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Search Results: 1 - 10 of 2885 matches for " degradation "
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Degradation of nucleic acids and nucleotides in several conditions with perspectives of retrieval: A review  [PDF]
José Martínez Reyes, Lenin Ejecatl Medina Orozco, Melitón Estrada Jaramillo, Iván Vera Romero, Agustina Ortiz Soriano
Advances in Bioscience and Biotechnology (ABB) , 2014, DOI: 10.4236/abb.2014.51006

Deoxyribonucleic acid (DNA) or oligonucleotides, can be modified in several ways as chemical degradation by electrophilic reaction, attack of radicals, hydrolytic deamination or oxidative damage caused by ionizing radiation. This work discussed these degradation mechanisms, determining the effects on these biomolecules. The actual knowledge about DNA damages only permits partial enzymatic repair treatments.

Thermal Stability and Degradation of Chitosan Modified by Cinnamic Acid  [PDF]
Mostafa Amin Diab, Adel Zak El-Sonbati, Mohamed Mohamed Al-Halawany, Dina Mohamed Diaa Bader
Open Journal of Polymer Chemistry (OJPChem) , 2012, DOI: 10.4236/ojpchem.2012.21003
Abstract: The reaction of chitosan with cinnamic acid gave the corresponding N-cinnamoyl chitosan (NCC) polymer. The chem-ical structure of the modified polymer was characterized by IR, 1H-NMR and elemental analysis. Thermogravim- etric analysis reveals that the thermal stability of chitosan polymer is greater than NCC polymer. The activation energies of thermal degradation of chitosan and NCC polymers were determined using Arrhenius relationship. Thermal degradation of NCC polymer was studied and the products of degradation were identified by GC-MS technique. It seems that the mechanism of degradation of NCC polymer is characterized by elimination of low-molecular weight radicals. Combination of these radicals and random scission mechanism along the backbone chain are the main source of the degradation products.
Isolation and Identification of Ammonia Nitrogen Degradation Strains from Industrial Wastewater  [PDF]
Cai-Hong Yu, Ya Wang, Tao Guo, Wan-Xin Shen, Ming-Xin Gu
Engineering (ENG) , 2012, DOI: 10.4236/eng.2012.411101
Abstract: Nine strains of ammonia nitrogen degradation strains from C1 to C9 were isolated from industrial wastewater to study their degradation and conversion of ammonia nitrogen. The results showed that C2 strain with a high degradation activiity of ammonia nitrogen, and the ammonia nitrogen degradation rate of the activated C2 strain was 93% within 24 h when the initial concentration of ammonia nitrogen was 200 mg/L under the conditions of inoculation 10%, temperature 35?C, pH 7.0, rotation 200 r/min. And C2 was identified as Bacillus amyloliquefaciens.
Identification of water-borne bacterial isolates for potential remediation of organophosphate contamination  [PDF]
Rupa Iyer, Brian Iken
Advances in Biological Chemistry (ABC) , 2013, DOI: 10.4236/abc.2013.31018

Three water-borne bacterial isolates were collected from the Houston metropolitan area. Each isolate was capable of growing upon carbon limited media inoculated with the organophosphorus (OP) compound paraoxon. All isolates were able to efficiently metabolize paraoxon and, to a lesser degree, methyl parathion to p-nitrophenol. 16S rDNA genome sequencing with universal bacterial primers identified the isolates as species belonging to the genera Aeromonas, Steno- trophomonas, or Exiguobacterium. All screened isolates harbor organophosphorus degradation (opd) genes that are approximately 99% similar over approximately 660 base pairs sequenced to one first isolated from Sphingobium fuliginis ATCC 27551 (formerly Flavobacterium sp. ATCC 27551). Additionally, two isolates KKWT11, identified as a putative Senotro- phomonas maltophilia, and KKBO11, identified as a putative Exiguobacterium indicum, were found to possess genomic DNA that closely matched a metallo- beta-lactamase that has been reported to function as a methyl parathion degradation (mpd) gene suggesting that both of these strains are prime candidates for wastewater remediation of a broad range of OP compounds.

Degradation of Chitin and Chitosan by a Recombinant Chitinase Derived from a Virulent Aeromonas hydrophila Isolated from Diseased Channel Catfish  [PDF]
Dunhua Zhang, John M. Bland, Dehai Xu, Siyin Chung
Advances in Microbiology (AiM) , 2015, DOI: 10.4236/aim.2015.59064
Abstract: A chitinase was identified in extracellular products of a virulentAeromonas hydrophilaisolated from diseased channel catfish (Ictalurus punctatus). Recombinant chitinase (rChi-Ah) was produced inEscherichia coli. Purified rChi-Ah had optimal activity at temperature of 42and pH 6.5. The affinity (Km) for chitosan was 4.18 mg·ml-1withVmaxof 202.5 mg·min-1·mg-1. With colloidal chitin as substrate, rChi-Ah generated N,N’-diacetyl-glucosamine predominantly. Conversion of chitosan (≥75% deacetylated) by rChi-Ah revealed five major products: 2 to 4 units of
Comparison of Threshold Power between Methylene Blue Degradation and KI Oxidation Reaction Using Ultrasound  [PDF]
Daisuke Kobayashi, Chiemi Honma, Hideyuki Matsumoto, Katsuto Otake, Atsushi Shono
Open Journal of Acoustics (OJA) , 2018, DOI: 10.4236/oja.2018.84006
Abstract: Ultrasound is used in various chemical reaction processes, and these reactions are influenced by ultrasonic frequency. A threshold power is required for the ultrasonic degradation reaction and oxidation reaction caused by hydroxyl radicals, and the cavitation threshold power is also influenced by frequency generally. In this study, the effects of frequency on the threshold power of methylene blue degradation and KI oxidation were investigated in the range between 22.8 kHz and 1640 kHz. The threshold power of KI oxidation reaction increased with increasing frequency. This phenomenon well agrees with previous study, and it is revealed that the generation of I-3ion is caused by oxidation reaction of Iˉ ions with hydroxyl radicals. On the other hand, the threshold power of methylene blue degradation reaction was not affected by frequency. The ultrasonic degradation of methylene blue is considered to be caused by hydroxyl radicals, and there is a linear relationship between degradation rate constant and sonochemical efficiency value. However, it is guessed that the degradation of methylene blue is occurred inside cavitation bubble by pyrolysis at high frequency regions.
Modelling Livestock Activities and Environmental Sustainability: The African Case  [PDF]
Eisa Abdalla Abdelgalil, Suleiman Ibrahim Cohen
Journal of Environmental Protection (JEP) , 2010, DOI: 10.4236/jep.2010.11001
Abstract: This paper develops a dynamic model of grazing land degradation. The model illustrates the relationship between live-stock levels and grazing land degradation over time. It identifies the mechanisms by which the factors internal to the livestock local production system and those drawn from the larger economic context of livestock marketing influence livestock-grazing land relationship. The paper shows that overstocking leads to degradation which leads to declining relative prices of livestock as quality declines and mortality increases. As relative price of livestock falls, consumption increases. The increased consumption and mortality ultimately leads to lower livestock population, which leads to de-creased degradation. The model results show that medium term dynamics of grazing land degradation are quite differ-ent from long term dynamics. It is shown that although grazing land sustainability situation is adverse in the medium term, yet it is favourable in the long term. The livestock system is dynamic and can adjust when longer term system dy-namics are allowed to play out. Part of the adjustment mechanism is built in the livestock system and the other part comes from the economic system. The built-in adjustment mechanism works through the two-way relationship between the stock and degradation. The external adjustment mechanism, originating from the economic system, works through economic growth, relative prices and foreign trade. In the medium term, opportunistic management strategy and poli-cies that facilitate access to grazing land and water are crucial for mitigating degradation. The results suggest that the views of the mainstream range management paradigm and the new thinking of range ecology can be reconciled.
Degradation of Lindane (γ-HCH) in a Mollisol as Effected by Different Soil Amendments  [PDF]
Gunjan Bhatia, Anjana Srivastava, Prakash Chandra Srivastava
Journal of Environmental Protection (JEP) , 2011, DOI: 10.4236/jep.2011.29138
Abstract: Soil amendments play an important role in management of pesticide residues. In this study, incubation experiment was conducted using the surface (0 - 15 cm) sample of a mollisol supplied with different soil amendments (farmyard manure, cow-dung slurry, pyrite and gypsum) to investigate the effect of amendments on the dissipation of lindane in mollisols. Dissipation of lindane in soil was studied at eight consecutive samplings (0, 1, 3, 5, 7, 10, 15 and 30 d). The results indicated that soil amendments could promote the degradation of lindane in soil. After 30 d of incubation 79% degradation was observed in the untreated soil (without any amendment) whereas, in the case of farmyard manure and cow-dung slurry amended soils, 83% and 91% degradation was observed, respectively. The pyrite and gypsum amendments also enhanced the degradation of lindane in soils, but the effect was less pronounced as compared to the organic amendments. Enhanced degradation in soil treated with organic amendments could be attributed to stimulated microbial activity after the addition of organic amendments. These addition, under different soil management conditions, minimize the persistence of lindane and consequently the risk of leaching and seepage into aquifers.
A Validated Rapid Stability-Indicating Method for the Determination of Related Substances in Vardenafil Hydrochloride by Ultra-Performance Liquid Chromatography  [PDF]
Kishore Kumar Kakumani, Kameswara Rao Chimalakonda, Rama Koti Reddy Yarram, Mukkanti Khagga
American Journal of Analytical Chemistry (AJAC) , 2012, DOI: 10.4236/ajac.2012.31009
Abstract: A novel, sensitive, stability indicating RP-LC method has been developed for the quantitative determination of Varde- nafil and its related impurities in both bulk drugs and Pharmaceutical dosage forms. Effective chromatographic separation was achieved on a C18 stationary phase with simple mobile phase combination delivered in a simple gradient pro- gramme and quantitation was by ultraviolet detection at 210 nm. The mobile phase consisted of a buffer and acetonitrile delivered at a flow rate 0.25 ml?min–1. Buffer consisted of 20 mM Ammonium bi carbonate, pH adjusted to 5.0 by using ortho Phosphoric acid. In the developed UPLC method the resolution (Rs) between vardenafil and its four potential impurities was found to be grater than 2.0.Regrreation analysis showed an r value (correlation coefficient) grater than 0.999 for vardenafil and its four impurities. This method was capable to detect all four impurities of vardenafil at a level of 0.25 μg.mL–1 with respect to test concentration of 500 μg?ml–1 for a 2 μl injection volume. The inter and intra day precision values for all four impurities and for vardenafil was found to be with in 2.0% RSD. The method showed good and consistent recoveries for vardenafil in bulk drugs (98.8% - 100.9%), pharmaceutical dosage forms (100.5% - 101.5%) and its all four impurities (99.8% - 102.5%).The test solutions was found to stable in acetonitrile for 48 h. The drug was subjected to stress conditions of hydrolysis, oxidation, photolysis, and thermal degradation. Considerable degradation was found to occur in peroxide hydrolysis. The stress samples were assayed against a qualified reference standard and the mass balance was found close to 99.9%. The developed RP-LC method was validated with respect to linearity, accuracy, precision and robustness.
Degradation Behaviors of Thai Bombyx mori Silk Fibroins Exposure to Protease Enzymes  [PDF]
Chuleerat Wongnarat, Prasong Srihanam
Engineering (ENG) , 2013, DOI: 10.4236/eng.2013.51010

The degradation behaviors of Thai Bombyx mori called Samrong and Nanglai silk fibroins exposure to protease enzymes; protease XIV, protease XXIII and α-chymotrypsin type II were studied in this work. The degradation behaviors were expressed by their weight loss, morphological and secondary structure changes as well as thermal properties. Samrong showed higher percentage of weight loss than Nanglai. SEM micrographs indicated that silk fibroin were de- stroyed and showed many holes on their fiber surfaces. All of silk samples were increasable destroyed when exposure to the protease enzyme for long incubation period. With thermal analysis, both silk fibroin presented the thermal stability in the same profile. The result suggested that the selected silk fibroin should be composed of similar pattern of amino acids and their ratios. However, the protease susceptibility of each silk fibroin slightly varied in case of morphology observation. This might be affected by their genetic variety.

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