Poly , template

Microstructure. Interest in PVP microstmcture and the potential for tacticity has been reviewed (39,40). PVP generated by free radicals has been shown to be atactic except when polymerization is conducted in water. In this case some syndiotacticity is observed (40). In the presence of syndiotactic templates of poly(methacryhc acid) (or poly(MAA)), VP will apparentiy polymerize with syndiotactic microstmcture, although proof is lacking (41—45). The reverse, polymerization of MAA in the presence of PVP, affords, as expected, atactic poly(MAA) (46,47). 

SG sols were synthesized by hydrolysis of tetraethyloxysilane in the presence of polyelectrolyte and surfactant. Poly (vinylsulfonic acid) (PVSA) or poly (styrenesulfonic acid) (PSSA) were used as cation exchangers, Tween-20 or Triton X-100 were used as non- ionic surfactants. Obtained sol was dropped onto the surface of glass slide and dried over night. Template extraction from the composite film was performed in water- ethanol medium. The ion-exchange properties of the films were studied spectrophotometrically using adsorption of cationic dye Rhodamine 6G or Fe(Phen) and potentiometrically by sorption of protons. 

The one-pot synthesis of 9 described above appears to afford only modest yields of azacrowns. One might wonder why any crown at all would be formed under non-high dilution conditions intended to yield only open-chained material. Vogtle suggests that this can be explained in terms of template, steric and entropy effects . These factors are of doubtless significance, but it is interesting to note that in the synthesis of poly-azamacrocycles, Richman and Atkins found that there was no significant template effect observed. The question of the template effect in Ihe syntheses of 9 has recently been addressed by Kulstad and Malmsten They conclude that the formation of 9 is assisted by the presence of alkali metal cations. 

Self-assembly of poly iodide networks on templates with crown ethers, thia- and thiazacrown ethers as ligands 98CSR195. 

By Naylor and Gilliam62, d (pT)6 was condensed in the presence of Poly A with carbodiimide to give d-(pT)12 with a yield of 5%. In the experiment of Shabarova and Prokofiev67, d-(pA)2 preactivated in the form of an amino add amidate was condensed on Poly U to give products with a yield of 10%. Uesugi and Ts o68 studied the condensation of (2 MeIp)6 or (2 MeIp)s in the presence of a Poly C template. The relative overall yield of the oligomer products was 43 to 71%. 

The authors found that the yield of 30-mer (a product with 5—6 linkages) was not much smaller than that of 10-mer or 12-mer. These facts indicate that the stability of the complex between the oligonucleotides and the complementary template is the most important factor in determining the extent of the condensation. The strong influences of template polymer (Poly C) are demonstrated in Fig. 9, in which the elution profile is shown of the polymerization products of (2 MeIp)6 in the presence of Poly C (B) and in their absence (A). 

Quaternary ammonium bromides and hydroxides (quats) are applied as templates in the synthesis of zeolites with relatively high Si/Al ratio. Examples will be given of the use of mon-, di-, poly- and associated quats as templates in zeolite growth. Templated zeolites of the MFI-type can be grown in a lateral or in an axial way onto metal supports, providing promising composite systems, for separation and catalysis, respectively. 

The use of ordered supramolecular assemblies, such as micelles, monolayers, vesicles, inverted micelles, and lyotropic liquid crystalline systems, allows for the controlled nucleation of inorganic materials on molecular templates with well-defined structure and surface chemistry. Poly(propyleneimine) dendrimers modified with long aliphatic chains are a new class of amphiphiles which display a variety of aggregation states due to their conformational flexibility [38]. In the presence of octadecylamine, poly(propyleneimine) dendrimers modified with long alkyl chains self-assemble to form remarkably rigid and well-defined aggregates. When the aggregate dispersion was injected into a supersaturated... 

The head-to-tail-coupling reactions described above are potentially useful in the design of dynamic combinatorial libraries. Features of these reactions include the rapid and reversible formation of carbon-carbon bonds, multifunctional ene-imine building blocks, and formation of stereo centers upon ene-imine linkage. Support for template-directed synthesis utilizing ene-imine building blocks is the formation of a poly ene-imine species that could recognize 3 -GGA-5 sequences of DNA.48 It is noteworthy that some polyene-imines are helical and could form a triple helix with DNA. 

The poly(C)-directed oligoguanylate synthesis from guanosine 5 -phosphoric 2-methylimidazolide has been studied kinetically.11571 An intermediate elongation process on polycytidylate acting as template is illustrated schematically below. 

Oligomerization of 2-MeImpG and 2-MeImpA by means of poly(C,U) random copolymer templates produced a variety of oligo(G,A)s.[160]... 

In the reaction of unprotected uridine with tri(imidazolyl-l)phosphine (ratio 1 1.5) under mild conditions (THF, — 78° to 0 °C, 10 min) and subsequent oxidation with iodide, two types of polymers [(Up)n (n = 2-6) and (Up)nU (n = 2—5)] are formed. Additives such as metal cations or polynucleotides (poly U and poly A) acting as templates in the oxidation process showed a significant effect on the ratio of the 3, 5 -linked to 2, 5 -linked oligomer 17 177 ... 

The family of poly(pyrazol-l-yl)borates has been widely used as supporting ligands in nickel coordination chemistry.556,557 Complex (191) is an example, where unusual cysteine coordination is achieved at a tris(pyrazolylborate)nickel(II) template.601 (191) undergoes rapid reaction with molecular oxygen to presumably form a sulfinate. 

Tao C, Zheng S, Mohwald H, Li J (2003) CdS crystal growth of lamellar morphology within templates of poly electrolyte/surf actant complex. Langmuir 19(21) 9039-9042... 

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. 

Variations The poly(A) tailing kit (Ambion) produces a mRNA population with varying lengths of poly(A) tails, controlled by altering poly(A) polymerase concentrations and incubation times. An alternate method to incorporate a poly(A) tail is to clone a defined stretch of adenosines/ thymidines into the > UTR of the template pDNA. To allow transcripts to finish on an adenosine, the insert should be followed by a restriction site for an enzyme that cleaves 5 of the last antisense strand thymidine, such as Nsi I. In this way, the poly (A) tail can be incorporated directly into the... 

If poly(U)-dependent polyphenylalanine synthesis is to be measured, the amount of template to be used is 5 fig/reaction mixture, the Mg acetate concentration is increased to 12 mM, and the amino acid mixture is omitted. 

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