Nucleosides In Solution Research Articles

Adenine nucleosides in solution: circular dichroism studies and base conformation.

Adenosine, AMP, S-adenosylhomocysteine, S-adenosylmethionine, aristeromycin and 25 other synthetic adenosine analogs modified in the 4' or 5' positions show certain groups of different circular dichroism (CD) spectra. Both positive and negative Cotton effects can occur in the long-wavelength part (250-270 nm) of the spectra. Molar ellipticities [theta] range from -6000 (in adenosine 5'-carboxylate) to +4000 deg. cm2 dmol-1 (in 5'-deoxy-5'iodoadenosine), including some compounds with small, polar 5'-substituents in which low-intensity bands are found in signed pairs. Most of these adenosine derivatives that have the same adenine chromophore and a ribofuranose moiety unsubstituted in the 2' and 3' positions prefer an anti-conformation of the adenine base, as evidenced by proton magnetic resonance spectroscopy. In the majority of cases, electronic perturbations of the chromophore or major alterations of the assymmetric sugar residue can be excluded as sources of the CD variations. Therefore a correlation of the long-wavelength CD bands with the glycosyl torsion angle phiCN is suggested, where the gauche, gauche/anti combination which is typical of AMP in the crystal and in solution (phiCN approximately -40degrees, [theta] negative) is one reference point and a region for phiCN = 0degrees ([theta] positive) is assigned to compounds with space-filling substituents such as S-adenosylmethionine. Both negative and positive Cotton effects can be associated with the anti conformation range. Within this series, the base conformation of novel nucleoside structures could be predicted from CD measurements. The CD spectrum gives no indication, however, of whether a certain torsion angle is the result of a rigid structure (as in AMP) or the average value of a molecule with high rotational freedom (as in 5'-deoxyadenosine). The conformations of aristeromycin and 4'-thioadenosine are discussed in relation to adenosine, and a structure-determining effect of the 4' bridge atom is noted.

Adenine nucleosides in solution: stabilisation of the anti-conformation by C-5' substituents.

Proton magnetic resonance spectra of 30 adenine nucleosides have been obtained in dilute (0.001 to 0.05 M) aqueous or dimethyl sulfoxide solutions and have been analysed with respect to structure‐dependent variations of the purine proton chemical shifts. In 2H2O the resonance signal of H‐8 shows a marked dependence upon the nature of substituents linked to C‐4′ of adenine ribofuranoside derivatives and upon the presence of a 2′: 3′‐O‐isopropylidene group while H‐2 is relatively unaffected. Therefore the chemical shift difference, δH‐8–δH‐2 =Δδ, may serve as an indicator of intramolecular ribose‐base interact ons. Δδ varies with the chemical nature of C‐4′ or C‐5′ substituents in the order: ammonium, sulfonium (0 ppm) < hydrogen < hydroxyl ∼ amino < thio < halogen < phosphate, carboxylate (0.4 ppm), and decreases with increasing chain length of these substituents. These results suggest the existence of electrostatic and dipolar repulsion or, in the majority of cases, attractive forces between the C‐5′ and C8‐H regions of adenine nucleosides which have been previously demonstrated for 5′‐nucleotides only. They imply a strong preference of most adenosine derivatives with unsubstituted 2′ and 3′‐hydroxyl groups for the anti‐conformation range and the gauche, gauche C‐5′ conformation. In dimethyl sulfoxide, basically the same situation exists but different substituents exhibit smaller individual Δδ variations than in water, indicating different solvation shells. In this solvent two additional conformation‐stabilizing contributions can be recognized, viz. an interaction of the bridge oxygen (O‐4′) of ribose with adenine, and a hydrogen bond between H‐8 and a 5′‐carboxylate anion. This energetic stabilisation of the anti and g,g‐conformers by most types of adenosine C‐5′ substituents supports the “rigidity” concept of nucleotides, extending it to the nucleoside level. The only exception found is 5′‐nitromethyladenosine in which ultraviolet, circular dichroism and magnetic resonance spectra suggest rotation of the adenine base to a “non‐classical” conformation due to base‐chain π‐electron interaction. The anti‐conformation of the adenosine derivatives used in this study can in some cases be correlated with their enzymatic deamination by adenosine and AMP aminohydrolase.

Conformation of nucleosides: Dipole moments of pyrimidine nucleosides

The dipole moments of a series of model pyrimidine nucleosides were determined experimentally. Comparison was made between the experimental values and those vectorially calculated as a function of nucleoside conformation. This analysis alone does not permit the unequivocal determination of the conformation of the nucleoside in solution, but taken together with the circular dichroism data from the adjoining paper (Rabczenko, A., Jankowski, K. and Zakrzewska, K. (1974) Biochim. Biophys. Acta) suggests: (i) the possibility of the existence of isopropylidene derivatives in dioxane in a mixture of syn and anti conformers; (ii) the conformational equilibrium of the N ag S type for a model nucleoside with a non-rigid sugar moiety.

Heterocyclic N‐glycosyl derivatives. XIV. Preparation of some N‐(2,3‐dideoxyglycopyranosyl)benzotriazoles by hydrogenation of N‐(pent‐ and hex‐2‐enopyranosyl)benzotriazoles

AbstractCatalytic hydrogenation of a series of N‐(pent‐ and hex‐2‐enopyranosyl)benzotriazoles afforded the corresponding saturated N‐glycosyl derivatives having the same anomeric configuration as the starting compounds. The conformations of all compounds obtained were determined by nmr spectroscopy. The hexopyranosyl nucleosides in solution adopt the Cl conformation. On the other hand, pentopyranosyl nucleosides exist as a mixture of the two chair conformers in equilibrium, with the IC or CI (L) form predominating.

Conformational analysis of nucleosides in solution by quantitative application of the nuclear Overhauser effect.

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTConformational analysis of nucleosides in solution by quantitative application of the nuclear Overhauser effectRoger E. Schirmer, Jeffrey P. Davis, Joseph H. Noggle, and Phillip A. HartCite this: J. Am. Chem. Soc. 1972, 94, 8, 2561–2572Publication Date (Print):April 1, 1972Publication History Published online1 May 2002Published inissue 1 April 1972https://doi.org/10.1021/ja00763a001RIGHTS & PERMISSIONSArticle Views129Altmetric-Citations70LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (1 MB) Get e-Alerts Get e-Alerts

Optical properties and conformation of pyrimidine nucleosides in solution

A modified empirical rule relating the sign of the long wave-length Cotton effect in the ORD of pyrimidine nucleosides to their conformation is given, and illustrated by means of a novel projection diagram.

Optical properties and conformation of purine nucleosides in solution

The relationship between the sign and magnitude of the long wave-length Cotton effect in the ORD of purine nucleosides and their conformation is illustrated by means of a projection diagram.

Optical rotatory dispersion of nucleic acid derivatives. 8. The conformation of pyrimidine nucleosides in solution.

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTOptical Rotatory Dispersion of Nucleic Acid Derivatives. VIII. The Conformation of Pyrimidine Nucleosides in Solution*T. R. Emerson, R. J. Swan, and Tilo L. V. UlbrichtCite this: Biochemistry 1967, 6, 3, 843–850Publication Date (Print):March 1, 1967Publication History Published online1 May 2002Published inissue 1 March 1967https://doi.org/10.1021/bi00855a026RIGHTS & PERMISSIONSArticle Views108Altmetric-Citations101LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (658 KB) Get e-Alerts Get e-Alerts