3 research outputs found
Interaction of Heme Proteins with Anionic Polyfluorene: Insights into Physiological Effects, Folding Events, and Inhibition Activity
Because of the toxicity caused by the heme redox-active
iron proteins,
their elevated levels, localization, and accumulation in the brain,
many forms of neurodegenerative diseases, such as Alzheimer’s
disease, Parkinson’s disease, and Huntington’s disease,
occur as a result of which the brain becomes vulnerable to oxidative
stress, ultimately resulting in neuronal death. An anionic water-soluble
conjugated polyfluorene derivative polyÂ(9,9-bisÂ(6-sulfate hexyl) fluorene-<i>alt</i>-1,4-phenylene) sodium salt (P1) that binds Fe<sup>3+</sup> proteins with very high selectivity and sensitivity is reported
here. The photophysical properties of P1 were modified by the interaction
with ferric heme-containing proteins cytochrome <i>c</i> (C<i>c</i>), methemoglobin (MetHb), and hemin. P1 was
found to be highly sensitive toward Fe<sup>3+</sup> heme proteins
as compared to nonmetalloproteins. We observed that the respective
activities of ferric heme proteins were inhibited and proteins were
unfolded, due to modification in their heme microenvironment in the
presence of the polymer P1. The observations reported in this article
provide the first example for the use of a water-soluble conjugated
polymer in applications, such as (1) to detect small quantities of
iron proteins in aqueous medium/physiological condition with the highest <i>K</i><sub>sv</sub> values of 2.27 × 10<sup>8</sup> M<sup>–1</sup> for C<i>c</i>, 3.81 × 10<sup>7</sup> M<sup>–1</sup> for MetHb, and 5.31 × 10<sup>7</sup> M<sup>–1</sup> for hemin; (2) to study the physiological effects
of heme metalloproteins; (3) to visualize the folding events in real
time; and (4) the inhibition activity of metalloproteins can be selectively
studied using a conjugated polymer based assay system rapidly without
interference from nonmetalloproteins at biological pH. All this is
achieved by generating optical events, taking advantage of the bright
fluorescence of anionic polyfluorene P1 in this case, that can be
observed and monitored by modification in the absorption and emission
color in real time
Exploration of Energy Modulations in Novel RhB-TPE-Based Bichromophoric Materials via Interactions of Cu<sup>2+</sup> Ion under Various Semiaqueous and Micellar Conditions
Novel bichromophoric materials <b>TR-A</b> and <b>TR-B</b> consisting of an entirely new combination
of TPE and RhB units were developed to explore the optimum conditions
of energy modulations via pH variation and Cu<sup>2+</sup> interaction
at various water contents of CH<sub>3</sub>CN. Interestingly, <b>TR-A</b> and <b>TR-B</b>, at 60 and 70% water contents,
respectively, favored the optimum Cu<sup>2+</sup>-mediated energy
modulations from TPE to RhB and thus achieve the brightest orange
emissions of free RhB with complete disappearance of aggregation-induced
emission (AIE) from TPE. Furthermore, various micellar conditions
of triton-X-100, SDS, and CTAB were employed to adjust energy modulations
of <b>TR-A</b> and <b>TR-B</b> at high water contents
(at 80 and 90%, respectively). The incorporation of RhB into triton-X-100
micellar cavities disrupted AIE from TPE; thus, none of the energy
modulations from TPE to RhB occurred even in the presence of Cu<sup>2+</sup> ion. Interestingly, the micellar conditions of anionic surfactant
(SDS) favored the increased local concentration of Cu<sup>2+</sup> ions in the vicinity of scavangable RhB and facilitated the generation
of noncyclic free RhB in situ via bright-orange emissions
Novel Water-Soluble Cyclodextrin-Based Conjugated Polymer for Selective Host–Guest Interactions of Cationic Surfactant CTAB and Reverse FRET with Rhodamine B Tagged Adamantyl Guest
A new
water-soluble π-conjugated main-chain polymer <b>P1</b> bearing a β-cyclodextrin (β-CD) pendant was
designed and synthesized. The aggregation and disaggregation of <b>P1</b> generated faded yellow-greenish and bright-yellow emissions,
respectively. The inclusion complexation capability of <b>P1</b> through β-CD pendant with a cationic surfactant cetylÂtrimethylÂammonium
bromide (CTAB) guest and associative interactions of <b>P1</b> with Fe<sup>3+</sup> through triazole spacers resulted in significantly
enhanced and completely diminished emission profiles of <b>P1</b> in pure water, respectively. Interestingly, ADRhB as another rhodamine
B (RhB) tagged adamantyl guest was transformed into ADRhBÂ(O), i.e.,
the open form of ADRhB, to generate RhB emission in the presence of
Fe<sup>3+</sup> ion selectively for the pendent host β-CD of <b>P1</b>, and the further interaction of ADRhBÂ(O)/Fe<sup>3+</sup> with <b>P1</b> prevailed a completely quenched RhB emission
via the inclusion complexation of adamantyl terminal of ADRhBÂ(O) in
β-CD. Moreover, stronger interactions of CTAB with β-CD
further generated RhB emission of ADRhBÂ(O) even in the presence of
acceptor <b>P1</b>. Finally, a novel β-CD bearing water-soluble <b>P1</b> with selective and strong interactions of CTAB toward disaggregation
events in pure water, and further electrostatic repulsion and utilization
of RhB via RhB-tagged adamantyl guest ADRhBÂ(O) as a donor revealed
the reverse-fluorescence resonance energy transfer (FRET) process
of <b>P1</b>