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H Philipp, 

dsRed had dimerization problems, but Roger Tsien addressed that by expressing Tomato as a tandem dimer.  Two FP's in a single tag makes it twice as bright (allowing for loss to quenching and homo-FRET) and lets them to form an intramolecular dimer rather than grab outside an outside binding partner like dsRed did.  Do you mean that Tomato forms tetramers?  That would be news to me.  

cheers, 


TF

Timothy Feinstein, PhD
Visiting Research Associate 
Laboratory for GPCR Biology
Dept. of Pharmacology & Chemical Biology
University of Pittsburgh, School of Medicine 
BST W1301, 200 Lothrop St.
Pittsburgh, PA  15261

On Feb 21, 2013, at 4:38 PM, Philipp Steffen wrote:

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> 
> Hi Julia,
> 
> it might be important to keep in mind that tdtomato forms dimers. If you are planning to study molecular kinetics using FRAP (e.g. extract estimates for the diffusion coefficient or rate constants of binding reactions) it would be better to chose a fluorescent proteins that does not easily dimerizes. For other studies, this might not be a concern.
> 
> Best regards,
> 
> Philipp
> 
> ********************************************
> Philipp A. Steffen
> Postdoctoral fellow - Ringrose laboratory
> Institute of Molecular Biotechnology
> Dr. Bohr-Gasse 3
> 1030 Vienna
> Austria
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> 
> On Feb 21, 2013, at 10:19 PM, Julia Edgar wrote:
> 
>> *****
>> To join, leave or search the confocal microscopy listserv, go to:
>> http://lists.umn.edu/cgi-bin/wa?A0=confocalmicroscopy
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>> 
>> Dear All
>> Does anybody have experience in using td-tomato fluorescent protein for FRAP?
>> I will be grateful to hear about your experiences.
>> Thanks in advance
>> Julia 
>> 
>> Julia Edgar
>> University of Glasgow
>> UK