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A nuclease activity has been purified from the nuclei-kinetoplast fraction of Leishmania. This enzyme, termed endonuclease M (Endo M), is shown by electrophoresis in a denaturing polyacrylamide gel to be associated with a single polypeptide of molecular mass 52 kDa. Physical analysis of the enzyme indicates that it has a sedimentation coefficient S20,w of 4.5S, a Stoke's radius of 32.5 A, and a native molecular mass of 53 kDa. The final Mono Q purified Endo M possesses both DNase and RNase activities. It acts as an endonuclease by introducing random single-stranded nicks into the supercoiled DNA molecules, that often leads to its linearization due to nicking at the opposite strands, and subsequent degradation of the DNA with further incubation. Single-stranded DNA is twice preferred to double-stranded DNA as substrate. Single-stranded RNA is also degraded rapidly and is competitive as a substrate with single-stranded DNA. RNA:DNA hybrids, however, are largely resistant to the Endo M digestion. 相似文献
3.
Poly(ethylene oxide)‐g‐gellan polysaccharide nanocarriers for controlled gastrointestinal delivery of simvastatin
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Herein, a novel gellan polysaccharide‐based amphiphilic copolymer was synthesized for the development of simvastatin‐loaded micellar nanoparticles. The nanoparticles were explored for their controlled drug release and improved pharmacodynamic potentials. The copolymer was characterized by Fourier transform infrared spectroscopy (FTIR) and elemental analysis. The onset of copolymer micellization was detected by fluorescence spectroscopy. Simvastatin was loaded into micellar particles by solvent evaporation method and the particles were then characterized by microscopic and light scattering techniques. The physical state of drug was studied by X‐ray diffraction analysis. Pharmacodynamic assessment of the micellar preparations was done on rabbit models. The copolymer formed micellar nanoparticles in water. Critical micellar concentration was 9.12mg/l. The micellar particles (426.8–912.6nm) entrapped a maximum of 18.86% drug. Higher negative zeta potential indicated physical stability of micellar systems. A simple diffusion mechanism was operative in the event of comparatively faster drug release in pH6.8 phosphate buffer solution. No significant drug‐copolymer interaction was traced by FTIR spectroscopy. The amorphization of drug into micellar particles reduced LDL‐cholesterol level by ~45% in hyperlipidemic rabbits and this was about 2.5 times higher than pure drug dispersion. Copolymer micellar nanoparticles of simvastatin could control cholesterol level in hyperlipidemic rabbits and thus had potential in drug delivery applications. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42399. 相似文献
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Hedgehog Antagonist Pyrimidine–Indole Hybrid Molecule Inhibits Ciliogenesis through Microtubule Destabilisation
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Harleen Khatra Pragya Paramita Khan Sankha Pattanayak Jhuma Bhadra Bilal Rather Saikat Chakrabarti Taniya Saha Prof. Surajit Sinha 《Chembiochem : a European journal of chemical biology》2018,19(7):723-735
One of the crucial regulators of embryonic patterning and tissue development is the Hedgehog‐glioma (Hh‐Gli) signalling pathway; its uncontrolled activation has been implicated in different types of cancer in adult tissues. Primary cilium is one of the important factors required for the activation of Hh signalling, as it brings the critical components together for key protein–protein interactions required for Hh pathway regulation. Most of the synthetic and natural small molecule modulators of the pathway primarily antagonise Smoothened (Smo) or other effectors like Hh ligand or Gli. Here, we report a previously described Hh antagonist, with a pyrimidine–indole hybrid (PIH) core structure, as an inhibitor of ciliogenesis. The compound is unique in its mode of action, as it shows perturbation of microtubule dynamics in both cell‐based assays and in vivo systems (zebrafish embryos). Further studies revealed that the probable targets are α‐tubulin and its acetylated form, found in the cytoplasm and primary cilia. PIH also showed axonal defasiculation in developing zebrafish embryos. We thus propose that PIH antagonises Hh signalling by repressing cilia biogenesis and disassembling α‐tubulin from its stabilised form. 相似文献
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Bikash Sadhukhan Naba Kumar Mondal Soumya Chattoraj 《Clean Technologies and Environmental Policy》2014,16(6):1015-1025
In this study, response surface methodology (RSM) was employed for the removal of methylene blue (MB) from aqueous solution using neem (Azadirachta indica) bark dust (NBD) as a bioadsorbent. The influence of various process parameters namely initial concentration (500–1,000 mg L?1), bioadsorbent dose [0.20–1.50 g (100 mL)?1], pH (5–12), and stirring rate (250–650 rpm) was taken as an input parameter. A total of 29 biosorption experimental runs were carried out employing the detailed conditions designed by RSM based on the Box–Behnken design (BBD). Response surface plots were studied to determine the interaction effects of main factors and optimum conditions of process. Regression analysis showed good fit of the experimental data to the second-order polynomial model with coefficient of determination (R 2) value of 0.9760 and model F value of 40.68. The predicted R 2 value is 0.8979. In addition, results reported in this research demonstrated the feasibility of employing NBD as bioadsorbent for MB removal. 相似文献
7.
S. Sarkar A. Chourasia S. Maji S. Sadhukhan S. Kumar B. Adhikari 《Bulletin of Materials Science》2006,29(5):475-484
For tissue engineering purpose two gelatin based polyester urethane scaffolds of different compositions were prepared from
lactic acid, polyethylene glycol 400 (PEG 400) and characterized by FTIR, XRD for their mechanical and morphological properties
using SEM and optical microscopic analyses. Degradation and swelling studies of gelatin based polyester urethane scaffolds
in phosphate buffer saline (PBS) were performed. Human keratinocyte cells were cultured within these scaffolds, which showed
good cell adherence and proliferation. 相似文献
8.
Jhuma Debbarma M. Jaya Prakash Naik 《Fullerenes, Nanotubes and Carbon Nanostructures》2019,27(6):482-485
In recent years, graphene oxide (GO) and reduced graphene oxide (r-GO) are being produced using graphite powder as precursor material but the preparation of graphene derivatives from a non-graphitic material without an additional oxidizing agent has not been reported so far. In this work, an agrowaste namely sugarcane bagasse was subjected to pyrolysis at three different temperatures, bypassing the use of toxic chemicals and graphite as a precursor. The chemistry of the effect of temperature and time on the development of graphitic planes in a non-graphitic material was studied. The formation of nanosheets of GO suggested that aromatization and condensation of the glucose monomers might have taken place which led to the glycosidic bond formation, further converging into polyaromatic rings on pyrolysis. The GO was further reduced at 95?°C using thiourea which resulted in the formation of r-GO after 8?hrs. 相似文献
9.
There has been considerable interest, both academic and industrial, in developing synthesis processes for making polymeric nanoparticles. Our effort relied on the nanoassembly concepts of block macromolecules in solutions to prepare particles with a hard core made of crosslinked plastics and a soft shell made of low T(g) elastomer. By a suitable variation of the composition, polymer molecular weight and solute concentration, we were able to produce spherical, ellipsoidal, cylindrical, and chain-like nanoparticles. Under microscopes, the chain-like nanoparticles displayed very rich conformational features in diluted and dense states. Our observation on the conformation characters of the nanochains in 3D diluted state agreed well with the proposition of the self-avoid coil model. However, in 2D dense state, our observation on the nanochains appeared to be in contradiction with the segregated globule model proposed by de Gennes. 相似文献
10.
Mriganka Sadhukhan Manas Kumar Kundu Tanmay Bhowmik Sudip Barman 《International Journal of Hydrogen Energy》2017,42(15):9371-9383
Finding efficient electrocatalyst for oxidation of small organic molecules such as methanol (CH3OH), formic acid (HCOOH), formaldehyde (HCHO) etc. is essential for the development of their respective direct fuel cells. We report here highly dispersed platinum nanoparticles (PtNPs) on carbon nitride (CNx) were successfully synthesized by the ultrasound mediated sodium borohydride reduction of H2PtCl6 in presence of CNx nanosheets. This platinum–carbon nitride (Pt/CNx) composite exhibited superior electrocatalytic activity towards oxidation of CH3OH, HCOOH and HCHO in acid media. The mass activity, onset potential, tolerance to carbon monoxide (CO) poisoning and long term durability for the catalytic oxidation of CH3OH, HCOOH, HCHO on Pt/CNx catalyst in acid media is much higher than that of commercial Pt/C catalyst. The mass activity of Pt/CNx catalyst at ~0.64 V (forward scan) is 310 mA/mgPt which is 2.7 time higher than that of commercial Pt/C for methanol oxidation. The electrooxidation of HCOOH on Pt/CNx occurs via dual mechanism with greatly enhanced oxidation through dehydrogenation pathway in comparison with commercial Pt/C. The mass activity on Pt/CNx at 0.3 V (vs. NHE) is 25 times higher than that of Pt/C for oxidation of HCOOH. The superior catalytic activity and durability of this Pt/CNx catalyst can be attributed to high dispersion of PtNPs and strong catalyst support interaction. 相似文献