acquired by an inverted microscope (IX71, Olympus), illuminating samples
by a W lamp. Fluorescence micrographs are collected by exciting with
a Hg lamp through a 20× objective of another inverted microscope
(Eclipse Ti, Nikon) and collecting emission maps by a charge-coupled
device (CCD) detector (Digital Sight-U2, Nikon). Confocal fluorescence
imaging is performed by an inverted microscope equipped with a laser
scanning confocal head (A1R-MP, Nikon). To this aim, samples are excited
by a laser diode (λexc = 408 nm) through a 20×
objective, whereas the emitted light is collected by the same objective
and measured by a spectral detection unit equipped with a multianode
photomultiplier (Nikon).