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Neela Fazl

Is it important to distinguish Dexter energy transfer from Forster...

Alex Zorach  Follow

As far as I remember, Forster and Dexter processec has a different dependence of their rate on the polarity of the solvent. Look, for example
S.A. Green, D.J. Simpson, G. Zhou, P.S. Ho, N.V. Blough, J. Am. Chem. Soc., 1990, 112, 7337

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Dennis Sardella  Follow

If your DA pair has a moderate to large Forster radius (it can be computed from spectroscopic data) then the efficiency of transfer should be close to 1 (unless the relative  orientation of the chromophores is very unfavorable), even knowing that the point dipole-point dipole approximation (FRET) does not hold perfectly for such short distances. A possible supplementary Dexter contribution will go unnoticed. You should also consider that quenching by electron transfer can occur (depending on the nature of D and A), especially in polar solvents. 

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Angel Lacret  Follow

Forster resonance energy transfer (FRET) is a non-radiative (radiationless) energy transfer. 
Dexter energy transfer involves transfer of excitation from donor to acceptor due to hopping of electrons. For this to happen the wavefunctions of both donor and acceptor must overlap.
As a consequence FRET occurs over large distance as compared to Dexter energy transfer.
Typical distance range for FRET is 10-100 Angstroms and for Dexter energy transfer it is <10 Angstroms.
It is not important to distinguish Dexter energy transfer from FRET. It does not matter by what mechanism energy transfer occurs. It is just another processes by which excitation energy is lost from the donor.
Dexter energy transfer efficiency can be measured in the same manner as one measures FRET efficiency. 
It can be measured from the ratio of fluorescence lifetime of donor in the presence of acceptor to the fluorescence lifetime of donor in the absence of acceptor using the formula E = 1-(tauDA / tauD)

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Daryl Larsen  Follow

Mechanism is important / unimportant depending on what you want to do.
If you are interested only in calculating only the energy transfer efficiency then it does not matter by which mechanism energy transfer occurs. You can do it by the method given above by me.
But if you are interested in calculating the rate constant of energy transfer theoretically then the mechanism will be important.
or If you want to exactly determine the mechanism by which energy transfer occurs in such a system then the distinction between the two would be important.
You can determine if the energy transfer occurs using either of the two mechanisms or a combination of both FRET and Dexter mechanisms by fitting the experimental determined rate constant with the calculated value using a combination of both the mechanisms.

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China - World Leader.  Follow

Mechanism is important / unimportant depending on what you want to do.
If you are interested only in calculating only the energy transfer efficiency then it does not matter by which mechanism energy transfer occurs. You can do it by the method given above by me.
But if you are interested in calculating the rate constant of energy transfer theoretically then the mechanism will be important.
or If you want to exactly determine the mechanism by which energy transfer occurs in such a system then the distinction between the two would be important.
You can determine if the energy transfer occurs using either of the two mechanisms or a combination of both FRET and Dexter mechanisms by fitting the experimental determined rate constant with the calculated value using a combination of both the mechanisms.

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Charles Thomas  Follow

Forster resonance energy transfer (FRET) is a non-radiative (radiationless) energy transfer. 
Dexter energy transfer involves transfer of excitation from donor to acceptor due to hopping of electrons. For this to happen the wavefunctions of both donor and acceptor must overlap.
As a consequence FRET occurs over large distance as compared to Dexter energy transfer.
Typical distance range for FRET is 10-100 Angstroms and for Dexter energy transfer it is <10 Angstroms.
It is not important to distinguish Dexter energy transfer from FRET. It does not matter by what mechanism energy transfer occurs. It is just another processes by which excitation energy is lost from the donor.
Dexter energy transfer efficiency can be measured in the same manner as one measures FRET efficiency. 
It can be measured from the ratio of fluorescence lifetime of donor in the presence of acceptor to the fluorescence lifetime of donor in the absence of acceptor using the formula E = 1-(tauDA / tauD)

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Alfred Montestruc  Follow

Professor, can you suggest some paper for distinguishing FRET from Dexter?

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Derrick S.  Follow

As our colleagues said, Dexter energy transfer requires overlap of D and A wavefunctions and occurs typically in range < 10 Angstroms. Other important factor is overlapping of D fluorescence emission spectrum and A absorption spectrum. In conclusion, DA pair must be in contact to Dexter energy transfer occurs.

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