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排序方式: 共有272条查询结果,搜索用时 15 毫秒
191.
Das T Mallick SK Paul D Bhutia SK Bhattacharyya TK Maiti TK 《Journal of colloid and interface science》2007,314(1):71-79
In this study a major lectin called Concanavalin A (ConA) has been micropatterned on a glass substrate by microcontact printing and the patterns have been characterized with fluorescent and atomic force microscope for their uniformity. Interaction of the patterns with mammalian cells has been investigated by culturing L929 mouse fibroblast cells on the ConA printed glass surface. Cell culture results obtained from the microcontact printed patterns have also been compared and benchmarked with another patterning technique named micromolding in capillaries (MIMIC). It has been revealed that in spite of molecular level heterogeneity and agglomeration of protein molecules in microcontact printed form, they can still interact with cell surface glycoproteins, impede the mobility of membrane receptor which results in altered morphology of the fibroblast cells. 相似文献
192.
Damla Yaprak Dr. Eike T. Spielberg Dr. Tobias Bäcker Mark Richter Dr. Bert Mallick Prof. Dr. Axel Klein Prof. Dr. Anja‐Verena Mudring 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(21):6482-6493
In the search for uranium‐based ionic liquids, tris(N,N‐dialkyldithiocarbamato)uranylates have been synthesized as salts of the 1‐butyl‐3‐methylimidazolium (C4mim) cation. As dithiocarbamate ligands binding to the UO22+ unit, tetra‐, penta‐, hexa‐, and heptamethylenedithiocarbamates, N,N‐diethyldithiocarbamate, N‐methyl‐N‐propyldithiocarbamate, N‐ethyl‐N‐propyldithiocarbamate, and N‐methyl‐N‐butyldithiocarbamate have been explored. X‐ray single‐crystal diffraction allowed unambiguous structural characterization of all compounds except N‐methyl‐N‐butyldithiocarbamate, which is obtained as a glassy material only. In addition, powder X‐ray diffraction as well as vibrational and UV/Vis spectroscopy, supported by computational methods, were used to characterize the products. Differential scanning calorimetry was employed to investigate the phase‐transition behavior depending on the N,N‐dialkyldithiocarbamato ligand with the aim to establish structure–property relationships regarding the ionic liquid formation capability. Compounds with the least symmetric N,N‐dialkyldithiocarbamato ligand and hence the least symmetric anions, tris(N‐methyl‐N‐propyldithiocarbamato)uranylate, tris(N‐ethyl‐N‐propyldithiocarbamato)uranylate, and tris(N‐methyl‐N‐butyldithiocarbamato)uranylate, lead to the formation of (room‐temperature) ionic liquids, which confirms that low‐symmetry ions are indeed suitable to suppress crystallization. These materials combine low melting points, stable complex formation, and hydrophobicity and are therefore excellent candidates for nuclear fuel purification and recovery. 相似文献
193.
Behavior of Highly Diluted Electrolytes in Strong Electric Fields—Prevention of Alumina Deposition on Grading Electrodes in HVDC Transmission Modules by CO2‐induced pH‐Control 下载免费PDF全文
Dr. Immo Weber Dr. Bert Mallick Dipl.‐Ing. Matthias Schild Dr. Sabine Kareth Dr. Ralph Puchta Prof. Dr. Dr. h.c. mult. Rudi van Eldik 《Chemistry (Weinheim an der Bergstrasse, Germany)》2014,20(38):12091-12103
Alumina deposition on platinum grading electrodes in high voltage direct current (HVDC) transmission modules is an unsolved problem that has been around for more than three decades. This is due to the unavoidable corrosion of aluminum heat sinks that causes severe damage to electrical power plants and losses in the range of a million Euro range per day in power outage. Simple experiments in a representative HV test setup showed that aluminates at concentrations even below 10?8 mol L?1 can deposit on anodes through neutralization by protons produced in de‐ionized water (κ≤0.15 μS cm?1) at 20–35 kV (8 mA) per electrode. In this otherwise electrolyte‐poor aqueous environment, the depositions are formed three orders of magnitude below the critical precipitation concentration at pH 7! In the presence of an inert electrolyte such as TMAT (tetramethylammonium‐p‐toluenesulfonate), at a concentration level just above that of the total dissolved aluminum, no deposition was observed. Deposition can be also prevented by doping with CO2 gas at a concentration level that is magnitudes lower than that of the dissolved aluminum. From an overview of aqueous aluminum chemistry, the mystery of the alumina deposition process and its inhibition by CO2 is experimentally resolved and fully explained by field accumulation and repulsion models in synergism with acid–base equilibria. The extraordinary size of the alumina depositions is accounted for in terms of proton tunneling through “hydrated” alumina, which is supported by quantum chemical calculations. As a consequence, pulse‐purging with pure CO2 gas is presented as a technical solution to prevent the deposition of alumina. 相似文献
194.
K.?Mallick P.?MarcqEmail author 《The European Physical Journal B - Condensed Matter and Complex Systems》2003,36(1):119-128
We study analytically and numerically the noise-induced transition between an absorbing and an oscillatory state in a Duffing oscillator subject to multiplicative, Gaussian white noise. We show in a non-perturbative manner that a stochastic bifurcation occurs when the Lyapunov exponent of the linearised system becomes positive. We deduce from a simple formula for the Lyapunov exponent the phase diagram of the stochastic Duffing oscillator. The behaviour of physical observables, such as the oscillators mean energy, is studied both close to and far from the bifurcation.Received: 8 August 2003, Published online: 19 November 2003PACS:
05.40.-a Fluctuation phenomena, random processes, noise, and Brownian motion - 05.10.Gg Stochastic analysis methods (Fokker-Planck, Langevin, etc.) - 05.45.-a Nonlinear dynamics and nonlinear dynamical systems 相似文献
195.
Arabinda Mandal Bula Singh Rupendranath Banerjee Subrata Mukhopadhyay 《Journal of Coordination Chemistry》2017,70(10):1723-1738
In acid-media ([H+] = 0.01–0.06 M), each of the thiol compounds, D-penicillamine (PEN, LPH2) and captopril (CAP, LCH2) exist in several proton-dependent forms which can reduce the superoxo complex [(en)(dien)CoIII(O2)CoIII(en)(dien)]5+ (1) to the corresponding peroxo [(en)(dien)CoIII(O2)CoIII(en)(dien)]4+ (2) or the hydroperoxo complex [(en)(dien)CoIII(OOH)CoIII(en)(dien)]5+ (3). The observed first-order rate constants, ko,P and ko,C for PEN and CAP increase with the increase in [TPEN] and [TCAP] (which are the analytical concentrations of the respective thiols) but decrease with the increase in the media-acidity ([H+]) and the media ionic strength (I). The protolytic equilibria in aqueous solution allow several potentially reducing forms to coexist for both PEN (LPH3+, LPH2, LPH?, and LP2?) and CAP (LCH2, LCH?, LC2?) but the kinetic analyses reveal that the order of reactivity for the species are LPH3+ ~ LPH2 <<< LPH? and LCH2 < LCH? <<< LC2?, respectively. The predominance and higher reactivities of the anionic species, LPH? and LC2? are supported by the negative slopes of the plots of ko,P or ko,C versus I. Moreover, a large value of kH/kD for PEN suggests an inner-sphere electroprotic reaction pathway while the absence of such effect for CAP strongly supports an outer-sphere electron transfer reaction. These propositions are supported by the structural features of LPH? and LC2?. 相似文献
196.
Facile Surfactant‐Free Synthesis of p‐Type SnSe Nanoplates with Exceptional Thermoelectric Power Factors 下载免费PDF全文
Dr. Guang Han Dr. Srinivas R. Popuri Dr. Heather F. Greer Dr. Jan‐Willem G. Bos Prof. Wuzong Zhou Prof. Andrew R. Knox Dr. Andrea Montecucco Dr. Jonathan Siviter Dr. Elena A. Man Dr. Martin Macauley Prof. Douglas J. Paul Prof. Wen‐guang Li Dr. Manosh C. Paul Dr. Min Gao Dr. Tracy Sweet Prof. Robert Freer Dr. Feridoon Azough Dr. Hasan Baig Dr. Nazmi Sellami Prof. Tapas K. Mallick Prof. Duncan H. Gregory 《Angewandte Chemie (International ed. in English)》2016,55(22):6433-6437
A surfactant‐free solution methodology, simply using water as a solvent, has been developed for the straightforward synthesis of single‐phase orthorhombic SnSe nanoplates in gram quantities. Individual nanoplates are composed of {100} surfaces with {011} edge facets. Hot‐pressed nanostructured compacts (Eg≈0.85 eV) exhibit excellent electrical conductivity and thermoelectric power factors (S2σ) at 550 K. S2σ values are 8‐fold higher than equivalent materials prepared using citric acid as a structure‐directing agent, and electrical properties are comparable to the best‐performing, extrinsically doped p‐type polycrystalline tin selenides. The method offers an energy‐efficient, rapid route to p‐type SnSe nanostructures. 相似文献
197.
Singh RS Mukherjee K Banerjee R Chaudhuri A Hait SK Moulik SP Ramadas Y Vijayalakshmi A Rao NM 《Chemistry (Weinheim an der Bergstrasse, Germany)》2002,8(4):900-909
Although detailed structure-activity, physicochemical and biophysical investigations in probing the anchor influence in liposomal gene delivery have been reported for glycerol-based transfection lipids, the corresponding investigation for non-glycerol based simple monocationic transfection lipids have not yet been undertaken. Towards this end, herein, we delineate our structure-activity and physicochemical approach in deciphering the anchor dependency in liposomal gene delivery using fifteen new structural analogues (lipids 1-15) of recently reported non-glycerol based monocationic transfection lipids. The C(14) analogues in both series 1 (lipids 1-6) and series 2 (lipids 7-15) showed maximum efficiency in transfecting COS-1 and CHO cells. However, the C(12) analogue of the ether series (lipid 3) exhibited a seemingly anomalous behavior compared with its transfection efficient C(10) and C(14) analogues (lipids 2 and 4) in being completely inefficient to transfect both COS-1 and CHO cells. The present structure-activity investigation also convincingly demonstrates that enhancement of transfection efficiencies through incorporation of membrane reorganizing unsaturation elements in the hydrophobic anchor of cationic lipids is not universal but cell dependent. The strength of the interaction of lipids 1-15 with DNA was assessed by their ability to exclude ethidium bromide bound to the DNA. Cationic lipids with long hydrophobic tails were found, in general, to be efficient in excluding EtBr from DNA. Gel to liquid crystalline transition temperatures of the lipids was measured by fluorescence anisotropy measurement technique. In general (lipid 2 being an exception), transfection efficient lipids were found to have their mid transition temperatures at or below physiological temperatures (37 degrees C). 相似文献
198.
Summary The preparation of isomeric complexes [OsIIIX2L2]ClO4· H2O [{(4)} and (5): X = Cl or Br, L(1) = 2-(phenylazo)-pyridine (L1) or 2-(m-tolylazo)pyridine(L2)] via stereo-retentive oxidation of the corresponding osmium(II) precursors [(2) and (3), respectively] is described. The complexes were characterized using spectroscopic and electrochemical methods. The low-spin (idealized t
2g
5
; S = 1/2) paramagnetic complex ions display characteristic osmium(III) e.p.r. spectra in frozen (-196° C) MeCNPhMe. In dry MeCN solution, the OsX2N4 unit exhibits irreversible [OsX2L2]2+/[OsX2L2]+ and reversible [OsX2L2]+/[OsX2L2] couples at ca. 1.8 and 1.0 V versus saturated calomel electrode (s.c.e.), respectively. The use of (4)/(5) as an oxidant is noted. 相似文献
199.
Dramatic influence of the orientation of linker between hydrophilic and hydrophobic lipid moiety in liposomal gene delivery 总被引:1,自引:0,他引:1
Rajesh M Sen J Srujan M Mukherjee K Sreedhar B Chaudhuri A 《Journal of the American Chemical Society》2007,129(37):11408-11420
A number of prior studies have demonstrated that the DNA-binding and gene transfection efficacies of cationic amphiphiles crucially depend on their various structural parameters including hydrophobic chain lengths, headgroup functionalities, and the nature of the linker-functionality used in tethering the polar headgroup and hydrophobic tails. However, to date addressing the issue of linker orientation remains unexplored in liposomal gene delivery. Toward probing the influence of linker orientation in cationic lipid mediated gene delivery, we have designed and synthesized two structurally isomeric remarkably similar cationic amphiphiles 1 and 2 bearing the same hydrophobic tails and the same polar headgroups connected by the same ester linker group. The only structural difference between the cationic amphiphiles 1 and 2 is the orientation of their linker ester functionality. While lipid 1 showed high gene transfer efficacies in multiple cultured animal cells, lipid 2 was essentially transfection incompetent. Findings in both transmission electron microscopic and dynamic laser light scattering studies revealed no significant size difference between the lipoplexes of lipids 1 and 2. Findings in confocal microscopic and fluorescence resonance energy transfer (FRET) experiments, taken together, support the notion that the remarkably higher gene transfer efficacies of lipid 1 compared to those of lipid 2 presumably originate from higher biomembrane fusogenicity of lipid 1 liposomes. Differential scanning calorimetry (DSC) and fluorescence anisotropy studies revealed a significantly higher gel-to-liquid crystalline temperature for the lipid 2 liposomes than that for lipid 1 liposomes. Findings in the dye entrapment experiment were also consistent with the higher rigidity of lipid 2/cholesterol (1:1 mole ratio) liposomes. Thus, the higher biomembrane fusibility of lipid 1 liposomes than that of lipid 2 liposomes presumably originates from the more rigid nature of lipid 2 cationic liposomes. Taken together, the present findings demonstrate for the first time that even as minor a structural variation as linker orientation reversal in cationic amphiphiles can profoundly influence DNA-binding characteristics, membrane rigidity, membrane fusibility, cellular uptake, and consequently gene delivery efficacies of cationic liposomes. 相似文献
200.
Zakaria Baka Claire Godier Laureline Lamy Abhik Mallick Varvara Gribova Agathe Figarol Lina Bezdetnaya Alicia Chateau Zoé Magne Marie Stiefel Dounia Louaguef Philippe Lavalle Eric Gaffet Olivier Joubert Halima Alem 《Macromolecular bioscience》2023,23(3):2200434
Ovarian cancer remains a major public health issue due to its poor prognosis. To develop more effective therapies, it is crucial to set-up reliable models that closely mimic the complexity of the ovarian tumor's microenvironment. 3D bioprinting is currently a promising approach to build heterogenous and reproducible cancer models with controlled shape and architecture. However, this technology is still poorly investigated to model ovarian tumors. In this study, a 3D bioprinted ovarian tumor model combining cancer cells (SKOV-3) and cancer associated fibroblasts (CAFs) are described. The resulting tumor models show their ability to maintain cell viability and proliferation. Cells are observed to self-assemble in heterotypic aggregates. Moreover, CAFs are observed to be recruited and to circle cancer cells reproducing an in vivo process taking place in the tumor microenvironment. Interestingly, this approach also shows its ability to rapidly generate a high number of reproducible tumor models that can be subjected to usual characterizations (cell viability and metabolic activity; histology and immunological studies; and real-time imaging). Therefore, these ovarian tumor models can be an interesting tool for high throughput drug screening applications. 相似文献