Nitrogen modified bases

By chemically reacting with nitrogen and oxygen atoms in DNA, these compounds can modify bases in DNA so as to distort the normal pattern of base pairing. If these modified nucleotides are not repaired, they allow an Incorrect nucleotide to be incorporated during replication. This type of carcinogen includes ethylmethane sulfonate (EMS), dimethyl sulfate (DMS), and nitrogen mustards. 

The bases found in DNA are either purines (adenine or guanine) or pyrimidines (cytosine or thymine), although some modified bases are found, such as 5 methyl cytosine. Ribonucleic acid contains adenine, cytosine, and guanine as in DNA, but thymine is usually replaced by uracil, which lacks the 5-methyl group present in thymine (Fig. 2.2). In some types of RNA, unlike DNA, modified bases are common. In both DNA and RNA the base is attached through a nitrogen to the... 

Subramanian NP, Li XG, Nallathambi V, Kumaragum SP, Colon-Mercado H, Wu G, Lee JW, Popov BN (2009) Nitrogen-modified carbon-based catalysts for oxygen reduction reaction in polymer electrolyte membrane fuel cells. J Power Sources 188(1) 38 4... 

Oh HS, Oh JG, Lee WH, Kim HI, Kim H (2011) The influence of the structuial properties of carbon on the oxygen reductimi reaction of nitrogen modified carbon based catalysts. Int J Hydrogen Energy 36 8181-8186... 

Nallathambi V, Li X, Lee J-W, Popov BN (2008) Developement of nitrogen-modified carbon-based catalysts for oxygen reduction in PEM fuel cells. ECS Trans 16 405-417... 

Presumes a metabolizable energy density of 16.74 kJ/g of dry matter based on the modified Atwater values of 14.64, 35.56, and 14.64 kJ/g for protein, fat, and carbohydrate (nitrogen-free extract, NEE), respectively. Rations greater than 18.83 kJ/g should be corrected for energy density rations less than 16.74 kJ/g should not be corrected for energy. To convert kj to kcal, divide by 4.184. 

Three generations of latices as characterized by the type of surfactant used in manufacture have been defined (53). The first generation includes latices made with conventional (/) anionic surfactants like fatty acid soaps, alkyl carboxylates, alkyl sulfates, and alkyl sulfonates (54) (2) nonionic surfactants like poly(ethylene oxide) or poly(vinyl alcohol) used to improve freeze—thaw and shear stabiUty and (J) cationic surfactants like amines, nitriles, and other nitrogen bases, rarely used because of incompatibiUty problems. Portiand cement latex modifiers are one example where cationic surfactants are used. Anionic surfactants yield smaller particles than nonionic surfactants (55). Often a combination of anionic surfactants or anionic and nonionic surfactants are used to provide improved stabiUty. The stabilizing abiUty of anionic fatty acid soaps diminishes at lower pH as the soaps revert to their acids. First-generation latices also suffer from the presence of soap on the polymer particles at the end of the polymerization. Steam and vacuum stripping methods are often used to remove the soap and unreacted monomer from the final product (56). 

SNCR programs typically employing liquid additive formulations based on urea (carbamide, NH2CONH2), together with stabilizers and modifiers, are particularly useful. The additive is sprayed into the combustion area, after the burner. The use of such additives reduces the NOx level by between 50 and 90% by converting NOx into harmless nitrogen and water. 

PLA/PCL-OMMT nano-composites were prepared effectively using fatty amides as clay modifier. The nano-composites shows increasing mechanical properties and thermal stability (Hoidy et al, 2010c). New biopolymer nano-composites were prepared by treatment of epoxidized soybean oil and palm oil, respectively plasticized PLA modified MMT with fatty nitrogen compounds. The XRD and TEM results confirmed the production of nanocomposites. The novelty of these studies is use of fatty nitrogen compoimds which reduces the dependence on petroleum-based surfactants (Al-Mulla et al., 2011 Al-Mulla et ah, 2011 Al- Mulla et ah, 2010c). 

Al-Mulla, E.A.J., Suhail, A. H. and Aowda, S. 2011. A. New biopolymer nanocomposites based on epoxidized soybean oil plastidzed poly(lactic add)/fatty nitrogen compounds modified clay Preparation and characterization. Industrial Crops and Products 33. 23-29. 

Theoretical studies aimed at rationalizing the interaction between the chiral modifier and the pyruvate have been undertaken using quantum chemistry techniques, at both ab initio and semi-empirical levels, and molecular mechanics. The studies were based on the experimental observation that the quinuclidine nitrogen is the main interaction center between cinchonidine and the reactant pyruvate. This center can either act as a nucleophile or after protonation (protic solvent) as an electrophile. In a first step, NH3 and NH4 have been used as models of this reaction center, and the optimal structures and complexation energies of the pyruvate with NH3 and NHa, respectively, were calculated [40]. The pyruvate—NHa complex was found to be much more stable (by 25 kcal/mol) due to favorable electrostatic interaction, indicating that in acidic solvents the protonated cinchonidine will interact with the pyruvate. 

The above comparison indicates that the rate acceleration induced by CD is more pronounced than that of the other tertiary nitrogen bases. This fact also indicates that in CD a cooperative effect should exist between the quinuclidine nitrogen and the quinoline ring, The cooperative effect is in force if the modifier is in a shielded form. 

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