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At least 145 records · Page 8Linked to original sources
PubMed1980

The influence of some pterins on the circadian rhythmicity of hydroxyindole-O-methyl transferase in the pineal gland of 42-day old male Wistar rats.

The influence of three pterin derivatives on the diurnal fluctuations of HIOMT (hydroxyindole-O-methyl transferase) activity was studied in the isolated pineal glands of 42-day old male Wistar rats during the month of October. The method used permitted the separate determination of four HIOMT activities. --Reduced neopterin stimulated the methylation of the substances, 5-HTP, 5-HT and 5-HIAA (see abbreviations in Material and methods), during the night. HIOMT action on the combinations N-Ac-5-HT/5-HTL was shifted to a later moment in the dark period. --Pterin-6-aldehyde stimulated HIOMT action on 5-HT during the daytime. HIOMT action on the substrates 5-HTP, 5-HIAA and N-Ac-5-HT/5-HTL was shifted towards an earlier period. --Isoxanthopterin did not exert any influence on diurnal variation in the four HIOMT activities. It may be concluded that reduced neopterin and pterin-6-aldehyde influenced the activity and the circadian rhythmicity of 5-methoxyindole synthesis. Those alterations might be important in the regulation of reproduction.

5-Hydroxytryptophan↗
PubMed1995

Incorporation of a fluorescent guanosine analog into oligonucleotides and its application to a real time assay for the HIV-1 integrase 3'-processing reaction.

We have synthesized a highly fluorescent (quantum yield 0.88) guanosine analog, (3-methyl-8-(2-deoxy-beta-D-ribofuranosyl) isoxanthopterin (3-Mi) in a dimethoxytrityl, phosphoramidite protected form, which can be site-specifically inserted into oligonucleotides through a 3',5'-phosphodiester linkage using an automated DNA synthesizer. Fluorescence is partially quenched within an oligonucleotide and the degree of quench is a function of the fluorophore's proximity to purines and its position in the oligonucleotide. As an example of the potential utility of this class of fluorophores, we developed a continuous assay for HIV-1 integrase 3'-processing reaction by incorporating 3-MI at the cleavage site in a double-stranded oligonucleotide identical to the U5 terminal sequence of the HIV genome. Integrase cleaves the 3'-terminal dinucleotide containing the fluorophore, resulting in an increase in fluorescence which can be monitored on a spectrofluorometer. Substitution of the fluorophore for guanosine at the cleavage site does not inhibit integrase activity. This assay is specific for the 3'-processing reaction. The change in fluorescence intensity is linear over time and proportional to the rate of the reaction. This assay demonstrates the potential utility of this new class of fluorophore for continuous monitoring of protein/DNA interactions.

Base Sequence↗
PubMed2004

Formation of an intramolecular triple-stranded DNA structure monitored by fluorescence of 2-aminopurine or 6-methylisoxanthopterin.

The parallel (recombination) 'R-triplex' can accommodate any nucleotide sequence with the two identical DNA strands in parallel orientation. We have studied oligonucleotides able to fold back into such a recombination-like structure. We show that the fluorescent base analogs 2-aminopurine (2AP) and 6-methylisoxanthopterin (6MI) can be used as structural probes for monitoring the integrity of the triple-stranded conformation and for deriving the thermodynamic characteristics of these structures. A single adenine or guanine base in the third strand of the triplex-forming and the control oligonucleotides, as well as in the double-stranded (ds) and single-stranded (ss) reference molecules, was substituted with 2AP or 6MI. The 2AP*(T.A) and 6MI*(C.G) triplets were monitored by their fluorescence emission and the thermal denaturation curves were analyzed with a quasi-two-state model. The fluorescence of 2AP introduced into an oligonucleotide sequence unable to form a triplex served as a negative control. We observed a remarkable similarity between the thermodynamic parameters derived from melting of the secondary structures monitored through absorption of all bases at 260 nm or from fluorescence of the single base analog. The similarity suggests that fluorescence of the 2AP and 6MI base analogs may be used to monitor the structural disposition of the third strand. We consider the data in the light of alternative 'branch migration' and 'strand exchange' structures and discuss why these are less likely than the R-type triplex.

2-Aminopurine↗
PubMed2004

Use of pteridine nucleoside analogs as hybridization probes.

The pteridine nucleoside analog 3-methyl isoxanthopterin (3-MI) is highly fluorescent, with a quantum yield of 0.88, and it can be synthesized as a phosphoramidite and incorporated into oligonucleotides through a deoxyribose linkage. Within an oligonucleotide, 3-MI is intimately associated with native bases and its fluorescence is variably quenched in a sequence-dependent manner. Bend ing, annealing, binding, digestion or cleavage of fluorophore-containing oligonucleotides can be detected by monitoring changes in fluorescence properties. We developed a single step method for detecting annealing of complementary DNA sequences using 3-MI-containing oligonucleotides as hybridization probes. One of the complementary strands contains the fluorophore as an insertion and when annealing occurs, the fluorophore bulges out from the double strand, resulting in increased fluorescence intensity. We have examined the sequence dependency, optimal strand length and impact of multiple fluorophores per strand in terms of brightness and impact on the annealing process. We describe the application of this technique to the detection of positive PCR products using an HIV-1 detection system. This sequence-dependent hybridization technique can result in fluorescence intensity increases of up to 27-fold. Fluorescence intensity increases are only seen upon specific binding to bulge-generating complements, removing issues of high background from non-specific binding.

Fluorescence↗
PubMed1991

Concentrations and patterns of released pterins of various animal cell cultures.

Neopterin, biopterin, pterin, 6-hydroxymethylpterin and isoxanthopterin were determined in the supernatants of various animal cell cultures. The different cell lines showed distinct variations in the concentrations as well as in the pattern and total amount of the released pterins. In cells from the same organ but from diverse species differences in pattern and release were found. Cell lines derived from primates had a high release of neopterin. A further difference resulted from the origin of fetal or adult organs. Neoplastic cell lines showed different patterns of pterins, dependent on the type of tumour. Primary cultures from embryonic bovine lung had the highest total amount of released pterins in all cell lines examined.

Animals↗
PubMedDate not supplied

Multiphoton excitation of fluorescent DNA base analogs.

Multiphoton excitation was used to investigate properties of the fluorescent DNA base analogs, 2-aminopurine (2AP) and 6-methylisoxanthopterin (6MI). 2-aminopurine, a fluorescent analog of adenine, was excited by three-photon absorption. Fluorescence correlation measurements were attempted to evaluate the feasibility of using three-photon excitation of 2AP for DNA-protein interaction studies. However, high excitation power and long integration times needed to acquire high signal-to-noise fluorescence correlation curves render three-photon excitation FCS of 2AP not very useful for studying DNA base dynamics. The fluorescence properties of 6-methylisoxanthopterin, a guanine analog, were investigated using two-photon excitation. The two-photon absorption cross-section of 6MI was estimated to be about 2.5 x 10(-50) cm(4)s (2.5 GM units) at 700 nm. The two-photon excitation spectrum was measured in the spectral region from 700 to 780 nm; in this region the shape of the two-photon excitation spectrum is very similar to the shape of single-photon excitation spectrum in the near-UV spectral region. Two-photon excitation of 6MI is suitable for fluorescence correlation measurements. Such measurements can be used to study DNA base dynamics and DNA-protein interactions over a broad range of time scales.

2-Aminopurine↗
PubMed1997

Inhalation of the nitric oxide synthase cofactor tetrahydrobiopterin in healthy volunteers.

Pulmonary endothelial dysfunction is the hallmark of acute lung injury. Impaired pulmonary endothelial nitric oxide (NO) production in this event has been described. Tetrahydrobiopterin (BH4) is an essential cofactor for NO synthase and modulator of its activity. At high local concentrations, BH4 provokes local vasodilation in vivo in healthy individuals. At lower concentrations, BH4 selectively and locally restores disturbed NO-dependent vasodilation in patients with endothelial dysfunction. In this preliminary study, we therefore investigated the feasibility of BH4 inhalation in five healthy human volunteers. Inhalation of buffered, aqueous BH4-dihydrochloride solution was well tolerated; despite the buffer, BH4 stability was completely preserved. Resorption of inhaled BH4 was demonstrated by significantly increased BH4 levels in plasma and urine. Inhaled BH4 did not alter pulmonary function and had no effect on systemic hemodynamic values. Our data demonstrate that inhalation is a novel method for local BH4 administration, offering a basic therapeutic tool for investigation of restoration of impaired NO-dependent vasodilation due to pulmonary endothelial dysfunction.

Administration, Inhalation↗
PubMed1987

Chemotaxis towards pteridines during development of Dictyostelium.

Following a previous study indicating a sensitivity to folate during the developmental phase of Dictyostelium discoideum, a series of pteridines were investigated for their ability to induce amoebal chemotaxis during development of this organism. Several compounds were found to resemble folate in their ability to induce chemotaxis of both vegetative amoebae and amoebae developing during the first few hours of starvation. One compound, L-monapterin, was distinct in showing chemotactic activity only during the developmental phase after approximately 12 h of starvation. Tests using the polymerization of cytoskeletal actin as an assay for a cellular response correlated with chemotaxis showed that 10 nM-L-monapterin was a potent inducer of this response and that responsiveness appeared only after 12 h of development. The timing of these events may be correlated with the formation of tips containing stalk cells that occurs in multicellular aggregates at approximately 12 h, and suggests a role for L-monapterin (or a naturally occurring, closely related pteridine) in cell sorting. The evolutionary significance of the roles of pteridines is discussed.

Actins↗