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Jangir DK Charak S Mehrotra R Kundu S 《Journal of photochemistry and photobiology. B, Biology》2011,105(2):143-148
5-Fluorouracil (5FU) is an anticancer chemotherapeutic drug which exerts cytotoxic effect by inhibiting cellular DNA replication. In the present study, we explore the binding of 5FU with DNA and resulting structural and conformational changes on DNA duplex. UV-visible, Fourier transform infrared (FTIR) and circular dichroism (CD) spectroscopic techniques were employed to explore these interactions. A constant concentration of calf thymus DNA was incubated with varying concentrations of 5FU. UV-visible and FTIR spectroscopic results revealed that intercalation is the primary mode of interaction between 5FU and nitrogenous bases of the nucleic acid. The binding constant was found to be 9.7×10(4); which is indicative of moderate type of interaction between 5FU and DNA duplex. It was also observed that 5FU intercalates slightly more between AT base pairs compared to GC pairs. FTIR and circular dichroism spectroscopic results revealed that 5FU disturbs native B-conformation of DNA though, DNA remains in its B conformation even at higher concentrations of 5FU. 相似文献
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Seema Kothari Vinita Sharma Pradeep K. Sharma Kalyan K. Banerji 《Journal of Chemical Sciences》1992,104(5):583-589
Kinetics of oxidation of aliphatic aldehydes, to the corresponding carboxylic acids, by bis(2,2′-bipyridyl)copper(II) permanganate (BBCP) has been studied. The reaction is first order with respect toBBCP. Michaelis-Menten type kinetics were observed with respect to the aldehyde. The formation constants for the aldehyde-BBCP
complexes and the rates of their decomposition, at different temperatures, have been evaluated. Thermodynamic parameters for
the complex formation and the activation parameters for their decomposition have also been determined. The reaction is catalysed
by hydrogen ions; the acid-dependence being of the form:k
obs = a +b [H+]. The oxidation of MeCDO exhibited a substantial kinetic isotope effect (k
H/k
D = 4.33 at 303 K). The role of aldehyde hydrate in the oxidation process has been discussed. A mechanism involving formation
of permanganate ester and its slow decomposition has been proposed. 相似文献
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Static dielectric constant values of the binary mixtures of N-methylformamide with formamide, N,N-dimethylformamide and N,N-dimethylacetamide
have been measured in the whole composition range at 303 K. The Kirkwood correlation factor values of the amide–amide mixtures
were determined from the measured values of the static dielectric constant and high-frequency limit dielectric constant. The
evaluated values of the excess dielectric constant and deviation in the Kirkwood correlation factor infer that deviations
of their mixture values occur from the mole-fraction mixture law. Results confirm that there are strong hydrogen-bond interactions
between unlike molecules of amide–amide mixtures and that 1:1 complexes are formed. 相似文献
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A series of substituted dienophiles 1—10 and three 1,2-diazadienes namely D-1, D-2, D-3 were chosen to understand the reactivity and selectivity of Diels-Alder cycloaddition. The global and local electrophilicity patterns have been evaluated on a series of cycloaddition reactions to assess the reaction pathways (NDAC/IEDDAC) using the absolute scale of electrophilicity proposed by Parr et al. Regional electrophilicity at the active sites of the reagents involved in Diels-Alder processes has been described on a quantitative basis using local or regional electrophilicity index i.e. Fukui function. Good qualitative/quantitative comparison was found between molecular energy gaps and global electronic parameters, which has been employed to assess the cycloaddition pathways successfully. 相似文献
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Three‐dimensional (3D) scaffolds formed from natural biopolymers gelatin and chitosan that are chemically modified by galactose have shown improved hepatocyte adhesion, spheroid geometry and functions of the hepatocytes. Galactose specifically binds to the hepatocytes via the asialoglycoprotein receptor (ASGPR) and an increase in galactose density further improves the hepatocyte proliferation and functions. In this work, we aimed to increase the galactose density within the biopolymeric scaffold by physically blending the biopolymers chitosan and gelatin with an amphiphlic β‐galactose polypeptide (PPO‐GP). PPO‐GP, is a di‐block copolymer with PPO and β‐galactose polypeptide, exhibits lower critical solution temperature and is entrapped within the scaffold through hydrophobic interactions. The uniform distribution of PPO‐GP within the scaffold was confirmed by fluorescence microscopy. SEM and mechanical testing of the hybrid scaffolds indicated pore size, inter connectivity and compression modulus similar to the scaffolds made from 100 % biopolymer. The presence of the PPO‐GP on the surface of the scaffold was tested monitoring the interaction of an analogous mannose containing PPO‐GP scaffold and the mannose binding lectin Con‐A. In vitro cell culture experiments with HepG2 cells were performed on GLN‐GP and CTS‐GP and their cellular response was compared with GLN and CTS scaffolds for a period of seven days. Within three days of culture the Hep G2 cells formed multicellular spheroids on GLN‐GP and CTS‐GP more efficiently than on the GLN and CTS scaffolds. The multicellular spheroids were also found to infiltrate more in GLN‐GP and CTS‐GP scaffolds and able to maintain their round morphology as observed by live/dead and SEM imaging. 相似文献
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The oxidation of primary alcohols by sodium N-chloroethylcarbamate in acid solution, results in the formation of corresponding aldehydes. The reaction is first order with respect to the oxidant and alcohol. The rate increases with an increase in acidity. The oxidation of α,α-dideuterioethanol exhibited a primary kinetic isotope, kH/kD = 2.11 at 298 K. The value of solvent isotope effect k(H2O)/k(D2O) = 2.23 at 298 K. Addition of ethyl carbamate does not affect the rate. (EtOC(OH)NHCl)+ has been postulated as the reactive species. Plots of (log k2 + Ho) against (Ho + log[H+]) are linear with the slope, ?, having values from 1.78–1.87. This suggested a proton abstraction by water in the rate-determining step. The rates of oxidation of alcohols bearing both electron-withdrawing and electron-donating groups are more than that of methanol. A concerted mechanism involving transfer of a hydride ion from the C? H bond of the alcohol tothe oxidant and removal of a proton from the O? H group by a water molecule has been proposed. 相似文献
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