EGFP:mCherry FRET pair will work and it works for us.
You should try EGFP-tdTomato. tdTomato is a good acceptor than mCherry. The brightness of tdTomato is 95 and mCherry is 17. EGFP spectral overlap is good with tdTomato.

Ammasi Periasamy, Ph.D.
Director, Keck Center for Cellular Imaging (KCCI)
Professor of Biology and Biomedical Engineering
Biology, Gilmer Hall (064), McCormick Rd
University of Virginia
Charlottesville, VA 22904
Voice: 434-243-7602 (Office); 982-4869 (lab)
Fax:434-982-5210; Email:[log in to unmask]
http//:www.kcci.virginia.edu
************************
Workshop on FRET Microscopy, March 9-13, 2010
http://www.kcci.virginia.edu/workshop/workshop2010/index.php
*************************


-----Original Message-----
From: Confocal Microscopy List [mailto:[log in to unmask]] On Behalf Of Soren Prag
Sent: Wednesday, September 30, 2009 12:59 PM
To: [log in to unmask]
Subject: FRET pair

I am currently redesigning some FRET probes and therefore I have the
opportunity to optimize my FRET pair.
Due to limited lasers available I am restricted to 488nm (EGFP) as donor. So
my question is which acceptor to use. 

Does anyone know of direct comparisons between EGFP:mCherry and EGFP:TagRFP,
and TagGFP:mCherry and TagGFP:TagRFP, and/or does anyone know a better FRET
pair working with the 488nm/561nm lasers?

I am planning to compromise and do both sensitized FRET and fluorescent
lifetime.

Thanks for your help,

Soren

Instituto de Medicina Molecular
Faculdade de Medicina da Universidade de Lisboa 
sprag at fm.ul.pt