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PubMed1980

NMR studies in the syn-anti dynamic equilibrium in purine nucleosides and nucleotides.

The syn in equilibrium anti equilibrium conformation about the glycosidic bond of purine nucleosides and 5'-nucleotides in different solvent systems has been investigated by means of 1H NMR spectroscopy. Quantitative values for the conformer populations were improved, relative to previous results, by a detailed study of, and a resultant derived correction for, the influence of the sugar exocyclic group conformation on the chemical shifts of the sugar ring protons. This was achieved with the aid of nucleosides and nucleotides fixed in the conformations gauche-trans [derivatives of 8,5'-(R)-cyclo] and trans-gauche [derivatives of 8,5'-(S)-cyclo]. The results of 13C NMR confirmed those obtained by 1H NMR. The measured values of the vicinal coupling constants between H-1' and the C-8 and C-4 carbons were employed to evaluate approximately the glycosidic angles chi of the nucleosides in the conformations syn and anti. A critical examination is made of the applicability of relaxation methods, involving analysis of spin-lattice relaxation time of protons (T1) and the Overhauser effect, to determine the conformation of the base about the glycosidic bond; interpretations are provided for the lack of agreement between these methods and those based on chemical shifts in the present study. The foregoing resuls are also applied to an examination of the effect of the conformation of the base about the glycosidic bond on the enzymatic reactions catalyzed by 5'-nucleotidase and adenosine deaminase.

Adenosine↗
PubMed2002

Roles of nucleosides and nucleotide mixture in small bowel transplantation.

OBJECTIVES: We investigated the effect of nucleosides (NSs) and nucleotides (NTs) on the intestine and intestinal graft in a model of syngenic small bowel transplantation, with the fetal rat intestine as a graft. METHODS: Two-centimeter jejunal segments from Lewis rats at 19 d of gestation were transplanted into the abdominal walls of 5-wk-old Lewis rats by using a non-vascular anastomotic technique. After transplantation, the rats were assigned to one of two groups: group 1 did not receive NS or NT and group 2 was supplemented with NS and NT. The grafts and graft recipients were examined morphologically 14 d after transplantation according to conventional histologic and immunohistochemical studies of neurons and smooth muscles. RESULTS: Group 1 gained little body weight, even though both groups received similar amounts of food. The grafts in group 1 showed poor development in length, diameter, and wet weight. They also showed poor villi development, abnormalities in nerve distribution, and degeneration of muscle layer structure on histologic and immunohistochemical studies. CONCLUSIONS: We found that NS and NT are essential nutrients for intestinal growth and maintenance of structures in fetal small bowel transplantation.

Animals↗
PubMed2000

Pharmacology of nucleoside and nucleotide reverse transcriptase inhibitor-induced mitochondrial toxicity.

OBJECTIVE: This paper reviews the function of the mitochondria and the mechanisms by which nucleoside and nucleotide reverse transcriptase inhibitors (NRTIs) cause mitochondrial toxicity. BACKGROUND: Highly active antiretroviral therapy (HAART) reduces rates of morbidity and mortality due to HIV disease. However, long-term treatment with these drugs may be associated with adverse effects. Nucleoside and nucleotide analogues are potent inhibitors of HIV reverse transcriptase and have become the cornerstone of HAART. Unfortunately, these drugs have also been shown to inhibit cellular polymerases, most notably mitochondrial DNA polymerase gamma. RESULTS: Studies of the NRTIs in enzyme assays and cell cultures demonstrate the following hierarchy of mitochondrial DNA polymerase gamma inhibition: zalcitabine > didanosine > stavudine > lamivudine > zidovudine > abacavir. In vitro investigations have also documented impairment of the mitochondrial enzymes adenylate kinase and the adenosine diphosphate/adenosine triphosphate translocator. Inhibition of DNA polymerase gamma and other mitochondrial enzymes can gradually lead to mitochondrial dysfunction and cellular toxicity. The clinical manifestations of NRTI-induced mitochondrial toxicity resemble those of inherited mitochondrial diseases (ie, hepatic steatosis, lactic acidosis, myopathy, nephrotoxicity, peripheral neuropathy, and pancreatitis). Fat redistribution syndrome, or HIV-associated lipodystrophy, is another side effect attributed in part to NRTI therapy. The morphologic and metabolic complications of this syndrome are similar to those of the mitochondrial disorder known as multiple symmetric lipomatosis: suggesting that this too may be related to mitochondrial toxicity. The pathophysiology of less common adverse effects of nucleoside analogue therapy, such as diabetes, ototoxicity, and retinal lesions, may be related to mitochondrial dysfunction but have not been adequately studied. CONCLUSION: NRTls can block both HIV reverse transcriptase and mitochondrial DNA polymerase gamma. Inhibition of the latter enzyme is the most likely cause of the adverse effects associated with these drugs.

Animals↗
PubMedDate not supplied

PROSIT: pseudo-rotational online service and interactive tool, applied to a conformational survey of nucleosides and nucleotides.

A Pseudo-Rotational Online Service and Interactive Tool (PROSIT) designed to perform complete pseudorotational analysis of nucleosides and nucleotides is described. This service is freely available at http://cactus.nci.nih.gov/prosit/. Files containing nucleosides/nucleotides or DNA/RNA segments, isolated or bound to other molecules (e.g., a protein) can be uploaded to be processed by PROSIT. The service outputs the pseudorotational phase angle P, puckering amplitude numax, and other related information for each nucleoside/nucleotide detected. The service was implemented using the chemoinformatics toolkit CACTVS. PROSIT was used for a survey of nucleosides contained in the Cambridge Structural Database and nucleotides in high-resolution crystal structures from the Nucleic Acid Database. Special cases discussed include nucleosides having constrained sugar moieties with extreme puckering amplitudes, and several specific DNA/RNA helices and protein-bound DNA oligonucleotides (Dickerson-Drew dodecamer, RNA/DNA hybrid viral polypurine tract, Z-DNA enantiomers, B-DNA containing (L)-alpha-threofuranosyl nucleotides, TATA-box binding protein/TATA-box complex, and DNA (cytosine C5)-methyltransferase complexed with an oligodeoxyribonucleotide containing transition state analogue 5,6-dihydro-5-azacytosine). When the puckering amplitude decreases to a small value, the sugar becomes increasingly planar, thus reducing the significance of the phase angle P. We introduce the term "central conformation" to describe this part of the pseudorotational hyperspace in contrast to the conventional north and south conformations.

Nucleic Acid Conformation↗
PubMed1984

Antibodies to guanylic acid: fractionation and specificities.

Guanylic-acid-specific antibodies were elicited in rabbits, using as immunogen pG linked through 5'-phosphate to thyroglobulin. Specificity and affinity of antibodies to nucleotides, nucleosides, DNA, and RNA were studied by their binding to radioactive ligands and competition experiments. Guanylic-acid-specific antibodies do not bind to deoxyguanylic acid and have an average association constant of 10(7) M-1 at 4 degrees C. Binding of the antibodies to 3H-RNA is G-specific. The antibodies do not bind to 32P-ssDNA or 32P-dsDNA. The pG-specific antibodies could be separated into different fractions by affinity chromatography. These fractions, though specific to pG, differ in their cross-reactivities to nucleosides and nucleotides.

Animals↗
PubMed1985

Chromatographic separation as selection process for prebiotic evolution and the origin of the genetic code.

A model for the evolution of a translation apparatus has been suggested where oligonucleotides in a hairpin conformation act as primordial adapters. Specifically activated amino acids are assumed to be attached to these hairpin molecules. For the specific activation, a chromatographic separation of, e.g. ala and CMP from gly and GMP can be accomplished on silica (e.g. of volcanic origin) with aqueous salt solutions. Other adsorbents like clays (kaolin, bentonite, montmorillonite), different silicates (florisil, magnesium trisilicate, calcium silicate, talc), hydroxyapatite, barium sulfate, calcium carbonate, calcium fluoride and titanoxide have been examined as model systems for the separation of nucleotides, nucleosides and amino acids on mineral surfaces. The possible role of chromatographic separation of amino acids for the formation of proteinoids, composed of selected amino acids, is also considered.

Amino Acids↗
PubMed1990

Phosphorescence of nucleic acids and DNA components at 77 K.

The emission spectra of nucleic acids, pyrimidine and purine nucleotides, nucleosides and bases and a series of pyrimidine derivatives were obtained using UV light excitation in glasses (ethanol and 2:1 mixtures of ethylene glycol and water (EG-H2O); also partly in butyronitrile and 2-methyltetrahydrofuran) at 77 K. The quantum yields of fluorescence phi f and phosphorescence phi p of some 30 compounds are presented; for several substituted uracils they are reported for the first time. The values cover a range from phi f = 0.0002 and phi p = 0.001 for uracil in ethanol to phi f = 0.50 for guanosine in acidic ethanol and phi p = 0.095 for guanosine-5'-monophosphate in EG-H2O (pH 6-7). The phosphorescence lifetime tau p at 77 K ranges from about 0.3 s (uracil moiety) to 3 s (adenine moiety). The measured tau p, phi f and phi p values are compared with those available in the literature.

DNA↗
PubMed2006

Stereochemical and regiochemical trends in the selective detection of saccharides.

Several discreet sugar-boronate complexes exist in solution. This is due to the complex equilibria between isomeric species of even the simplest monosaccharides. In the current investigation, we determine the regio- and stereochemical features of the various equilibrating sugar isomers that induce signal transduction in boronic acid chemosensors such as 1 as well as 2 and 3. We present a unique example of a chemosensor (1) that is selective for ribose, adenosine, nucleotides, nucleosides, and congeners. As a result of this study, we are able to predict and achieve selective fluorescence and colorimetric responses to specific disaccharides as a consequence of their terminal sugar residue linkage patterns and configurations. We also find that the combined use of chemosensors exhibiting complementary reactivities may be used cooperatively to obtain enhanced selectivity for ribose and rare saccharides.

Adenosine↗
PubMed1995

Cerebrospinal fluid purine metabolites and pyrimidine bases after brief febrile convulsions.

Adenosine monophosphate, inosine monophosphate, inosine, adenosine, guanosine, adenine, guanine, hypoxanthine, xanthine, uric acid, and pyrimidines bases were determined in cerebrospinal fluid (CSF) of 52 children after simple febrile seizures and in a control group of 63 children. There was no statistically significant difference between the two groups for any of these metabolites, suggesting that simple febrile seizures (SFS) neither significantly disturb the metabolism of nucleotides, nucleosides, or bases nor significantly deplete neuron adenosine ATP levels. Therefore, they do not appear to constitute a threat of neuronal damage.

Child, Preschool↗
PubMed1987

Depressor and pressor actions of purine nucleosides and nucleotides in the anaesthetized rat.

In pentobarbitone-chloralose anaesthetized rats, the effects of aortic administration of various purine compounds on systemic arterial pressure were investigated. All animals were pretreated with atropine and guanethidine to (largely) eliminate reflex neurogenic cardiovascular adjustments, and drugs influencing purine receptors, prostaglandin synthesis, etc. were used for analytical purposes. The compounds used were adenosine (AD) and its slowly degradable analogue, 2-chloroadenosine (2-chloro), adenosine-5'-triphosphate (ATP) and its slowly degradable analogues beta, gamma-methyleneATP (beta,gamma-meATP) and alpha,beta-methyleneATP (alpha,beta-meATP). Control cardiac output measurements before, at and after the peak pressure changes in some experiments revealed that they were at least 80% due to changes in systemic resistance, i.e. dominated by shifts in resistance vascular tone. Adenosine, 2-chloro, ATP and beta,gamma-meATP all elicited depressor (vasodilator) responses. 2-chloro was more potent than AD. Furthermore, the results suggest that the depressor action of ATP involves P1-purinoceptors, following the rapid degradation of ATP to AD, and probably also other mechanisms. The stable ATP analogues caused prompt pressor (vasoconstrictor) responses, where alpha,beta-meATP was more potent than beta,gamma-meATP. The latter compound also produced delayed (probably P1-purinoceptormediated) depressor actions, presumably via slow degradation to AD.

2-Chloroadenosine↗