Fluorescence spectroscopy picosecond time range

Thus we investigated the energy flow in Erythrobacter sp. strain OCh 114 with the time-resolved fluorescence spectroscopy in the picosecond time range. We found fast energy transfer from B806 to B870 (within 6 ps), and also detected the presence of the new type of Bchl-form. 

In this study, we adopted two kinds of fluorescence spectroscopy, steady-state and the time-resolved spectroscopy in the picosecond time range, for the analysis of energy flow in whole cells of the marine dinoflagellate Protogonyalux tamarensis under the excitation condition of peridinin. Results show unique fluorescence components in this species and characteristic energy flow among them. 

The major reasons for using intrinsic fluorescence and phosphorescence to study conformation are that these spectroscopies are extremely sensitive, they provide many specific parameters to correlate with physical structure, and they cover a wide time range, from picoseconds to seconds, which allows the study of a variety of different processes. The time scale of tyrosine fluorescence extends from picoseconds to a few nanoseconds, which is a good time window to obtain information about rotational diffusion, intermolecular association reactions, and conformational relaxation in the presence and absence of cofactors and substrates. Moreover, the time dependence of the fluorescence intensity and anisotropy decay can be used to test predictions from molecular dynamics.(167) In using tyrosine to study the dynamics of protein structure, it is particularly important that we begin to understand the basis for the anisotropy decay of tyrosine in terms of the potential motions of the phenol ring.(221) For example, the frequency of flips about the C -C bond of tyrosine appears to cover a time range from milliseconds to nanoseconds.(222)... 

Stimulated fluorescence appears with a delay of about 500 fs relative to the A [ absorption, although both absorption and fluorescence stem from the same state, proved by decay measurements with picosecond time-resolved spectroscopy. This delayed appearance of stimulated fluorescence is caused by a quickly increasing and short-lived absorption A0 located in nearly the same spectral range as the fluorescence. The authors assumed that the instant absorption A0 is caused by a state located slightly below the level reached by excitation with 4eV. This state 2,... 

The possibility of increasing the emission of rhodamine B (RhB) as a result of its interaction with surfeice plasmons (SFs) created by copper nanoparticles (Cu NPs) has recentiy been presented. The optical absorption and emission of RhB with Cu NPs incorporated into glass films formed the by sol-gel method were studied by steady-state and picosecond spectroscopy. The observed increased luminescence is the result of interaction of the excited state of the dye with scattered light created by copper plasmons and possible energy transfer from the excited Cu NPs that occurs in the femtosecond time range. The steady-state absorption, excitation, fluorescence, and lifetimes excited by picosecond pulses were measured. The quantum efficiencies of the films were obtained by a comparative method [61]. 

Picosecond fluorescence studies were applied by Winnik and co-workers [72] for studies of temperature-induced phase transition of pyrene-labelled hydroxypropylcellulose (HPC-Py) in water. Temperature dependence of the fluorescence emission ratio of excimer to monomer emission (Ie/Im) showed a significant increase of excimer emission in a temperature range 283-313 K, then a decrease to a constant value at 319 K. Two excimer bands were observed when time-resolved spectroscopy was used i) a broad, structureless band with a maximum at 420 nm and a corresponding lifetime of 250 ps and ii) the well-known band of pyrene excimer, with a maximum at 470 nm and a lifetime of 68 ns. In the initial time region, 0-150 ps, monomer emission was observed, with a simulation by a superposition of three components (377, 398 and 421 nm). They observed only one excimer emission above the LCST and that was with a maximum at 470 nm. They concluded that the LCST implies a complete disruption of the ordered microstructures, which were created in cold water. 

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