Claudin subtype-specific differences in homo- and heterophilic cis-interactions in cell suspension. HEK cells were cotransfected with CFP- and YFP-fusion proteins (e.g., Cld5CFP/ Cld5YFP), detached from the culture plate and single cell suspension prepared by pipetting. a FRET-analysis by flow cytometry. As a measure for the FRET-efficiency, the FRET-ratioFC was calculated.*p < 0.02, n = 3–5, for each sample>2,500 coexpressing cells were analyzed. b FRET-analysis by spectrofluorometry. As a measure for the FRET-efficiency, the FRET-ratioS was calculated. In addition to indicated pairs, the FRET-ratioS was for all pairs but not Cld3/Cld2 and Cld3/Cld5Y148A significantly higher than for the negative control (Cld5/CRFR1). *p < 0.01, n = 4–16