  We realize a biochemical filtering process by introducing a buffer in a
biocatalytic signal-transduction logic system based on the function of an
enzyme, esterase. The input, ethyl butyrate, is converted into butyric acid-the
output signal, which in turn is measured by the drop in the pH value. The
developed approach offers a versatile "network element" for increasing the
complexity of biochemical information processing systems. Evaluation of an
optimal regime for quality filtering is accomplished in the framework of a
kinetic rate-equation model.
