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Topic: Nucleobase


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In the News (Sat 16 Dec 17)

  
  Purine Nucleobase Transport in Amastigotes of Leishmania mexicana: Involvement in Allopurinol Uptake -- Al-Salabi and ...
Purine Nucleobase Transport in Amastigotes of Leishmania mexicana: Involvement in Allopurinol Uptake
nucleobase transporter that is responsible for the uptake of
A Leishmania major nucleobase transporter responsible for allopurinol uptake is a functional homolog of the Trypanosoma brucei H2 transporter.
aac.asm.org /cgi/content/full/49/9/3682   (3977 words)

  
 TSRI - News and Publications
Alternatively, interaction with a cationic nucleobase might activate the 2´ oxyanion nucleophile, or the nucleobase could act as a general acid to protonate the leaving group during the breaking of 5´ oxygen-phosphorus bonds (Fig.
A cationic nucleobase should contribute electrostatic stabilization to the transition state for both cleavage and ligation reactions, because the transition state is identical in forward and reverse reactions.
In contrast, a nucleobase that contributes general acid catalysis to the cleavage reaction should contribute general base catalysis to ligation as the 5´ oxygen becomes the nucleophile and the 2´ oxygen becomes the leaving group.
www.scripps.edu /news/sr/sr2003/mb0322.html   (663 words)

  
 Functional Differences in Nucleoside and Nucleobase Transporters Expressed on the Rabbit Corneal Epithelial Cell Line ...
Uptake of adenine was inhibited by purine nucleobases but not by the nucleosides or pyrimidine nucleobases and was independent of sodium, energy, and nitrobenzylthioinosine.
Nucleoside and nucleobase transporters on rabbit cornea and corneal epithelial cell line, SIRC, are functionally different, undermining the utility of the SIRC cell line as an in vitro screening tool for elucidating the corneal permeation mechanism of nucleoside analogs.
The observed differences in the nucleoside/ nucleobase transporter types expressed on the isolated rabbit cornea and SIRC cell line may thus be evolutionary in nature or could be the result of cell culture conditions.
www.aapsj.org /view.asp?art=ps050215   (4343 words)

  
 Nucleobase polymers   (Site not responding. Last check: 2007-11-03)
Interestingly, one copper-containing adenylated template displayed a remarkable enzyme-like activity of oxygen insertion between an aromatic C-H bond; an activity reminiscent of hydroxylase/oxidase protein enzymes that catalyze biosynthesis of tyrosine and catecholamines.
We are currently applying the knowledge of nucleobase polymer catalysis to other interesting chemical and biochemical reactions.
The constituent heterocyclic nucleobases are bestowed with suitably predisposed metal ion binding sites, which are invoked for the generation of interesting supramolecular structural paradigms.
home.iitk.ac.in /~sverma/Research.htm   (403 words)

  
 The Scripps Research Institute - Scientific Report 2004
Rescue increased with decreasing pH for both cleavage and the reverse reaction of ligation, arguing against a role for the rescuing nucleobase as a general acid because a nucleobase that contributes general acid catalysis in the cleavage pathway should provide general base catalysis in ligation.
Analysis of the concentration dependence of nucleobase rescue at high and low pH indicated that protonation promotes catalysis within the nucleobase-bound ribozyme complex but does not stabilize nucleobase binding in the ground state.
The exogenous nucleobase stacks between A7 and A9 in the pocket left by the G8 deletion, restoring active-site architecture.
www.scripps.edu /news/sr/sr2004/mb04fedor.html   (742 words)

  
 Stereoselective glycosylation process for preparing 2'-deoxy-2',2'-difluoropurine and triazole nucleosides - Patent ...
The protecting groups are attached to the nucleobase derivative (R") before it is reacted with the alpha-anomer enriched carbohydrate of formulas II and V and are removed subsequent thereto.
Preferred amino protecting groups (W) for purine nucleobase derivatives are selected from the group consisting of alkylcarbonyls, haloalkylcarbonyls and arylcarbonyls such as pivaloyl, trifluoroacetyl, naphthoyl, formyl and acetyl.
This makes the nucleobase derivative more aromatic and enhances the reactivity of the nucleobase derivative with the alpha-anomer enriched carbohydrate of formulas II and V. It is most convenient to enolize the keto oxygens and provide silyl protecting groups for them.
www.freepatentsonline.com /5821357.html   (6293 words)

  
 Berry & Associates, Inc.
The hydrogen bonding pattern of the 2-aminopurine nucleobase (N1 acceptor, H-N2 donor) is isomeric with that of adenosine (N1 acceptor, H-N6 donor).
The 2'-deoxyribonucleoside phosphoramidite 8-Aza-7-deaza-dA CEP, also known as PPA CEP, features a nucleobase that is isosteric with adenine but offers a different pi-electron distribution and thus an altered dipole moment, resulting in stronger stacking interactions in oligonucleotides.
The uracil nucleobase is identical to that found in uridine except that it is attached to the ribose ring via C5 rather than N1, i.e., it is a C-nucleoside.
www.berryassoc.com   (2762 words)

  
 Functional and Molecular Characterization of Nucleobase Transport by Recombinant Human and Rat Equilibrative Nucleoside ...
Inhibition of hypoxanthine uptake by nucleobases, nucleosides, NBMPR, and dipyridamole.
NBMPR and Dipyridamole Inhibition of Nucleobase Transport by Recombinant hENT2-- Uridine transport by recombinant hENT2 produced in oocytes is inhibited by NBMPR and dipyridamole in the micromolar concentration
Kinetic parameters calculated from the mediated component of transport (uptake in RNA-injected oocytes minus uptake in oocytes injected with water alone) are presented in Table I.
www.jbc.org /cgi/content/full/277/28/24938   (6228 words)

  
 2002 Molecular Parasitology Meeting: Abstract Book Online   (Site not responding. Last check: 2007-11-03)
All Kinetoplastid parasites studied to date are unable to synthesize purines de novo and rely on purine nucleobase and nucleoside acquisition across the parasite plasma membrane by specific permeases.
Together these results demonstrate that LmNT3 is a new member of the ENT family with primary affinity for nucleobases and is likely to play a major role in purine nucleobase incorporation in Leishmania.
These results also suggest that nucleobase transporters in kinetoplastid parasites are unrelated to any of the three families of classical nucleobase transporters that have been identified previously in bacteria, fungi, and plants.
www.mbl.edu /mpm/mpm-2002/abstracts/abstract.php?id=77   (231 words)

  
 NWO - Template Polymer Architectures, Based on Nucleobase Interactions   (Site not responding. Last check: 2007-11-03)
When ATRP of thymine monomers, using cytosine-functional initiators is performed in the presence of this template, complexation of the complementary nucleobases will result in copying the template characteristics onto the newly formed polymer.
Other effects that will be investigated are spacer length between backbone and nucleobase, and different types of backbones.
The combination of template design, the availability of all 4 nucleobase monomers and the use of ATRP as polymerization technique will create the optimal conditions for the occurrence of template polymerization.
www.nwo.nl /projecten.nsf/pages/1600113094   (371 words)

  
 [No title]
The pyrimidine nucleobases uracil and cytosine are particularly attractive candidates for modification in PNA because of the wealth of established chemistry for them.
Another facile route to nucleobase modification that we have pursued is via the cross-coupling between terminal alkynes and a halogenated nucleobase, either uracil or cytosine.
We have found that the luminescent properties of these compounds varies with the nature of the substituent on the 5-membered ring ("R") and are currently investigating their use as DNA probes.
publish.uwo.ca /~rhhudson/Research.htm   (708 words)

  
 OhioLINK ETD: Sivakova, Sona
The use of protected rather than natural nucleobases allows for additional structural control to be built into the systems.
We have prepared a series of supramolecular telechelic monomers, where nucleobase derivatives were attached to the ends of a variety of cores.
A dramatic increase in melting temperature occurred upon attachment of a terminal nucleobase compared to unfunctionalized polytetrahydrofurans.
www.ohiolink.edu /etd/view.cgi?case1112726513   (380 words)

  
 Triple-stranded DNA - Wikipedia, the free encyclopedia
For example, a nucleobase T binds to a Watson-Crick base-pairing of T-A by Hoogsteen hydrogen bonds between an AxT pair (x represents a Hoogsteen base pair).
In this triplex, a nucleobase A binds to a T-A base pair and a G to a C-G pair.
Since the nucleobases on the third strand have to be reversed, the homopurine third strand is antiparallel to the homopurine strand of the original duplex.
en.wikipedia.org /wiki/Triple-stranded_DNA   (298 words)

  
 Dr. Scott Landfear - Parasitology, Leishmania
This result implies that the nucleobase transporters of these parasites are ENT family members and are not related to other nucleobase transporters previously identified in fungi or plants.
This gene has been expressed in a mutant strain of yeast that is deficient in nucleobase transport and shown to promote uptake of the 4 purine nucleobases.
Overall, these studies have defined for the first time the nucleobase transporters of trypanosomatid protozoa and extended the function of the ENT family of permeases to those that are committed to the uptake of nucleobases.
www.ohsu.edu /microbiology/landfear.html   (3354 words)

  
 Cloning, Heterologous Expression, and in Situ Characterization of the First High Affinity Nucleobase Transporter from a ...
Cloning, Heterologous Expression, and in Situ Characterization of the First High Affinity Nucleobase Transporter from a Protozoan -- Burchmore et al.
of the genes encoding nucleoside and nucleobase transporters.
nucleobase transport capacity of trypanosomes (39) is mediated
www.jbc.org /cgi/content/full/278/26/23502   (3501 words)

  
 ScienceDaily: Environmental Triggers May Promote Human Genetic Variation   (Site not responding. Last check: 2007-11-03)
Human DNA is constantly barraged by a variety of environmental agents, including UV light and chemicals, as well as by reactive oxygen species (ROS), which are produced as byproducts of normal metabolic reactions or as molecular executors of host defense.
These agents may cause the nucleobases in DNA to spontaneously undergo a chemical transformation known as oxidation.
One might intuitively expect the distribution of aberrant 8-oxoG nucleobases to be randomly distributed throughout the genome, but in their new study, Dr. Yusaku Nakabeppu and his colleagues demonstrated otherwise.
www.sciencedaily.com /releases/2006/04/060430225905.htm   (1882 words)

  
 University of the Pacific
The mode of action of these compounds appears to be their interaction with the purine nucleobases of DNA.
An understanding of the reactions using simple nucleobase derivatives such as 9-ethyladenine and 9-ethylguanine is important to understand the coordination chemistry of metals to nucleobases since this is proposed to be the source of anticancer activity of these dimetal systems.
As a result of binding to nucleobases, the metal is able to alter the biological system such that replication is halted and cell death occurs.
www.uop.edu /college/chemistry/eday.htm   (510 words)

  
 Characterization of novel Na+-dependent nucleobase transport systems at the blood-testis barrier -- Kato et al. 290 ...
Characterization of novel Na+-dependent nucleobase transport systems at the blood-testis barrier -- Kato et al.
In the testis, nucleosides and nucleobases are important substrates
nucleobases, whereas uracil uptake was inhibited only by pyrimidine
ajpendo.physiology.org /cgi/content/abstract/290/5/E968   (273 words)

  
 Artificially expanded genetic information system: a new base pair with an alternative hydrogen bonding pattern -- Yang ...
complementary nucleobases, from the major to the minor groove).
nucleobase heterocycles is not required during the synthesis
The data in Table 2 indicate that a dZ:dP nucleobase pair is
nar.oxfordjournals.org /cgi/content/full/34/21/6095   (3712 words)

  
 substitution1
By contrast, the presence of strong nucleophiles [ e.g.
sulfur-containing (bio)molecules] facilitates the dissociation of N-bound nucleobases from the Pt coordination sphere.
In this work we explore the factors controlling the dissociation of different Pt-nucleobase complexes in aqueous solution in the presence of various nucleophiles giving special emphasis on the mechanism of the substitution reactions.
users.utu.fi /arpalah/substitution1.htm   (132 words)

  
 Organic and Biomolecular Chemistry Articles   (Site not responding. Last check: 2007-11-03)
unit) of a nucleobase in a nucleotide can be modulated by the chemical nature of the 2
-bis-ethylphosphates (Table 1) are well correlated with the change in dipole moment for the respective nucleobases after protonation or de-protonation.
-modified duplexes in the antisense, siRNA or in triplexes by many workers in the field, is a result of alteration of the pseudoaromatic character of the nucleobases engineered by alteration of the chemical nature of the 2
www.rsc.org /Publishing/Journals/OB/article.asp?doi=b601460g   (316 words)

  
 Substituent effects on the pairing and polymerase recognition of simple unnatural base pairs -- Hwang and Romesberg 34 ...
as nucleobase analogs for simplicity.) We have systematically
The unnatural nucleobases were evaluated as substrates for Kf by measuring initial rates at which a [
The parental benzene scaffold is the smallest nucleobase
nar.oxfordjournals.org /cgi/content/full/34/7/2037   (4588 words)

  
 Bioinorganic Chemistry Special Feature: Canonical and unconventional pairing schemes between bis(nucleobase) complexes ...
Bioinorganic Chemistry Special Feature: Canonical and unconventional pairing schemes between bis(nucleobase) complexes of trans-a2PtII: Artificial nucleobase quartets and CH...N bonds -- Freisinger et al.
between aromatic protons of nucleobases and endocyclic N atoms
nucleobases exist that pair through two cyclic H bonds each
www.pnas.org /cgi/content/full/100/7/3748   (3140 words)

  
 Molecular studies of nucleoside and nucleobase transport proteins
Both hENT1 and hENT2 transport a broad range of purine and pyrimidine nucleosides, while hENT2 is also capable of transporting nucleobases.
These proteins turned out to be members of a novel family that we have designated the equilibrative nucleoside transporter (ENT) family.
Expression of PfENT1 in Xenopus oocytes showed that it was indeed a transporter, catalysing the saturable uptake of a wide range of both nucleosides and nucleobases.
www.astbury.leeds.ac.uk /Report/2000/Baldwin.2.htm   (867 words)

  
 e-Polymers   (Site not responding. Last check: 2007-11-03)
However, this polymerization technique is uncontrolled and therefore not ideal for use with template polymerizations.
This research intends to use Watson-Crick base pairing for, supramolecular interactions between complementary nucleobase functionalized telechelic polymers and intends to use ATRP as a polymerization technique for nucleobase directed template polymerization.
A versatile synthetic route has been developed to achieve all four nucleobase-functionalized monomers, which have been polymerized using ATRP in DMSO as a solvent.
www.e-polymers.org /abstract_shw.cfm?Abstract_id=330   (299 words)

  
 V E R Ö F F E N T L I C H U N G S V E R Z E I C H N I S   (Site not responding. Last check: 2007-11-03)
"Transition Metal Complexes of Pyrimidine Nucleobases and their Derivatives", B. Lippert in "Handbook of Nucleobase Complexes", Volume I, J. Lusty (Ed.), CRC Press, Boca Raton, 9 - 46 (1990).
"A Model Compound for the Interaction of Thallium(I) with Nucleobases: Crystal and Molecular Structure of (Nitrato)(1-methylcytosine)thallium(I)", O. Renn, H. Preut, B. Lippert, Inorg.
On the Possible Structural Role of Aqua Ligands in Metal-Modified Nucleobase Pairs", S. Menzer, M. Sabat, B. Lippert, J. Am.
www.chemie.uni-dortmund.de /groups/lippert/publications.html   (3081 words)

  
 Application of the Mars Organic Analyzer to Nucleobase and Amine Biomarker Detection | SpaceRef - Space News as it ...
The Mars Organic Analyzer (MOA), a portable microfabricated capillary electrophoresis instrument being developed for planetary exploration, is used to analyze a wide variety of fluorescamine-labeled amine-containing biomarker compounds, including amino acids, mono and diaminoalkanes, amino sugars, nucleobases, and nucleobase degradation products.
The nucleobases cytosine and adenine, which contain an exocyclic primary amine, were effectively labeled, separated, and detected at concentrations
To test the general applicability of the MOA for biomarker detection, amino acids and mono- and diamines were extracted from bacterial cells using both hydrolysis and sublimation followed by analysis.
www.spaceref.com /news/viewsr.html?pid=22755   (783 words)

  
 Nucleus
/ cell growth and/or maintenance => metabolism => nucleobase, nucleoside, nucleotide metabolism
/ cell growth and/or maintenance => metabolism => nucleobase, nucleoside, nucleotid=> transcription
/ cell growth and/or maintenance => metabolism => nucleobase, nucleoside, nucleotid=> transcription => transcription, DNA-dependent G=> transcription, from Pol III promoter
www.biostat.harvard.edu /complab/SP/nuc-predictions.htm   (1049 words)

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