Search results for "Nucleoside"

Nucleoside uptake in male germ cells of the polychaeteNereis virens

1997

Summary Uptake of inosine and guanosine was measured in male germ ceils of the polychaete Nereis virens at different stages of development. In spermatogonia I (spg I) and spermatid stages, total inosine uptake at 12°C and ambient concentrations of 100 μmol/1 was relatively low (10–50 nmol·ml of packed cell volume pcv−l·h−1). A rapid increase (150–300 nmol·ml of pcv-1·h−1) was found during transition from spg I to spg II with a subsequent decline to low values (10–30 nmol·ml of pcv−1·h−1) in spermatocyte and spermatid stages. This transient increase may be related to the proliferative activity of spg I stages leading to spg II stages, which increases the demand of purine precursors for nucle…

Metabolite supply in oocytes of Nereis virens: role of nucleosides

1999

Gamete development in Nereis virens and other nereidid polychaetes is organized in a simple way. Follicular tissues are absent and the germ cells develop floating freely in the coelomic fluid, which thus serves as the vehicle for the supply of substances required for oocyte growth. This overview focusses on the role of exogenous purine nucleosides for the growing oocytes. Eleocytes, a coelomic cell type which is proliferated in large amounts at the beginning of sexual maturation, supply purine nucleosides to support nucleic acid synthesis in the oocytes. Eleocytes can store large amounts of purine nucleotides (up to 50 µ mol ml−1 cell vol.) in the form of AMP and ADP. During oogenesis, thes…

Uptake and Metabolism of Purine Nucleosides and Purine Nucleoside Analogues by Cells

1979

Since the discovery of purine nucleotides and purine nucleosides, 1847 by Liebig (1) (inosinic acid) and 1885 by Schulze et al. (2) (guanosine),it was only relatively recently that purine- and purine-nucleoside analogues have been considered to be effective antitumor or antiviral agents. It is due to Prusoff, Schabel and S.S. Cohen that on the other hand pyrimidine nucleoside analogues have already been used clinically as drugs for a number of years.

Synthesis and preliminary biological evaluation of a new pyridocarbazole derivative covalently linked to a thymidine nucleoside as a potential target…

2003

The therapy of human cancer is one of the more pursued goals by medicinal chemistry research. Most of the compounds clinically used as a treatment owe their efficacy to their cytotoxic interaction (direct or indirect) with nuclear DNA. This interaction results in the inhibition of DNA synthesis and the degradation of nucleic strands. Ellipticine is a naturally occurring 6H-pyrido[4,3-b]carbazole alkaloid endowed with antitumor activity, and several ellipticine derivatives have been used in clinical trials. We previously reported some 1,4-dimethyl-9H-carbazole derivatives structurally related to ellipticine. The purpose of our research was to transform the pyridocarbazole in a prodrug so tha…

Partial purification and some properties of a nucleoside phosphotransferase of chick embryos.

1978

A nucleoside phosphotransferase purified about 40fold from chick embryos utilizes efficiently as phosphate donors deoxyribonucleoside and pyrimidine ribonucleoside monophosphates, whereas the pyrimidine deoxyribonucleoside appear to be the preferred acceptors of phosphate. The enzyme is very unstable to heat, dilution and dialysis. A marked enhancement in the stability is caused by nucleotides and it seems associated with the formation of an aggregated state of the protein.

Unified model for the ultrafast decay of pyrimidine nucleobases.

2006

Ultrafast decay processes detected after absorption of UV radiation in gas-phase pyrimidine nucleobases uracil, thymine, and cytosine are ascribed to the barrierless character of the pathway along the low-lying 1(pipi*) hypersurface connecting the Franck-Condon region with an out-of-plane distorted ethene-like conical intersection with the ground state. Longer lifetime decays and low quantum yield emission are on the other hand related to the presence of a 1(pipi*) state planar minimum on the S1 surface and the barriers to access other conical intersections. A unified model for the three systems is established on the basis of accurate multiconfigurational CASPT2 calculations, whereas the ef…

Pseudouridine: Still mysterious, but never a fake (uridine)!

2014

International audience; Pseudouridine () is the most abundant of >150 nucleoside modifications in RNA. Although was discovered as the first modified nucleoside more than half a century ago, neither the enzymatic mechanism of its formation, nor the function of this modification are fully elucidated. We present the consistent picture of synthases, their substrates and their substrate positions in model organisms of all domains of life as it has emerged to date and point out the challenges that remain concerning higher eukaryotes and the elucidation of the enzymatic mechanism.

2014

In the resurging field of RNA modifications, quantification is a bottleneck blocking many exciting avenues. With currently over 150 known nucleoside alterations, detection and quantification methods must encompass multiple modifications for a comprehensive profile. LC–MS/MS approaches offer a perspective for comprehensive parallel quantification of all the various modifications found in total RNA of a given organism. By feeding 13C-glucose as sole carbon source, we have generated a stable isotope-labeled internal standard (SIL-IS) for bacterial RNA, which facilitates relative comparison of all modifications. While conventional SIL-IS approaches require the chemical synthesis of single modif…

MPP1 links the Usher protein network and the Crumbs protein complex in the retina.

2007

Contains fulltext : 53571.pdf (Publisher’s version ) (Closed access) The highly ordered distribution of neurons is an essential feature of a functional mammalian retina. Disruptions in the apico-basal polarity complexes at the outer limiting membrane (OLM) of the retina are associated with retinal patterning defects in vertebrates. We have analyzed the binding repertoire of MPP5/Pals1, a key member of the apico-basal Crumbs polarity complex, that has functionally conserved counterparts in zebrafish (nagie oko) and Drosophila (Stardust). We show that MPP5 interacts with its MAGUK family member MPP1/p55 at the OLM. Mechanistically, this interaction involves heterodimerization of both MAGUK mo…

Purification of nucleoside phosphotransferase from mucosa of chicken intestine

1983

The authors describe the purification procedure and some properties of a nucleoside phosphotransferase obtained from chicken intestinal mucosa, the tissue of which in preliminary studies showed the highest specific activity. Sepharose 6B chromatography and electrophoresis on polyacrylamide gel subdivided the enzyme into many forms which represent various levels of an associated multisubunit protein derived by assembly of a component at lower molecular weight. Nucleotide protectors regulate the equilibrium among these different forms, favoring the production and the stabilization of supramolecular complexes of nucleoside phosphotransferase. Similar results were obtained with enzyme purified …