pH-driven instabilities in chemical systems

The main aim of my project is to find new feedback driven enzymatic systems and to develop new biochemical oscillators. Such systems help in the understanding of nonlinear behaviour in biological systems and may also find applications in, for example, drug delivery or material science.
The first step was to obtain a clock behaviour and bistability in a new enzymatic system, the urea/urease/sulphuric acid reaction. A kinetic model has been proposed and compared with the experimental results.
Secondly, front propagation has been also observed in space under specific range of conditions and the results have been analysed theoretically by expansion of the model into spatial dimension.
Additionally irregular oscillations in the urea/urease/acetic acid system in flow were observed. Attempts to explain this behaviour theoretically have been made and discussed.
In order to produce more robust, regular oscillations in the urea/urease reaction, literature and experimental investigations of reactions that could provide negative feedback were made. The most obvious strategy to obtain a pH oscillator is to find an H+ autocatalytic reaction, in which case the best candidates from organic reactions was hydrolysis of esters to produce a carboxylic acid. Simple general models have been proposed and several examples of esters have been investigated experimentally.
Apparently one of the investigated esters, acetyl salicylic acid, exhibited very interesting behaviour from the perspective of chemical locomotion. The motion of aspirin has been analyzed qualitatively under different set of conditions.