Fluorescence-emission spectra

The six major proteins of milk, asl-, o s2-, and /c-casein, jS-lactoglobulin, and a-lactalbumin, contain at least one tryptophan residue [57], the fluorescence of which allows the monitoring of the structural modifications of proteins and their physicochemical environment during the coagulation processes. Emission fluorescence spectra of the protein tryptophanyl residues were recorded for the milk coagulation kinetics induced by... 

FIGURE 5.25 Emission fluorescence spectra (/ex = 340 nm) of dendron 31 (50 mM) upon removal of the Boc trigger upon incubation in 1 1 MeOH/DMSO mixture with 2% aqueous solution of Bu4NOH. (See the color version of this figure in Color Plates section.)... 

Photophysical Processes in Pi butyl 4,4 -Sulfonyldibenzoate (4,4 -SD). The UV absorption spectra of dibutyl 4,4 -sulfonyl-dibenzoate (4,4 -SD) in both HFIP and 95% ethanol showed similar absorptions. The corrected excitation and emission fluorescence spectra of 4,4 -SD in HFIP at 298°K showed a structured excitation with band maxima at 236, 286, and 294 nm and a structured emission exhibiting band maxima at 322, 372, and 388 nm. The uncorrected excitation and phosphorescence spectra of 4,4 -SD in a 95% ethanol glass at 77°K displayed excitation band maxima at 268, 282, and 292 nm with strong phosphorescence emission with band maxima at 382, 398, and 408 nm with a mean lifetime (t) of 1.2 sec. 

Capitan-Vallvey et al. [43] has developed a spectrofluorimetric method for the quantitative determination of flufenamic, mefenamic and meclofenamic acids in mixtures by recording emission fluorescence spectra between 370 and 550 nm with an excitation wavelength of 352 nm. The excitation-emission spectra of these compounds are deeply overlapped which does not allow their direct determination without previous separation. The proposed method applies partial least squares... 

Fluorescence spectrofluorimetry is a type of electromagnetic spectroscopy that generates absorbance and emission fluorescent spectra, giving insights into biomolecular structure. 

FIGURE 14. Excitation and emission fluorescence spectra of humic and fulvic acids from various soil and aquatic sources (Plechanov et al., 1983). 

Another development, also with a history in chemistry, is second-order calibration, where rank annihilation was developed for analyzing data from typically hyphenated instruments. This includes excitation-emission fluorescence spectra of different samples, liquid chromatography with ultraviolet (UV) detection for different samples and gas chromatography with mass spectrometric detection for different samples, giving an array. An illustration is given in Figure 10.2. 

Beltran JL, Ferrer R, Guiteras J, Multivariate calibration of polycyclic aromatic hydrocarbon mixtures from excitation-emission fluorescence spectra, Analytica Chimica Acta, 1998a, 373, 311-319. 

Features of fluorescence spectra. The excitation and emission fluorescence spectra of Tb3+, Tb-DNA, Tb-RNA, Tb3+-PCA, Tb3+-PCA-RNA, Tb3+-PCA-DNA are shown in Fig. 1(a) and (b). No characteristic fluorescence of Tb3+ was observed in Tb3+. Tb-DNA and Tb-RNA systems, but Tb3+-PCA system emits three strong characteristic fluorescence peaks of Tb3+ located at 489 nm, 546 nm and 587 nm, which correspond to the 5D4-7F6, 5D4-7F5 and 5D4-7F4 transitions of Tb3+, respectively. The maximum excitation wavelength was 320 nm. The fluorescence intensity of the Tb3+-PCA system was strongly quenched with the addition of nucleic acids. However, the quenching fluorescence intensity of RNA is much stronger than that of DNA. We chose a peak of excitation wavelength 320 nm, and... 

Figure 2. Emission fluorescence spectra obtained at different laser power intensities under excitation with Ar laser in a 1 mol% of Nd oxyfluoride glass sample. Emission spectrum of a 1 mol% of Nd " oxyfluoride glass ceramic sample (GC) obtained using a furnace under Ar laser excitation.

Figure 9-6. UV absorption and emission fluorescence spectra of Y3AW (—) and Y3W (--) analogs of hirudin fragment 1-47. The fluorescence spectrum of free Y3AW analog was multiplied by sixfold. All measurements were carried out at 25°C in 5-mM Tris-HCl buffer, pH 8.0, containing 0.2-M NaCl and 0.1% PEG-8000, at a protein concentration of 2)xM. Sample excitation was at 280 nm.

Figure 9-7. Disulfide oxidative folding of Y3AW analog monitored by fluorescence spectroscopy. (A) UV-absorption spectra of free tryptophan (W, —) and 7-azatryptophan (AW, —), acting as energy acceptors, and fluorescence spectrum of tyrosine (Y, ---), acting as an energy donor. Emission fluorescence spectra of Y3AW (B) and Y3W (C) in the reduced (—) and disulfide oxidized, native state (-). All spectra were taken at 25°C by exciting the samples (5 xM) at 280nm in 0.1-M NaHCOs, pH 8.3, except for that of the fully reduced form, which was recorded in 0.1-M morpholinoethane sulfonic acid buffer, pH 6.0. This pH value is sufficiently low to impair disulfide formation for at least 4 hours (not shown) and, concomitantly, avoid protonation of N -atom of the azaindole nucleus, which has a pKj value of 4.5 [94].

Figure 1 Synchronous excitation/emission fluorescence spectra. (Reproduced with permission from Kelly CA, Law RJ, and Emerson HS (2000) Methods for the analysis of hydrocarbons and polycyclic aromatic hydrocarbons (PAH) in marine samples. Aquatic Environmental Protection Analytical Methods, CEFAS Lowestoft 12, 18pp. British Crown.)...

However, the emission fluorescence spectra obtained for the P-lactoglobulin permeate solutions (acquired upon ultraflltration using the lOkDa membrane) reveals a substantial broadening of the emission band accompanied by a red shift in the fluorescence emission maximum. In contrast, the permeation of P-lacto-globulin solutions using membranes of the same material with 30kDa cut-off... 

Relations between F 750 and PS Ij PS II activities, f 750 kinetics were also studied on cell free extracts (after sonication see material and methods). The 10 000 g supernatant fraction (= S 10 000) exhibited a significant variable F 750, although generally weaker than in whole cells ((Fo-Fm)/Fm = 0,5 versus 0,6 for 680 nm excitation beam). This fraction retained appreciable PS I electron transport activities. The presumption of a relationship between PS I and F 750, as suggested by action spectrum, had to be established. Treatment of cyanobacterial cells by 2-hydroxydiphenyl (2 H-D) led to PS II inactivation (Thomas, Mousseau 1981). 2 H-D treated cells (300 mM, 34 h or 50 h incubation time) were tested for PS II electron transport activity (H20->p-Benzoquinone). PS I activity was appreciated on S 10 000 (red. DAD— Methylviologen). F 750 properties and emission fluorescence spectra were measured at the same time. A good correlation was found between disappearance of F 695 (Fig. 6), loss of PS II activity (Table I) and between evolution of F 750 emission (Fig. 6), PS I activity (Table I) and F 750 kinetics (Fig. 7, Table I). 

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