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Dear microscopists,

I'm looking for a reliable source of the FRET spectral overlap integral 
formula. I was unable to decipher it form the original Forster's paper 
(http://onlinelibrary.wiley.com/doi/10.1002/andp.19484370105/epdf). Most 
often I've encountered it in the form as on Wikipedia (https://en.wikipedia.
org/wiki/F%C3%B6rster_resonance_energy_transfer), that is in wavelength 
units and lambda^4 factor. But in some papers (http://pubs.rsc.org/en/
content/articlepdf/2013/cp/c3cp50173f), formula (4), it's in the wavenumber 
units and a nu^(-4) factor.

The problem is the two formulas are mathematically incompatible (I believe).
Given nu=1/lambda and the integral substitution rule (http://tutorial.math.
lamar.edu/Classes/CalcI/SubstitutionRuleIndefinite.aspx) there should be 
another nu^(-2) "Jacobian", yielding nu^(-6). Or alternatively, if the "nu"-
formula is correct, then a lambda^(-2) factor would lead to lambda^2 in the 
well know formula...

To sum up, I believe either one or the other part of the formula (5.5) here 
(https://books.google.com/books?id=GXWAAQAAQBAJ&pg=PT117) is wrong. Btw, the
same should apply to formula (5.6) in the same book (if the link does not 
work, it's "FRET - Förster Resonance Energy Transfer: From Theory to 
Applications"), as the two ways to normalize the spectrum are very 
different...

I found one experimental paper in favor of the "lambda"-version (http://www.
pnas.org/content/63/1/23.full.pdf), see fig 6. But can anyone point me 
towards the origin of the formula?

Thanks, zdenek




-- 

Zdenek Svindrych, Ph.D.

W.M. Keck Center for Cellular Imaging (PLSB 003)

University of Virginia, Charlottesville, VA 

http://www.kcci.virginia.edu/

tel: 434-982-4869