The Belousov−Zhabotinsky (BZ) reaction has been applied to give autonomous dynamic behaviors to artificial systems. This reaction is conducted in an aqueous system, but it produces some hydrophobic intermediates, such as bromine. On the basis of previous works about reactions in the lipid bilayer, we investigated how liposome membranes (water−oil interface) affect the BZ reaction. Herein diacylglycerophosphocholine (PC) molecules with a variety of hydrocarbon tails were selected as components of liposomes, and the BZ reaction in the presence of the liposomes was characterized. As a result, membrane fluidity was the main characteristic leading to changes in the reaction behavior. The decrease of the frequency of oscillations was relevant to membrane fluidity, suggesting the interaction of bromine species in the hydrophobic site of the liposomes. In addition, the heterogeneous membrane (s o +l d ) of DMPC showed a fast decrease in the amplitude of oscillations. Conclusively, characteristics of the hydrophobic environment play a role in the reaction.
The Belousov−Zhabotinsky (BZ) reaction is an oscillating reaction due to periodic oscillations that happen in the concentration of some intermediates. Such systems can be applied together with hydrophobic membranes to create an autonomous behavior in artificial systems. However, because of a complex set of reactions happening in such systems, the interferences caused by hydrophobic membranes are not easily understood. In this study, we tested lipid membranes composed of trimethylammoniumpropane (TAP) and phosphate (PA) lipids in an attempt to break down how the polar region of phosphatidylcholine (PC) lipid membranes affect the BZ reaction. According to our findings, the trimethylammonium group and membrane fluidity are crucial to change the frequency of oscillations in the reaction. In addition, the results also indicate a possible complexation of cerium ions with membranes with a phosphate head group.
Oscillating reactions are reactions
in which it is possible to
observe oscillations in the concentrations of some reaction intermediates.
The reaction studied here is composed of acetone, sulfuric acid, bromate,
oxalic acid, and Ce(IV). Chemical oscillators may have different behaviors
in batch, for example, the presence of an induction period and change
of oscillations’ pattern. A much rarer event is the presence
of a break, or pause, between two groups of oscillations, which is
shown by this system. To better determine the conditions under which
this behavior occurs, we built several phase diagrams for the initial
concentrations of reactants. These phase diagrams show that there
is a well-defined range of concentrations that produce a pause in
the oscillations. The initial bromate concentration is special because
increasing this concentration eliminates the pause in the oscillations,
but a further increase can make a pause appear again. These results
can be interpreted considering that the reaction mechanism is controlled
by at least two intermediates. In addition, this work presents a representative
set of data that must be acknowledged by any detailed proposal of
mechanism for this oscillating reaction.
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