both in vitro and in living cells. Membrane overlay assays were used to test the interaction between purified proteins in vitro and bimolecular fluorescence complementation assays, for interactions in living cells. Added calcium is essential for interaction in vitro; however, in living cells, calcium elevation causes translocation of the NCALD-S100B complex to the membrane-rich, perinuclear trans-Golgi network in COS7 cells, suggesting that the response is independent of specialized structures/molecules found in neuronal/glial cells. Similar results are also observed with hippocalcin, a closely related paralog; however, the interaction appears less robust in vitro. The N-terminal region of NCALD and HPCA appear to be critical for interaction with S100B based on in vitro experiments. The possible physiological significance of this interaction is discussed. 相似文献
130.
A new version of a numerical algorithm for the Lagrangian treatment of incompressible fluid flows with free surfaces is developed. The novel features of the present method are the adoptions of the Lagrangian finite element method and the velocity correction technique. The use of the velocity correction approach makes the computational scheme extremely simple in algorithmic structure. Hence, the present method is particularly attractive for large-scale problems. The techniques discussed here are applied to some two-dimensional sloshing problems, which may indicate the versatility and effectiveness of the present method. 相似文献