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At least 235 records · Page 13Linked to original sources
PubMed1984

Brain NADH redox state monitored in vivo by fiber optic surface fluorometry.

A new approach for the evaluation of brain energy metabolism in awake animals became possible as UV transmitting optical fibers became available. A variety of surface fiber optic fluorometers / reflectometers which were developed during the past decade enabled the monitoring of intramitochondrial NADH redox state in unanesthetized animals. The bundle of flexible fibers was connected to the brain via a cemented light guide holder implanted epidurally. The two signals obtained, 366 nm reflectance and 450 nm fluorescence, are subjected to various artifacts not connected to the intramitochondrial NADH redox state. In our system, the effects of movement artifacts and changes in blood oxygenation are negligible while the effects of tissue absorption or blood volume changes are considerable and could be minimized by subtraction of the two signals (1:1 ratio) providing the corrected fluorescence signal. The brain was exposed to various physiological and pathological conditions which resulted in the increase or decrease in the level of NADH. Under anoxia, hypoxia and ischemia, oxygen availability decreased and the metabolic state of the brain became more reduced (state 4-5 transition). When the brain was activated by seizures, spreading depression of hyperbaric oxygenation NADH became more oxidized (state 4-3 transition).

Animals↗
PubMed1993

Estimation of total DNA in crude extracts of plant leaf tissue using 4',6-diamidino-2-phenylindole (DAPI) fluorometry.

A method of estimating total double-stranded DNA in crude extracts of citrus leaf tissue by evaluating the enhancement of fluorescence intensity of 4',6-diamidino-2-phenylindole (DAPI) was assessed. For pure citrus DNA and citrus leaf tissue crude extract each in the presence of 100 ng/ml DAPI, excitation spectral response curves converged at excitation wavelength of 360 nm. At this excitation wavelength, maximum fluorescence intensity occurred across a range of emission wavelengths from 445 nm to 460 nm. The appropriate excitation and emission wavelengths were shown to be 360 nm and 450 nm, respectively. Fluorescence intensity increased linearly with DNA concentration and non-DNA components of the tissue homogenates had negligible effect on fluorescence at these wavelengths. Sodium dodecyl sulfate (SDS) in the incubation solution resulted in some suppression of DAPI-DNA fluorescence and produced a non-linear response to changing DNA concentration. The method should be applicable to DNA quantitation from crude tissue extracts of any plant species.

DNA↗
PubMed1994

Analysis of anisotropy decays in terms of correlation time distributions, measured by frequency-domain fluorometry.

We describe the theory and practical aspects of analyzing fluorescence anisotropy decays in terms of correlation times distributions. In our model the rotational motions of the fluorophores were described using Gaussian or Lorentzian distributions of the correlation times. The theory is presented both for time and frequency-domain measurements, although the simulations and measurements are focused on the frequency-domain measurements of the anisotropy decays. Analysis of simulated data is presented to illustrate the nature of the data and the resolution which can be expected with presently available frequency-domain measurements. Additionally, we describe experimental data for samples where one can reasonably expect a single exponential and/or discrete multi-exponential correlation time distributions, and for samples where the anisotropy decay might be expected to display a distribution of correlation times. These samples include small single tryptophan peptides in propylene glycol, the single tryptophan residue in S. Nuclease, and the single tryptophan residue in the native and partially unfolded states of ribonuclease T1.

Amino Acid Sequence↗
PubMed2005

Detection of PCBs in natural waters by front face fluorometry on solid sorbent on account of their fluorescence quantum yields and interaction with humic substances.

A method for the detection of PCBs in natural water, based on extraction/concentration with tab shaped elements cut from C18 fiber glass SPE disks coupled with a fluorescence detection has been evaluated. The potential of the method was estimated through the measurement of the fluorescence quantum yields in acetonitrile and limits of detection (LOD) of 11 PCBs congeners and Arochlors 1221 and 1242 in pure water. Most of the LOD values are within the range of PCB concentrations found in highly polluted waters (<1microg l(-1)) and thus confer some interest to the method. However, as expected, naturally present humic substances was shown to compete with the solid phase for PCBs adsorption thus reducing the capability of the method when applied to natural waters. A Stern-Volmer plot of the fluorescence signal reduction in the presence of various type of humic substances leads to apparent sorption coefficients (K(DOC)) significantly higher than the literature values determined for PCBs or for polycyclic aromatic hydrocarbons, indicating that besides complexing PCBs, humic substances may also block some of the adsorption sites at the sorbent surface. An increase of the pH up to 11 was shown to reduce the negative effect of humic substances but their preliminary total denaturation or destruction appears as a prerequisite condition for taking full advantage of the present method.

Adsorption↗
PubMed2005

A novel separation-free assay technique for serum antibodies using antibody bridging assay principle and two-photon excitation fluorometry.

A new technique for separation-free detection of antigen-specific antibodies is presented. The new technique employs antibody bridging assay principle and the recently developed ArcDia TPX fluorescence detection technology. According to the assay scheme, antibody molecules from the sample bind with one arm to an antigen on polymer microspheres and with the other arm to a fluorescently labeled secondary antigen reagent. Consequently, fluorescent immunocomplexes are formed on the surface of microspheres in proportion to the concentration of the analyte in the sample. The fluorescence signal from individual microspheres is measured by means of two-photon excited fluorescence detection. In order to demonstrate the applicability of the new assay technique, an assay for anti-adenovirus antibodies was constructed. The function of the assay method was tested both with monoclonal anti-adenovirus antibody preparation (standard analyte), and with positive serum samples. Standard class-specific ELISA was used as a reference method. The new assay method provides comparable sensitivity and precision, and wider dynamic range for IgG antibodies than the ELISA method. The standard curve showed linear response (R(2)=0.999) with a dynamic range of three orders of magnitude, detection limit (mean+3S.D.) of 8 pM, and intra-assay signal precision of 5%. Applicability of the new method for clinical serodiagnostics is discussed.

Animals↗
PubMed2005

An immunoassay for the pathological form of the prion protein based on denaturation and time resolved fluorometry.

Concern about the possible secondary spread of variant Creutzfeldt-Jakob disease (vCJD) through blood transfusion and blood products has increased the need for a sensitive and rapid test for the identification of PrP(Sc) in specimens collected non-invasively from living persons. Furthermore, an accurate estimate of the prevalence of pre-clinical vCJD in the British population would be possible if there were such a test that could be applied to specimens available readily (e.g. blood and urine). As a first step towards that goal, we have developed a simple and sensitive test for the detection of PrP(Sc) in peripheral tissues and brain of vCJD patients, based on the differential extraction of PrP(Sc) with guanidine hydrochloride. The prion protein (PrP) isoforms are extracted sequentially from homogenized tissue by applying two different concentrations of this chaotropic agent. Each extraction yields a fraction of the PrP isoforms with different solubilities in guanidine hydrochloride. Quantitation of the two fractions (relatively insoluble or relatively soluble) using time resolved fluorescence (DELFIA) as a reporter system allows differentiation between PrP(Sc) infected and non-infected tissues. The assay has a detection limit of 10 pg PrP, is robust and could be automated.

Brain↗
PubMed2005

Monitoring aerobic sludge digestion by online scanning fluorometry.

With sludge samples from two wastewater treatment plants, batch experiments of aerobic sludge digestion were conducted under different dissolved oxygen (DO) and solids concentrations. A fluorometer capable of online excitation and emission scanning was used to monitor the digestion process. Three major fluorescence peaks were observed. The peak at excitation/emission maxima of 290/350 nm was attributed to the fluorescence of proteinaceous materials in the sludge, with tryptophan residues being the primary contributor. The sources for the other two peaks (at 370/430 nm and 430/510 nm) remain unknown. The well-known biological fluorescence from reduced nicotinamide adenine dinucleotides (NADH and NADPH), at excitation/emission maxima of 340/460 nm, was found very weak in the aerobic digestion systems studied. It was buried under the broad peak at 370/430 nm and was detectable only in the early stage of the experiment that had the highest solids loading (at 4.8%) and was operated under low DO (0.2-1.0mg/L) conditions. On the other hand, the profile of the protein fluorescence (PF) correlated well with that of the volatile solids (VS) reduction in all the experiments. A semi-empirical exponential decay function was developed, which described well the profiles of both normalized VS and normalized PF. The feasibility of following the real-time performance of aerobic sludge digestion by monitoring PF was clearly demonstrated.

Bacteria, Aerobic↗
PubMed1978

Picosecond fluorometry in primary events of photosynthesis.

Many laboratories in different countries are involved in the study of the mechanism of conversion of light energy into chemical energy, namely photosynthesis. As is evident from the literature, the initial phases of photosynthesis, which determine the character of this process, proceed at time intervals of 10(-8) and 10(-13) s. They are associated with absorption of light quanta and energy transfer from the molecules of light-harvesting antenna (LHA) chlorophyll and accesory pigments to the reaction centers (RC), where the key reaction of photosynthesis occurs: photo-induced charge separation. Evidently it is of importance to study experimentally the process that occurs within the 10(-8) -10(-13)s time domain.

Fluorometry↗