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PubMed1976

On the structure of the cofactor in the complex formed with thymidylate synthetase, 5,10-methylenetetrahy-drofolate and 5-fluoro-2'-deoxyuridylate.

A study was undertaken to ascertain whether dihydrofolic acid is produced in the complex formed with 5,10-methylenetetrahydrofolate, 5-fluorodeoxyuridylate and thymidylate synthetase, as suggested by ultraviolet difference spectral studies. The complex was formed using the cofactor specifically labeled with tritium at the 6-position. After dissociation by equilibration with unlabeled cofactor, it was demonstrated that the tritium remained exclusively at the 6-position. Had oxidation of the cofactor occurred within the complex to give a methylated enzyme form, tritium should have been transferred to the one-carbon unit of the cofactor. It was also found that the difference spectrum of the ternary complex which resembles that of dihydrofolic acid can also be produced by substituting an analog of the cofactor which is not susceptible to oxidation. The results described here demonstrate that oxidation of the cofactor does not occur in the ternary complex and suggest that the unusual ultraviolet spectrum results from perturbations of a chromophore of the bound cofactor.

Fluorodeoxyuridylate↗
PubMed1991

Determination of a guanosine-malonaldehyde adduct in urine by high-performance liquid chromatography with a thiobarbituric acid reaction detector.

A new method for the determination of a guanosine-malonaldehyde adduct, beta-D-ribofuranosylpyrimido[1,2-a]purin-10(3H)-one (GMA), in rat and human urine is described. The method involves rapid pretreatment using, in sequence, polyamide, ion-exchange and reversed-phase cartridges; determination is by means of high-performance liquid chromatography with a thiobarbituric acid reactor in series with a fluorescence detector. This device can quantitatively determine the adduct at the sub-picomole level. This rapid, selective and sensitive method is suitable for the determination of guanine-malonaldehyde adducts in biological samples, such as human and rat urine. A semi-preparative method for the extraction and purification of these adducts from rat urine and for their identification by mass spectrometry and high-performance liquid chromatography with ultraviolet detection is also reported.

Animals↗
PubMed1993

Quantitative analysis of phosphorothioate oligonucleotides in biological fluids using fast anion-exchange chromatography.

Phosphorothioate oligonucleotides are potentially useful as anti-viral drugs. Classical DNA extraction methods are not as effective on short single-stranded DNA as with longer double-stranced chains. The classical method of phenol-chloroform extraction followed by ethanol precipitation is difficult to quantify, thus monitoring of the pharmacological disposition of these compounds is subject to error. A method has been devised and validated for extraction and analysis of modified oligonucleotides from biological fluids such as urine and serum based on protein kinase digestion and phenol-chloroform extraction. Due to the high native ultraviolet absorbance of the oligomers, detection limits in the low ppb range were obtained without derivatization.

Chromatography, Ion Exchange↗
PubMed1991

Imaging Jupiter's aurorae from H3+ emissions in the 3-4 micrometers band.

Since H3+ was first spectroscopically detected on Jupiter, there has been considerable interest in using this simple molecular ion to probe conditions existing in the planet's auroral regions. Here we present a series of images of Jupiter recorded at wavelengths sensitive to emission by H3+, which reveal the spatial distribution of excited H3+ molecular ions in the jovian ionosphere, as seen from Earth. We believe that they provide high-spatial-resolution images of polar aurorae on Jupiter. They suggest that the intensity of the auroral emission can vary on a timescale of an hour, a shorter period than had previously been noted. We also find that the spatial distribution of H3+ emissions correlates only partially with the loci of auroral activity inferred from ultraviolet and longer-wavelength infrared observations. The H3+ emission may therefore be controlled by auroral processes that are different from those responsible for the ultraviolet and infrared emissions.

Astronomical Phenomena↗
PubMed2001

[Study on the reaction mechanism and application of eldest amine basic dye with nitrite].

In this paper, the reaction of eldest amine basic dye with nitrite in hydrochloric acid medium by ultraviolet-visible spectrometry, electrochemistry analysis, Fourier transform infrared spectrometer and nuclear magnetic resonance was studied systematically. The reaction of its structure and effect was preliminarily understood. It is realized that there is diazotization-coupling or diazo-reaction mechanism, generating triazene or diazo-compound. It has magnificent meaning for perfecting, applying this kind of basic dye and instituting a ultraviolet-visible spectrometry or electrochemistry analysis new method of measuring nitrite.

Amines↗
PubMed2000

[Data processing for interferogram of ultraviolet Fourier transform spectrometer].

The method of data processing for interferogram is described in this paper. The interferogram of a mercury lamp has been measured in experiment by means of ultraviolet Fourier Transform Spectrometer in developing. The apodization function that we have chosen is four-term Blackman-Harris window function and a fitting polynomial has been used for phase correction of Fourier Transform spectra based on the least square method. The ultraviolet emission lines of high precision have been obtained by use of this method.

Electronic Data Processing↗
PubMed2004

A calibrated gray scale for forensic ultraviolet photography.

The human eye is an important tool for observing evidence, and visual evidence in turn may be documented onto a photographic medium. The human eye is generally sensitive only to a narrow band of the electromagnetic spectrum from about 700 nm (red) to about 400 nm (violet/blue). It is possible to extend the range of radiations over which evidence may be documented by using the natural ultraviolet sensitivity of photographic films. However, photographing evidence with ultraviolet radiation ultimately involves presenting the information to subjects who may have no prior experience at viewing these wavelengths. This study shows that it is necessary to use a calibrated ultraviolet reflecting gray scale to allow meaningful interpretation of results.

Contusions↗