Color-Changing Probes Shed Light on Protein Sensing

A novel fluorescent probe library is developed by a research team including scientists from the University of Electro-Communications, Tokyo. The findings are published in the journal Analytical Chemistry.

The ability to visualize, detect and track specific proteinsis highly desirable for scientists working in a variety of disciplines, such as disease diagnostics and cell biology. To this end, 'fluorogenic probes' are often used - molecular dyes which bind to target molecules and fluoresce in response to the surrounding microenvironment. Some probes hold the ability to change color and 'turn on' (known as CCTO), emitting a much brighter light upon recognition of the target molecule.

There are some issues with the use of fluorogenic probes. For example, adding a fluorescent molecule (or fluorophore) into a peptide or ligand capable of binding to the target can sometimes inhibit correct binding, causing a weak link. Moreover, current fluorogenic probes are built only for certain specific protein-ligand pairs, and the search is on for a way to find probes suitable for a wider range of targets.

Now, Masumi Taki and co-workers at the University of Electro-Communications in Tokyo, together with co-workers in Japan and the USA, have synthesized a diverse fluorogenic probe library using a form of the fluorescent dye Prodan and phage display technology based on bacteriophage T7.

The team selected the protein glutathione S-transferase (GST) as their target for a proof-of-concept study. Their probe library yielded GST-specific CCTO probes, which changed color upon binding from yellow to cyan. The intensity of the cyan fluorescence also increased upon target recognition. The color-change ability is most highly prized, because an obvious signal such as this can result in less ambiguous read-outs when searching for specific targets.

Further trials using the new probe library will help Taki and his team determine its advantages and limitations.