On 2014 Mar 18, George McNamara commented:

There are several publications on multimeric FPs, including these on 6xFPs:

Genové G, Glick BS, Barth AL. Brighter reporter genes from multimerized fluorescent proteins. Biotechniques. 2005 Dec;39(6):814, 816, 818 passim. PubMed PMID: 16382897. http://www.ncbi.nlm.nih.gov/pubmed/16382897

Nguyen TA, Sarkar P, Veetil JV, Koushik SV, Vogel SS. Fluorescence polarization and fluctuation analysis monitors subunit proximity, stoichiometry, and protein complex hydrodynamics. PLoS One. 2012;7(5):e38209. doi: 10.1371/journal.pone.0038209. PubMed PMID: 22666486; PubMed Central PMCID: PMC3364239. http://www.ncbi.nlm.nih.gov/pubmed/22666486 See especially Figure 4a, which shows a dimer of V6 is ~12x brighter than Venus, http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3364239/figure/pone-0038209-g004/

I also want to give a shout out to Robinett et al, who put 512 GFP's in one diffraction limited spot (plus some nuclear GFP smog from overexpression) in Fig 4A of: Robinett CC, Straight A, Li G, Willhelm C, Sudlow G, Murray A, Belmont AS. In vivo localization of DNA sequences and visualization of large-scale chromatin organization using lac operator/repressor recognition. J Cell Biol. 1996 Dec;135(6 Pt 2):1685-700. PubMed PMID: 8991083; PubMed Central PMCID: PMC2133976. http://www.ncbi.nlm.nih.gov/pubmed/8991083 http://jcb.rupress.org/content/135/6/1685.long (PDF)

On 2014 Mar 18, George McNamara commented:

There are several publications on multimeric FPs, including these on 6xFPs:

Genové G, Glick BS, Barth AL. Brighter reporter genes from multimerized fluorescent proteins. Biotechniques. 2005 Dec;39(6):814, 816, 818 passim. PubMed PMID: 16382897. http://www.ncbi.nlm.nih.gov/pubmed/16382897

Nguyen TA, Sarkar P, Veetil JV, Koushik SV, Vogel SS. Fluorescence polarization and fluctuation analysis monitors subunit proximity, stoichiometry, and protein complex hydrodynamics. PLoS One. 2012;7(5):e38209. doi: 10.1371/journal.pone.0038209. PubMed PMID: 22666486; PubMed Central PMCID: PMC3364239. http://www.ncbi.nlm.nih.gov/pubmed/22666486 See especially Figure 4a, which shows a dimer of V6 is ~12x brighter than Venus, http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3364239/figure/pone-0038209-g004/

I also want to give a shout out to Robinett et al, who put 512 GFP's in one diffraction limited spot (plus some nuclear GFP smog from overexpression) in Fig 4A of: Robinett CC, Straight A, Li G, Willhelm C, Sudlow G, Murray A, Belmont AS. In vivo localization of DNA sequences and visualization of large-scale chromatin organization using lac operator/repressor recognition. J Cell Biol. 1996 Dec;135(6 Pt 2):1685-700. PubMed PMID: 8991083; PubMed Central PMCID: PMC2133976. http://www.ncbi.nlm.nih.gov/pubmed/8991083 http://jcb.rupress.org/content/135/6/1685.long (PDF)