The rate constant k_q governing de-excitation of fluorescence via quenching by a molecule of quencher, Q, depends on the concentration of Q in solution. Thus, k_q = (k_q*) x [Q] . The fluorescence lifetime = 1/(k_f +k_i+k_q).

a) Show that _o / = 1 + k_qo , where o is the fluorescence lifetime in the absence of quencher.

b) Let k_f = k_i = 10⁹ /s and k_q* = 10¹²/(s x M) and plot

i) _o/ vs [Q] and

ii) quantum yield vs [Q] for 0 [Q] 10 mM.