A: Relative fluorescence intensity at 515 nm of SITS – labeled αA-crystallins interacting with LYI – labeled βL- crystallin.

<p>Time – dependent increase in acceptor fluorescence in emission intensity is due to subunit exchange. Increase in the relative fluorescence intensity at 515 nm is due to energy transfer from the SITS – labeled protein to the LYI – labeled protein. SITS – labeled αA- wt (♦), αA_1–172(▪), αA_1–168 (▴) and αA_1–162 (•) were incubated with LYI – labeled βL- crystallin. Each curve was analyzed with the best curve fit of the data to the exponential function F_t/F₀ = A₁+A₂ e^−kt. B: Relative fluorescence intensity at 426 nm of SITS – labeled αA-crystallins interacting with LYI – labeled βL- crystallin. Time – dependent decrease in donor fluorescence in emission intensity is due to subunit exchange. Decrease in the relative fluorescence intensity at 426 nm is due to energy transfer from the SITS – labeled protein to the LYI – labeled protein. SITS – labeled αA- wt (♦), αA_1–172(▪), αA_1–168 (▴) and αA_1–162 (•) were incubated with LYI – labeled βL- crystallin. Each curve was analyzed with the best curve fit of the data to the exponential function F_t/F₀ = A₁+A₂ e^−kt.