Figure 3.

Simultaneous RLC-GFP fluorescence and myosin SHG in vivo by 2-P excitation. Infrared light at 810 nm excites fluorescence at ∼500 nm (green) and SHG at 405 nm (blue) in the wide view of the trunk skeletal muscles in the tail (left) and in the close-up of two individual fibers (right). The I-band, with actin but no myosin, and the M-line, without myosin cross bridges, are dark in comparison to the A-band, which contains both myosin cross bridges and actin. The A-band shows both GFP fluorescence and SHG signals indicating colocalization of RLC-GFP with the cross bridge. Sarcomere length is ∼2.1 μm.