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A new displacement probe based on pyrrolidinyl peptide nucleic acid was designed and evaluated for DNA sequence recognition. The probe was prepared by combining an N-terminally fluorophore-modified pyrrolidinyl peptide nucleic acid (Flu- or TMR-acpcPNA) and a 3’-Dabcyl-modified DNA as a quencher. Fluorescence studies showed that the fluorophore in the acpcPNA strand was efficiently quenched by the quencher strand. After some optimisation, the fluorescence was significantly restored upon the addition of the complementary DNA target, while the fluorescence stayed at a low level with the addition of mismatched DNA. Even with double-stranded DNA analytes, the high specificity of the PNA-based displacement probes allowed unambiguous discrimination between complementary and single mismatched DNA targets. Furthermore, immobilisation of the probes onto agarose resin could also recognise only the complementary DNA, thereby demonstrating its potential as a practical DNA sensor.

Bacteria frequently manifest distinct phenotypes as a function of cell density in a phenomenon known as quorum sensing (QS). This intercellular signalling process is mediated by “chemical languages” comprised of low-molecular weight signals, known as autoinducers, and their cognate receptor proteins. As many of the phenotypes regulated by QS can have a significant impact on the success of pathogenic or mutualistic prokaryotic–eukaryotic interactions, there is considerable interest in methods to probe and modulate QS pathways with temporal and spatial control. Such methods would be valuable for both basic research in bacterial ecology and in practical medicinal, agricultural, and industrial applications. Toward this goal, considerable recent research has been focused on the development of chemical approaches to study bacterial QS pathways. In this Perspective, we provide an overview of the use of chemical probes and techniques in QS research. Specifically, we focus on: (1) combinatorial approaches for the discovery of small molecule QS modulators, (2) affinity chromatography for the isolation of QS receptors, (3) reactive and fluorescent probes for QS receptors, (4) antibodies as quorum “quenchers,” (5) abiotic polymeric “sinks” and “pools” for QS signals, and (6) the electrochemical sensing of QS signals. The application of such chemical methods can offer unique advantages for both elucidating and manipulating QS pathways in culture and under native conditions.