Recombination fluorescence

Petushkov, V. N., Gibson, G. B., and Lee, J. (1995). Properties of recombinant fluorescent proteins from Photobacterium leiognathi and their interaction with luciferase intermediates. Biochemistry 34 3300-3309. 

Recombination fluorescence has been used to study the decay of radical ion pahs generated photolytically.288 Simulation of quantum beats caused by hyperfine interaction in the R and R+ enable the values of hfc to be determined for very short-lived species. In the case of one R excellent agreement with the value of hfc as determined by ESR is reported. The primary reaction in the photolysis of 1-arylalkyl radicals (128) is the heterolytic cleavage of the -halogen (X), generating the radical cation (129).289... 

Sauer Jr, MC, Jonah CD, Naleway CA. (1991) Study of the reactions of geminate ions in irradiated scintillator, hydrocarbon solutions using recombination fluorescence and stochastic simulations. JPhys Chem 95 730-740. 

Figure 4. The decay of recombination fluorescence for solution of 10 M p-terphenyl-i/u and 3x10 M diphenylsulphide-c io in isooctane in various magnetic fields [23]. For convenience, the curves are shifted relative to each other. The oscillating component comes from the recombination of the singlet-bom pairs (diphenylsulphide-r io)V(p-terphenyl-(/i4). ...

Fig. 8.16 Scheme of the individual steps in the process of intrinsic photogeneration of charge-carrier pairs, Mp - M, in a molecular C7stal. The charge carriers are polarons (p). a Sq = neutral ground state S], S2, S3 are singlet excitons. Rate constants k/ i for autoionisation, kn for radiationless and kr for radiative intramolecular recombination (fluorescence), b bound charge-carrier pairs... 

Production of Recombinant Fluorescent Chemokine-Encoding Baculoviruses... 

For production of recombinant fluorescent chemokine fusion proteins Trichoplusia ni 5B1-4 cells (H5 high five cells) are grown at 27 °C in suspension cultures in Insect-Xpress medium in 1800 mL Fembach culture flasks. Importandy, the cells grow without FCS facilitating purification of the chemokine from the culture supernatant. 

Recombinant fluorescent chemokine fusion proteins are purified from insect cell culture supernatants by sequential chromatography using... 

Fluorescence measurements indicate that the chlorophyll cation Is formed only In active reaction centres. Charge recombination fluorescence is quenched by the addition of DBMIB, whilst the fluorescence from inactive reaction centres and free chlorophyll is unchanged [4]. 

This paper confirms the assignment of the 37 ns component to charge recombination of P680 Ph and that of the 6.5 ns component to uncoupled chlorophyll which is not connected with this process. The amount of uncoupled chlorophyll present in the D1/D2 preparations and the fluorescence quantum yield of the recombination fluorescence are also calculated. 

P680 ) were calculated over the temperature range 77-277 K from time resolved measurements on active D1/D2 samples over this range (see table 1). The quantum yield for the recombination fluorescence (( >j) from the D1/D2 particle at temperatures below 277 K... 

Recombination fluorescence The first excited singlet state becomes populated by recombination of radical ions and electrons or by recombination of radical ions of opposite charge (Scheme 7.2). 

The ionization energy of TMPD in solid and liquid solutions of hydrocarbons was studied by biphotonic ionization and detection of recombination fluorescence (Bullot and Gauthier, 1976). Generally, the photoionization threshold decreased on going from the solid to the liquid phase. The following sequence was observed ... 

Figure 5. Simulated fluorescence kinetics (right) as a function of recording wavelength and a fluorescence polarization P=(Iu - + lx ) excitation spectrum at 935 nm (upper left panel) at 77 K. Recombination fluorescence is taken into account. Transition dipole moments of antenna molecules are randomly orientated in the membrane plain. Dipole moment orientation of RC special pair is fixed as indicated by arrow in the center of PSD model used (lower left panel). All curves are averaged over 30 random sets of antenna molecul orientations. Other conditions as in Fig. 1...

A second key assumption which was discussed in the original paper is that the steady-state fluorescence is not dominated by delayed fluorescence. The precise origins of delayed fluorescence, especially components with lifetimes shorter than tens of ns and are not dependent on magnetic fields, is not yet clear [20,211. It is generally believed that all components involve recombination from ion-pair states, P X. Because the delayed, recombination fluorescence involves an activated process, it is reasonable to expect that the field dependence should be very strong, in contrast to the approximately quadratic dependence which is observed 5. Furthermore, the contribution in... 

Saik, VO. and Lipsky, S., Magnetic field effects on recombinant fluorescence comparison of VUV and fast electron excitation, Chem. Phys. Lett., 264, 649, 1997. 

In the above reaction scheme Solv" ", C-RH+, S represent the solvent cation, cyclohexane cation and hexafluorobenzene (HFB) anion respectively. The spin-dynamics of S and c-RH+ determine the magnetic field effect, since the spin wave-function for the ion pair (S / c-RH+) evolves differently at the different magnetic field strengths. The intensity of recombination fluorescence of the solution is determined by the rate of radiative deactivation of S [reaction (7)], which is accumulated within the simulation program. Although this model is not a complete description of the radiolysis of n-hexane which contains a solution of HFB and cyclohexane, it does however, take into account the most important aspect of the proposed relaxation mechanism, namely cross recombination. A more detailed reaction scheme for the radiolysis of n-dodecane is considered later in this chapter (in Sect. 8.6), which takes into account the excited state chemistry as well as spin-exchange reactions. 

Due to cross-recombination of the (S+ / e ) pair, the rate of reaction (6) is greatly reduced for a linear spur, producing less D, which in turn leads to less fluorescence. In addition, because of more cross-recombination of the (D+ / e ) pair in the linear structure there is less produced via reaction (4), which in turn has the effect of further depleting the recombination fluorescence via reaction (10). 

It was found that contact interactions of the intermediates [reactions (11)-(17)] (i) acted as an extra source of spin relaxation for spin-correlated D+ / e pairs and (ii) decreased the frequency of annihilation for D. The former is due to spin exchange in reactions (3) and (15)-(17), as these reactions have the effect of incoherently changing the spin states of the correlated pairs the latter is due to the enhancement of the singlet-triplet intersystem crossing of S in reactions (13)-( 15), which depletes S and the frequency of reaction (6). Hence this results in a subsequent decrease in the yields of D and D as well. This analysis was also found to be true by Borovkov [36]. It can also be seen from Fig. 8.13 that the contribution of the annihilation of triplet solutes to the recombination fluorescence intensity becomes comparable with reaction (4) at 30ns time range at the luminophor concentration of about 20 mM. 

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