A simple label free detection system based on changes in the optical properties of gold that is capable of monitoring low levels of protein-peptide interactions has been developed by scientists in Japan. The technique shows potential for use as miniaturized protein detecting chips for proteomic studies.

The technique developed by Hisakazu Mihara and co-workers at the Tokyo Institute of Technology, Japan, is based on a characteristic property of gold which is detectable in blue/violet light and known as anomalous reflection (AR). Genetically engineered peptide sequences containing a dye that monitors binding properties are assembled onto gold surfaces. A protein called calmodulin (CaM) is known to interact with the peptide sequence on the chip and is added to the gold surface. This causes the reflectivity of the gold surface to decrease as CaM forms a layer over the gold substrate. CaM binds better than any other protein tested, indicating that the system is sufficient to discriminate interactions of interest.

In this post genome-sequencing era, much attention has been focused on developing technologies for the analysis of whole protein function. One of the most promising approaches is the use of microarray technologies that allow large scale analysis of whole protein functions within a single experiment. These are usually based on capture agents for protein detection immobilized on a solid surface, and often rely on fluorescent marker measurements. Label free detection methods, for example surface plasmon resonance spectrometry (SPR) have previously been developed, but these often involve bulky and expensive instrumentation. 

With further work to improve the sensitivity Mihara says that 'the AR technique would become an indispensable high throughput screening method in both biological studies and diagnostics'. 

Katherine Vickers