Functional monomers and polymers. XXXXI. Template polymerization of methacryloyl-type monomers containing nucleic acid bases

In due consideration of the specific base–base interaction that exists between nucleic acid molecules, the free radical polymerization of N-β-methacryloyloxyethyl derivatives of adenine, thymine, and theophylline initiated by azobisisobutyronitrile (AIBN) was studied in the presence of N-β-methacryloyloxyethyl-type polymers which have complementary nucleic acid bases as template polymers. The rate of polymerization of N-β-methacryloyloxyethyladenine was accelerated when poly(N-β-methacryloyloxyethyluracil) or -thymine was present in the polymerization system. The effect of the stereoregularity of the template polymers, as well as polymerization temperature and the sort of solvents used on the rate of polymerization, was studied and discussed in some detail. The results suggest that the interaction between complementary bases plays a role in template polymerization behavior.     

Synthesis of poly(vinyl alcohol) containing asymmetric nucleic acid base derivatives as grafted pendants

The preparations of new model polymers of polynucleotides with linear poly(vinyl alcohol) (PVA) backbones and an optically active nucleic acid base derivative as a pending side chain are described. (±)-, (+)-, and (?)-2-(thymin-1-yl)propionic acid were grafted onto PVA through ester bonds by direct coupling with dicyclohexylcarbodiimide (DCC) in the presence of highly active catalyst 4-pyrrolidinopyridine (PPY) to give optically active graft polymers. The corresponding monomer and dimer models have been prepared.     

Spectroscopic studies of poly(vinylamine) containing optically active thymine derivatives as grafted pendants

The optical properties of poly(vinylamine) containing optically active (+)- or (?)-2-(thymin-1-yl) propionyl groups as grafted pendants (PT) and the related monomer (MT) and dimer models (DT) were investigated by UV, circular dichroism (CD), and NMR spectroscopy. Highly syndiotactic PT has a smaller hypochromicity versus MT and a larger optical rotation than the less syndiotactic PT in various solutions. These results are attributed to an interaction between the configurational arrangement of thymines, the conformation of the polymers, and base stacking between thymines. The interactions of these polymers with poly(adenylic acid) (polyA) were also studied and the results compared with other vinyl-type nucleic acid model polymers. The isomers of the optically active dimer models [prepared from meso and (dl)-2,4-diaminopentane] were separated. The CD spectra of (+)-D(?)T in CHCl₃ and trifluoroethanol (TFE) displayed extremely solvent-dependent exciton coupling of the π–π^* (B_2u) transition of the base chromophore, which was not observed in the other models or polymers, except the meso-type dimer model (meso)-D-(?)T. This coupling decreased with increasing solvent dielectric constant, while UV hypochromicity increased. This behavior as well as the 360-MHz NMR spectra suggest that (+)-D(?)T exists in an extended form in solvents of low dielectric constant and gradually assumes a stacked conformation as the dielectric constant increases.     

Synthesis of poly(vinylamine) containing asymmetric nucleic acid base derivatives as grafted pendants

The preparations of new model polymers of polynucleotides with stereoregular poly(vinylamine) (PVAm) backbones and an optically active nucleic acid base derivative as a pending side chain are described. The grafting of (±)-, (+)-, and (?)-2-(thymin-1-yl) propionic acid to linear PVAm prepared either by hydrolysis of poly(vinyl acetamide) or poly(vinyl-t-butyl carbamate) has proven to be more difficult than the case of polyethyleneimine. This may be due to a combination of the low solubility and steric factors of PVAm. PVAm formed a complex with oximes such as ethyl-2-hydroxyimino cyanoacetate (EHICA), which activates the amino group of PVAm; it became soluble in polar solvents and gave higher percent graft. These carboxylic acid derivatives were grafted onto PVAm through amide bonds by direct coupling with sulfonic acid esters of hydroxybenzotriazoles to give optically active graft polymers. These coupling agents were found to be much superior reagents than DEPC regarding racemization. The related monomer and dimer model compounds were also prepared by the same method from 3-aminopentane and (?)-, (+)-, and meso-2,4-diaminopentane, respectively. The dimer models were separated and purified by HPLC to give models for isotactic, heterotactic, and syndiotactic polymer models. The enantiomeric purity of the optically active monomer model was determined by 360-MHz NMR spectroscopy using optically active shift reagents.     

Singlet excitation transfer from poly rA to bound dye at 77 K

The fluorescence of poly rA frozen in an aqueous medium containing sugar is half-quenched by bound dyes at a fractional concentration ≈ 0.01, smaller by an order-of-magnitude than that required to sensitize the room-temperature fluorescence of dyes bound to nucleic acid polymers. There is no quenching of the fluorescence of similarly frozen adenosine solutions having the same absolute concentrations of base and dye.     

Synthesis of copoly(vinylamine-vinylalcohol) containing two kinds of asymmetric nucleic acid base derivatives as grafted pendants

Preparation of new model polymers of polynucleotides with poly(vinylamine-vinylalcohol) [P(Vam-Val)] backbones and different kinds of nucleic acid base derivatives as grafted pendants is described. At first, the grafting of (?) and (±)-2-(thymin-1-yl)propionic acid [(?) and (±)TPA] onto linear P(Vam-Val) at the amino group via an amide bond was carried out in a mixed solvent of ethanol-dimethylformamide by selective N-acylation of the active ester of N-hydroxy-5-norbornene-2,3-dicarboximide (HONB) or N-hydroxysuccinimide (HOSu). This procedure gave the corresponding hydroxyl polymers P[Vam(?)T-Val] and P[Vam(±)T-Val]. In addition, direct, low temperature esterification was used to graft (?), (±)TPA, and (±)-2-(uracil-1-yl)propionic acid, [(±)UPA], onto the hydroxyl polymer at the hydroxyl group via an ester bond. This process gave the corresponding copoly(Vam-Val) with different or the same kinds of nucleic acid base derivatives. P[Vam(?)-Ve(?)T], P[Vam(±)T-Ve(±)T], P[Vam(?)T-Ve(±)U], and P[Vam(±)T-Ve(±)U] are representative examples. The related monomer and segmental model compounds were also prepared by this method; 3-aminopentane, 3-pentanol, 3-amino-1-propanol, and threo-2-amino-4-pentanol were employed in the syntheses. The segment models were separated and purified using HPLC techniques.     

Functional Monomers and Polymers Containing Nucleic Acid Bases: Experiments on Template Polymerization

In order to see how the specific base-base interactions observed between complementary nucleic acid bases can be realized for free-radical polymerization systems, the template polymerization of methacrylate type monomers containing nucleic acid bases in the presence of template polymers containing complementary bases was studied. Stereoregular polymers were chosen as the template polymers. The radical copolymerization of the monomers containing complementary nucleic acid bases was also studied in different solvents.     

γ-核酸碱基取代丙基甲基二乙氧基硅烷的合成及其聚合反应研究

本文以Υ-溴丙基甲基二乙氧基硅烷分别与尿嘧啶、胸腺嘧啶、腺嘌呤和5-氟尿嘧啶进行烷基化反应,制得了四种含有核酸碱基或5-氟尿嘧啶的新型有机硅单体。通过它们的缩聚反应,合成了六种侧基含核酸碱基或5-氟尿嘧啶的聚硅氧烷。     

PROBING PHOTODYNAMIC DAMAGE IN NUCLEIC ACIDS WITH A DAMAGE-SPECIFIC DNA BINDING PROTEIN: A COMPARISON OF THE B and Z DNA CONFORMATIONS

—We have employed a damage-specific DNA binding protein from human cells as a probe for base damage in polymers irradiated with white light in the presence of methylene blue. Protein-recognizable damage is introduced only into guanine-containing polymers and quenching of damage introduction by H₂O and sodium azide suggest the involvement of a singlet oxygen mechanism. Using poly d(G-m⁵C), we have demonstrated that the left-handed double helical Z conformation is much less susceptible to guanine photooxidation than is the usual B conformation. We speculate that this difference in reactivity may reflect steric hindrance at the purine C-4 position and could provide some insight into the initial steps of the reaction between singlet oxygen and guanine in nucleic acid polymers.     

Potentiometric and viscosimetric titration of poly(N-acyldehydroalanines) containing asymmetric nucleic acid base derivatives as pendant groups

The potentiometric and viscosimetric titration curves of poly(N-acetyldehydroalanine) (PNAcDHA) were compared with those of the nucleic acid base-containing dehydroalanine backbone polymers poly{(+ ?) and (?)? [2-(thymin-1-yl]{propanoamido}propenoic acid} (PTDHA and P(?)TDHA)). The behavior of PNAcDHA was similar to polyacids such as poly(acrylic acid), but PTDHA and P(?)TDHA displayed very strong nearest neighbor interactions, since the pH curves had an additional inflection at half neutralization that was sensitive to the ionic strength of the medium and the viscosity curves showed little expansion of the polymer coil with increasing ionization. NAcDHA–TDHA copolymers were prepared which showed similar behavior. These results suggested that PTDHA and P(?)TDHA were extended and conformationally restricted in aqueous solution compared to PNAcDHA, findings that agreed with the results of spectroscopic studies of these polymers.     

Lanthanide ions as luminescent chromophores for the liquid chromatographic detection of polynucleotides and nucleic acids

Europium(III) and terbium(III) can be used as luminescent chromophores for the liquid chromatographic detection of certain nucleotides and nucleic acids. The method is dependent upon an energy transfer from the nucleic acid to the lanthanide ion. Of the base moieties, only xanthine, guanine, and thiouridine have appropriate excited state energy levels for efficient energy transfer. The lanthanide ion can be added in a pre- or post-column mode. The applicability of the method was demonstrated for the detection of homologous polynucleotides such as poly X and poly G. The method was also used to detect transfer RNA from Escherichia coli.     

Functional monomers and polymers. XXXXVII. Complex formation of stereoregular methacryloyl-type polymers containing nucleic acid bases

The complex formation between a poly(N-β-methacryloyloxyethyl) derivative of adenine with one of thymine or uracil was studied in dimethyl sulfoxide and ethylene glycol mixture by ultraviolet (UV) spectroscopy. For the polymer pairs containing complementary nucleic acid bases both hypochromicity and hyperchromicity were found. Stereoregularity of the polymers, as well as the conditions for measurement of, for example, solvent, temperature, and time, affected the complex formation. Both inter- and intramolecular interaction of polymers in solution were discussed in some detail.     

Nucleic acid base grafted polyethylenimine. Cytosyl pendant groups synthesis and characterization

Poly(N-acyl ethylenimine) of various molecular weights was synthesized by the cationic ring-opening polymerization of 2-H-2-oxazoline and 2-methyl-2-oxazoline. Acid hydrolysis afforded the linear poly(ethylenimine) which was used in the following grafting reactions. Vapor pressure osmometry, gel permeation chromatography and viscosity measurements were used to characterize the polymers synthesized. Potassium 2-(cytos-1-yl)propanoate and potassium 3-(cytos-1-yl)butanoate were synthesized in good yield from the nucleic acid base. These cytosyl pendant groups were grafted onto the poly(ethylenimine) using 4-chloro-1-(4-chlorobenzenesulfonyl)benzotriazole, 93% graft, and norborn-5-ene-2,3-carboximido diphenyl phosphate, 70% graft. Grafting of the t-butoxycarbonyl and n-butoxycarbonyl protected cytosyl pendant groups resulted in a 47% and 40% graft, respectively.     

Grafting of optically active nucleic acid base derivatives onto poly(vinylamine) as polynucleotide analogs

Polynucleotide analogs consisting of poly(vinylamine) as the backbone and optically active thymine and adenine derivatives as the pendants were synthesized. The pendants were prepared by the addition reaction of the nucleic acid base to ethyl crotonate followed by hydrolysis. The pendants were resolved using brucine as the resolving agent and an acetone-water mixture as the fractional crystallization solvent. The active esters of the pendants also were prepared. Poly(vinylamine) was isolated from water employing a weak acid, N-hydroxysuccinimide (HOSu), to protect the amino group of the poly(vinylamine). Model reactions for grafting were examined. Grafting reactions were carried out by reacting the active esters with the PVAm.6HOSu complex at room temperature.     

Synthesis of novel poly(xylylenyl benzimidazole)s

Novel poly(xylylenyl benzimidazole)s (PXBI) with methyl substituents on the xylylene units were synthesized by high-temperature polycondensation techniques. Two different tetraamine hydrochlorides were condensed independently with 2,5-dimethyl-1,4-benzene diacetic acid and 2,4-dimethyl-1,5-benzene diacetic acid in polyphosphoric acid (PPA) to yield different poly(xylylenyl benzimidazole)s. Their syntheses, characterization, and properties such as density, viscosity, solubility, crystallinity, and thermal stability were described. Two model benzimidazoles (MBI) were also synthesized from o-phenylene diamine (OPDA) and the above two diacetic acids to confirm the formation of polymers from the tetraamines. The polymers thus obtained had high intrinsic viscosities in the range of 0.67-0.94 dl/g and were stable up to 450°C.     

Study on modification of polymers with the aid of the Schmidt reaction

A study of the Schmidt reaction on several polymers with pendant carboxylic and ketone moieties was carried out. Four polymers were used as starting materials: (1) poly(methyl vinyl ketone), (2) poly(acrylic acid), (3) a copolymer of methyl vinyl ketone and acrylic acid, and (4) a copolymer of styrene and acrylic acid. Most reactions were conducted in an acetic acid medium with the exception of one reaction on poly(acrylic acid) which was done in dioxane and another on copolymer of styrene and acrylic acid done in chloroform. It was found that a Schmidt reaction on poly(acrylic acid) in acetic acid solution will lead to intermolecular reactions of the intermediate with the solvent in preference to reactions with neighboring carboxyl groups on the polymer backbone. A tendency of poly(acrylic acid) to form cyclic anhydrides under these reaction conditions interferes with the yield of acetamide units.     

Efficient and sequence-specific DNA-templated polymerization of peptide nucleic acid aldehydes

On the basis of the distance-dependence of DNA-templated reductive amination reactions and of recent findings of D. Lynn and co-workers, we developed DNA-templated polymerizations of synthetic peptide nucleic acid (PNA) aldehydes. The coupling reactions proceed in a highly efficient and sequence-specific manner, even in the presence of mixtures of PNA aldehydes of different sequence. Synthetic peptide nucleic acid polymers containing as many as 40 PNA units (representing 10 consecutive coupling reactions) were formed efficiently. The ease of preparing PNAs containing tailor-made functional groups together with these findings raises the possibility of evolving synthetic sequence-defined polymers by iterated cycles of translation, selection, PCR amplification, and diversification previously available only to biological macromolecules.     

Adhesive polymer: Intermacromolecular interaction in fluid solution studied by fluorescence depolarization method

The fluorescence depolarization of the anthryl groups attached to poly(styrene-maleic anhydride) [P(St-MA)] has been examined in mixtures of various acrylic adhesive polymers with toluene for weight fractions ranging from 0 to 0.25. It is clear that the relative mean rotational relaxation time of the anthryl groups sharply increases with increasing concentration of poly(2-ethylhexylacrylate) (PEHA) containing about 5% acrylic acid units and 10% vinyl acetate units. It may be concluded that an excellent adhesive polymer is made with acrylic acid units as agents for intra- and interaction and vinyl acetate units as depression agents for acrylic acid units and agents for strong PEHA-P(St-MA) interaction.     

Functional monomers and polymers. CXXXII. Template polymerization of methacrylamide derivatives containing nucleic acid bases

Free-radical polymerizations of methacrylamide derivatives containing nucleic acid bases were studied in the presence of the polymethacrylamide having complementary nucleic acid bases as template polymers. The rate of the polymerization did not show remarkable difference in the presence or the absence of the template polymer. A stable polymer complex, however, was precipitated from the polymerization system, and was found to be different in a thermal analysis from the polymer complex which was obtained by mixing of the complementary polymers in solution. Free-radical copolymerizations in the presence of the template polymers also supported the template polymerization.     

Synthesis of stereoregular poly(alkyl malolactonates)

Optically pure methyl, ethyl, isopropyl, and benzyl (R)-malolactonate were prepared from (S)-(-)-malic acid and were polymerized in the bulk with tetraethylammonium benzoate as the initiator to yield high-molecular-weight, crystalline polymers. The optical purity of methyl and benzyl malolactonate was determined by ¹H NMR spectroscopy of the β-lactone complexed with a chiral europium shift reagent. Enantiomeric excesses of 100% were found (the experimental error was 3%). Optically active poly(β-malic acid) was obtained from optically active poly[benzyl (S)-malate] by catalytic hydrogenolysis of the pendent benzyl esters. Ethyl and benzyl (R)-malolactonate were also copolymerized, and the benzyl esters of the resulting copolymer were converted into carboxylic acid units by hydrogenolysis.