quenchingoffluorescence

quenchingoffluorescence内容摘要：

f the plex. Such cases of quenching via plex formation were first described by Gregorio Weber. In the case of static quenching the lifetime of the sample will not be reduced since those fluorophores which are not plexed – and hence are able to emit after excitation – will have normal excited state properties. The fluorescence of the sample is reduced since the quencher is essentially reducing the number of fluorophores which can emit. Static Quenching In some cases, the fluorophore can form a stable plex with another molecule. If this groundstate is nonfluorescent then we say that the fluorophore has been statically quenched. F + Q FQ [ F ] [ Q ]]FQ[aK]Q[1]F[ ]FQ[]F[[ F ]]F[ .0 at o t KII [FQ] = Ka [F][Q] I0/I [Q] If both static and dynamic quenching are occurring in the sample then the following relation holds: I0/I = (1 + kq t0[Q]) (1 + Ka[Q]) In such a case then a plot of I0/I versus [Q] will have an upward curvature due to the [Q]2 term. However, since the lifetime is unaffected by the presence of quencher in cases of pure static quenching, a plot of t0/t versus [Q] would give a straight line I0/I [Q] t0/ t Nonlinear SternVolmer plots can also occur in the case of purely collisional quenching if some of the fluorophores are less accessible than others. Consider the case of multiple tryptophan residues in a protein – one can easily imagine that some of these residues would be more accessible to quenchers in the solvent than other. I0/I [Q] In the extreme case, a SternVolmer plot for a system having。