Fluorescence Intensity Curve Research Articles

Quenching of fluorescence of Rhodamine 610 in binary and ternary mixture solutions

The sensitized fluorescence emission from bimixtures, Coumarin 500 (donor) + Rhodamine 610 (acceptor) and Rhodamine 610 (donor) + Nile Blue 590 (acceptor) and also from the ternary mixture, Coumarin 500 (donor) + Rhodamine 610 (inter mediator) + Nile Blue 590 (acceptor), have been measured as a function of dye concentration and excitation wavelength using a fluorescence spectrophotometer. The spectroscopic parameters for the bimixtures have been estimated from the concentration dependence of the peak fluorescence intensity curves.

Critical Demicellization Concentration of Diethylammonium Perfluorononanoate and Diethylammonium Tetradecyl Sulfate Mixture in Aqueous Solution

Abstract The micellar pseudophase diagram of diethylammonium perfluorononanoate (DEAPFN) and diethylammonium tetradecyl sulfate (DEATS) was determined by both conductivity and fluorescence probe methods. The conductivity measurements gave unusually low dissociation degrees of counter ion for DEAPFN-rich regions in contrast to those for DEATS-rich region. The micelles in a DEAPFN-rich region have high microviscosities, suggesting a micellar growth. The existence of the second cmc indicated the presence of two types of mixed micelles, but the mutual solubility of fluorocarbon and hydrocarbon surfactants in micellar pseudophase showed significant differences between DEAPFN–DEATS and LiPFN–LiTS systems. Third inflection points on both conductivity and fluorescence intensity curves were observed for DEAPFN–DEATS system. This suggests the presence of a critical demicellization concentration (CDC).

Synthesis of fluorescent derivatives of 7-methylguanine through reaction with 2-aryl-substituted malondialdehydes: analysis by HPLC with fluorescence detection

Fluorescent derivatives of 7-methylguanine were prepared through reaction with 2-arylsubstituted-malondialdehydes and analysed by reversed-phase HPLC with fluorescence detection. Reaction of carbons 1 and 3 of the malondialdehyde molecule at the N1 and N 2 positions of 7-methylguanine yielded fluorescent tricyclic structures. Two novel fluorescent derivatives of 7-MeG were obtained, namely, 7-(3,4-dimethoxyphenyl)-10-oxo-1-methyl-9,10-dihydropyrimido[1,2- a]purine (yield 15–34%) and 7-(1-naphthyl)-10-oxo-1-methyl-9,10-dihydropyrimido[1,2- a]purine (yield 56–70%) after reaction with 3,4-dimethoxyphenylmal-ondialdehyde and 1-naphthylmalondialdehyde, respectively which were characterized by IR, NMR, MS and UV and fluorescence spectroscopy. The fluorescence intensity of the derivatives was found to be 10–20-fold higher than the intrinsic fluorescence of 7-methylguanine. Concentration versus fluorescence intensity curves exhibit linearity in the picomole to nanomole range. The 2-aryl-substituted malondialdehydes were used to analyse the concentration of 7-methylguanine in neutral hydrolysates obtained from calf thymus DNA samples alkylated with dimethyl sulfate. The results obtained indicate their potential as reagents for the analysis of alkylated guanines in biological samples. Molecular modeling calculations were carried out to generate lowest energy spatial configurations. The results obtained indicated that the aryl-substituents on the malondialdehyde moiety do not lie in the same plane as the tricyclic moiety of the fluorescent derivatives with implications for their fluorescence properties.

Direct Evidence for β-Cyclodextrin-Induced Aggregation of Ionic Surfactant below Critical Micelle Concentration

The fluorescence emission of p-dimethylaminochalcone (DMAC) has been monitored in β-cyclodextrin (β-CD) and cetyltrimethylammonium bromide (CTMAB) or sodium dodecylsulfate (SDS) mixture. In the presence of a fixed amount of β-CD, a peak-shaped variation is observed in the curve of DMAC fluorescence intensity vs. surfactant concentration below critical micelle concentration (cmc). The peak height is dependent on β-CD concentration, and no peak is noted in the absence of β-CD. Such a peak-shaped variation in DMAC fluorescence emission is shown to be direct evidence for β-CD-induced aggregation of the surfactant below cmc in aqueous solution. The 1:1 surfactant/β-CD inclusion complex is the hydrophobic source inducing the aggregation.

Mammalian inositol monophosphatase: the identification of residues important for the binding of Mg2+ and Li+ ions using fluorescence spectroscopy and site-directed mutagenesis.

The fluorescence properties of residue Trp-219 in inositol monophosphatase are sensitive to the ionization of neighbouring groups. The pH-dependent changes in the fluorescence emission intensity and wavelength of maximum emission appear to arise as the result of two separate ionizations in the proximity of Trp-219, namely due to the ionization of His-217 and Cys-218. By studying the curve of fluorescence intensity against pH, given by the mutants Cys-218-->Ala or His-217-->Gln, the pK of His-217 was determined to be 7.54 and the pK of Cys-218 was estimated to be about 8.2. These mutants have altered kinetic parameters for catalytic Mg2+ ions and inhibitory Mg2+ and Li+ ions. The Cys-218-->Ala mutant enzyme is not subject to inhibition by concentrations of Mg2+ ions up to 400 mM and has a specific activity of 156% of the maximum obtainable activity of the native enzyme. The His-217-->Gln mutant enzyme shows reduced sensitivity to inhibition by Mg2+ and Li+ ions, and has a specific activity of 110% of that obtainable for the native enzyme.

Sub-picosecond fluorescence study of the LDS 751 dye molecule in ethanol

A time-dependent fluorescence Stokes shift study of the LDS 751 (styryl 8 ) dye molecule in ethanol solution is presented. Fluorescence intensity curves were recorded with sub-picosecond time resolution at various wavelengths using the fluorescence upconversion method. From the experimental curves, time-resolved fluorescence spectra have been reconstructed, allowing the calculation of the spectral shift correlation function c( t)=[ ν ( t)- ν (∞)]/[ ν (0)- ν (∞)]. We find c( t) of LDS 751 in ethanol at room temperature to be well described by a monoexponential function with a 1/ e time of 5±1 ps.

An estimation of the distribution functions of doped Tb 3+ and Nd 3+ in glasses by fluorescence measurements

The distribution functions of doped Tb 3+ and Nd 3+ in silicate, germanate, borate and phosphate glasses, in which cross-relaxation among active ions plays an important role, have been estimated by fluorescence measurements. In order to analyze both the steady state and the transient fluorescence characteristics, a non-linear model for the resonant energy transfer has recently been developed. The experimental fluorescence intensity and decay curves, measured as a function of acceptor concentration, suggested a modified distribution function, which included the effect of the segregation of donors and acceptors. The number of segregated Tb 3+ ions at the second nearest neighbor position around a Tb 3+ ion was estimated to be 0.1–3.4, depending on the host glass.

時間分解顕微蛍光法によるヒト歯牙自己蛍光の測定 加齢による蛍光特性の変化

Human teeth fluoresce as a result of illumination by UV-light. The fluorescence characteristics of human teeth were investigated with respect to aging using microscope fluorometry. To measure nanoscecond decay features of a tooth's fluorescence, a microscope fluorometer equipped with an air-discharge pulsed lamp was devised. The fluorescence intensity and fluorescence decay curve were found to be age dependent in dentin tissue; the fluorescence intensity increased and the fluorescence decay time decreased with increasing human age. Ancient teeth showed more intense fluorescence with a shorter decay time than that of the modern teeth. This may result from a gradual maturation of fluorescent cross-linked collagen, which increases with age.

Dynamic microstructure and hydration of peroxidized membrane of rat cardiac mitochondria and effects of adriamycin.

Nanosecond time-resolved fluorometry of diphenyl hexatriene, DPH, fluorescence was used to study the effects of lipid peroxidation caused by NADH or adriamycin treatment on the dynamic microstructure of mitochondrial membranes from rat myocardium. Isolated mitochondria were incubated with NADH, FeCl3, and ADP, or with adriamycin. Parameters for microdynamics were calculated from the fluorescence intensity and anisotropy decay curves for DPH fluorescence. Peroxidized lipids were measured as malondialdehyde (MDA) resulting from the thiobarbiturate reaction. As peroxidized lipids accumulated, the membrane viscosity increased and the wobbling angle of the phospholipids decreased. The structural changes induced in unsaturated phospholipids by peroxidation probably increased the friction of neighboring phospholipids and restricted the range of their wobbling motion. The fluorescence intensity and fluorescence lifetimes decreased significantly when MDA was higher than 10 nmol/mg protein. These alterations in the behavior of DPH fluorescence strongly suggest that the hydration of the phospholipid layer of the mitochondria is occurring as a consequence of lipid peroxidation, since the fluorophore, DPH, is hydrophobic and its fluorescence is known to be quenched by increasing the dielectric constant of the surrounding media. The present results provide experimental supports to the hypothesis of membrane hydration induced by lipid peroxidation.

Phenotypic and functional characteristics of human newborns' B lymphocytes.

It has been demonstrated two major facts concerning human newborns' B lymphocytes: 1) they differentiate poorly into Ig-producing cells and 2) they express CD5 and CD1c membrane proteins. We have further analyzed human newborns' B cell characteristics and found that approximately half of them express activation Ag, i.e., 4F2 and IL-2R, both associated in significant proportions with CD23 and Bac-1. These membrane Ag were found both on CD5(+) and CD5(-) B cells. Newborns' B cells do not exhibit other activation markers because they express surface IgD, and because their size, RNA, and DNA contents do not differ from those of adults' B cells, indicating that they are in the G0/G1 cell cycle phase. Newborns' B cell proliferation can be induced by rIL-2, rIL-4, low m.w. B cell growth factor, and by Staphylococcus aureus protein A. It is presently difficult to build a hypothesis accounting for all the specific findings made on newborns' B cells. It is not known for instance whether CD5(+) and (-) B cells belong to distinct subsets as suggested by the fluorescence intensity curve obtained with an anti-CD5 antibody or to distinct stages in a unique pattern of B cell maturation during fetal and newborn life. This may indicate that partially activated B cells actually produce natural polyspecific autoantibodies of the IgM isotype found in newborns' human serum.

X-ray standing wave method applied to the structural study of Langmuir-Blodgett films

An X-ray standing wave field excited during Bragg diffraction in 59 monolayers of lead stearate was used as a structural probe to determine the distance from the manganese atom plane to the nearest lead atom plane in a Langmuir-Blodgett film with a heterostructure (two monolayers of manganese stearate superimposed on top of the lead stearate layers). In this experiment, the intensities of Pb Lα and Mn Kα fluorescent X-rays excited by the standing wave field were measured as a function of the glancing angle of a monochromatized (13.4 keV) synchrotron X-ray beam. These two fluorescence intensity curves were compared with the calculated ones.

Validation of the SCM-test for the diagnosis of cancer

The basic aspects of the SCM-test are summarized. A derivation of the fluorescence intensity vs time curve is given as well as that of the polarization as a function of time. These curves are found to be in excellent agreement with the experimental results. The test is applied to the lymphocytes of twenty-six healthy individuals and of thirty-three cancer patients. No false negative results were obtained. Seven cancer patients were found to be negative after various intervals from the removal of the tumour. The most important technical difficulties and pitfalls are discussed in order to facilitate the reproduction of the test by other researchers.

Spectrofluorihetric Determination Of Indenolol Hydrochloride And Its Dosage Forms

ABSTRACT A spectrofluorimetric method for the determination of indenolol hydrochloride and its tablets (Pulsan(R) 10 mg and 30 mg tablets) at room temperature is described. The method is simple, selective and sensitive enough for the determination of indenolol in nanomolar concentrations. Furthermore, the proposed method helps in the identification of the drug. The procedure involves establishment of the calibration curve and comparison of fluorescence intensity of standard solution of authentic indenolol hydrochloride to that of unknown sample under identical conditions and with reference to the linear part of the curve. The wavelengths employed for excitation and emission were 248 nm and 325 nm respectively.

Fluorescence quenching mechanisms of aromatic hydrocarbon-dicyanobenzene and-n.n-dimethylaniline systems in aqueous micellar solutions

Fluorescence quenching of pyrene and several other aromatic hydrocarbons by dicyanobenzenes as well as N,N-dimethylaniline has been observed in aqueous micellar solutions. The experimental results have been explained by means of equations for fluorescence intensity and decay curve derived on the basis of a simplified model.

Fluorescein dye-dilution technique and retinal circulation

Using theoretical models for the flow of fluourescein dye in retinal arteries and veins, we have determined the effects of optical absorption in blood of the incident excitation light and the emitted fluorescent light on the time course of measured fluorescence intensity, I(t). Our results indicate that I(t) curves recorded from arteries adequately represent the mean time course of the fluorescein concentration (C(t)), when either a circular or rectangular light-collecting aperture is used. I(t) curves recorded from veins adequately represent C(t), but only when a circular aperture of approximately the same diameter as that of the vessel is used. A two-point fluorophotometer, which provides simultaneous, on-line measurements of arterial and venous I(t) curves is described. Typical recordings obtained with the instrument are shown and the method employed to analyze the curves quantitatively is described in detail. This method, which consists of fitting the first passage of the fluorescence intensity curve with a log-normal function, provides results that are more accurate than those obtained using the standard exponential extrapolation method.

A kinetic model of the primary back reaction in photosynthesis of green plants

A model is proposed to explain the nonexponential decay kinetics of the primary back reaction of photosystem II and of delayed light in green plants. This model assumes that the primary back reaction is due to the recombination of the primary oxidized photoproduct Z + and the primary reduced photoproduct Q − which are embedded in a fixed position in the reaction center. The formation of a singlet exciton in the bulk chlorophyll molecules as a reaction intermediate is assumed possible. The basic assumption made in this model is that Q − and Z + can cause changes in its surrounding environment to such an extent that it can affect the structure of its neighboring centers. Using this model, the rate of the primary back reaction was calculated and was found to agree well with the experimental kinetic data of Bennoun (1970) . Also, theoretical curves of the kinetics of delayed light in the seconds region, of thermoluminescene and of chemiluminescence were calculated and were also found to agree well with experimental data. Glow curves and the fluorescence versus excitation light intensity curve were also discussed as further means of studying the primary back reaction.

Excited Species and Their Contribution to NO(β, γ) Fluorescence in the Photodissociation of N2O

The fluorescence intensity and the yield of the NO β bands, originating from photodissociation of N2O, was measured as a function of wavelength of incident light in the vacuum ultraviolet region. Photon energies required for the occurrence of the fluorescence are far less than the threshold energy to produce NO(A2 Σ+, B 2Πr) directly from N2O, indicating that the emission is due to secondary processes. The fluorescence intensity curve follows closely the absorption curve of N2O indicating that excited species responsible for the emission are produced from dissociation of electronically excited N2O rather than from the direct dissociation to these species. A mechanism of fluorescence is discussed on the basis of the threshold energy above which a specific photochemical process is possible. Reactions responsible for the β emission in the absorption region 1400 to 1550 Å of N2O are production of N(2D) and O(1S) followed by N(2D)+N2O→N2+NO(B 2Πr) and O(1S)+N2O→NO+NO(B 2Πr). In the region below 1400 Å, N(2P) and N2(B 3Πg, B′ 3Σu−) also can contribute to the emission. When NO was added to N2O, the fluorescence intensity increased considerably and the emission changed from β to γ bands. Reactions which produce the emission in the absorption region 1400 to 1550 Å are N2O→ lim hνN2(A 3Σu+)+O(3P)followed by N2(A 3Σu+)+NO→N2+NO(A 2Σ+). Below 1350 Å additional excited molecules N2(B 3Πg, B′ 3Σu−) can contribute to the emission in similar reactions.

The Properties of Bovine Growth Hormone: II. EFFECTS OF UREA

Abstract Increasing levels of urea increase the fluorescence intensity of bovine growth hormone at neutral pH and shift the pH zone of the transition that occurs in acid to higher pH values. Maxima in the fluorescence intensity curves occur above 3.6 m urea and are displaced to higher pH values at higher urea concentrations. Fluorescence polarization of the conjugate of the hormone with 1-dimethylaminonaphthalene-5-sulfonyl chloride undergoes a complicated series of changes as a function of urea concentration and pH. The pK value of the dimethylamino group of the 1-dimethylaminonaphthalene-5-sulfonyl conjugate of bovine growth hormone is abnormally low in aqueous solution and is gradually normalized by urea. From studies of these phenomena, and of ultraviolet difference spectra of the hormone in urea solutions, five new molecular conformations of bovine growth hormone are inferred. Even the most disorganized conformation, which is found in 9 m urea below pH 5, still appears to retain some organized structure. The helical regions of the bovine growth hormone molecule appear to remain largely intact, even in conformations that differ markedly from that of the native molecule.

Influence of copper and EDTA on the alkaline oxidation of adrenaline.

Abstract Adrenaline can be determined quantitatively in the presence of sulphite by measuring the maximum fluorescence obtained by oxidation in alkaline solution. The presence of copper in the solution quenches the fluorescence according to Stern-Volmer's law. Ethylenediaminetetra-acetic acid present in copper-free solutions has no influence on the fluorescence intensity curve. When copper is present as EDTA-complex the oxidation is strongly catalysed and the fluorescence maximum appears earlier the higher the concentration of complex. The reactions do not seem to be photochemically influenced.

Reversible Quenching by Oxygen of the Fluorescence of Polycyclic Hydrocarbons

DURING an investigation into the estimation of 3: 4-benzpyrene by fluorescence measurements, great differences in fluorescence intensity were observed according to the solvent used; for example, the fluorescence is about five times as intense in tetraline as in hexane. These differences were found to be entirely due to a quenching effect of dissolved oxygen. In the absence of oxygen, the fluorescence intensity curves of a series of benzpyrene concentrations are practically identical in all the solvents studied. The most striking feature of the quenching by oxygen is its complete and instantaneous reversibility. The fluorescence of a given solution which has been almost completely quenched by oxygen is immediately and completely restored to its original value if the oxygen is pumped off, and this cycle can be repeated indefinitely.