Fluorescence data

L. Eriksson, J. Trygg, E. Johansson, R. Bro, S. Wold, Orthogonal signal correction, wavelet analysis, and multivariate calibration of complicated process fluorescence data. Anal. Chim. Acta, 2000 420, 181-195. 

Calibration. In general, standards used for instrument calibration are physical devices (standard lamps, flow meters, etc.) or pure chemical compounds in solution (solid or liquid), although some combined forms could be used (e.g., Tb + Eu in glass for wavelength calibration). Calibrated lnstr iment parameters include wavelength accuracy, detection-system spectral responsivity (to determine corrected excitation and emission spectra), and stability, among others. Fluorescence data such as corrected excitation and emission spectra, quantum yields, decay times, and polarization that are to be compared among laboratories are dependent on these calibrations. The Instrument and fluorescence parameters and various standards, reviewed recently (1,2,11), are discussed briefly below. 

Room-temperature fluorescence (RTF) has been used to determine the emission characteristics of a wide variety of materials relative to the wavelengths of selected Fraunhofer lines in support of the Fraunhofer luminescence detector remote-sensing instrument. RTF techniques are now used in the compilation of excitation-emission-matrix (EEM) fluorescence "signatures" of materials. The spectral data are collected with a Perkin-Elraer MPF-44B Fluorescence Spectrometer interfaced to an Apple 11+ personal computer. EEM fluorescence data can be displayed as 3-D perspective plots, contour plots, or "color-contour" images. The integrated intensity for selected Fraunhofer lines can also be directly extracted from the EEM data rather than being collected with a separate procedure. Fluorescence, chemical, and mineralogical data will be statistically analyzed to determine the probable physical and/or chemical causes of the fluorescence. 

The fluorescence data were obtained by summarizing the intensity through the total image area. The results are the average of two different samples prepared in the same way. The gravimetric data are the average of measurements on five samples. 

C.N. Ho, G.D. Christian and E.R. Davidson, Application of the method of rank annihilation to quantitative analysis of multicomponent fluorescence data from the video fluorometer. Anal. Chem., 52 (1980) 1108-1113. 

J. Zhang, J.-H. Jiang, P. Liu, Y.-Z. Liang and R.-Q. Yu, Multivariate nonlinear modelling of fluorescence data by neural network with hidden node pruning algorithm. Anal. Chim. Acta, 344(1997) 29 0. 

In this study, the preliminary findings showed that the HPLC/fluorescence data were in agreement for all 12 carbamates with HPLC/ESI-MS/MS for most of the nine fruits and vegetables at the 1.0 ng g fortification level. The recoveries were generally within 70-120% however, at the 1.0 ng g level in each commodity, HPLC/ESI-MS (single-stage MS) had difficulty with interferences for three out of the 12 carbamate pesticides (aldicarb sulfoxide, aldicarb sulfone, and 3-hydroxycarbofuran), which made quantification impossible for these three compounds. 

To reduce intensity effects, the data were normalized by reducing the area under each spectrum to a value of 1 [42]. Principal component analysis (PCA) was applied to the normalized data. This method is well suited to optimize the description of the fluorescence data sets by extracting the most useful data and rejecting the redundant ones [43]. From a data set, PCA assesses principal components and their corresponding spectral pattern. The principal components are used to draw maps that describe the physical and chemical variations observed between the samples. Software for PCA has been written by D. Bertrand (INRA Nantes) and is described elsewhere [44]. 

Fig. 8. Dependence of (A) corrected diffusion coefficient (D), (B) steady-state fluorescence intensity, and (C) corrected number of particles in the observation volume (N) of Alexa488-coupled IFABP with urea concentration. The diffusion coefficient and number of particles data shown here are corrected for the effect of viscosity and refractive indices of the urea solutions as described in text. For steady-state fluorescence data the protein was excited at 488 nm using a PTI Alphascan fluorometer (Photon Technology International, South Brunswick, New Jersey). Emission spectra at different urea concentrations were recorded between 500 and 600 nm. A baseline control containing only buffer was subtracted from each spectrum. The area of the corrected spectrum was then plotted against denaturant concentrations to obtain the unfolding transition of the protein. Urea data monitored by steady-state fluorescence were fitted to a simple two-state model. Other experimental conditions are the same as in Figure 6.

The calcein-AM assay [82-84] and cytotoxicity assays (e.g., performed with doxorubicin) [77, 78] are both basically competition assays. The accumulation of a primary substrate (e.g., calcein-AM or doxorubicin) in the cytosol of living cells is measured after addition of a second substrate (also called modifier or reverser) that reduces the efflux of the primary substrate. In the case of the calcein-AM assay, the primary substrate, calcein-AM, is hydrolyzed as soon as it reaches the cytosol, and the highly fluorescent hydrolysis product (calcein) can be determined using fluorescence spectroscopy. The more effective the reversal agent, the stronger is the increase in calcein fluorescence. Data can be quantified in terms of inhibitory constants, IQ, of the reversal agent. 

The ultraviolet spectrum of the monosodium salt of luminol shows the absorptions of both the mono- and the dianion of luminol on addition of potassium tert. butylate the equilibrium is shifted to the dianion109). On the other hand, even small quantities of water shift the equilibrium back to the monoanion. The luminol dianion Lum2< ) was found to have a higher fluorescence efficiency than the monoanion. Absorption and fluorescence data for luminol, Lum< > and Lum2< > are listed in Table 4. 

A plot of the anthracene fluorescence intensity at 425 nm as a function of the reaction time is shown in Figure 2. Again, this figure exhibits the effect of the instrumental artifact in the initial fluorescence data however, examination of the final 90% of the profile reveals that the anthracene concentration profile closely follows a first order exponential decay. Although the photosensitization reaction is bimolecular, the anthracene concentration follows a pseudo-first-order profile since the initiator is present in excess (i.e. r = = kjCA where r, Q and CA represent... 

Data shown are representative of three independent experiments. Cytokine concentrations are in ng/ml. Expression of costimulatory molecules and LDL uptake is represented as Mean Channel Fluorescence. Data represent mean SEM., p < 0.05 for the comparison of untreated and NotoG-treated BMDC, or untreated and LDL-treated BMDC. 

Fluorescence data could be used to quantify oxygen demand values (chemical and biochemical) and total organic carbon values. Furthermore, the fluorescence spectral response can be apportioned to biodegradable (BOD) and non-biodegradable (COD-BOD) dissolved organics [71]. Other studies outline the advantages and drawbacks of the use of fluorescence techniques for waste-water quality monitoring [72,73]. 

Derive information relevant to mechanistic studies of singlet states (from UV-visible absorption spectra and from fluorescence data) and triplet states (from phosphorescence data). 

As outlined above, the spectra are distorted by the wavelength dependence of several components of the instrument. Correction of spectra is of major importance for quantitative measurements (determination of quantum yields and calculation of overlap integrals), for comparison of excitation and absorption spectra, and for comparison of fluorescence data obtained under different experimental conditions. 

The treatment of the fluorescence data can be represented theoretically by the way the probe was constructed. The number of parameters in the equations is dependent on and directly proportional to the number of components affecting the fluorescence signal. The theory described here is intended for a simple probe where the number of parameters involved in the equation have been kept to a minimum (i.e., the interaction of the NIR dye with the metal ions). In addition, it is assumed that no other components in the probe influence the properties of dye or metal. 

W. M. Reichert, J. T. Suci, J. T. Ives, and J. D. Andrade, Evanescent detection of adsorbed protein concentration-distance profiles Fit of simple models to variable-angle total internal reflection fluorescence data, Appl. Spectrosc. 41, 503-507 (1987). 

Lavastre s approach is valid, but the use of (a) less reactive brominated arenes and (b) the obvious lack of solubilizing groups restricts the value of this approach. Perhaps all of the 96 polymers would have to be made in a conventional approach and compared to the polymers obtained by the high-through-put method to draw further conclusions. In addition, the fluorescence was measured in situ, in a THF/diisopropylamine mixture in the presence of the Pd-Cu catalyst. That approach may have an intrinsic problem too, because it is known that PAEs are solvatochromic, and as a consequence, the obtained fluorescence data might be biased. However, with some tweaking this is a powerful method to obtain a cornucopia of different structures quickly and without too much synthetic effort, if the monomers are easily available. 

Problems with sampling measurements of NO have been discussed extensively in the literature. However, recent measurements by Nguyen et al. [20] show that measurements of NO using quartz probes are in agreement with laser-induced fluorescence data. 

Maximum (maximized) likelihood is a statistical term that refers to the probability of randomly drawing a particular sample from a population, maximized over the possible values of the population parameters. Selected entries from Methods in Enzymology [vol, page(s)] Theory, 210, 203 testing by simulations, 210, 225 computer applications for, 210, 233 fitting of sums of exponentials to dwell-time distributions, 207, 772 fluorescence data analysis, 210,... 

Finally, the deposits were heat treated at U00°C for 5 minutes under a N2 atmosphere. X-ray fluorescence data confirmed the presence of Cd and Se in the deposits with no other detectable impurities. CdSe photoelectrodes, 10 cm in area (2x5 cm) were prepared in this manner with a success rate of about 50. ... 

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