Conformational
Change-Induced Fluorescence of Bovine
Serum Albumin–Gold Complexes
Jacob
M. Dixon
Shunji Egusa
10.1021/jacs.7b11712.s001
https://acs.figshare.com/articles/journal_contribution/Conformational_Change-Induced_Fluorescence_of_Bovine_Serum_Albumin_Gold_Complexes/5849412
We
report new findings on the red fluorescent (λ<sub>em</sub> =
640 nm) bovine serum albumin (BSA)–gold (Au) compound initially
described by Xie et al. (<i>J. Am. Chem. Soc.</i> <b>2009</b>, <i>131</i>, 888–889) as Au<sub>25</sub> nanoclusters. The BSA–Au compounds were further reducible
to yield nanoparticles, suggesting that these compounds were BSA–cationic
Au complexes. We examined the correlations between BSA conformations
(pH-induced as well as denatured) and the resulting fluorescence of
BSA–Au complexes, to understand the possible cationic Au binding
sites. The red fluorescence of the BSA–Au complex was associated
with a particular isoform of BSA, the aged form (pH > 10) of the
five
pH-dependent BSA conformations, while the other conformations, expanded
(pH < 2.7), fast (2.7 < pH < 4.3), normal (4.3 < pH <
8), and basic (8 < pH < 10) did not result in red fluorescence.
There could be internal energy transfer mechanisms to produce red
fluorescence, deduced from excitation–emission map measurements.
The ensemble minimum number of Au(III) per BSA to yield red fluorescence
was <7. We illustrate the presence of multiple specific Au binding
sites in BSA, and present an interpretation of the fluorescence of
the BSA–Au complex, alternative to a single-site nucleation
of a neutral Au<sub>25</sub> nanocluster.
2018-01-23 00:00:00
Conformational Change-Induced Fluorescence
binding sites
energy transfer mechanisms
pH-dependent BSA conformations
fluorescence