Spectral Characteristics Of Fluorescence Research Articles

Spectral-Luminescent Study of the Acid–Base Equilibrium of 5-Aminouracil and 6-Aminouracil in Aqueous Solutions

The spectral fluorescence characteristics of 5-aminouracil (5AU) and 6-aminouracil (6AU) in neutral and alkaline aqueous solutions have been studied. With the use of the density functional theory, it has been shown that uracils preferentially dissociate at the N1–H bond. The acid–base equilibrium constants pKa1(5AU) = 9.4 and pKa1(6AU) = 8.95 were determined by a fluorescence method. It was concluded that the ultrashort lifetime of the excited singlets of 5AU and 6AU prevents the measurement of the acid–base equilibrium constant of uracils in an electronically excited state.

Current Problems of the Diagnostics and Treatment of Sepsis and Burn Injuries: The Modified Pathogenetic Concept

Background: The deep understanding of pathogenesis is a key moment in the formation of the modern strategy of modern medicine. We conducted the thorough analysis of the microscopic processes occurring in the bodies of patients with purulent-septic complications. The modified pathogenetic concept of the diagnostic and treatment model of diseases with septic complications is presented. The obtained information about the mechanisms of origin and development of these diseases is fundamentally important for finding the modern effective methods of treating patients. The aim of the research is to modify treatment tactics for patients with sepsis and burn injuries based on the modified pathogenetic concept using modern diagnostics, i.e. the method of fluorescence spectroscopy (MFS) and biomarkers. Materials and Methods: The proposed modified pathogenetic concept of the diagnostic and treatment model of diseases with purulent-septic complications along with standard methods was used successfully for effective treatment of 15 patients with sepsis and 25 with burn injuries. Results: 3 main scenarios of behaviour of spectral-fluorescence characteristics of patients with sepsis are illustrated. Spectral-fluorescence markers of sepsis were studied, which are informative 24 to 48 hours before the appearance of obvious clinical and laboratory signs of significant changes in the general somatic status of patients. Conclusions: The proposed diagnostic and therapeutic approach is new and fundamentally important for diagnostics and monitoring of the process of treatment of patients with purulent-septic diseases and burn injuries. An in-depth understanding of the dynamics of septic complications and the corresponding changes of the main markers of these diseases during treatment is especially relevant. The use of infusion therapy with solutions of donor albumin as an effective pathogenetic treatment is scientifically justified.

Spectral fluorescent study of Rhodamine 6G molecules embedded in different layers of one-dimensional polymer-based photonic crystals

The spectral characteristics of the fluorescence of Rhodamine 6G (Rh6G) molecules doped into different layers of one-dimensional photonic crystals (PCs) have been studied at various detection angles. The studied PCs differ in the spectral position of the photonic band gap (PBG) with respect to the Rh6G luminescence spectrum. A computation method of the density of PC`s electromagnetic modes have been proposed. The spectral characteristics of Rh6G fluorescence and computed relative density of electromagnetic modes versus the wavelength have been compared for different detection angles. The experimental and theoretical dependences demonstrate good agreement. Keywords: Photonic crystals, photonic band gap, density of electromagnetic modes, spin-coating method, polymers, cellulose acetate, poly(N-vinylcarbazole), dye, Rhodamine 6G, fluorescence spectra.

Исследование спектрально-флуоресцентных характеристик молекул родамина 6Ж, внедренных в различные слои одномерных фотонных кристаллов на основе полимерных пленок

The spectral characteristics of the fluorescence of Rhodamine 6G (Rh6G) molecules doped into different layers of one-dimensional photonic crystals (PCs) have been studied at various detection angles. The studied PCs differ in the spectral position of the photonic band gap (PBG) with respect to the Rh6G luminescence spectrum. A computation method of the density of PC`s electromagnetic modes have been proposed. The spectral characteristics of Rh6G fluorescence and computed relative density of electromagnetic modes versus the wavelength have been compared for different detection angles. The experimental and theoretical dependences demonstrate good agreement.

Photosensitizing properties of supramolecular systems based on chlorin e6

The novel supramolecular systems based on chlorine e 6 (Ce 6 ) are presented, and their optical absorption and fluorescence have been investigated. The influence of different excipients as poly-N-vinylpyrrolidone (PVP), polyethyleneglycol (PEG), bovine serum albumin (BSA), chitosan, Triton X-100 (TX-100) on spectral characteristics of these systems has been studied. The obtained spectral-fluorescence characteristics of Ce 6 -PVP, Ce 6 -PEG, Ce 6 -BSA, Ce 6 -TX-100 indicate disaggregation of chlorine e 6 molecules and their consecutive interaction with excipients in solutions and formation of molecular associates and molecular complexes. The system Ce 6 -chitosan is characterized by aggregation of pigments in solution that reduces photochemical activity of a photosensitizer. The fluorescence quantum yield j k of mentioned above supramolecular systems has been calculated. The results can be useful during the new method of controlled aggregation of photosensitizers as a part of supramolecular complexes development as well as for the purposes of new medicines of predictable photodynamic activity creation.

Spectral characteristics of fluorescence and circular dichroism of aflatoxin B1 reaction with its anti-idiotypic antibody

Aflatoxin B1 (AFB1) is a toxic secondary metabolite and sensitive methods for its analysis have been developed. In our lab, a number of works have been carried out, including exploitation of detection methods and production of anti-idiotypic antibody (Ab2) against Fab fragment of anti-AFB1 antibody (Ab1). In this paper, Ab2 was generated upon the immunization of mice with F(ab′)2 fragment, which was specific to AFB1 and obtained by pepsin digestion of Ab1. The characteristics of Ab2 was primarily investigated by indirect competitive enzyme-linked immunosorbent assay (icELISA), which indicated that Ab2, might bear an internal image of antigen AFB1 and was able to combine to F(ab′)2 in competition with AFB1, and the concentration of Ab2 to cause 50% inhibition of binding (IC50) was 131.8μg/mL. In addition, fluorescence and circular dichroism studies were designed to explore the mutual relationship among AFB1, F(ab′)2 and Ab2. The fluorescence spectroscopy implied that both AFB1 and Ab2 act as a quencher upon F(ab’)2, and the Ab2 could compete with AFB1 when both of Ab2 and AFB1 reacted with F(ab′)2. The circular dichroism (CD) spectrum suggested that both the binding of Ab2 and AFB1 on F(ab′)2 brought secondary conformation change of F(ab′)2, especially in the changes of α helix and β sheet. The research performed would provide unique insight into the comprehension of interaction among AFB1, F(ab′)2 and Ab2 as well as offer structural information for substitution researches of toxic antigen like AFB1.

Effect of Aging in the Structure of Silica Xerogels with Incorporation of Extract’s Leaves

The spectral fluorescence characteristics of extracts leaves embedded in silica xerogel matrix promoted by aged time was studied. We obtain a higher PSII stability for extract of leaves embedded in xerogel matrix, with concentration of 8 g / 20 ml and water to TEOS molar ratio of 11, which remain bioactive over a very long period of time, whereas for a water to TEOS molar ratio of 5 a blue-shift fluorescence is observed indicating the PSII denaturizing and formation of fluorescing aggregates associated with the activation of carotenoids radicals.

Point Investigation Method for Cancer Changed Tissues

In this paper we describe the method of point investigation for cancer changed tissues with application of fluorescence phenomenon. The measurements have been made using a specially constructed scanning setup and fiber sensors. The experiment with investigation of endogenous fluorescence has been made on different types of slide tissues (e.g. breast and intestine tumor or precancerous and pathological skin tissues). The obtained spectral characteristics of fluorescence, with typical intensity peaks in 480–520 nm range, have explicitly outlined healthy and pathologically changed areas. The intensity of detected fluorescence determines the evaluation of disease advancement. Moreover, the ability to scan the surface of a tissue sample with constantly moving step of scanning setup in X–Y axis allows us to present the results in a spatial distribution of fluorescence intensity.

Solid Phase Synthesis of N-Alkyl-bis-o-aminobenzamides for Metal Ion Sensing Based on a Fluorescent Dansyl Platform

In this paper, we report the synthesis on Merrifield's resin of alkyl-bis-o-aminobenzamides labeled with a fluorescent dansyl group for use in metal ion recognition. The influence of alkyl groups with different long chains (n = 1, 2, 4, 6) on the spectral fluorescence characteristics was studied. The sensing properties of the beads were evaluated by packing the resins into a flow-through cell for use in a FIA (flow injection analysis)format. Results demonstrated that for those materials with a longer alkyl chain, the fluorescence emission increased upon Li+, Na+, K+, Ca2+, and Mg2+ addition with a higher sensitivity for Mg2+. On the contrary,a fluorescence quenching was observed when Cu2+, Fe3+, or Zn2+ ions were added. The potential applicability of the sensing approach described in this paper for magnesium ions and the sensing response mechanism are outlined.

5218 誘導放出を用いた液体膜厚さ計測手法の開発 : 蛍光特性の影響(S65-5 潤滑膜計測技術,S65 トライボロジーの基礎と応用)

5218 誘導放出を用いた液体膜厚さ計測手法の開発 : 蛍光特性の影響(S65-5 潤滑膜計測技術,S65 トライボロジーの基礎と応用)

Improved Routine Bio-Medical and Bio-Analytical Online Fluorescence Measurements Using Fluorescence Lifetime Resolution

Fluorescence techniques are widely used as sensitive detection methods in bio-analytics. The use of the bio-physical parameter fluorescence lifetime additional to the spectral characteristics of fluorescence has the potential to improve fluorescence-related detection methods in terms of selectivity in signal recognition, robustness against disturbing influences, and the accessibility of novel bio-chemical process parameters. This article describes the technical set up of a time-resolving instrument with either a fixed time-gated detection principle for improved evaluation of tissue metabolism by an online monitoring of the tissue autofluorescence or a direct fluorescence lifetime detection principle for lifetime-based fluorescent assays.

Selective quenching of the fluorescence of core chlorophyll-protein complexes by photochemistry indicates that Photosystem II is partly diffusion limited.

The spectral characteristics of fluorescence quenching by open reaction centres in isolated Photosystem II membranes were determined with very high resolution and analysed. Quenching due to photochemistry is maximal near 687 nm, minimal in the chlorophyll b emission interval and displays a distinctive structure around 670 nm. The amplitude of this 'quenching hole' is about 0.03 for normalised spectra. On the basis of the absorption spectra of isolated chlorophyll-protein complexes, it is shown that these quenching structures can be exactly described by assuming that photochemistry lowers the fluorescence yield of the reaction centre complex (D1/D2/cytb (559)) plus CP47, with quenching of the former complex being approximately double that of the latter complex. These data, which qualitatively indicate that there are kinetically limiting processes for primary photochemistry in the antenna, have been analysed by means of several different kinetic models. These models are derived from present structural knowledge of the arrangement of the chlorophyll-protein complexes in Photosystem II and incorporate the reversible charge separation characteristic of the exciton/radical pair equilibration model. In this way it is shown that Photosystem II cannot be considered to be purely trap limited and that exciton migration in the antenna imposes a diffusion limitation of about 30%, irrespective of the structural model assumed.

Chlorophyll fluorescence at 77 K in intact leaves: Characterization of a technique to eliminate artifacts related to self-absorption

Due to the optical density of photosynthetic tissues the spectral characteristics of fluorescence emitted at 77 K directly from frozen plant material are distorted by differential re-absorption of the emitted light: the emission band related to PSII can be lowered by more than 80%, relative to the PSI band and the profile of the excitation spectra becomes flattened. It is demonstrated that such distortion cannot be neglected as its extent varies from sample to sample. A technique is introduced to eliminate sample artifacts related to self-absorption: subcellular small particles are prepared from rapidly cooled leaves and then 'diluted' without re-thawing at a concentration corresponding to about 5 μg chlorophyll·cm(-3) into a matrix consisting of ice and quartz particles. The photochemical pigment apparatus is expected to remain fixed in the in vivo state. Different kinds of plant material is used and it is demonstrated how this preparative approach allows to study the in vivo distribution of energy between the two photosystems from pure 77 K spectrofluorimetry, even when the optical properties of whole leaves or thalli normally would exclude quantitative analysis.

Off-line liquid chromatographic-mass spectrometric studies of fluorescent β-aminothiol- o-phthalaldehyde derivatives

A liquid chromatographic separation and selective post-column derivatization of six β-aminothiols with o-phthalaldehyde is reported. The presence of both primary amine and thiol functional groups in these compounds makes it possible to derivatize with o-phthalaldehyde alone, eliminating the need for external thiol addition. The structures of the fluorescent derivatives formed in this procedure were determined by off-line liquid chromatography—gas chromatography—mass spectrometry. Spectral fluorescence characteristics for the β-aminothiol- o-phthalaldehyde derivatives are also reported.

A note on the fluorescence characteristics of particles that pkss through glass‐fiber filters1

The spectral characteristics of fluorescence from material that passes through a glass‐fiber filter suggests that the population of small cells is made up of cyanobacteria and other algae. The latter appear not to be diatoms or dinoflagellates as they contain little or no carotenoid protein such as fucoxanthin.

Detection of Mold Contamination in Corn by Optical Measurements

Abstract A nondestructive technique has been developed for detecting mold contamination in individual kernels of corn by fluorometry based on the fact that the fluorescence from the kernel is quenched or reduced on mold-contaminated corn. Four optical properties (total fluorescence and the spectral characteristics of fluorescence, transmittance, and reflectance) were measured in an exploratory test. The test samples consisted of 10 mold-contaminated (slight to severe contamination) and 10 sound corn kernels. The optical measurements were compared to determine which technique would be most effective in distinguishing between sound and mold-contaminated corn. The best criterion of mold contamination in corn kernels was the ratio between 2 measurements of the fluoresced energy (at 442 and 607 nm). The results indicated that the contaminated kernels could be distinguished from the sound ones with less than 5% error.