29 research outputs found
Gas phase studies of N-heterocyclic organic species using mass spectrometry
No full textThis dissertation focuses on the examination of thermochemical properties, including gas phase acidities, proton affinities and tautomerism of two types of N-heterocyclic organic species: damaged nucleobases and 1,2,3-triazoles via mass spectrometry methods (bracketing method on FTMS and Cooks kinetics method on LCQ) and theoretical studies (quantum mechanical calculations). Reactivities of N-heterocyclic carbenes as organocatalysts were also studied in the gas phase. 3-Methyladenine DNA glycosylase II (AlkA), which is found in Escherichia coli, is an enzyme that cleaves a wide range of damaged nucleobases from DNA. Herein we study the 3-methylated AlkA purine substrates, 3-methyladenine, non-substituted purine and and a potential AlkA substrate, 6-chloropurine. We found that the damaged nucleobases are more acidic than normal nucleobases. Resulting from this increasing of acidity, it is expected that damaged nucleobases are easier to be cleaved from the DNA chain since their conjugate bases should be better leaving groups. We also find that the gas phase acidities correlate with AlkA excision rate. Thus, the results lend support to the theory that AlkA differentiates among substrates by cleaving those nucleobases which are the most facile to remove. We also focus on studying the gas phase properties of 1,2,3-triazoles, which, compared with their applications, are largely unknown. The gas phase acidities and proton affinities of benzotriazole, 4-phenyl-1,2,3-triazole, substituted 4-phenyl-1,2,3-triazoles are discussed herein. Moreover, the tautomerism prevalence of 4-phenyl-1,2,3-triazole is acertained by ion-molecule reaction coordinate analysis and H/D exchange studies. In order to study the reaction mechanism of N-heterocyclic carbenes catalyzed reactions such as benzoin condensation, we synthesized a thiazolium catalyst with ethyl sulfonyl group on C4 position of five-membered thiazolium ring. Upon deprotonation, the thiazolium-based carbene is given a negative charge, which renders the visibility for both the carbene and reaction intermediates via mass spectrometry. We herein isolate and study the fragmentation pattern of both free carbene and reaction intermediates using ESI-MS/MS technique. As comparison, we also employ an imidazolium-based NHC to study the benzoin condensation via mass spectrometry and characterize the catalyst as well as the intermediates.Ph. D.Includes bibliographical referencesby Kai Wan
Mechanics of inhomogeneous turbulence and interfacial layers
No full textThe mechanics of inhomogeneous turbulence in and adjacent to interfacial layers bounding turbulent and non-turbulent regions are analysed. Different mechanisms are identified according to the straining by the turbulent eddies in relation to the strength of the mean shear adjacent to, or across, the interfacial layer. How the turbulence is initiated and the topology of the region of turbulence are also significant factors. Specifically the cases of a layer of turbulence bounded on one, or two, sides by a uniform and/or shearing flow, and a circular region of a rotating turbulent vortex are considered and discussed.
The entrainment processes at fluctuating interfaces occur both at the outer edges of turbulent shear layers, with and without free-stream turbulence (e.g. jets, wakes and boundary layers), at internal boundaries such as those at the outside of the non-turbulent core of swirling flows (e.g. the ‘eye-wall’ of a hurricane) or at the top of the viscous sublayer and roughness elements in turbulent boundary layers. Conditionally sampled data enables these concepts to be tested. These concepts lead to physically based estimates for critical modelling parameters such as eddy viscosity near interfaces, entrainment rates, maximum velocity and displacement heights
Hepatoprotective potential of isolated flavonoids from Trapa natans L. against the paracetamol induced oxidative stress in rats
Get PDF910-917Overdose of paracetamol causes liver toxicity, due to oxidative stress by the reactive oxygen species (ROS) that increases
the levels of ALT and AST, and reduces the level of the antioxidant enzymes. Flavonoids are a source of natural antioxidants
that assist in neutralization of ROS. Several studies have suggested that flavonoids can help protect the liver. The Water
Chestnut, Trapa natans L. plants have long been used in the traditional system of medicine and possess considerable
antioxidant potential. In this study, we tried to isolate flavonoids from T. natans L. and evaluate the hepatoprotective potential
of the isolated compound. We isolated flavonoids from the extract of the aerial part of plant and characterized by UV, IR, NMR
and Mass spectroscopy. The isolated flavonoid was induced orally once a day (30 mg/kg). The test drug (isolated compound)
could lower the elevated levels of serum enzymes such as glutamate oxaloacetate transaminase (AST), serum glutamate
pyruvate transaminase (ALT), alkaline phosphatase (ALP) and total bilirubin. Silymarin (30 mg/kg) was taken as a standard
drug that exhibits significant hepatoprotective activity against the paracetamol induced hepatotoxicity model in Wistar albino
rats. The histopathological study of rat liver also strengthens biochemical evaluation analysis. Based on the experimental
results, it can be concluded that the isolated flavonoids act as hepatoprotective agents in rats
Treatment with Green Tea Prevents Intracerebroventricular Streptozotocin Induced Cognitive Impairment and Oxidative Stress in Mice.
No full textAssessment of in vivo wound healing potentiality of Trapa natans L. leaves on different wound models in rat
No full text739-745The primary goal of this study was to assess the wound healing potentiality of Trapa natans L. Excision and incision models were used to evaluate wound healing activity. For the excision model experiment was conducted for 21 days and for the incision model experiment continued for 10 days. Experimental animals were divided into four groups, the control group received simple ointment, the animal of the standard group treated with 0.2% w/w soframycin ointment, and the test groups received T. natans extract ointment (2.5% w/w & 5% w/w). Wound healing was determined by the rate of contraction, the time required for epithelization, collagen cell formation, the amount of hydroxyproline present in the wound site, and wound-breaking strength. Experimental results of the test showed a comparatively higher rate of contraction, lesser epithelization period, and higher hydroxyproline amount present in the wound area. These results were strengthened by the histopathological studies of the healing area tissues. When the standard and test groups were compared to the control group, statistically significant data were found (p<0.001). The test group had better wound-healing properties as compared to the control group. From the result of this study, it was revealed that T. natans L. is an excellent herbal alternative for treating wounds
Treatment with Green Tea Prevents Intracerebroventricular Streptozotocin Induced Cognitive Impairment and Oxidative Stress in Mice
Get PDFGreen tea polyphenols have demonstrated significant antioxidant, anticarcinogenic, anti-mutagenic and antidiabetic in numerous human, animal and in vitro studies. Hence present study was design to evaluate the influence of green tea in streptozotocin induced oxidative stress in mice. Morris water maze, Elevated plus maze and passive avoidance apparatus was used for the evaluation of learning and memory. Brain thiobarbituric acid reactive substance was also estimated. Intracerebroventricular administration of streptozotocin reduces the learning and memory and increase the concentration of thiobarbituric acid reactive substance in mice. Green tea significantly improves the learning and memory and reverses the increase thiobarbituric acid reactive substance concentration in mice. The result of present study indicates that green tea improve the learning and memory. It also reduces the streptozotocin induced oxidative stress
Theoretical and mass spectrometric studies of damaged nucleobases and analogs toward understanding glycosylase mechanisms
No full textThe focus of this thesis is the examination of the thermochemical properties, primarily the gas phase acidity, proton affinity, and leaving group (LG) ability of damaged nucleobases and related species via mass spectrometry (FT-ICR, ion trap) and theoretical studies (quantum mechanical calculations). Our main hypothesis is that the study of intrinsic, gas-phase properties of the damaged nucleobases will lend insight into the mechanism of their excision from DNA. We study damaged nucleobases and analogs that are cleaved from DNA by various glycosylases: uracil-DNA glycosylase (UDG), 3-methyladenine glycosylase II (AlkA), and MutY glycosylase. The LG ability of the N1-deprotonated 3-methyluracil anion relative to the N1-deprotonated 3-methylthymine anion is examined in the context of the UDG enzymatic reaction that excises uracil but not thymine from DNA. We confirmed that despite the close acidities uracil is a much better LG in the gas phase. Another interesting disparity between the LG ability and acidity is discovered for uracil substrates: when we examined hydrochloric acid and 3-methyluracil in the gas phase we found that despite similar acidities, chloride is a better LG than N1-deprotonated 3-methyluracil. We propose that the difference in LG ability is due to the different natures of the LGs (resonance vs. inductive stabilization). To test the hypothesis, a series of pyridone substrates were designed and examined. AlkA is an enzyme that cleaves a wide range of damaged bases from DNA. Herein we examine 3- and 7-methylated AlkA purine substrates. The damaged nucleobases are found to be more acidic than the normal nucleobases. Because of this increased acidity, the damaged bases would be expected to be more easily cleaved from DNA by AlkA (their conjugate bases should be better LGs). We find that the acidity correlates to the AlkA excision rates, which lends support to an AlkA mechanism wherein the enzyme provides a nonspecific active site, and nucleobase cleavage is dependent on the intrinsic N-glycosidic bond stability. The acidities and proton affinities of adenine and six adenine analogs that were designed to test various features of the enzyme MutY are also studied to allow better understanding of the mechanism of adenine removal by MutY.Ph. D.Includes bibliographical referencesIncludes vitaby Anna Michelso
Transition metal complexes with N, S donor ligands as synthetic antioxidants: Synthesis, characterization and antioxidant activity
No full textIrrigation with domestic wastewater: Responses on growth and yield of ladyfinger Abelmoschus esculentus and on soil nutrients Author Details Publication Data
No full textAbstract Domestic wastewater is generated continuously and in large quantities. It can serve as an alternative water nutrient source for irrigation. In the present study Abelmoschus esculentus L. (Ladyfinger) was irrigated using untreated wastewater (T1), treated wastewater (T2) and rainwater (T3) in pot experiments. The effect was seen on nutrient fortication, growth and yield of the plant and the nutrient status of the soil. Additionally the build up of Cr, Cu and Zn from the irrigation water were anlayzed in different parts of the plant biomass and in the soil. The sapling survival rate was found to be 87% in T1 followed by T2 and T3. Root shoot ratio under different treatments was found in the order T3 (0.46) >T2 (0.35) >T1 (0.31). The chlorophyll a, b and carotene content in the leaves (mg g -1 ) was found to be 6.3, 0.5, 0.9 under T1, 4.8, 0.4, 0.8 under T2 and 3.2, 0.3, 0.5 under T3 respectively and all the three varied in the order T1>T2>T3. The same trend was found in case of total dry matter (g) T1 (6.3) >T2 (3.7) >T3 (2.3) at p<0.05. There was a considerable increase in nutrients in the soil under T1 and T2 as compared to T3 after final harvest. The organic matter (% ), NO 3 -N and PO 4 3-(mg kg -1 ) content post harvest soil was found to be 3.4, 71, 90 under T1 and 2.9, 52, 63 under T2 respectively. Also, there was an increase in cations Na, K, Ca and Mg in the soil irrigated with T1 and T2 after the final harvest. Thus irrigation with wastewater generally increased soil fertility. Only a small percentage of the heavy metal was bioaccumulated by the plant parts from the irrigation water. There was hardly any metal accumulation in fruits. Bulk of the metal ions remained in the soil
Ultrasound processing of coffee silver skin, brewer’s spent grain and potato peel wastes for phenolic compounds and amino acids:a comparative study
No full textAwareness towards utilizing food-processing by-products are increasing in health as well as environmental purview. Coffee silver skin (CSS), potato peel (PP) and brewer’s spent grain (BSG) are voluminous by-products in their respective processing industries. The present study compared these three by-products for their prospective utilization in producing polyphenols-rich aqueous extracts by using ultrasound-assisted extractions (UAE). A probe-type sonicator was used for ultrasound treatments. The total phenolic contents in the extracts were assessed by Folin-Ciocalteu assay, while the phenolic profiles of the extract was characterized by LC-Q-TOF mass spectrometry. The microstructure of the samples after UAE was evaluated by scanning electron microscopy (SEM). Ultrasound treatment enhanced the rate of extraction and recovered 2.79, 2.12 and 0.66 mg gallic acid equivalents/g of TPC from CSS, PP and BSG, respectively in 30 min, which correspond to recoveries of 97.6%, 84.5% and 84.6%, respectively, compared to conventional solid–liquid extractions carried out for 24 h. The extraction yield was dependent on the particle size of the raw materials and the highest yield was obtained from the materials with 100–250 µm particle size. The SEM imaging revealed that ultrasound treatment caused prominent tissue damage. Extracts contained mainly hydroxycinnamic acid derivatives of phenolic acids. PP and CSS had the highest amounts of umami free amino acids (0.13 mg/g in each), while BSG contained the highest amount of essential amino acids (92 mg/g). The present work shows that CSS, PP and BSG are good sources of polyphenols and UAE can be employed to enhance the extraction efficiency as means of a green approach.</p
