Ultraviolet-induced Fluorescence Research Articles

In vitro evidence for UV-protection of the eye by the corneal epithelium mediated by the cytoplasmic protein, RNA, and ascorbate.

(1) To evaluate the effect of ribonucleic acid (RNA) and ascorbate on UV-absorption and their impact on ultraviolet-induced (UV) fluorescence from various proteins, and (2) to compare RNA and DNA reduction of protein fluorescence. These informations will be useful for later work on the UV-filtering effect of the corneal epithelium. Spectrophotometry and spectrofluorimetry. (1) RNA and ascorbate caused a significant UV-absorption and reduced the fluorescence from various water-soluble proteins, the degree of reduction varying independently from one protein to the other. (2) RNA and DNA showed protein fluorescence reduction of roughly the same order. The results are discussed both in the context of UV-protection of the cell nucleus in general, and the possible UV-filtering effect for the eye of bovine corneal epithelium.

A method for measuring microquantities of DNA.

Quantitative analysis of DNA content represents a critical step when only very small amounts of nucleic acids are available. The DNA content of a small RNA-free sample can be measured in a simple and precise way using a two-dimensional approach. DNA samples are spotted on the surface of an agarose gel containing ethidium bromide (EtBr) and the ultraviolet-induced low-light fluorescence emitted by EtBr molecules intercalated into the DNA is evaluated. The high sensitivity and reproducibility of this quantitative method has been obtained using an advanced analysis system capable of distinguishing low-light fluorescent patterns, as in the case of DNA stained with EtBr, from the background. Use of an internal standard is necessary because the intensity of the signal is due to the aperture of camera diaphragm and to gel conditions. Using this two-dimensional analysis system it is possible to obtain rapid and precise quantitation of as little as 2 ng of DNA.

The use of fluorescence in the measurement of local liquid content in transient multiphase flows

The theoretical basis of a technique we proposed recently for the measurement of local-instantaneous liquid fractions in highly dispersed two-phase flows is developed. The technique is based on the measurement of ultraviolet-induced fluorescence, and the theoretical approach is to carry out numerical experiments accounting for refractions in the radiation transport path and for the randomness in the flow field (i.e., droplet positions and sizes). These numerical experiments indicate that for a properly selected measurement volume (defined by positioning of the fibers) refractions have a small impact and the measurement is predictable and robust. We also present experimental data that demonstrate this excellently predictable behavior.

FLUTE: FLUORESCENT TECHNIQUE FOR TWO-PHASE-FLOW LIQUID-FRACTION MEASUREMENTS

Abstract A new technique for the local, instantaneous (limited only by the speed of the data acquisition system; current rates possible in the 100 kHz range) measurement of liquid fraction in two-phase flows is described. The technique is based on a combined absorption/emission radiation mechanism tailored to a highly accurate linear response over the whole (0 to 1) liquid fraction range. In the particular application demonstrated here, ultraviolet-induced fluorescence (in the liquid phase) is used, but in principle other combinations of radiation are possible. The technique is essentially non-intrusive in that transmission of the incident ultraviolet radiation and the emitted fluorescence are effected by miniature optical fibers, and the measuring volume is at the intersection of their optical paths some distance away from the fibers. This distance and the size of the measuring volume can be tailored to the particular application. The technique provides a unique measuring capability, especially for highl...

Laser dentistry: root canal diagnostic technique based on ultraviolet-induced fluorescence spectroscopy.

A diagnostic technique to detect residual tissues at different levels of the root canal during an endodontic treatment is presented. The diagnostic system is based on ultraviolet-induced fluorescence spectroscopy and uses suitable optical fibers for local delivery of excitation light and to collect back fluorescence spectra. Spectra of root canal tissues have been obtained from split teeth by labeling with a fluorescent solution. Residual tissue can be discriminated in respect to healthy dentin because of their different spectral responses: the spectral shape of the first response shows a clear peak at 530 nm because of a selective absorption of the fluorescent dye, whereas for the second response, the spectral curve monotonically increases toward ultraviolet wave-lengths with no particular structure. This technique has been tested on unsplit teeth simulating operative conditions. A compact spectroscopic system has been devised that can be easily integrated in an excimer laser system to perform residual tissue detection during laser cleaning of the canals.

Ultraviolet-induced autofluorescence of arbuscular mycorrhizal root infections: an alternative to clearing and staining methods for assessing infections

Arbuscules in vesicular–arbuscular mycorrhizal (VAM) infections in untreated roots autofluoresced when viewed with an epifluorescence microscope. Ultraviolet-induced fluorescence was observed with the same filtering system used to detect fluorescein staining. Plant roots were examined from five plant families, grown under a variety of conditions, and infected with several species of VAM fungi. In every case, autofluorescent arbuscules were observed. Vesicles, spores, and hyphae did not autofluoresce under these same conditions. Fluorescence was not observed in ectomycorrhizae or pathogenic fungal infections. Cut mycorrhizal root segments from greenhouse- and field-grown plants were evaluated for infection using ultraviolet light and clearing and staining. No significant differences were found in the percent VAM infection as determined by the two methods on the same root segments. Applications and considerations in the use of the ultraviolet method for measuring infections as well as some preliminary observations on using fluorescein diacetate are discussed.

Aflatoxin-Producing Strains of Aspergillus flavus Detected by Fluorescence of Agar Medium Under Ultraviolet Light

The fluorescence method of detecting aflatoxin-producing strains of Aspergillus flavus and related species utilizes the ultraviolet-induced fluorescence of aflatoxin produced in a modified Czapek's solution agar containing corn steep liquor, HgCl(2), and (NH(4))H(2)PO(4) instead of NaNO(3). The presence of aflatoxin is confirmed by thin-layer chromatography of CHCl(3) extracts of the fluorescing agar.

Elastin: Locus and Characteristics of Chromophore and Fluorophore

Elastin, the main component of elastic tissue and ligament, is a yellow, insoluble, elastic protein exhibiting brilliant ultraviolet induced fluorescence in the visible region of the spectrum. Neither the color nor fluorescence can be explained by the presently documented amino acid composition, or by theories of secondary structure. Both the chromophore and fluorophore are degraded by conventional acid hydrolysis but may be freed, intact, from peptide linkage only by acid hydrolysis carried out under reducing conditions. That the chromophore or fluorophore are not related to the desniosines, as previously reported, is demonstrated by their rapid adsorption from a hydrolyzate onto charcoal, when the desmosines remain in the colorless non-fluorescent supernatant. In the free state the chromophore and fluorophore behave as easily oxidizable ampholytes possessing aromatic character. They are not readily eluted from polystyrene based ion exchangers.Elastin was digested with elastase and pronase to give 65 % h...

Effect of temperature on X-ray-induced light emission from powders of amino acids and trypsin

The following was observed in studies of the effect of temperature on the intensity of X-ray-induced emission from powders of aromatic amino acids and proteins: The thermal coefficients for quenching of both fluorescence and phosphorescence are much different at temperatures below about 150 °K and above 240 °K. The ratios of the coefficients measured in the two temperature regions varied from 3 to 50 in the four compounds studied. The E q for tryptophan fluorescence in powders exposed to X-rays near 300 °K is much less than the coefficient for quenching ultraviolet-induced fluorescence from tryptophan in solution. The quenching coefficient for fluorescence is invariably smaller than that for phosphorescence. The E q = 0.21 ± .07 eV per molecule for the quenching of trypsin phosphorescence in the range T > 200 °K is essentially the same as that for tyrosine phosphorescence. This value is approximately twice that of 0.1 eV per molecule for the thermal enhancement of trypsin inactivation by ionizing radiations in the same temperature range. Crude measurements suggest that the thermal coefficient for quenching of trypsin fluorescence is also less than the corresponding activation energies for trypsin inactivation. Analysis of the data has led to the following conclusions: (1) Quenching is a function of the macromolecular organization of proteins. (2) Thermal enhancement of enzyme inactivation yields does not depend critically upon indiscriminate quenching to prevent emissive loss of potential inactivating energy from the irradiated molecules. (3) Either the interaction of specific excited aromatic residues with radiosensitive structures does not provide a large contribution to enzyme inactivation or the specific interactions account for only a small fraction of total quenching. The present results emphasize again the differences between the excitation events produced by X-ray-induced electrons and low-energy ultraviolet. Although trypsin fluorescence appears to be from tryptophan, X-rays cause a great enhancement in trypsin of phosphorescence typical of that from tyrosine: excitations by “ionizing” radiations must be involved in intersystem crossing with high probability. “Red” components not found in ultraviolet-induced emission are also observed.

Liquid scintillators X. Some aryl substituted phenanthrenes and dihydrophenanthrenes, and relatedp-terphenyls andp-quaterphenyls determination of Kallmann parameters

A number of new 2- and 2,7-aryl substituted phenanthrenes, 3,4-dihydrophenanthrenes, and 9,10-dihydrophenanthrenes, as well as some relatedp-quaterphenyls andp-terphenyls, were tested as liquid scintillation solutes. Also determined were the compounds' ultraviolet absorption spectra, ultraviolet-induced fluorescence spectra, and Kallmann parameters. On the basis of these measurements, it was possible to correlate to some degree structure and scintillation ability. Some interesting results regarding conjugation and co-planarity in the linear polyphenyls were also obtained.