J. Biol. Chem., Vol. 262, Issue 30, 14487-14491, 10, 1987
Time-resolved fluorescence of apoferritin and its subunits
N Rosato, A Finazzi-Agro, E Gratton, S Stefanini and E Chiancone
Consiglio Nazionale delle Ricerche, Center of Molecular Biology, Rome, Italy.
The decay of the intrinsic fluorescence of the apoferritin polymer and its
subunits has been studied by pulse and phase shift techniques. Both
techniques show that the fluorescence decay of all the samples tested
cannot be described by a single exponential function. The fluorescence
decay data of the apoferritin subunits obtained with either technique can
be fitted satisfactorily with a function resulting from the sum of two
exponential components. However, the polymer data obtained with the high
resolution phase shift technique operated either by synchrotron radiation
or by a mode-locked argon ion laser can be fitted better using a bimodal
gaussian continuous distribution of lifetime components. The molecular
basis for this distribution of lifetime values may lie in the heterogeneity
of the tryptophan environment generated by the assembly of the subunits
into the polymer. The binding of the first 100 irons to apoferritin
quenches the intrinsic fluorescence without affecting the lifetimes in a
proportional way. This finding may be taken as an indication that the
quenching of the tryptophan fluorescence induced by the binding of iron has
both static and dynamic components.
CiteULike 
Complore 
Connotea 
Del.icio.us 
Digg 
Reddit 
Technorati What's this?
