Template-dependent synthesis

DNA polymerase. An enzyme that catalyzes template-dependent synthesis of DNA from its dNTP precursors. 

Full details have now appeared of the stereoselective synthesis of 1,5,9-triphosphacyclododecane systems by oxidative liberation from molybdenum and chromium complexes of the macrocycle, obtained by coordination-template controlled reactionsMolybdenum complexes have also been used in the coordination-template dependent synthesis of the macrocyclic P,S system 151. A non-template synthesis of the 14-membered P2S2 macrocycle, 152, isolated in two isomeric forms, has been described. Halogenation of the cyclometallated phosphine 153 leads to a rearrangement, with the formation of the di-phosphinobiphenyl system 154, from which the free diphosphine can be liberated... 

In the template-dependent synthesis, the nucleotides are polycondensed in the presence of a natural or synthetic nucleic acid acting as template. Here, the nucleotides are incorporated according to a specific sequence determined by the template by the complementary base-pairing principle. From a mixture... 

In a template-dependent synthesis, nucleotides are incorporated in a specific sequence into a polynucleotide according to the complementary base pairing principle. The molecular weight of the polymers synthesized depends on the length of the template. However, slippage can occur The chain formed by replication can slide along the template chain ... 

Diels-Alder and Friedel-Crafts reactions, and amidation and reductive amination. The template-dependent synthesis of a palladium catalyst has been reported, and multi-step syntheses have been described including the synthesis of macromolecules. ... 

Figure 2. Electrochemical template-controlled synthesis of nanoparticles on nanostructured monolayer. The size of nanoparticles depends on the reduction charge and can be adjusted easily. (Reprinted from Ref [18], 2005, with permission from Wiley-VCH.)...

Notice the particular features of this kind of ohgonucleotide the hexameric sequence is said to be self-complementary, since two identical molecules can form a duplex via Watson and Crick bases. It may also be noted from Figure 7.5 that two parallel pathways compete for the formation of the template T, namely the template-dependent, autocatalytic pathway, and the template-independent, non-autocatalytic one. This competition is the reason why the initial rate of the autocatalytic synthesis was found to be proportional to the square root of the template concentration -something that von Kiedrowski and colleagues called the square-root law of autocatalysis. As Burmeister (1998) put it ... 

The retroviral genomic RNA serves as the template for synthesis of a double-stranded DNA copy, the provirus (Figure 49-4). Synthesis of the provirus is mediated by a virus-encoded RNA-dependent DNA polymerase, or reverse transcriptase. The provirus is translocated to the nucleus and is integrated into host DNA. Transcription of this... 

In this chapter we examine the synthesis of RNA on a DNA template and the postsynthetic processing and turnover of RNA molecules. In doing so we encounter many of the specialized functions of RNA, including catalytic functions. Interestingly, the substrates for RNA enzymes are often other RNA molecules. We also describe systems in which RNA is the template and DNA the product, rather than vice versa. The information pathways thus come full circle, revealing that template-dependent nucleic acid synthesis has standard rules... 

Although the existence of this enzyme may not be surprising, the mechanism by which it acts is remarkable and unprecedented. Telomerase, like some other enzymes described in this chapter, contains both RNA and protein components. The RNA component is about 150 nucleotides long and contains about 1.5 copies of the appropriate CyKx telomere repeat. This region of the RNA acts as a template for synthesis of the T -G strand of the telomere. Telomerase thereby acts as a cellular reverse transcriptase that provides the active site for RNA-dependent DNA synthesis. Unlike retroviral reverse transcriptases, telomerase copies only a small segment of RNA that it carries within itself. Telomere synthesis requires the 3 end of a chromosome as primer and proceeds in the usual 5 —>3 direction. Having syn-... 

Whatever the nature of the template, among possible applications such as catalysts, grafting supports, or filtration medium, the use of MTS for chromatography applications has been claimed for years. However, this latter application requires the ability to synthesize homogeneous batches of spherical particles with a mean diameter at least equal to 5 pm. Such particles were observed only once, in a pH-dependent synthesis of MCM-41 particles, performed by Yang, Ozin and co-workers [1], Most of the time, the synthesis of submicrometer-size particles of MCM-41 or MCM-48 materials was only reported [2-4], We present the synthesis of MSU-X silica with perfectly controlled size and shape suitable for chromatography applications. 

This at once raises the question Could RNA ever have arisen without the help of enzymes, without replicases Experiments by Leslie Orgel and his co-workers12 suggest that this was possible. It was found that zinc ions, found today as cofactors in all replicases, are excellent catalysts for the 3 -5 union of nucleotides, thus allowing the template-instructed synthesis of polymers. This was first demonstrated with poly-C as template. If activated G and A nucleotides are offered, in equal concentration, then G is preferentially incorporated into the product by a factor, depending on reaction conditions, between 30 and 200. 

All enzymes that make DNA in a template-dependent fashion require a primer. How does the use of a primer increase the fidelity of DNA synthesis, and why is this primer usually RNA ... 

DNA-dependent synthesis of RNA in E. coli is catalyzed by one enzyme, consisting of five polypeptide subunits. The complete holoenzyme is composed of four polypeptides (the core enzyme) and an additional polypeptide that confers specificity for initiation at promoter sequences in the DNA template. 

SAM-dependent methylation of salicylic acid. The salicyl alcohol derivative salicin, found in many species of willow (Salix species Salicaceae), is not derived from salicylic acid, but probably via glucosylation of salicylaldehyde and then reduction of the carbonyl (Figure 4.27). Salicin is responsible for the analgesic and antipyretic effects of willow barks, widely used for centuries, and the template for synthesis of acetylsalicylic acid (aspirin) (Figure 4.27) as a more effective analogue. 

Like other DNA polymerases, reverse transcriptases are primer-and template-dependent. They also possess an RNase H activity (H stands for hybrid) that can degrade the RNA template after it is used for synthesis of the first DNA strand. The enzyme then can copy the first strand of DNA to make a double-stranded molecule. 

Fig. 10 Model protocell systems, a An encapsulated polymerase (polynucleotide phos-phorylase) can synthesize RNA from nucleoside diphosphates such as ADP [79,80], b RNA can be synthesized by a template-dependent T7 RNA polymerase [83], c Proteins such as green fluorescent protein (GFP) can be synthesized by an encapsulated translation system [84], If mRNA coding for hemolysin is also present, the hemolysin forms a pore in the lipid bilayer. Amino acids then permeate the bilayer, and protein synthesis can continue for several days [85]...

Synthetic polymers containing either desoxyribonucleotide or ribonucleotide strands are known to stimulate the in vitro DNA synthesis by RNA tumor viruses. Some inhibitors of the DNA-polymerase reaction in RNA tumor viruses are known to exhibit a template-primer specificity6, 7 34 Table 22 shows the inhibition of template-dependent DNA polymerase activity of FLV by DEAE-F at various concentrations. The reaction catalyzed by poly (dl - dC) is most strongly stimulated by DEAE-F. Thus at 20 pg/reaction mixt. of DEAE-F the incorporation of 3H—dGMP is almost 4 times that of control. 

The principal motivation for studying these sugar-based microemulsion glasses came from the observation that water-oil-surfactant mixtures are extensively for nanomaterials synthesis with the central idea of switching dynamic self-assembly into chemically and mechanically stable supramolecular materials. Template polymerisations are classified as synergistic or transcriptive templating depending on whether the template itself participates in the reaction. 

Biopolymers are either synthesized by template-dependent or template-independent enzymatic processes. For the synthesis of nucleic acids and proteins a template is required, whereas all other polymers are synthesized by template-independent processes. The templates for nucleic acids are desoxyribonucleic acids or ribonucleic acids depending on the type of nucleic acid synthesized. For proteins, the template is messenger ribonucleic acid (mRNA). This has different impacts on the structure and on the molecular weights (MWs) of the polymers. Although both nucleic acids and proteins are copolymers with each type consisting of 4 or 22 different constituents, respectively, the distribution of the constituents is absolutely defined by the matrix and is not random. Furthermore, each representative of the two polymers has a defined MW. Polymers synthesized in template-dependent processes are monodisperse. All this is different in polymers synthesized by template-independent processes first of all, these polymers are polydisperse secondly, if these polymers are copolymers, the distribution of the constituents is more or less fully random. 

In this chapter, we focus on the synthesis of polyhydroxyalkanoic acids (PHA) and cyanophycin (cyanophycin granule polyperptide, CGP) and the key enzymes PHA synthase (PhaC) and cyanophycin synthetase (CphA), respectively. Both polymers are synthesized by template-independent processes. The issue of template dependency and template independency will be illustrated in more detail with polymers consisting of amino acids. 

The best investigated mechanism, distributed ubiquitously in Hving matter, is the template-dependent ribosomal synthesis of proteins. Here the amino acids are activated by adenylation catalyzed by aminoacyl-tRNA synthetases [1]. 

Asymmetric synthesis of N-methyl-a-amino esters.2 This morpholine can be used as a chiral template for synthesis of N-methyl-a-amino esters. Thus reaction with an alkylcopper involves displacement of the phenylthio group by an alkyl group by the usual Sn2 process with inversion (about 90 10). In contrast, reaction with an alkylzinc iodide involves substitution with essentially complete retention, possibly via an iminium intermediate. The alkylated product (2) is then oxidized to an oxazinonc (3), which on treatment with vinyl chloroformate followed by hydrolysis provides N-methyl-a-amino esters (4) in high optical purity. This approach to chiral amino acids is unusual in that eiiher enantiomer can be formed from the same template depending on the choice of the organometallic reagent. Unfortunately, the chiral auxiliary (expensive) is not recovered for reuse. 

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