Fluorescence spectra recording

The indole chromophore of tryptophan is the most important tool in studies of intrinsic protein fluorescence. The position of the maximum in the tryptophan fluorescence spectra recorded for proteins varies widely, from 308 nm for azurin to 350-353 nm for peptides lacking an ordered structure and for denatured proteins. (1) This is because of an important property of the fluorescence spectra of tryptophan residues, namely, their high sensitivity to interactions with the environment. Among extrinsic fluorescence probes, aminonaphthalene sulfonates are the most similar to tryptophan in this respect, which accounts for their wide application in protein research.(5)... 

Steady-state fluorescence spectra recorded after the addition of the NDI or PM I acceptor to the bisporphyrin tweezer ( rrl = 660 nm), demonstrated substantial quenching (75%) with increasing quantities of the NDI or PM I acceptors. Time-resolved emission spectra recorded in toluene for the complex 26 were biexponential containing a dominant short-lived CS components (80 ps, -95%) attributed to photoinduced ET from donor porphyrin to NDI, and a minor long-lived component (Ins, 5%). The lifetime of the dominant short-lived CS state is increased two- to threefold relative to covalently linked systems under similar conditions of solvent, donor-acceptor distance and thermodynamics [37]. Charge recombination rates from 1.4 to 3.8 x 1()9s 1 were observed, depending on whether the NDI or PM I acceptor was bound within the cavity. 

Step 3 Students will analyze emission spectra obtained in steps 1 and 2 using the Burstein equation. For the fluorescence spectra recorded in step 1, the Burstein equation should yield theoretical spectra that match the recorded spectra. However, this will not be the case for the tyrosine-tryptophan mixture. 

Fig. 11 Laser-induced fluorescence spectra recorded from Napl-doped PMMA samples (1.2 wt%) after their irradiation with a single pump pulse at 248 nm at laser fluences below a, and above b the corresponding ablation thresholds. For comparison purposes, the spectra have been scaled. The figure also illustrates the approximate deconvolution of the probe spectrum into the emission bands of the suggested species (the Nap2 spectrum is recorded in the photolysis of high-concentration NapI solution, while the NapH/PMMA spectrum is recorded from PMMA doped with 0.08 wt% NapH)...

Fig. 12 Laser-induced fluorescence spectra recorded from Napl-doped PMMA samples (1.2 wt%) after their irradiation with a single pump pulse a at 248 nm and b at 308 nm at laser fluences about 1.5 times the corresponding ablation thresholds...

Fig. 16 Laser-induced fluorescence spectra recorded from NapI/PMMA (0.4 wt%) irradiated with the indicated number of pulses (at 248 nm) at the two indicated fluences...

As a typical example, Fig. 1.13 shows fluorescence spectra recorded from an LB film of DPOPP (for the absorption spectra, see Fig. 1.9). The exciting light was polarized parallel to the dipping direction. 

The decay profiles gave no indication of displaced EB, provided the concentration of DAP " was kept below ca. 120 iM, although excitation and detection wavelengths were optimized in favor of preferentially observing intercalated dye. Furthermore, the fluorescence spectral records showed that added DAP was present exclusively in the intercalated form and that, under the experimental conditions, none was bound to the polynucleotide surface or free in solution. Gated fluorescence spectra, recorded at different times after the excitation pulse, were identical within experimental error and remained in excellent agreement with those recorded by steady-state methods. 

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