Poly , additives Primers

Under certain circumstances DNA has both primer and template activities. For example, the addition of mononucleotides is to the 3 end of the growing DNA primer. This presents a problem with regard to how the other strand is synthesized. Biochemists have looked hard but unsuccessfully for an enzyme that can add deoxyribonucleotides onto the 5 end of DNA primers. Such a primer should contain a triphosphate on the hydroxyl group of the 5 end. Although a very active 5 -exonuclease, actually part of DNA polymerase I, has made the search for such an activated 5 end extremely difficult, investigators conclude that a polymerase able to use such a primer probably does not exist. On the contrary, good evidence suggests that the synthesis of both strands is by the known DNA poly-merases. 

Additionally, compounds such as a-arginyl aspartic acid dipeptide, modified cyanophycin containing less arginine, and poly-a,P-DL-aspartic acid were used as primers by the respective CphA [76],... 

An extensive study on anticorrosion properties of PANI, PPy and PEDOT used as additives was reported in [88]. Results indicate that the protection against corrosion imparted by the formulations modified by the addition of poly(3,4-ethylenedioxythiophene) doped with poly(styrene sulphonate), PANI-ES and, especially, PANI-EB is significantly higher than that of the unmodified epoxy paint. Thus, results evidence that some CP compositions can inhibit the steel corrosion and, therefore, small concentrations of these materials would be used to replace conventional inorganic corrosion inhibitors currently used in primer paints. In Table 10.6, some examples of the... 

Polymerase Polymerase is an enzsyme that catalyzes the addition of nucleotide to DNA or RNA. Figure 20.21a shows the crystal stmcture of the poly adenylate polymerase (PAP) from Saccharomyces cerevisiae (Papl) at 2.6 A resolution. The crystal contains a large 20 x 30 x 45-A cleft bounded by three globular domains. The catalytic palm domain and the COOH— terminal domain form the walls of the cleft rather than sitting at its base. The catalytic function of PAP resides in its NH2— terminal domain. Two divalent cations (orange) are shown bound to the active site and to the phosphates of the incoming 3 -dATP(red). The mononucleotide primer is shown in yellow. 

Experiments have been carried out on the effect of edeine on the DNA synthesis in vitro in a mixture consisting of four deoxyribonucleotide triphosphates, DNA polymerase and DNA as a primer. Both DNA and DNA polymerase were obtained from E. coli B. The experimental conditions were as described by Lehman (Lehman et aL, 1958). Addition of 10 [xg of edeine decreased the incorporation of radioactive dTTP into the newly formed DNA by about 50%. Similar inhibition was found for the synthesis of poly dAT (unpublished data) in a system of DNA polymerase from E. coli B and poly AU as a primer )Lee-Huan and Cavalieri, I963). Since edeine does not bind to the primers, the inhibition of DNA synthesis is presumably brought about by the action of edeine on the DNA polymerizing enzymes. 

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