Connectin, also called titin, a giant elastic protein of striated muscle (-3000kDa), mainly consists of fibronectin type III and immunoglobulin C2 globular domains, the β-sheets of which are largely parallel to the main axis of the molecule. One connectin molecule runs through the I band and binds onto the myosin filament up to the M line starting from the Z line. It positions the myosin filament at the center of a sarcomere. Connectin is also responsible for resting tension generation. Biodiversity of the connectin family exists in invertebrate muscle.
Ultrafast spectroscopy is a powerful technique to investigate primary processes in photoreceptive pigments. Here I review the history, recent progress and perspective of ultrafast spectroscopic studies applied to retinal proteins. Femtosecond pulse generation enabled us to look directly into the excited state dynamics of retinal proteins, and hence we now know that one of the fastest reactions in photochemistry occurs in our eyes. Applications of ultrafast spectroscopy to native and modified retinal proteins as well as their chromophores in solution have provided noteworthy results on the isomerization processes of the retinal chromophore. In particular, the classical one-dimensional picture along isomerization coordinate is now being questioned.