Homopolymer tailing

Terminal transferase j Adds nucleotides to the 3 ends of DNA. Homopolymer tailing. 

Fig. 1 Schematic outline of procedures employed in the synthesis of a cDNA gene copy from a polyadenylated mRNA template, insertion of the cDNA into a bacterial plasmid vector by a homopolymer tailing strategy, and cloning of the recombinant plasmid in an Escherichia coli host.

Adds a phosphate to the 5 -0H end of a polynucleotide to label it or permit ligation Adds homopolymer tails to the 3 -0H ends of a linear duplex Removes nucleotide residues from the 3 ends of a DNA strand Removes nucleotides from the 5 ends of a duplex to expose single-stranded 3 ends Removes terminal phosphates from either the 5 or 3 end (or both)... 

Figure 3. One orientation cloning and its application - Steps for directional cDNA cloning in Agt22. The experimental details of the procedure are presented in the text. At indicates the polyA tail of mRNA, C, G, T indicate the oligonucleotide primer-adapter which has a dC, dG, and dT homopolymer tail, respectively. SP6 and T7 indicate promoters for SP6 and T7 polymerase.

Epichlorohydrin Elastomers without AGE. ECH homopolymer, polyepichlorohydrin [24969-06-0] (1), and ECH—EO copolymer, poly(epichlorohydrin- (9-ethylene oxide) [24969-10-6] (2), are linear and amorphous. Because it is unsymmetrical, ECH monomer can polymerize in the head-to-head, tail-to-tail, or head-to-tail fashion. The commercial polymer is 97—99% head-to-tail, and has been shown to be stereorandom and atactic (15—17). Only low degrees of crystallinity are present in commercial ECH homopolymers the amorphous product is preferred. 

Saturated 2,2 -bis-5-oxazolones (10) react with diamines under mild conditions to form polyamides (34) of high molecular weight in quantitative yield [Eq. (21)]. These polymers are composed of dicarboxylic acid, a-amino acid, and diamine units in a regular arrangement of both head-to-tail and tail-to-tail amide groups. They represent a cross between conventional polyamides and a-amino acid homopolymers. A feature of this polymerization is that no small molecules such as H2O, NHg, or CO2 are lost during reaction. 

For analyzing structure-property relationships, a variety of PEO-g-PVA copolymers were prepared, differing in the VAc-to-PEO ratio and the molar mass of PEO. The analysis of the copolymers by IR and 1H- and 13C-NMR showed the presence of both PEO and PVA. A small C=0 absorption was still present and was explained by a nonquantitative saponification. SEC showed polydispersities (Mw/M ) of around 5, with a small tailing to the low molar mass side. The latter was probably caused by the relatively low molar mass PVA homopolymer formed by the chain transfer reaction of VAc, both to the PEO and its acetate functionality. 

Macromolecules have also been specifically designed and synthesized for use as emulsifiers for lipophilic materials and as stabilizers in the colloidal dispersion of lipophilic, hydrocarbon polymers in C02. We have demonstrated the amphiphilicity of fluorinated acrylate homopolymers, such as PFOA, which contain a lipophilic, acrylate like backbone and C02-philic, fluorinated side chains (see Fig. 3) [103]. It has been demonstrated that a homopolymer which physically adsorbs to the surface of a polymer colloid prevents agglomeration by the presence of loops and tails (see Fig. 4) [113]. The synthesis of this type of... 

Experimentally, the form of 4>(z) has been recently established for adsorbed homopolymers and terminally anchored tails by the Bristol group (17,20). Knowing 4>(z) one may then calculate the r.m.s. thickness of the adsorbed layer. Previous measurements of the "thickness" (1-4) have usually involved ellipsometry (flat surfaces) or some hydrodynamic technique (particles). In neither case can the calculated thickness be unambiguously related to 4>(z), although recent theoretical work by Cohen Stuart et al. (21), to be discussed at this meeting, has made an attempt to relate the hydro-dynamic thickness, 6, to < >(z). 

Terminal deoxynucleotidyl transferase normally adds homopolydeoxynucleotide tails to single-stranded DNA primers in the presence of a deoxynucleoside triphosphate and magnesium. If cobalt is used instead, not only does double-stranded DNA become an acceptable substrate, but ribonucleotides or homopolymer deoxyribo-nucleotide tracts may be added to all forms of duplex DNA at their 3 -ends, regardless of whether these are staggered or even.162 This allows terminal labelling for sequence analysis at the cleavage sites of restriction endonucleases,162- 183 or tail formation for in vitro studies on recombinant DNA.162... 

During the polymerization process the normal head-to-tail free-radical reaction of vinyl chloride deviates from the normal path and results in sites of lower chemical stability or defect sites along some of the polymer chains. These defect sites are small in number and are formed by autoxidation, chain termination, or chain-branching reactions. Heat stabilizer technology has grown from efforts to either chemically prevent or repair these defect sites. Partial structures (3—6) are typical of the defect sites found in PVC homopolymers (2—5). 

The occupied areas Sl per adsorbed polymer at the air-water interface estimated from adsorbances for IEI and POE were almost equal and independent of the KBr concentration. The thickness of the adsorbed POE did not exceed 15 A while that of the adsorbed IEI increased with decreasing KBr concentration and was about 1.5 times as large as the root mean-square end-to-end distance of the ionene homopolymer with the same M in bulk solution. It was concluded that POE, which is non-ionic and hydrophilic, is adsorbed in a nearly flattened conformation with short loops and trains. On the other hand, IEI is adsorbed a in tail-train-tail conformation in which the oxyethylene block lies flat on the air-water interface and the ionene tails are elongated to the bulk solution. 

Ribbed helices (costal helices) are important in organic chemistry because linear polymers contain side chains as well as backbones. We may, then, discern not only the catenal helix of the backbone, but the intercostal helix formed by all of the ribs and the infracostal helicesof the individual side chains. The intercostal helix may be iterative (as in an isotactic head-to-tail vinyl polymer or homogeneous poly-a-amino acid) or non-iterative (as in a random copolymer, an atactic polymer or typical protein). The intracostal helices can best be analyzed as short-chain crooked lines, as in Section III. Important as costal helicity is, it is secondary to catenal helicity and we therefore limit our attention to the primary helicity, that of long chains. Indeed, we limit our attention to catenal helices having chain motifs of two atoms and two bonds as found in head-to-tail vinyl homopolymers ... 

Along with the isomerism of linear copolymers due to various distributions of different monomeric units in their chains, other kinds of isomerisms are known. They can appear even in homopolymer molecules, provided several fashions exist for a monomer to enter in the polymer chain in the course of the synthesis. So, asymmetric monomeric units can be coupled in macromolecules according to "head-to-tail" or "head-to-head"—"tail-to-tail" type of arrangement. Apart from such a constitutional isomerism, stereoisomerism can be also inherent to some of the polymers. Isomers can sometimes substantially vary in performance properties that should be taken into account when choosing the kinetic model. The principal types of such an account are analogous to those considered in the foregoing. The only distinction consists in more extended definition of possible states of a stochastic process of conventional movement along a polymer chain. 

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