Comparison of the performance of the novel red dyes with the benchmark dyes Atto647N and KK114. (a) Overview image of the nucleus of a fixed PtK2 cell showing the Nup153 subunit of the nuclear pore complex immunolabeled with the different dyes coupled to secondary antibodies. Confocal microscopy (left) fails to discriminate individual nuclear pore complexes, whereas STED microscopy (right) identifies essentially each individual complex. (b) Comparison of confocal and STED recordings of the benchmark dyes Atto647N and KK114. Similar comparison between the novel red dyes in (c). Only subdiffraction resolution microscopy enables the accurate size determination (between 40 and 60 nm) of the labeled structures. The novel dye conjugates KK1119, KK9046, STAR635 and STAR635P display superior contrast and less background labeling than Atto647N. All data is raw.